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Petrography, diagenesis, and facies analyses as well as the depositional environments of the late Campanian-Maastrichtian sequence in southwestern Iraq are studied in five keyholes. The sequence incorporates parts of the Hartha, Shiranish and Tayarat Formations. The Hartha Formation comprises creamy and organodetrital dolomite, grey dolomitic marl, and evaporites. The Shiranish Formation is composed of grey marl and claystone, whereas the Tayarat Formation is composed of grey ash, along with tough and fossiliferous dolomitic limestone inter-bedded with grey mudstone layers and/or wisps. Several diagenetic processes affected the sequence, such as neomorphic replacement, dissolution, dolomitization, and sulphate development. Some of these processes obliterated the primary textures. The late Campanian-Maastrichtian sequence consists of three microfacies (Dolomitic Intraclastic Limestone, Dolomitized Biomicrite, and Biomicrosparite Microfacies) and two lithofacies (Mudrock and Sulphates-Rock Lithofacies), in addition to Fine- to Medium-Crystalline Dolomite Lithotype. The Hartha Formation is evaporitic, possibly with supratidal sabkha deposits. The overlying Tayarat and Shiranish Formations reflect deposition in a warm tropical to subtropical reefal and open marine conditions, as deduced from faunal assemblages. Some effects of deep marine condition are evident by the presence of Shiranish facies. The sequence represents deposition in the central reef- fore reef area. The absence of isolated back-reef lagoon facies suggests that the reef was patchy without isolation of water in the middle shelf region. However, at the top of the sequence, i.e. at the end of the Cretaceous Period, restricted lagoons seem to have dominated the studied succession. [ABSTRACT FROM AUTHOR]

Abstract Fossil caridean shrimp of Palaemonidae are reasonably common in Cretaceous and Oligocene deposits of Brazil. Reexamination of species assigned to Pseudocaridinella Martins-Neto and Mezzalira, 1991b, indicate that a new genus, Bahiacaris n. gen., must accommodate one of the referred species, Bahiacaris roxoi new combination. Palaemonidae invaded freshwater in South America by the late Early Cretaceous. Highlights • A new genus of shrimp. • Revision of our understanding of Brazilian shrimp. • Description of criteria necessary to evaluate shrimp taxa. [ABSTRACT FROM AUTHOR]

Abstract A new species of "guitarfish" from the Lower Cretaceous Tlayúa Formation of Puebla, Mexico is here described as † Tlalocbatos applegatei gen. et sp. nov. The new species is based on a nearly complete articulated specimen and represents the first chondrichthyan from this formation. The inclusion of a new character and two additional taxa into a phylogenetic analysis based on previous studies generates a novel phylogenetic hypothesis of batoid phylogeny. Paraphyly of the "guitarfishes" is corroborated, although a new clade was recovered comprising the modern Platyrhinidae plus † Britobatos primarmatus as the sister group of the node formed by † Stahlraja , † Tlalocbatos , plus the Trygonorrhinidae. † Tlalocbatus differs from other batoids by the following combination of characters: nasal capsules with horn-like anterior processes; homodont dentition; presence of a well-developed median uvula; lateral uvulae not differentiated; pectoral propterygium, extending as far as the anterior part of the nasal capsules; two radials articulating directly with the scapulocoracoid, between the mesopterygium and the metapterygium; two dorso-lateral nuchal cartilages, unfused with the synarcual; and an elevated number of post-synarcual centra (115–118). The distribution of † Stahlraja († Tlalocbatos (trygonorrhinids)), suggests that this clade originated in the western part of the Tethys-Caribbean region with a later dispersion westward towards the Pacific. Highlights • A new fossil Batoidea from the Cretaceous of Mexico, † Tlalocbatos applegatei, is described. • The paraphyletic status of the "guitarfishes" is corroborated. • Our hypothesis of distribution suggests that the clade f† Stahlraja († Tlalocbatos (trygonorrhinids)), has originated in the western part of the Tethys-Caribbean with a later dispersion westwards towards the Pacific. [ABSTRACT FROM AUTHOR]

The Western Carpathian Meliata Superunit (Meliaticum) includes a heterogeneous group of units—the blueschist-facies Bôrka Nappe and the very low-grade chaotic complexes—polygenous mélange containing material derived from various tectonic settings (Jaklovce Unit) and Jurassic oceanic sediments with olistostrome bodies (Meliata Unit s.s.). The high pressure/low temperature (HP/LT) metamorphism, development of tectonic mélanges and synorogenic sediments took place simultaneously during the Middle-Late Jurassic in connection with closing of the Meliata Ocean. We present some new data concerning composition of variegated mélanges related to the subduction-accretion processes of the Meliata Ocean and its continental margins. The polygenous mélange contains a mixture of fragments of HP/LT up to unmetamorphosed sedimentary and volcanic rocks, including blueschist-facies radiolarites. New electron microprobe chemical age data of monazites from metasediments of the Bôrka Nappe cluster in two peaks—earliest Cretaceous ages are interpreted in terms of post-exhumation, renewed burial during formation of the Meliatic accretionary wedge. The mid-Cretaceous ages might record the thermal relaxation during the thick-skinned nappe stacking and exhumation of the neighbouring Veporic metamorphic dome. In addition, we describe two distinct types of tourmalines and epidotes occurring in the Bôrka blueschists that document the prograde HP and retrograde LP metamorphic events. Detritus of the blueschist-facies rocks appears for the first time in the heavy mineral spectra of the Barremian-Aptian platform limestones. These limestones occur as clasts, together with glaucophanite pebbles, in the Albian-Cenomanian flysch formations of the Pieniny Klippen Belt (Klape Unit). We also review occurrences of other blueschist and ophiolitic erosional products in Cretaceous clastic formations and suggest that all have a Meliatic provenance. [ABSTRACT FROM AUTHOR]

Abstract The Kelasu Thrust Belt is a key area for oil and gas exploration within the Tarim Basin of China, an area containing abundant oil and gas resources but where the processes that controlled hydrocarbon accumulation remain unclear. This study reconstructs the accumulation history of hydrocarbons within the Kelasu Thrust Belt by studying multiple sets of fluid inclusions from the Cretaceous reservoirs using laser Raman, infrared spectroscopy, fluorescence spectroscopy, total scanning fluorescence, and PTV simulation analyses. The resulting data yield the following results. (1) Three types of Cretaceous hydrocarbon-bearing fluid inclusions are present, and they record three periods of hydrocarbon accumulation. Period I involved low-maturity medium oil as recorded by the presence of yellow–green fluorescent oil inclusions, with this accumulation occurring between the Neogene Jidike and Kangcun stages (20–5 Ma). Period II involved high-maturity light oils (or condensates) that are recorded by the presence of blue–white fluorescent oil inclusions, with this accumulation occurring during the early Kuche stage (5–2.5 Ma). Period III involved the significant accumulation of gas, as recorded by non-fluorescent gas inclusions, during and after the late Kuche stage (2.5–0 Ma). (2) Inclusion PVT simulations indicate that the pressures during the trapping of oil inclusions within the west Kelasu reservoirs increase with increasing capture temperature, suggesting that west Kelasu Cretaceous oil reservoirs formed over a short period of time. In contrast, the trapping pressures of oil inclusions within the east Kelasu area are invariant with increasing trapping temperature, indicating that the formation of east Kelasu Cretaceous oil reservoirs was a relatively slow and gradual process. This most likely relates to the fact that the east Kelasu reservoirs are close to the hydrocarbon generation centre in an area with sufficient hydrocarbon supply, with hydrocarbon accumulation processes involving all of the stages of hydrocarbon generation recorded by the source rocks in this area. In comparison, the west Kelasu reservoirs are far from the hydrocarbon generation centre and as such record only one phase of oil filling. (3) Significant tectonism associated with the uplift of the South Tianshan Mountain during the late Kuche stage caused widespread changes to Cretaceous paleo-oil reservoirs in this area. This led to some Cretaceous paleo-oils being transported to shallower traps to form secondary oil reservoirs, whereas others were transported to the surface and were lost, with residual paleo-oils were also changed to condensate gas as a result of gas washing after the addition of large amounts of late-stage gas. Highlights • The Cretaceous fluid inclusions record three periods of hydrocarbon accumulation. • Period I and II were associated with medium and light oils, Phase III was gas filling. • The temperature and pressure at the time of hydrocarbon accumulation were determined. • The loss of Cretaceous paleo-oil reservoirs was a result of three different processes. [ABSTRACT FROM AUTHOR]

Abstract The Mesozoic (especially the Cretaceous) sequences in the northern South China Sea (SCS) are important potential targets of oil and gas exploration; however, they are currently poorly understood. We use organic petrology and geochemistry to evaluate the hydrocarbon potential and study depositional environment of the Cretaceous black mudstones and shales from the Dayawan Section in the Guangdong Province, China. These mudstones and shales yield total organic carbon (TOC) contents of 0.63%–2.76% and most samples meet the requirement for higher TOC source rocks. Organic matters in the mudstones and shales were sourced mainly from higher plants as well as subordinate benthic macroalgae. Organic petrology and geochemical data suggested that the organic matters were dominated by Type-III and minor Type-II, and generally have low thermal maturity. Thus, we evaluated the black mudstones and shales have a potential for hydrocarbon generation (especially gas prone). Pr/Ph, trace elements, and mixture source of organic matter suggested that these black mudstones and shales formed in a coastal–lacustrine environment, characterized by weakly oxidizing−weakly reducing conditions and low-salinity. A marine transgression developing in the middle part of the section was recognized. Generally, the northern SCS, which exhibits the more marine influence, likely contains source rocks with higher TOC contents and better organic matter types. The Cretaceous source rocks with higher liquid hydrocarbon generation potential may occur locally in the Pearl River Mouth Basin. Highlights • The Lower Cretaceous black shales develop in the Dayawan section, Guangdong. • The shales have high TOC, low thermal maturity, and Type-III organic matter. • The shales formed in weakly oxidizing− weakly reducing offshore lacustrine settings. • An early Cretaceous marine transgression resulted in these black shales. • Black shales located away from volcanism in SCS may have hydrocarbon potential. [ABSTRACT FROM AUTHOR]

