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The topography of the Harlik Mountain has a strong impact on the formation of current arid climate in the Turpan-Hami Basin. However, it is still controversial if Harlik Mountain experienced significant exhumation during the Middle to Late Cenozoic according to the previous thermochronology studies. The features of the Oligocene to Miocene sediments in the foreland basin could provide productive information for resolving the debates. The peak ages of detrital apatite fission track analysis of the Oligocene–Miocene sandstone in the Turpan-Hami Basin are well comparable with the cooling age records of the Harlik Mountain rocks, indicating that the Oligocene–Miocene Taoshuyuanzi Formation in the basin was mostly derived from the Harlik Mountain. The stratigraphic sequence exhibits coarsening upward, reflecting that the source area was in a tectonically active period during the deposition process. Heavy mineral assemblages also suggest that the unstable minerals in the sediment increased significantly at the end of the deposition. Moreover, the proportion of apatite increased up-section, while the garnet content decreased significantly, indicating that the Carboniferous metamorphic rocks have been gradually eroded out and more intrusive rocks have been exposed to the surface. These observations suggest that the Harlik Mountain experienced exhumation during the Oligocene to Miocene, and the denudation depth afterward was probably less than 2.5 km according to the previously apatite (U-Th)/He data. The Oligocene–Miocene exhumation probably acted as one of the triggers for the heavy drought of the Turpan-Hami Basin during the Middle–Late Neogene. [ABSTRACT FROM AUTHOR]

Glacial sediment research using thin sections began post-1945. Microsedimentology examines sediments at the microscopic level deriving insights into the processes of glacial erosion, transport, and deposition. Two issues exist (1) the difficulty by some in recognizing microstructures in thin section and (2) the absence of quantitative data making data reproduction difficult. The latter is hard to resolve but more image capture and software methodologies are now becoming available at reasonable costs. Thin sections are two-dimensional sections of three-dimensional objects, and this must be considered when measurements, fabrics and other data are assessed. Research into the microaspects of glacial sediments followed a typical scientific trajectory: thin sections description with little uniformity or common "language" for observed microstructures: standardization allowed comparison between different sediments; with standardization, came an open-ended classification; and with cross-comparison with multiple thin sections—a quantitative means of study needs developed. It has become apparent that the basic principles of structural geology had to be applied. Thus, micromorphology has subsumed into a microsedimentological study of glacial sediments where stress parameters, structural fabrics and the mapping of deformation structures and contextual integration allows an understanding of how these sediments have been formed. Examples of the development stages of glacial micromorphology/sedimentology are presented here as well as discussion of future avenues of study. In addition, multiple thin sections are used to illustrate the many aspects of glacial micromorphology and the parameters necessary to understand glacial sedimentology and the processes of glacial sedimentation. [ABSTRACT FROM AUTHOR]

Geophysical and geochemical methods were applied to detect the subsurface setting of an Upper Pleistocene-Holocene fluvial incised-valley where a travertine body intercalates between alluvial deposits of the Tiber river (central Italy), at Prima Porta (close to Rome). This study allowed us to provide more information regarding the local stratigraphic architecture and structural features, as a reference analogue to similar settings: i.e., hard (stiff) lithic travertines buried below fine and loose alluvial plain covers. Two Electrical Resistivity Tomography (ERT) profiles, interpreted and calibrated using previously collected litho-stratigraphic data from a borehole, identified a massive body, with a relatively high resistivity that correlates with the travertine deposit of Prima Porta. In addition to ERT, ambient noise measurements, processed with the HVSR technique and 2D array, and seismic refraction tomography were carried out; HVSR data were highly consistent with ERT results and allowed to discriminate between the travertine body and the silty-sand channels and overbank deposits, which were attributed to the Tiber river's evolution during Upper Pleistocene-Holocene. Finally, the presence of cracks/fractures could be inferred, as suggested by slight polarisation effects recorded in the HVSR results and soil-gas anomalies. [ABSTRACT FROM AUTHOR]

Buried karst features result from a complex interplay between carbonate bedrock and structural geology. The enhancement of carbonate aquifers through this interplay creates hydrogeologically complex subsurface drainage networks and highly variable surface topographies. This article reports on the sediment fill and fossil pollen record from a large enclosed negative karst landform at Coolough, near Galway City in the west of Ireland. The landform was discovered during the preliminary site investigation for the proposed N6 Galway City Ring Road. Major joint sets developed in the Carboniferous (Mississippian) Limestone bedrock govern the local hydrogeology and structural evidence suggests that a local fault has controlled the east–west propagation of the deep enclosed depression. Fluvial and lacustrine palaeoenvironments are interpreted from the sediments infilling the enclosed depression, within which three discrete diamicts are identified, potentially representing distinct phases of glaciation. Pollen assemblages, which reflect palaeoenvironments of open woods and grasslands, have been correlated with other deposits in Ireland and Europe and suggest a minimum date of the Early Pleistocene for the oldest of the diamicts, and thus an upper age limit on the development of the karst depression. Fluvial disturbance to the deposit is evident and is likely to be responsible for the chronological discrepancy between the Early Pleistocene and Middle Pleistocene sediments both recorded from the deposit infill. The findings of this multidisciplinary study contribute to an understanding of Quaternary landscape evolution in western Ireland. [ABSTRACT FROM AUTHOR]