Abstract The palyno-organic facies aspects of the subsurface Lower Cretaceous core samples are extensively investigated in three wells in the northern part of the Western Desert of Egypt. These wells are Burg El Arab-1 and Mamura-1, Mersa Matruh-1 (BAX-1, MAX-1 and MMX-1 respectively). The study is based on the palynofacies and organic geochemical analyses. The palynofacies examination includes a statistical analysis of the different classes of organic particles by cluster analysis and principal component analysis (PCA). This analysis leads to identify 4 palynofacies types (A, B, C 1 and C 2) which are dominated by various levels of terrestrial floral materials. The paleoenvironmental settings that are attributed to these palynofacies types are the distal suboxic-oxic, proximal oxic, transitional oxic and highly distal oxic. The principal component analysis (PCA) differentiates between these palynofacies types mathematically by the biplot of components 1 and 2. The component 1 corresponds to distance from the terrestrial floral sources. The identification of quantity, type, quality and thermal maturity of organic matter is discussed depending on the palynofacies and organic geochemical analyses. The thermal maturity is assessed digitally by measuring the RGB color channels in the spore images and their corresponding thermal alteration index (TAI incorporated with values of T max). These measures are integrated in burial history models with geothermal gradient and depositional history. The study reveals that most of the core samples represent generally fair to good enriched sources of gas prone type III kerogen and less mixed gas-oil type II/III kerogen. Additionally, some occasional high levels of organic conversions are recorded. The burial history models indicate that oil expulsion window initiated in the Cretaceous. The examinations indicate mature oil sources in the Alam El Bueib Formation in MMX-1 well. The organic geochemical parameters are correlated versus the component 1 and sum of all components of PCA. The correlation coefficients (R2) pointed to good correlation between the oxygen index (OI), TOC and S 2 and lower correlation with hydrogen index (HI). Highlights • A comprehensive palyno-organo facies analysis for the core samples from the subsurface Lower Cretaceous. • Four palynofacies types were identified each represent a specific paleoenvironmental setting. • Geochemical analysis reveals fair to good sources with gas prone type III and less mixed gas-oil type II/III kerogens. • The examinations indicate mature oil sources in the Alam El Bueib Formation in MMX-1 well. [ABSTRACT FROM AUTHOR]

Abstract The complex geometry of carbonate systems is influenced by a multitude of physical as well as biological processes. The Lower Cretaceous carbonates of Northern Oman are characterised by a variability of regional-scale geometries with expected vertical and lateral facies variations. The main environmental and tectonic controls acting on the depositional processes of the Lower Cretaceous ramps and platforms through space and geological time (in 4 dimensions) are only partially understood. In this study, we use a 4D DionisosFlow Forward Stratigraphic Modelling (FSM) approach to explore the role of: (i) eustasy; (ii) subsidence; (iii) initial paleobathymetry, and (iv) wave energy, to generate carbonate stacking patterns and heterogeneities. Carbonate production was maintained constant through deposition. Multi-disciplinary and multi-scale datasets were used (i.e. seismic, well and field data) to constrain the FSM input parameters and sensitivity analysis was carried out to validate or refute some depositional model hypotheses. Results show that basement topography and eustasy have the greatest influence on the progradational geometries and the lateral continuity of clinoform architectures during the Tithonian to Valanginian second-order super-sequence. In the Valanginian to Aptian super-sequence, subsidence was the primary control for the observed aggradational stacking pattern. Lateral and vertical stacking of carbonate lithologies, textures as well as facies are thus apprehended through this FSM approach, leading to a better assessment of petroleum systems elements as reservoir, seal and trap. Highlights • Quantitative study of Lower Cretaceous Carbonates in Oman using forward numerical modelling. • Sensitivity analysis of input such as basement geometry, diffusion coefficient, wave energy, eustasy and subsidence. • Results demonstrates that existing conceptual model of geometry of basement is consistent with the geometries of clinoforms. • The need for differential subsidence to explain some aspects of the regional trends is demonstrated through the model. [ABSTRACT FROM AUTHOR]

Abstract Structural data and cross-cutting relationships in the Xolapa Complex around Puerto Escondido, southern Mexico, indicate the development of two pre-Cenozoic folding systems recorded, in part, by migmatites. The older system is defined by gently SW-plunging, vertical open folds (FS1), related to a southwestward extension. A subsequent FS2 folding system is defined in turn by slightly SE-plunging, northwest-facing asymmetric folds, related to a northeastward transpression. The comparison between our structural data and those available in the literature indicate that both FS1 and FS2 are pervasive in the whole Xolapa Complex. In addition to the reciprocal link between orientation, lineation distribution, and kinematics between folding systems, higher strain components of FS2 and FS1 yield a strikingly similar direction but opposite sense, suggesting a paired tectonic cycle of opening (FS1) and closure (FS2) of a Xolapa Complex basin. From the comparison between crosscutting relationships in the study area and a compilation of U-Pb zircon data from the literature, we deduce that the opening of the Xolapa basin occurred sometime between 158 and 129 Ma; this is between the termination of the continental Nazas arc and the early stages of the extensional Guerrero arc. On the other hand, the closure of the Xolapa basin (FS2) took place between 94 and 72 Ma. Highlights • Two pre-Cenozoic folding systems (FS) affected the entire Xolapa Complex. • Older FS1 suggests the southwestward Chortís Block detachment from mainland. • Younger FS2 suggests the northeastward Chortís Block collision to mainland. • FS1 and FS2 occurred at ca. 158-129 Ma, and ca. 94-72 Ma, respectively. • Intervening Xolapa basin opened and closed to allow the Chortís Block transport. [ABSTRACT FROM AUTHOR]

Abstract Thirty mudstone samples from coastal exposures of the Northumberland Formation on Hornby Island, British Columbia, Canada, yielded diverse dinoflagellate cyst and terrestrial sporomorph assemblages. A late Campanian age for the formation has been well defined through magnetostratigraphy, macrofossil biostratigraphy, and geochemical studies of the Hornby Island section. Dinoflagellate cyst taxa corresponding to 61 genera are exceptionally well preserved and include specimens referable to at least 68 formally established species. The earliest occurrences of Canninginopsis maastrichtiensis , Druggidium cf. discretum , Phanerodinium belgicum , Renidinium cf. vitilaire , Senegalinium simplex , Spiniferella cornuta , and Xenicodinium delicatum sensu Slimani et al. are reported along with the most recent occurrence of Senoniasphaera protrusa , extending their stratigraphic ranges into the upper Campanian. The palynomorph assemblages support a late Campanian age. Two dinoflagellate cyst ecozones are recognized (ecozone 1 and ecozone 2). Assemblages suggest sediment deposition in an inner shelf environment with moderate to high nutrient input and primary productivity. Highlights • High diversity in first northeast Pacific study of Mesozoic dinoflagellate cysts. • Dinoflagellate cysts reinforce late Campanian age for the Northumberland Formation. • Two distinct ecozones recognized within the Northumberland Formation section. • Palynomorphs support inner shelf setting with moderate to high primary productivity. • Palynomorphs indicate mid-latitude position for the Cretaceous Nanaimo Basin. [ABSTRACT FROM AUTHOR]

Micropores of shale are significant to the gas content and production potential of shale, which has been verified in the research of marine shale gas; while, few studies have been conducted on lacustrine shales. This study collected 42 samples from three wells in the Late Cretaceous Qingshankou Formation of the southern Songliao Basin, NE China, and investigated these samples by the focused ion beam‐scanning electron microscope (FIB–SEM) and nitrogen adsorption analysis techniques. Four types of micropores were identified in the samples, i.e., intergranular pore, intracellular pore, organic matter pore and microfracture. The pore structure type is characterized by open slit pores and "ink type" pores which are mainly 1.5–5 nm in diameter with mesopores as the main pores. The mesopores account for 74.01% of the pore volume and 54.68% of the pore surface area. Compared with the lacustrine shales from the Triassic Yanchang Formation in the Ordos Basin and Xujiahe Formation in the Sichuan Basin, the intergranular clay mineral interlayer pores are considered to be the main reservoir space for shale gas storage in the study area, followed by intraparticle pores, organic matter pores and microfractures. Maturity and micropore are the key controlling factors which affect the shale gas content of the Qingshankou Formation in southern Songliao Basin. [ABSTRACT FROM AUTHOR]

Post‐collisional volcanic rocks of Mesozoic age occur in the regions adjacent to Gerze, part of the southern Qiangtang Terrane of northern Tibet, China. Geochronological, geochemical, and whole‐rock Sr‐Nd isotopic analyses were performed on the volcanic rocks to better characterize their emplacement age and models for their origin. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U‐Pb zircon analyses yielded consistent ages ranging from 123.1±0.94 Ma to 124.5±0.89 Ma for six volcanic rocks from the study area. The intermediate volcanic rocks belong to the alkaline and sub‐alkaline magma series in terms of K2O+Na2O contents (5.9%–9.0%), and to the shoshonitic and calc‐alkaline series on the basis of their high K2O contents (1.4%–3.3%). The Gerze volcanic rocks are characterized by the enrichment of light rare earth elements [(La/Yb)N=34.9–49.5] and large–ion lithophile elements (e.g., Rb, Ba, Th, U, K, Pb, and Sr), slightly negative Eu anomalies (Eu/Eu*=0.19–0.24), and negative anomalies in high field strength elements (e.g., Nb, Ta, Hf and Ti), relative to primitive mantle. The samples show slightly elevated (87Sr/86Sr)i values that range from 0.7049 to 0.7057, and low ∊Nd(t) values from –0.89 to –2.89. These results suggest that the volcanic rocks studied derived from a compositionally heterogeneous mantle source and that their parent magmas were basaltic. The more mafic, parental magmas to the Gerze volcanic rocks likely underwent fractional crystallization of clinopyroxene, hornblende, biotite, and potassium feldspar, during ascent, with little to no crustal contamination, prior to their eruption/emplacement. While these volcanic rocks exhibit geochemical signatures typical of magmas formed in a destructive plate‐margin setting, it is plausible that their mantle source might also have acquired such characteristics in an earlier episode of subduction. [ABSTRACT FROM AUTHOR]

The ages and source of Late Cretaceous mafic dolerite dykes of the Songliao Basin were determined using geochronological, geochemical, zircon Hf, whole‐rock Sr–Nd isotopic, and zircon fission tract. The results show that (a) petrographic data reveal doleritic, poikiloblastic textures, and amygdale structures of the dolerite dykes. (b) LA‐MC‐ICP‐MS U–Pb analysis of zircons yielded an age of 70.0 ± 3.0 Ma of one of these mafic dykes in agreement with the zircon fission track age (69–68 Ma) of host rocks within uncertainty, placing them within the Late Cretaceous. (c) Geochemical researches indicate that the dykes are classified as the alkaline and tholeiitic series according to their major elements and characterized by high Na2O (2.79–4.89 wt.%), TiO2 (1.63–2.71 wt.%), and low K2O (0.46–2.45 wt.%). And they have enrichment of incompatible elements (e.g., K, Ti, Rb, Ba, Th, U, Nb, Ta, and REEs), high Rb/Sr (0.026–0.066), LaN/YbN (3.83–15.93), near‐chondritic HREEs ([Gd/Yb]N = 1.78–3.37), low Sm/Nd (0.202–0.282) ratios, and with negligible Eu anomalies (Eu/Eu* = 0.98–1.06). The dykes contain relatively low amounts of radiogenic Sr, as shown by (87Sr/86Sr)i values (0.7037–0.7045), and have positive values of εNd(t) (3.66–5.40) and εHf (t) (2.66–7.45), suggesting that the mafic dykes have been derived from partial melting of the depleted lithospheric mantle and contaminated by crust in the source region and formed in back‐arc rift settings caused by the subduction of the Pacific Oceanic Plate. All the above indicate large‐scale extensional event in Songliao Basin NE China at about 70 Ma. [ABSTRACT FROM AUTHOR]

The Cretaceous (Cenomanian, ~96 Ma) basaltic rocks of the Strand Fiord Formation of the Sverdrup Basin of the Canadian Arctic Archipelago, Nunavut, Canada, are a part of the High Arctic large igneous province. The basaltic suite reaches a thickness of almost 1,000 m on Axel Heiberg Island in its depocentre and over 700 m at the studied section. The rocks are variably fractionated tholeiitic basalts, which are geochemically similar to many other continental flood basalts, particularly to low Ti basalts of flood basalt provinces. Geochemical as well as Sr (87Sr/86Srinitial ~ 0.7045 to 0.7067) and Nd (ƐNd(t) ~ +1.3 to +4.3) isotopic signatures of the basalts were inherited during partial melting of spinel peridotite of an ancient subcontinental lithospheric mantle, which was modified around 0.7–0.9 Ga by a metasomatic event. The melting generating the Cretaceous basalts was probably triggered by a mantle plume but was also associated with basin rifting and stretching. There is evidence of plume‐induced doming and uplift of the crust prior to and during the eruption of the basalts as documented by the progression from marine sedimentation to subaerial/lacustrine and then back to marine sedimentation in the Sverdrup Basin centre. The basalts represent parts of the Early Cretaceous igneous province that is dispersed around the Arctic Ocean due to the opening of the Canada Basin, which is inferred to be related to a mantle plume. [ABSTRACT FROM AUTHOR]

This paper reports U–Pb ages of detrital zircons from a series of clastic and pyroclastic rocks from the Murui Formation in the southern Great Xing'an Range (GXR), NE China, with the aim of constraining the depositional age of this poorly dated unit. These data, combined with the petrographic and sedimentology characteristics of the rocks, are used to constrain the sediment sources and tectonic setting of the provenance and provide wider insight into the tectonic evolution of the southern GXR during the Late Mesozoic. Two lithic arkose samples have dominant age groups at 249–250, 159–160, 136–147, and 394–415 Ma, and 301–323, 278–288, 209–237, and 142–163 Ma, respectively. The U–Pb zircon data constrain the maximum depositional age of the Murui Formation to 136 ± 1 Ma, that is, the Early Cretaceous. A lithic–crystal tuff from the upper Murui Formation yielded zircons with a weighted mean U–Pb age of 136 ± 1 Ma (n = 47, mean square weighted deviation (MSWD) = 2.2), indicating that volcanic activity was contemporaneous with sedimentation of the Murui Formation. U–Pb dating of zircons from a pyromeride in the Baiyingaolao Formation that was erupted unconformably onto the Murui Formation yielded a peak age of ~120 Ma, which constrains the depositional age of the Murui Formation to 120–136 Ma. Further dating of detrital zircons shows a range of ages, indicating the various of sediment origins. The Late Jurassic to Early Cretaceous volcanic rocks in the GXR served as the principal detrital sources for the Murui Formation in the southern GXR. Grain size and modal analysis of the sediments shows that the depositional environment was a stable intracontinental fluvial setting, and the provenance of the detritus was most likely a magmatic arc. According to stratigraphic contact relations, the Baiyingaolao Formation is supposed to have obvious intervals with lower volcanic strata, which combined with disparities between the southern and northern GXR in terms of the duration of volcanism, magmatic events, and the depositional age of the Murui Formation. We can conclude that the restricted occurrence of the Early Cretaceous detritus between the earlier and later phases of volcanism suggests progressive exhumation of the southern GXR in the Early Cretaceous. These may relate to post‐orogenic extension related to oceanic subduction. The southern GXR remained a site of active sedimentation during the continental extension period across the whole of NE China in the Late Jurassic to Early Cretaceous. [ABSTRACT FROM AUTHOR]

The triggers of soft‐sediment deformation structures (SSDS) that are present in the deep‐water slope‐failure system of the Early Cretaceous Lingshandao Formation on Lingshan Island have been analysed on the basis of SSDS in 5 outcrops. The sediments in these outcrops are interpreted to have been deposited on a near‐shore submarine fan. The inner and middle fans were observed in Yangjiaodong, and the outer fan outcropped in Qiancengya, Dengta, and Chuanchang. The inner and middle fans are characterized by coarse‐grained debrites, turbidites, and rare SSDS, whereas the outer fan by fine‐grained debrites, turbidites, deformed sediments, and abundant SSDS. Based on sedimentary composition, element analysis and palaeo‐geographical indication of SSDS, the source area was supposed to be uplifted Sulu Orogen in an active continental margin. Combination with sedimentary environment, tectonic setting, and the space distribution of different scaled SSDS, seismicity was proposed to be the trigger of larger scaled SSDS, and small‐scale SSDS may be triggered by gravity loading, slump‐derived shear stress, and traction effect. The seismicity may respond to active tectonism and volcanism. Besides, time consistence between the Lingshandao Formation (~131–121 Ma), cooling events, sea‐level change, stable isotope excursion, and palaeo‐seismicity events suggested a catastrophic event, which may be related to two Early‐Cretaceous Anoxic Events (Faraoni Event, ~131 Ma; OAE 1a, ~120 Ma). [ABSTRACT FROM AUTHOR]

Abstract New palynostratigraphic data are presented for Upper Jurassic and Lower Cretaceous formations of the Mandawa Basin, southeastern Tanzania. A Late Jurassic (Kimmeridgian‑Tithonian) age is confirmed for the Kipatimu Formation, from which the terrestrial sporomorphs allow a rough correlation to the mid Oxfordian‑Tithonian Classopollis ‑ Araucariacites‑Shanbeipollenits Assemblage Zone. A dinoflagellate cyst assemblage recorded in the Mitole Formation correlates to the Dingodinium jurassicum–Kilwacysta assemblage as described from the Tithonian Trigonia smeei Bed of the Tendaguru Hill, southeast Tanzania. Dinoflagellate cyst assemblages in the upper Nalwehe Formation contain species typical of the Hauterivian‑Barremian, while the Kihuluhulu Formation contains marine microfloras of Aptian to Albian ages. The palynological records confirm the presence of sediments related to profound marine transgressions and subsequent sea-level high-stands in the Late Jurassic (Kimmeridgian‑Tihonian) and in the late Early Cretaceous (Aptian‑Albian). Highlights • The Late Jurassic Jurassic and Early Cretaceous formations are dated by palynomorphs. • The Kipatimu Fm is Kimmeridgian-Tithonian and the middle Mitole Fm Tithonian in age. • A Hauterivian-Barremian in inferred for the Nalwehe Fm. • The Kihuluhulu Fm contains Aptian–Albian palynomorphs of Aptian‑Albian age. • Marine transgressions occurred in the Kimmeridgian‑Tihonian and in the Apt-Albian. [ABSTRACT FROM AUTHOR]

Combined sedimentological and structural analysis was carried out in the field and on 2D seismic reflection profiles to recognize pre-orogenic structures in a Cretaceous fold-and-thrust belt. Detailed field observations were made in the Keszthely Hills, Western Hungary, while 2D seismic interpretation was carried out in the neighbouring Zala Basin. As a result, a fault-controlled intraplatform basin system was identified by a detailed analysis of bounding faults, and related outcrop-scale structures. The Norian-Rhaetian (227-201.3 Ma) synsedimentary faulting was associated with talus breccia formation, small-scale faulting, and dyke formation, in addition to slumping and other soft-sediment deformations. Based on the distribution of talus breccia, WNW-ESE-trending map-scale normal faults were identified in the Keszthely Hills, which is in agreement with the directly observed outcrop-scale synsedimentary faults. On seismic sections, similar WNW- or NW-trending Late Triassic normal faults were identified based on thickness variations of the syn-rift sediments and the presence of wedge-shaped bodies of talus breccia. Normal faulting occurred already in the Norian, and extensional tectonics was active through the Early and Middle Jurassic. The Late Triassic grabens of the western Transdanubian Range could be correlated with those in western part of the Southern Alps, and the Bajuvaric nappe system of the Northern Calcareous Alps. These grabens were situated on the proximal Adriatic margin, and they represent the first sign of the Alpine Tethys rifting. The locus of extension was laterally migrated westward, towards the distal Adriatic margin during Early and Middle Jurassic. [ABSTRACT FROM AUTHOR]

Lower Cretaceous syn-orogenic sediments derived from the obducted ophiolites of the Meliata-Maliac-Vardar (Neotethys) Ocean are typically found in the Dinarides and the Austroalpine units. Correlative flysch-type deposits linking both regions through the Southern Alps had been reported from the Bohinj area (NW Slovenia), but their stratigraphic and structural framework remained poorly known. Our research focused on stratigraphic and structural field studies in a 50 km2 area between Lake Bled and Lake Bohinj in the Julian Alps. The mixed carbonate-siliciclastic sediments, informally named the Studor formation, range in age from the Valanginian (possibly late Berriasian) to the Aptian. They occur on top of two different stratigraphic successions, which we assign to two separate nappes. The first succession consists of deep-water Middle Triassic to Lower Cretaceous deposits of the Bled Basin and belongs to the Pokljuka Nappe, which is the uppermost nappe of the Julian nappe stack. The second succession consists of Upper Triassic to Lower Jurassic platform carbonates and a thin Jurassic-Cretaceous deep-water sequence. This succession was deposited in the marginal area of the Julian Carbonate Platform/Julian High and now belongs to the underlying Krn Nappe. The original (Dinaric) thrust contacts between the Pokljuka and Krn nappes are obliterated by younger deformations. The present-day boundaries between these two nappes are steep NE-SW and younger NW-SE trending faults. The post-nappe deformation sequence characterizing the Alps-Dinarides transition zone has been recognized: (1) Oligocene-Early Miocene NW-SE contraction; (2) Early-Middle Miocene extension; and (3) Late Miocene to recent inversion and transpression. [ABSTRACT FROM AUTHOR]

The 700-m-thick Hauterivian to Albian section from the interior of the large, Adriatic Platform is exposed on Mljet and Korčula islands, Croatia. The cyclic platform consists of meter-scale parasequences, bundled into parasequence sets, superbundles and then into breccia-bounded depositional sequences. Spectral analysis of time series (cycle number vs. cycle thickness) shows peaks in the short-term eccentricity (95 to 130 kyr) bands and 160 to 200 kyr bands. Isotope samples from micrite matrix of mudstone and wackestone have δ 13 C values generally from −1.5 to +2‰ VPDB, and δ 18 O from −1 to −3.5‰ VPDB. Adriatic Platform δ 13 C values are shifted ~2‰ VPDB more negative than marine pelagic values. A δ 13 C and δ 18 O meteoric signal is limited to just beneath sequence boundaries, suggesting that the isotopic shift is due mainly to marine phreatic‐ and synorogenic burial diagenesis. Major excursions on the 5-point smoothed δ 13 C profile of the Adriatic Platform, tied biostratigraphically to δ 13 C curves from pelagic sections, include the oceanic anoxic events OAE1a, 1b, and 1c. Time series constructed from δ 13 C values (unsmoothed data) vs. stratigraphic position show peaks in the Milankovitch band, especially short-term eccentricity. Most positive peaks are near parasequence set boundaries (50 to 60%) and regressive parts of parasequences (20%). Although diagenetically shifted, the δ 13 C record retains a highly clipped memory of astronomically-driven global δ 13 C fluctuations albeit modified by platform water restriction during cyclic deposition. [ABSTRACT FROM AUTHOR]

this work focuses on one of the critical points of Earth's history when the Solar System passed through the most distant point of its galactic orbit. During this event, Earth may have suffered from maximum extension, associated with its relative proximity to the Sun at that time, followed by long‐term contraction related to its later distancing. This paper is based on generalized data on the Cretaceous evolution of the Earth as a whole and of East Asia in particular. The evidence suggests that major geological processes at this time may be interpreted as transitional changes in the state of Earth. A liquid nature of its core may have reacted to the gravitational and electromagnetic transformations. When the cosmic changes took place at 135–120 Ma, more turbulent flows in the outer core would have favoured the rise of voluminous magmatic plumes and associated fluid flows. These would substantially transform the mantle, crust, hydrosphere, biosphere and atmosphere. In particular, plume‐related melting of overlying subducting slabs and lower continental crust could have initiated numerous adakitic melts that formed the East Asian Adakitic Province. These and associated juvenile events produced numerous metallic ore, coal, gas and oil deposits. The Cretaceous is one of the most significant resource‐producing periods. [ABSTRACT FROM AUTHOR]

The study of Late Cretaceous magmatic rocks, developed as a result of magmatism and related porphyry mineralization in the northern Lhasa block, is of significance for understanding the associated tectonic setting and mineralization. This paper reports zircon chronology, zircon Hf isotope data, whole‐rock Sr–Nd isotope data, and geochemistry data of Balazha porphyry ores in the northern Lhasa block. Geochemical features show that Balazha ore‐bearing porphyries in the northern Lhasa block belong to high‐Mg# adakitic rocks with a formation age of ~90 Ma; this is consistent with the Late Cretaceous magmatic activity that occurred at around 90 Ma in the region. The age of adakitic rocks is similar to the molybdenite Re–Os model age of the ore‐bearing porphyries in the northern Lhasa block, indicating that the diagenesis and mineralization of both occurred during the same magmatism event in the Late Cretaceous. The Hf and Sr–Nd isotope data indicate that these magmatic rocks are the product of crust–mantle mixing. Differing proportions of materials involved in such an event form different types of medium‐acid rocks, including ore‐bearing porphyries. Based on regional studies, it has been proposed that Late Cretaceous magmatism and porphyry mineralization in the northern Lhasa block occurred during collision between the Lhasa and Qiangtang blocks. [ABSTRACT FROM AUTHOR]

The Maastrichtian crustacean fauna from Chiapas is illustrated and reviewed with reports of new taxa, including the marine isopod Palaega sp., described for the first time from the lower Maastrichtian Ocozocoautla Formation, represented by molted remains of the posterior carapace. New specimens and a neotype of the raninoid Vegaranina precocia (Feldmann et al., 1996) are illustrated and compared with specimens of Vegaranina sp. from the late Maastrichtian of France. New specimens of Carcineretes woolacotti Withers, 1922, from the late Maastrichtian of Chiapas are reported and recognized as the sole species of the genus, distributed in the upper Maastrichtian lithostratigraphic units from the Caribbean; the new specimens are compared with others of the same species and age from the Guinea Corn Formation in Jamaica and the Barton Creek Formation in Belize. Icriobranchiocarcinus tzutzu Vega new genus and species, is reported as a new member of the Icriocarcininae Števcic, 2005, a diverse subfamily of lithophylacid crabs, along with illustrations and discussion on Branchiocarcinus flectus (Rathbun, 1926) (Maastrichtian, Gulf and Atlantic plains), Icriocarcinus xestos Bishop, 1988 (Maastrichtian, Pacific of California and Baja California), and Lithophylax trigeri A. Milne-Edwards and Brocchi, 1879 (Cenomanian, France), in order to confirm that all of these species belong to the Lithophylacidae Van Straelen, 1936, but to different subfamilies (Lithophylacinae and Icriocarcininae) and genera. Parazanthopsis meyapaquensis Vega, Feldmann, García-Barrera, Filkorn, Pimentel & Avendaño, 2001, is compared with Palaeoxanthopsis cretacea (Rathbun, 1902) (late Maastrichtian, Brazil), and with Palaeoxantho libertiensis Bishop, 1986 (late Maastrichtian, Mississippi), in order to illustrate differences and confirm that these species belong to separate genera. Megaxantho zoque Vega, Feldmann, García-Barrera, Filkorn, Pimentel & Avendaño, 2001 is reviewed and compared to Menippe frescoensis Remy, 1960 (early Eocene, Senegal) and Menippe mercenaria (Say, 1818) (living species, Gulf of Mexico), to confirm the late Maastrichtian species from Chiapas should be recognized as Menippe zoque new combination, representing the oldest confirmed species for the genus. The age and lithostratigraphic units for all these Maastrichtian crustaceans from Chiapas is reviewed and corrected, based on recent data reported by other scientists, who defined the litho and biostratigraphy with macro and microfossils reported from the study area, nearby Tuxtla Gutiérrez and Ocozocoautla, Chiapas. A correlation between the late Maastrichtian lithostratigraphic units of Chiapas and those from the Caribbean region is confirmed, and their distribution in turn of the Chicxulub impact area in the Yucatán Peninsula is illustrated. [ABSTRACT FROM AUTHOR]

The Guojialing and Aishan plutons in the northern Jiaobei Terrane represent the magmatic products of the lithospheric thinning of the North China Craton in the Early Cretaceous. The exhumation history of the terrane in response to the thinning process and its effect on the formation and preservation of coeval gold deposits remain poorly constrained. Granodiorites from the Guojialing pluton and monzogranites from the Aishan pluton contain zircon grains with U-Pb ages of ca. 130 Ma and ca. 116 Ma, respectively. Using the Al-in-hornblende barometry, the Guojialing and Aishan plutons had crystallization pressures of 3.2–5.4 kbar (∼12 km) and 1.5–2.6 kbar (∼5 km), respectively. Using the hornblende-plagioclase thermometry, the Guojialing and Aishan plutons had crystallization temperatures of 628–697 °C and 702–745 °C, respectively. Fluid inclusion microthermometric data show that auriferous quartz veins in the Daliuhang deposit formed at temperatures between 243 and 322 °C at a depth of 7–11 km which was similar to the emplacement depth of the Aishan pluton. These thermobarometric and geochronological data reveal ∼7 km uplift between 130 Ma and 116 Ma, but negligible exhumation for the gold deposits after its formation until 116 Ma. Combining previous results, we envisage that the exhumation magnitude of the Guojialing intrusions were nearly the same in the wide area with slight differences between the core and margin of a single pluton. Numerous gold deposits in the Jiaobei Terrane formed during or after the late stage of rapid exhumation of granitoids, and were uplifted with similar depths to the Aishan pluton since ca. 116 Ma. The rapid exhumation of the Guojialing pluton was with the regional extension, and might be genetically associated with the intensive delamination of destabilized lithospheric root and dense residues. [ABSTRACT FROM AUTHOR]

The Jiaodong Peninsula at the southeastern periphery of the North China Craton (NCC) has undergone complex changes since the Mesozoic. A striking feature of the NCC is the widespread distribution of Late Mesozoic magmatic rocks, predominantly characterized by granitic intrusions. These igneous plutons are economically important due to their polymetallic mineralization and significant as geodynamic tracers of the regional tectonic evolution. Two representative Early Cretaceous granites (the Yashan and Yuangezhuang plutons) on the Jiaodong Peninsula were selected for multiple-thermochronometer studies to constrain a complete thermal history from their emplacement to near-surface conditions. We obtained biotite 40 Ar/ 39 Ar ages of two granites on the new generation Argus VI noble gas mass spectrometer. Two biotites registered identical 40 Ar/ 39 Ar plateau ages of ∼117 Ma, which are consistent within the error with their zircon U-Pb ages. This suggested that the two granites were emplaced at the same time and cooled rapidly to about 300 °C. The single crystal zircon (U-Th)/He (ZHe) dating for the two samples gave weighted mean ages of 93.5 ± 4.5 Ma and 93.3 ± 5.0 Ma. Combined with previously published geochronological data and the thermal inversion of the zircon low temperature thermochronological data, three phases of rapid cooling were identified for the two studied plutons: (1) the Early Cretaceous (117–110 Ma); (2) the Late Cretaceous (100–90 Ma); and (3) the Early Tertiary (65–50 Ma). The Early Cretaceous phase of cooling occurred in a regional extensional regime on the NCC characterized by various extensional structures. The Late Cretaceous cooling is consistent with the third episode of the “Yanshan Movement”, which caused a regional basin inversion event on the NCC. In comparison to the first two phases of rapid cooling, the Early Tertiary cooling was more gradual. This phase corresponded to a widely developed Eocene rift on the NCC and the reactivation of major boundary faults, such as the giant Tan-Lu Fault Zone and the Taihangshan Fault. [ABSTRACT FROM AUTHOR]

The Kuching Zone in West Sarawak consists of two different sedimentary basins, the Kayan and Ketungau Basins. The sedimentary successions in the basins are part of the Kuching Supergroup that extends into Kalimantan. The uppermost Cretaceous (Maastrichtian) to Lower Eocene Kayan Group forms the sedimentary deposits directly above a major unconformity, the Pedawan Unconformity, which marks the cessation of subduction-related magmatism beneath SW Borneo and the Schwaner Mountains, due to termination of the Paleo-Pacific subduction. The successions consist of the Kayan and Penrissen Sandstones and are dominated by fluvial channels, alluvial fans and floodplain deposits with some deltaic to tidally-influenced sections in the Kayan Sandstone. In the late Early or early Middle Eocene, sedimentation in this basin ceased and a new basin, the Ketungau Basin, developed to the east. This change is marked by the Kayan Unconformity. Sedimentation resumed in the Middle Eocene (Lutetian) with the marginal marine, tidal to deltaic Ngili Sandstone and Silantek Formation. Upsequence, the Silantek Formation is dominated by floodplain and subsidiary fluvial deposits. The Bako-Mintu Sandstone, a potential lateral equivalent of the Silantek Formation, is formed of major fluvial channels. The top of the Ketungau Group in West Sarawak is formed by the fluvially-dominated Tutoop Sandstone. This shows a transition of the Ketungau Group in time towards terrestrial/fluvially-dominated deposits. Paleocurrent measurements show river systems were complex, but reveal a dominant southern source. This suggests uplift of southern Borneo initiated in the region of the present-day Schwaner Mountains from the latest Cretaceous onwards. Additional sources were local sources in the West Borneo province, Mesozoic melanges to the east and potentially the Malay Peninsula. The Ketungau Group also includes reworked deposits of the Kayan Group. The sediments of the Kuching Supergroup are predominantly horizontal or dip with low angles and form large open synclines. Steep dips are usually restricted to faults, such as the Lupar Line. [ABSTRACT FROM AUTHOR]

The Jiaolai Basin, to the east of the Tan-Lu Fault Zone (TLFZ), is a Cretaceous NE-trending basin in eastern North China and has a multi-episodic evolution. Different from other contemporary NW-trending en-echelon graben systems west to the TLFZ, the origin of the Jiaolai Basin (three episodes: K 1 l , 135–120 Ma; K 2 q , 120–105 Ma; K 2 w , 88–65 Ma) cannot be simply explained by the sinistral displacement of the TLFZ at the beginning of the Early Cretaceous (around ca. 135 Ma). The purpose of this paper is to investigate the critical factors (e.g., bounding faults, tectonic setting, stress field) driving the development of the Jiaolai Basin and constraint its evolution. Three episodes of two-dimensional finite element models were generated in order to determine the roles of the boundary conditions and to reveal the tectonic development of the basin. When compared to the calculated maximum horizontal compressive stress (σ Hmax ) trajectories and the observed data, along with a comparison between the Von Mises Stress ( u Von ) and the depocenters of the basin, the calculated results can be well proved by the geological evidence both in stress field evolution and in the basin patterns. Our analysis show that the three episodes of the maximum principle stress trajectories changed from NE-SW (earlier Early Cretaceous, K 1 l ) NNE-SSW (later Early Cretaceous, K 1 q ) then E-W (Late Cretaceous, K 2 w ). Moreover, the results show a good consistency between the u Von and the depocenters in the basin through geological cross-sections. Via models we suggest that the origin and evolution of the Jiaolai Basin were controlled by three episodes of tectonic events, (i) the reactivated bounding faults and the post-orogenic extension of the Sulu Orogen during the earlier Early Cretaceous, (ii) the lithospheric delamination of the thickened lithosphere during the later Early Cretaceous, and (iii) the likely far-field effects produced by the collision between the Kohistan-Drags arc complex and Asia during the Late Cretaceous. The Jiaolai Basin evolved from extension to pull-apart experiencing volcanic activity during the three episodes of the Cretaceous. [ABSTRACT FROM AUTHOR]

Early Cretaceous tectono-magmatic activity in the eastern North China Craton has long been linked to cratonic destruction, but no systematic investigations about the geodynamic processes have been performed. Early Cretaceous diabases, lamprophyres, andesites and dacites are distributed in the western Shandong Peninsula, and these rocks have a close relationship as they formed synchronously. Zircon U-Pb dating results show that the diabases and lamprophyres formed dykes or sills at 133–127 Ma and that the andesites erupted at ∼125 Ma. The diabases could be divided into high- and low-Mg# value groups. The high-Mg# (>60) diabases have lower SiO 2 (48.44–54.68 wt%) and higher MgO (7.41–19.30 wt%) contents than the low-Mg# (<60) ones (SiO 2 : 52.90–56.41 wt%; MgO: 2.70–4.37 wt%). The lamprophyres (Mg# values of 58–70) exhibit low SiO 2 (45.04–49.99 wt%) and moderate MgO (4.77–9.87 wt%) contents. The diabases and lamprophyres are enriched in large ion lithophile elements (e.g., Ba, Th and U) and light rare earth elements, are depleted in Nb and Ta, and feature negligible Eu anomalies. They have lower zircon ε Hf (t) values (−12 to −19) and whole-rock ε Nd (t) values (2 to −12), with ( 87 Sr/ 86 Sr) i ratios of 0.7066–0.7097. The andesites and dacites have intermediate SiO 2 contents (60.10–64.95 wt%), high Mg# values (56–65), high Sr (1005–1300 ppm), and low Y (11.3–12.9 ppm) contents, with high Sr/Y ratios (78–115), showing adakitic affinity. They have lower zircon ε Hf (t) (−12 to −26) and whole-rock ε Nd (t) (−9 to −13) values and high ( 87 Sr/ 86 Sr) i ratios (0.7109–0.7111). We suggest that the diabases and lamprophyres were derived from the partial melting of enriched lithospheric mantle, and the parental magmas of some of them had more contribution from the asthenosphere. The andesites and dacites were derived from the partial melting of delaminated thickened lower crust with addition of mantle material. Since the late Mesozoic, local delamination may have occurred beneath the Shandong Peninsula. During the Early Cretaceous, the rollback process of the Paleo-Pacific slab beneath the Shandong Peninsula could have facilitated delamination of the lithospheric mantle, and enhances the activity of trans-lithospheric faults. [ABSTRACT FROM AUTHOR]

The dioritic dikes distributed in the Shanyang-Zhashui area of the South Qinling region play an important role in understanding the deep magmatic processes and tectonic evolution during the orogenic process. The zircon U Pb ages of the dioritic dikes indicate that they were emplaced at ∼144 Ma and therefore postdate the dikes that formed in the intracontinental orogenic background after the continental collision between the North China Block (NCB) and the South China Block (SCB). The dioritic dikes have SiO 2 contents of 56.86–64.93 wt%; K 2 O contents of 1.65–3.21 wt%; low MgO (1.50–2.66 wt%), Y (14.4–25.5 ppm) and heavy rare earth element (HREE) contents; low Mg # values (39.9–49); high Sr contents (528–4833 ppm); and high Sr/Y ratios (32.8–189). They exhibit highly fractionated REE and flat HREE patterns, strong enrichment in large ion lithophile elements (LILEs; e.g., Rb, Ba, and U) and depletion in high field strength elements (HFSEs) (e.g., Nb), as well as positive Sr and negative Ti anomalies. Furthermore, these dioritic dikes exhibit ( 87 Sr/ 86 Sr) i ratios ranging from 0.7048 to 0.7083, εNd(t) values ranging from −3.3 to −1.4, and εHf(t) values ranging from −4.1 to 1.6. The geochemical patterns of the dioritic dikes indicate that they possess adakitic characteristics. Moreover, the low MgO contents, Mg # values, Ni contents, Th/Ce ratios, and Sr Nd Hf isotopic features all indicate that these dioritic dikes were generated by the partial melting of thickened mafic lower crust. The high La/Yb and Sr/Y ratios, low Y and Yb contents, absence of significant Eu anomalies, flat HREE patterns, and low Nb/Ta ratios of these rocks suggest that the adakitic melts were derived from the melting of garnet-bearing amphibolite. The geochronologic, elemental and isotopic evidence suggests that the dioritic dikes may have formed in a locally extensional environment within an overall N-S compressional setting or during the transition from compressional to extensional environments in the Early Cretaceous. This process resulted in the upwelling of the asthenospheric or lithospheric mantle, causing partial melting of the mafic lower crust and forming the adakitic dioritic melts. [ABSTRACT FROM AUTHOR]

Recent studies show that the Cretaceous intracontinental and arc tectonomagmatism in Northeast Asia resulted from the intracontinental mantle plume under the North China Craton and its channel-like flow that was dragged into the underneath of the ancient arc, respectively. Although the southwest-to-northeast migration of the channel-like flow in the mantle wedge might have occurred along the Cretaceous margin from southeast China to southwest Japan, adakites, implying partial melting of the subducted oceanic crust, were only observed along southwest Japan. To understand the localized adakite occurrences, a three-dimensional numerical subduction model which covers the margin from southeast China to southwest Japan through the present East China Sea was formulated by considering the southwest-to-northeast migration of the channel-like flow in the mantle wedge. Our model calculations show that increased slab-surface temperatures under southeast China by the channel-like flow were lower than the solidus of the hydrated oceanic crust; no adakites were generated in southeast China. In contrast to that in southeast China, younging subducting slab from the Early to Late Cretaceous along the eastern East China Sea and southwest Japan allowed the channel-like flow to increase the slab-surface temperatures over the solidus; adakites were generated in the eastern East China Sea and southwest Japan. Our model calculations are consistent with the adakite occurrences in southwest Japan and the occurrences in the eastern East China Sea can be verified via oceanic drilling. [ABSTRACT FROM AUTHOR]

Cretaceous through Eocene strata of the Four Corners region provide an excellent record of changes in sediment provenance from Sevier thin-skinned thrusting through the formation of Laramide block uplifts and intra-foreland basins. During the ca. 125-50 Ma timespan, the San Juan Basin was flanked by the Sevier thrust belt to the west, the Mogollon highlands rift shoulder to the southwest, and was influenced by (ca. 75-50 Ma) Laramide tectonism, ultimately preserving a >6000 ft (>2000 m) sequence of continental, marginalmarine, and offshore marine sediments. In order to decipher the influences of these tectonic features on sediment delivery to the area, we evaluated 3228 U-Pb laser analyses from 32 detrital-zircon samples from across the entire San Juan Basin, of which 1520 analyses from 16 samples are newly reported herein. The detrital-zircon results indicate four stratigraphic intervals with internally consistent age peaks: (1) Lower Cretaceous Burro Canyon Formation, (2) Turonian (93.9-89.8 Ma) Gallup Sandstone through Campanian (83.6-72.1 Ma) Lewis Shale, (3) Campanian Pictured Cliffs Sandstone through Campanian Fruitland Formation, and (4) Campanian Kirtland Sandstone through Lower Eocene (56.0-47.8 Ma) San Jose Formation. Statistical analysis of the detrital-zircon results, in conjunction with paleocurrent data, reveals three distinct changes in sediment provenance. The first transition, between the Burro Canyon Formation and the Gallup Sandstone, reflects a change from predominantly reworked sediment from the Sevier thrust front, including uplifted Paleozoic sediments and Mesozoic eolian sandstones, to a mixed signature indicating both Sevier and Mogollon derivation. Deposition of the Pictured Cliffs Sandstone at ca. 75 Ma marks the beginning of the second transition and is indicated by the spate of near-depositional-age zircons, likely derived from the Laramide porphyry copper province of southern Arizona and southwestern New Mexico. Paleoflow indicators suggest the third change in provenance was complete by 65 Ma as recorded by the deposition of the Paleocene Ojo Alamo Sandstone. However, our new U-Pb detrital-zircon results indicate this transition initiated ~8 m.y. earlier during deposition of the Campanian Kirtland Formation beginning ca. 73 Ma. This final change in provenance is interpreted to reflect the unroofing of surrounding Laramide basement blocks and a switch to local derivation. At this time, sediment entering the San Juan Basin was largely being generated from the nearby San Juan Mountains to the north-northwest, including uplift associated with early phases of Colorado mineral belt magmatism. Thus, the detrital-zircon spectra in the San Juan Basin document the transition from initial reworking of the Paleozoic and Mesozoic cratonal blanket to unroofing of distant basement-cored uplifts and Laramide plutonic rocks, then to more local Laramide uplifts. [ABSTRACT FROM AUTHOR]

Fluvial systems represent a key component in source-to-sink analysis of ancient sediment-dispersal systems. Modern river channels and channel- related deposits possess a range of scaling relationships that reflect drainage-basin controls on water and sediment flux. For example, channel-belt sand-body thicknesses scale to bankfull discharge, and represent a reliable first-order proxy for contributing drainage-basin area, a proxy that is more robust if climatic regimes can be independently constrained. A database of morphometrics from Quaternary channel belts provides key modern fluvial system scaling relationships, which are applied to Cretaceous- to Paleocene-age fluvial deposits. This study documents the scales of channel-belt sand bodies within fluvial successions from the northern Gulf of Mexico passive-margin basin fill from well logs, and uses scaling relationships developed from modern systems to reconstruct the scale of associated sediment-routing systems and changes in scale through time. We measured thicknesses of 986 channel-belt sand bodies from 248 well logs so as to estimate the scales of the Cretaceous (Cenomanian) Tuscaloosa- Woodbine, Paleocene-early Eocene Wilcox, and Oligocene Vicksburg-Frio fluvial systems. These data indicate that Cenozoic fluvial systems were significantly larger than their Cenomanian counterparts, which is consistent with Cretaceous to Paleocene continental-scale drainage reorganization that routed water discharge and sediment from much of the continental United States to the Gulf of Mexico. At a more detailed level, Paleocene-early Eocene Wilcox fluvial systems were larger than their Oligocene counterparts, which could reflect decreases in drainage-basin size and/or climatic change within the continental interior toward drier climates with less runoff. Additionally, these data suggest that the paleo-Tennessee River, which now joins the Ohio River in the northernmost Mississippi embayment of the central United States, was an independent fluvial system, flowing southwest to the southern Mississippi embayment, or directly to the Gulf of Mexico, through the early Eocene. Changes in scaling relationships through time, and interpreted changes in the scales of contributing drainage basins, are generally consistent with previously published regional paleogeographic maps, as well as with newly published maps of paleodrainage from detrital-zircon provenance and geochronological studies. As part of a suite of metrics derived from modern systems, scaling relationships make it possible to more fully understand and constrain the scale of ancient source-to-sink systems and their changes through time, or cross-check interpretations made by other means. [ABSTRACT FROM AUTHOR]

An integrated study of comprehensive geochronological, geochemical, and Sr-Nd-Hf isotopic data was undertaken for the A-type Topcam pluton that intruded within the Sakarya Zone (NE Turkey) with the aims of elucidating its origin and tectonic significance and gaining new insights into the generation of aluminous A-type granites. New LA-ICP-MS zircon U-Pb crystallization ages of 72 and 73 Ma indicate emplacement in the Late Cretaceous time, just after extensive metaluminous I-type magmatism in the area. The pluton consists mainly of alkali feldspar, quartz, plagioclase, amphibole, and biotite with accessory minerals such as magnetite, apatite, and zircon. The outcrop is composed of granite, syenite, monzonite, and quartz monzonite and possesses a wide range of SiO 2 content (57–70 wt%) with elevated Ga/Al ratios and low Mg# (mostly < 43). The pluton is metaluminous to weakly peraluminous, with aluminium saturation index (ASI) (molar Al 2 O 3 /[CaO + K 2 O + Na 2 O]) values of 0.82 to 1.18, and belongs to the shoshonitic and ultra-potassic series. All the samples exhibit relative enrichment in light rare earth elements (LREE) and significant negative Eu (Eu/Eu* = 0.31 to 0.86) anomalies on the chondrite-normalized REE diagram. The rocks are enriched in some large ion lithophile elements (e.g., Rb, Th and Ba), and spidergrams show a relative depletion in Nb, Ti, and Sr. The granitic rocks of the pluton have identical 87 Sr/ 86 Sr (i) ratios ranging from 0.70518 to 0.70716, relatively low ε Nd ( t ) values varying from − 5.5 to − 0.4, and T DM ages (0.82–1.19 Ga). In situ zircon analyses show that the rocks have variable negative and positive ε Hf ( t ) values (− 5.5 to 5.9) and Hf two-stage model ages (742 to 1468 Ma), which are indicative of minor addition of juvenile material. Sr-Nd isotope modelling suggests mixing of 70–90% of lower crustal-derived melt with ~ 10–30% of mantle-derived melt at lower crust depths. The heat source for partial melting is provided by upwelling of hot asthenosphere triggered by slab roll-back events. Geochemical and isotopic data reveal that metaluminous A 2 -type granites were derived from partial melting of the Paleozoic lower continental crust dominated by mafic rocks in amphibolitic composition, with minor input of subcontinental lithospheric mantle-derived magma followed by subsequent limited fractional crystallization to generate a variety of rock types. From integrating all available data with the regional tectonic evolution in the Sakarya Zone and adjacent regions, we attribute generation of aluminous A 2 -type granites to a back-arc extension in the subduction zone, which is induced by the roll-back of the Neo-Tethyan oceanic slab around 72 Ma. Consequently, we conclude that these A-type granites were related to intensive extension tectonic, which peaked during the late Cretaceous (Maastrichtian) in response to the roll-back of the Neo-Tethyan oceanic slab, which is indicative of the final-stage subduction-related magmatism in the Sakarya Zone. [ABSTRACT FROM AUTHOR]

The Feie'shan greisen–type W–Sn deposit in the eastern Guangdong Province forms part of the Southeastern Coastal Metallogenic Belt (SCMB) in South China. Here we present zircon LA–ICP–MS U–Pb geochronology of the biotite granite which shows a weighted mean 206 Pb/ 238 U age of 134.7 ± 2.0 Ma, consistent with the zircon U–Pb, biotite 40 Ar– 39 Ar and molybdenite Re–Os ages in the previous study. The biotite granite is peraluminous and belongs to high–K calc–alkaline type. It is characterized by high SiO 2 , K 2 O, F, K 2 O + Na 2 O and FeO t /(FeO t + MgO), and low CaO, MgO, TiO 2 and P 2 O 5 contents, enrichment in Rb, Cs, Th and U, and depletion in Ba, Sr, Zr, Ti and P, with flat REE patterns and distinctly negative Eu anomalies, showing an A 2 –type affinity. The rocks also display extremely low Ba, Sr and Ti concentrations and high Rb/Sr, Rb/Ba and low CaO/(Na 2 O + K 2 O) ratios, indicating high degree of fractionation. Zircon grains from the granite have low Eu/Eu ⁎ and Ce 4 + /Ce 3 + ratios, suggesting low oxygen fugacity. The highly fractionated and reduced features imply that the Feie'shan mineralization is genetically related to the biotite granite. The ε Nd (t) values and zircon ε Hf (t) values of the biotite granite range from − 2.96 to − 1.95 and − 5.69 to 0.62, with two–stage Nd and Hf model ages (T DM2 ) of 1083 to 1164 Ma and 1150 to 1552 Ma, indicating that they were derived from magma hybridization between anatectic granitic and mantle–derived mafic magmas. In combination with previous studies, we propose a geodynamic model for the 145―135 Ma W–Sn mineral system and related magmatism in the southwestern domain of the SCMB. After ca. 145 Ma, the subduction orientation of the Izanagi plate changed from oblique to parallel with respect to the continental margin resulting in large–scale lithosphere extension and thinning, which led to the upwelling of asthenosphere. The ascending mantle–derived mafic magmas provided not only supplied the heat for crustal remelting but also added juvenile mantle–derived melts resulting in the formation of mafic dikes, and I– or A–type granitic intrusions related to the W–Sn ore mineral systems. [ABSTRACT FROM AUTHOR]

This work presents new data on the composition of volcanics, developed within the Alazeya Plateau of the Kolyma-Indigirka fold area (Northeast Russia), which indicate essential differences in their composition and, accordingly, different geodynamic settings of the formation of rocks. The studied igneous rocks are subdivided into two groups. Volcanics of the first group of the Late Cretaceous age, which are represented by differentiated volcanic rock series (from andesitobasalts to dacites and rhyolites), were formed under island arc conditions in the continent-ocean transition zone. Volcanics of the second group are ascribed to the tholeiitic series and were formed under the other geodynamic setting, which is associated with the regime of extension and riftogenesis, manifested in the studied area probably at the later stage. [ABSTRACT FROM AUTHOR]

Assemblages of planktonic foraminifera and dinoflagellate cysts were studied from the 359 m thick Padeha-Baghak composite section of the Abderaz Formation, eastern Koppeh-Dagh Basin, NE Iran. The formation consists mainly of light grey shales and marls with three chalky limestone beds in the upper part. Nine genera and 44 species of planktonic foraminifera and 39 genera and 85 species of dinoflagellate cysts are identified. Planktonic foraminifera are attributed to four biozones (Dicarinella primitiva-Marginotruncana sigali, Dicarinella concavata, Dicarinella asymetrica and Globotruncanita elevata zones). Two dinocyst superzones (Conosphaeridium striatoconum Superzone and the lower part of the Odontochitina porifera Superzone) with seven interval zones are recognized. These biozones suggest a late Turonian-early Campanian age for the Abderaz Formation in this part of the Koppeh-Dagh Basin. [ABSTRACT FROM AUTHOR]

The NE-striking Dunhua–Mishan Fault Zone (DMFZ) is one of two branches of the continental-scale sinistral Tan–Lu Fault Zone in NE China. The field data presented here indicate that the ca. 1000 km long DMFZ records two phases of sinistral faulting. The structures produced by these two phases of faulting include NE–SW-striking ductile shear belts and brittle faults, respectively. Mylonite-hosted microstructures and quartz c -axis fabrics suggest deformation temperatures of 450 °C–500 °C for the ductile shear belts. Combining new zircon U–Pb dates for 14 igneous rock samples analyzed during this study with the geology of this region indicates these shear belts formed during the earliest Early Cretaceous. This phase of sinistral displacement represents the initial formation of the DMFZ in response to the northward propagation of the Tan–Lu Fault Zone into NE China. A phase of Early Cretaceous rifting was followed by a second phase of sinistral faulting at 102–96 Ma, as evidenced by our new U–Pb ages for associated igneous rocks. Combining our new data with the results of previous research indicates that the DFMZ records a four-stage Cretaceous evolutionary history, where initial sinistral faulting at the beginning of the Early Cretaceous gave way to rifting during the rest of the Early Cretaceous. This was followed by a second phase of sinistral faulting at the beginning of the Late Cretaceous and a second phase of local rifting during the rest of the Late Cretaceous. The Cretaceous evolution of the DMFZ records the synchronous tectonic evolution of the NE China continent bordering the Pacific Ocean. Two phases of regional N–S compression generated the two phases of sinistral faulting within the DMFZ, whereas two-stage regional extension generated the two phases of rifting. The two compressive events were the result of the rapid low-angle subduction of the Izanagi and Pacific plates, whereas the two-stage extension was caused by the roll-back of these respective plates. The final closure of the Mongol–Okhotsk Ocean at the beginning of the Early Cretaceous intensified the synchronous compression in NE China, causing the northward propagation of the Tan–Lu Fault Zone. [ABSTRACT FROM AUTHOR]

Production of oil from shale and tight reservoirs accounted for almost 50% of 2016 total U.S. production and is projected to continue growing. The objective of our analysis was to quantify the water outlook for future shale oil development using the Eagle Ford Shale as a case study. We developed a water outlook model that projects water use for hydraulic fracturing (HF) and flowback and produced water (FP) volumes based on expected energy prices; historical oil, natural gas, and waterproduction decline data per well; projected well spacing; and well economics. The number of wells projected to be drilled in the Eagle Ford through 2045 is almost linearly related to oil price, ranging from 20 000 wells at $30/barrel (bbl) oil to 97 000 wells at $100/bbl oil. Projected FP water volumes range from 20% to 40% of HF across the play. Our base reference oil price of $50/bbl would result in 40 000 additional wells and related HF of 265 x 109 gal and FP of 85 x 109 gal. The presented water outlooks for HF and FP water volumes can be used to assess future water sourcing and wastewater disposal or reuse, and to inform policy discussions. [ABSTRACT FROM AUTHOR]

Detailed facies analysis of a 350 m long core of upper Campanian-Maastrichtian chalk at Stevns Peninsula, eastern Denmark, shows that four mudstone and wackestone chalk facies account for close to 95% of the succession, and that bioturbated mudstone chalk alone accounts for nearly 55% of the sediment. Sedimentation took place in deep water, below the photic zone and storm-wave base, and is characterized by decimetre to metre-scale variations in facies and trace fossil assemblages indicating repeated shifts in depositional environment. Integration of facies with published data on sea-surface temperature and accumulation rates suggests that sea-surface temperature is the most important parameter in controlling stratification of the water column and thereby, indirectly, the observed variations in depositional facies. However, bioturbated mudstone chalk occurs in all stratigraphic levels independent of accumulation rates and sea temperatures and is interpreted to represent a very broad set of deep water environmental conditions with an ample supply of calcareous nannofossil debris and intense bioturbation. Longer term shifts in deposition are best expressed by distribution of clay, flint and bioturbated micro-wackestone, bioturbated wackestone and laminated mudstone chalk facies, whereas the trace fossil assemblages appear less useful. The data set indicates overall shallowing over time with two distinctive events of clay influx to the basin during the late Campanian-earliest Maastrichtian and late Maastrichtian. [ABSTRACT FROM AUTHOR]

This paper analyses the diagenetic evolution of sandstones belonging to the Bajo Barreal Formation (Cretaceous) in the Golfo de San Jorge Basin (Patagonia, Argentina). The Bajo Barreal Formation includes the main reservoirs, which are located along the western area of the basin and is composed of sandstones, conglomerates, mudstones, tuffaceous mudstones and some layers of tuffs. The principal reservoirs comprise medium-to coarse-grained sandstones, which are dominated by feldspathic litharenites and contain minor amounts of litharenites and lithic arkoses. The authigenic minerals include kaolinite, smectite, chlorite, quartz overgrowths, microquartz and calcite, with minor proportions of megaquartz, siderite, analcime, laumontite, feldspar overgrowths and illite/smectite and chlorite/smectite mixed layers. Secondary porosity is much more important than primary porosity and is produced by the dissolution of feldspar, lithic clasts and clay cements. The diagenetic history of the Bajo Barreal sandstones can be divided into seven diagenetic stages, each of which is characterized by a specific assemblage of authigenic minerals and diagenetic processes. Eogenetic conditions occur in stages 1, 2, 3 and 4. Stage 1 corresponds to shallow burial characterized by the physical reduction of primary porosity by compaction; during stage 2, rim clay cements of chlorite, smectite and clinoptilolite, as well as thin quartz overgrowths, were formed. The precipitation of pore-filling cements of kaolinite, chlorite and smectite occurred during stage 3, while stage 4 records the intense dissolution of feldspar, lithic fragments and kaolinite cements. Mesogenesis occurs in diagenetic stages 5 and 6. The former corresponds to a new phase of authigenic kaolinite, while the latter records the significant dissolution of feldspar, lithic clasts and previous cements, which produced the highest values of secondary porosity. Finally, stage 7 corresponds to the highest degree of diagenesis in the Bajo Barreal Formation (mesogenesis), which resulted in the precipitation of cements of zeolites and calcite, as well as quartz and plagioclase overgrowths. [ABSTRACT FROM AUTHOR]

A series of Mesozoic rift basins formed in eastern China were associated with magmatic activity and subduction along the Eurasia, Izanagi and Pacific plate margins. The impact of magmatic activity on lacustrine sequence development was documented with well-log and 3-D seismic data from the Jupiter Depression in the North Yellow Sea Basin. We identified key surfaces, retrogradational and progradational parasequence sets, and defined the characteristics of systems tracts and the internal sequence components for the Lower Cretaceous (K 1 SQ1). A 2-D SEDPAK numerical stratigraphic forward modeling was used to further constrain sequence development in the Jupiter Depression by considering different modeling parameters and the spatial-temporal characteristics of magmatic activity. Modeling results were compared and matched with the sequence architecture observed from seismic and well interpretations. Magmatic activity impacts on the development of the K 1 SQ1 sequence in the North Yellow Sea Basin include topographic variation, lake level fluctuation, and sediment supply ratios. Results suggest that magmatic upwelling uplifted the northwestern area of the Jupiter Depression and formed its slope break during the late Jurassic or early Cretaceous. Along with uplifting, relative lake level dropped sharply and lake accommodation was reduced, but with increased sediment supply. Therefore, sediment accumulated along the slope break as a lowstand systems tract. Later on, as lake level continuously rose, transgressive and highstand systems tracts were developed. The proposed stacking pattern provides an analog, and a useful model, for lacustrine sequence development in response to magmatic activities in eastern China and other rift basins of similar tectonic setting. [ABSTRACT FROM AUTHOR]

Delta-front sand bodies with large remaining hydrocarbon reserves are widespread in the Upper Cretaceous Yaojia Formation in the Longxi area of the Western Slope, Songliao Basin, China. High-resolution sequence stratigraphy and sedimentology are performed based on core observations, well logs, and seismic profile interpretations. An evaluation of the reservoir quality of the Yaojia Formation is critical for further petroleum exploration and development. The Yaojia Formation is interpreted as a third-order sequence, comprising a transgressive systems tract (TST) and a regressive systems tract (RST), which spans 4.5 Myr during the Late Cretaceous. Within this third-order sequence, nine fourth-order sequences (FS9–FS1) are recognized. The average duration of a fourth-order sequence is approximately 0.5 Myr. The TST (FS9–FS5) mostly comprises subaqueous distributary channel fills, mouth bars, and distal bars, which pass upward into shallow-lake facies of the TST top (FS5). The RST (FS4–FS1) mainly contains subaqueous distributary-channel and interdistributary-bay deposits. Based on thin-sections, X-ray diffraction (XRD), scanning electron microscope (SEM) and high-pressure mercury-intrusion (HPMI) analyses, a petrographic study is conducted to explore the impact of the sedimentary cyclicity and facies changes on reservoir quality. The Yaojia sandstones are mainly composed of lithic arkoses and feldspathic litharenites. The sandstone cements mostly include calcite, illite, chlorite, and secondary quartz, occurring as grain coating or filling pores. The Yaojia sandstones have average core plug porosity of 18.55% and permeability of 100.77 × 10 −3 μm 2 , which results from abundant intergranular pores and dissolved pores with good connectivity. Due to the relatively coarser sediments and abundant dissolved pores in the feldspars, the FS4–FS1 sandstones have better reservoir quality than the FS9–FS5 sandstones, developing relatively higher porosity and permeability, especially the FS1 and FS2 sandstones. The source–reservoir–cap-rock assemblages were formed with the adjoining semi-deep lake mudstones that were developed in the Nenjiang and Qingshankou Formations. This study reveals the deposition and distribution of the delta-front sand bodies of the Yaojia Formation within a sequence stratigraphic framework as well as the factors controlling the Yaojia sandstones reservoir quality. The research is of great significance for the further exploration of the Yaojia Formation in the Longxi area, as well as in other similar lacustrine contexts. [ABSTRACT FROM AUTHOR]

A multidisciplinary study of the dolomitized bodies present in the Lower Cretaceous platform carbonates of Mt. Faito (Southern Apennines – Italy) was carried out in order to explore the connection between early dolomite formation and fluctuating climate conditions. The Berriasian-Aptian investigated succession is 466 m thick and mainly consists of shallow-water lagoonal limestones with frequent dolomite caps. The dolomitization intensity varies along the succession and reaches its peak in the upper Hauterivian-lower Barremian interval, where it is present a completely dolomitized interval about 100-m-thick. Field relations, petrography, mineralogy, and geochemistry of the analyzed dolomite bodies allowed identifying two populations of early dolomites, a fine-medium crystalline (FMdol) and a coarse crystalline dolomite (Cdol), both interpreted as the product of mesohaline water reflux. According to our interpretation, FMdol precipitated from concentrated brines in the very early stage of the reflux process, producing typical sedimentary features as dolomite caps. In the successive step of the process, the basin-ward ‘latent’ reflux precipitated Cdol from less concentrated brines. A peculiar feature of the studied succession is the great consistency between stratigraphic distribution of dolomite bodies and their geochemical signature. The completely dolomitized Hauterivian-Barremian interval, in fact, is characterized by geochemical values suggesting an origin from distinctly saltier brines. Considering that the observed near-surface dolomitization process is controlled by physical and chemical parameters reflecting the paleoenvironmental and paleoclimatic conditions during dolomite formation, we propose that the stratigraphically controlled dolomitization intensity reflects periodic fluctuations in the salinity of dolomitizing fluid, in turn controlled by long-term climate oscillations. The present work highlights that the stratigraphic distribution of early diagenetic dolomite may be used as proxy to define the climatic fluctuations that have influenced the sedimentary dynamics in the Early Cretaceous. Moreover, considering that a comparable early dolomite distribution is present also in the Dinaric Platform, we suggest that a regional scale climate control acted on early dolomite formation and distribution. Refining the knowledge of such a key control may have a significative impact on hydrocarbon reservoir characterization and exploration in the Periadriatic area. [ABSTRACT FROM AUTHOR]

Dinosaur trackways have rarely been reported in Cretaceous strata across the African continent. To the exception of ichnological occurrences in Morocco, Tunisia, Niger and Cameroon, our knowledge on the composition of Cretaceous dinosaur faunas mostly relies on skeletal evidence. For the first time, we document several dinosaur trackways from the Cretaceous of the Mamfe Basin in western Cameroon. Small and medium-size tridactyl footprints as well as numerous large circular footprints are present on a single horizon showing mudcracks and ripple marks. The age of the locality is considered Cenomanian-Turonian and if confirmed, this ichnological assemblage could be younger than the dinosaur footprints reported from northern Cameroon, and coeval with or younger than skeletal remains reported from the Saharan region. These trackways were left in an adjacent subsiding basin along the southern shore of the Benue Trough during a time of high-sea stand when the Trans-Saharan Seaway was already disconnecting West Africa from the rest of the continent. We predict that other similar track sites may be occurring along the margin of the Benue Trough and may eventually permit to test hypotheses related to provincialism among African dinosaur faunas. [ABSTRACT FROM AUTHOR]

Understanding the kinematics of pre-existing fractures under the present-day stress field is an indispensable prerequisite for hydraulically increasing fracture-induced rock permeability, i.e. through hydraulic stimulation, which forms the basis of economically viable exploitation of resources such as natural gas and geothermal energy. Predicting the likelihood of reactivating pre-existing fractures in a target reservoir at particular fluid injection pressures requires detailed knowledge of the orientations and magnitudes of the prevailing stresses as well as pore fluid pressures. In the absence of actual in-situ stress measurements, e.g. derived from boreholes, as is mostly the case in previously underexplored “frontier areas”, such predictions are often difficult. In this study, the potential of reactivating pre-existing fractures in a likely exploration region of the southern Karoo of South Africa is investigated. The orientations of the present-day in-situ stresses were assessed from surrounding earthquake focal mechanisms, implying c. NW-SE oriented maximum horizontal stress and a stress regime changing between strike-slip and normal faulting. A comparison with paleo-stress axes derived from inverted fault-slip data suggests that the stress field very likely did not experience any significant reorientation since Cretaceous times. Maximum possible in-situ stress magnitudes are estimated by assuming that these are limited by frictional strength on pre-existing planes and subsequently, slip and dilation tendency calculations were performed, assuming hydrostatic pore fluid pressures of c. 32 MPa at targeted reservoir depth. The results suggest that prevalent E-W and NW-SE oriented sub-vertical fractures are likely to be reactivated at wellhead pressures exceeding hydrostatic pore fluid pressures by as little as 2–5 MPa, while less prevalent sub-horizontal and moderately inclined fractures require higher wellhead pressures that are still technically feasible. Importantly, actual in-situ stress measurements are essential to test these theoretical considerations and to guide the design of safe and effective exploration linked to fracture manipulation, such as shale gas recovery. [ABSTRACT FROM AUTHOR]

Cretaceous pterosaurs tracksites are very rare worldwide. Until now,only one African Cretaceous site withtracks of ( Agadirichnus elegans and Pteraichnus ) was known. This makes the discovery of a new outcrop in the Upper Cretaceous of Anza (Morocco) the third manifestation of this type of footprint in Africa, extending the existence of such traces from the Coniacian-Santonian to the Maastrichtian. The site contains only manus tracks, which can be explained as a result of erosion of pes prints. The lack of pes prints and the morphometric characteristics of the manus prints only allow us to relate these prints to Agadirichnus , Pteraichnus or maybe to a new ichnogenus. It is possible that the trackmakers are related to Ornithocheiroidea or Azhdarchoidea superfamilies whose fossil bones have been found from the Late Cretaceous in Morocco. [ABSTRACT FROM AUTHOR]