This contribution presents the first results of compositional tomography of a geological sample. The volume render of 6 × 8 × 1 mm3 was constructed by assembling 63 compositional maps acquired in 21 min (19.5 s/layer) by laser‐induced breakdown spectroscopy (LIBS), which determines the chemical composition of the analysed spot from the light emitted by a plasma produced by the laser. This technique is, therefore, able to directly reveal the 3D distribution of chemical elements in a sample. As an example, the spatial distribution and 3D geometry of visible gold in an ultramafic schist are presented. Inasmuch as this newly developed portable LIBS instrument is able to the rapidly characterize the 3D geometry of any geological materials, it has a high potential to be useful for the mining industry and for a wide range of geosciences, such as structural geology, petrology, sedimentology and economic geology. [ABSTRACT FROM AUTHOR]

Abstract The Bengal Fan contains the most complete record of Himalayan climate and tectonics. As the largest fan system of the world it is fed by the Ganges-Brahmaputra river systems. International Ocean Discovery Program (IODP) Expedition 354 cored seven sites along an east-west core transect at 8°N in the lower Bengal Fan. We studied the Pleistocene sections of these sites to provide constraints on the depositional history of the last 1.25 Ma. Low-resolution bio- and magnetostratigraphic constraints identified two regionally-extensive hemipelagic units and intercalated turbidite deposits that provide a chronostratigraphic framework for the 320 km transect. Using a combination of lithostratigraphy and sediment physical properties that vary on orbital timescales, we tuned high-resolution data sets to the LR04 benthic δ18O isotope stack to obtain new constraints on the timing of depositional changes. Above the underlying Unit 1, which consists of Early to Middle Pleistocene turbiditic deposits, we divide four more units for the last 1.25 Ma: Unit 2, a Middle Pleistocene hemipelagic layer deposited at all sites from Marine Isotopic Stages (MIS) 37 to ∼17 (∼1.24–0.68 Ma) during the entire time of the Mid-Pleistocene Transition, when the Bengal Fan depocenter must have been distal to our transect; Unit 3, mostly turbidites with some intercalated hemipelgic sediments deposited from ∼MIS 16–∼13 (∼0.68–0.48 Ma), with sandy lithologies only found at the easternmost site on the west flank of the Ninetyeast Ridge; Unit 4, massive turbiditic sediments that started to dominate deposition with the Mid-Brunhes Transition (∼MIS 12) until MIS 7/8 (∼0.48–0.25 Ma), when the channel-levee system was focused east of the 85°E basement ridge at 8°N; and Unit 5, a Late Pleistocene hemipelagic layer at the top that spans MIS 7/8–1 (∼0.25 Ma to present) while the turbidite deposition was focused west of the 85°E basement ridge at 8°N. We find evidence that, on these timescales, deposition across the lower Bengal Fan changed with the evolution of Pleistocene climate, monsoon and sea-level history and hence responded to external controls on sediment accumulation and fan architecture rather than only fan-internal, autocyclic mechanisms. Highlights • First Pleistocene chronology for IODP Expedition 354 sites on lower Bengal Fan. • Gray-scale tuning to a δ18O isotope stack (LR04) in turbidite/hemipelagic setting. • Fan development responds to changes in climate, monsoon and sea level. • Deposition of five units changed with Mid-Pleistocene and Mid-Brunhes transitions. • Two hemipelagic layers constrain fan development and respond to orbital forcing. [ABSTRACT FROM AUTHOR]

Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to calculate the 3D orientations of a large number of elongate and platy objects (fossilized oyster shells) on a sedimentary bedding plane, developed to support the interpretation of possible depositional patterns, imbrications, or impact of local faults. The study focusses on more than 1900 fossil oyster shells exposed in a densely packed Miocene shell bed. 3D data were acquired by terrestrial laser scanning on an area of 459 m2 with a resolution of 1 mm. Bivalve shells were manually defined as 3D-point clouds of a digital surface model and stored in an ArcGIS database. An individual shell coordinate system (ISCS) was virtually embedded into each shell and its orientation was determined relative to the coordinate system of the entire, tectonically tilted shell bed. Orientation is described by the rotation angles roll, pitch, and yaw in a Cartesian coordinate system. This method allows an efficient measurement and analysis of the orientation of thousands of specimens and is a major advantage compared to the traditional 2D approach, which measures only the azimuth (yaw) angles. The resulting data can variously be utilized for taphonomic analyses and the reconstruction of prevailing hydrodynamic regimes and depositional environments. For the first time, the influence of possible post-sedimentary vertical displacements can be quantified with high accuracy. Here, the effect of nearby fault lines—present in the reef—was tested on strongly tilted oyster shells, but it was found out that the fault lines did not have a statistically significant effect on the large tilt angles. Aside from the high reproducibility, a further advantage of the method is its non-destructive nature, which is especially suitable for geoparks and protected sites such as the studied shell bed. [ABSTRACT FROM AUTHOR]

Recent oil discoveries in the L13-L15 sub-sag area in the Pearl River Mouth basin have inspired interest in Paleogene hydrocarbon targets. However, the structures and their control on reservoirs have not been completely studied. The aim of this paper is to address the tectonics and Eocene sedimentation based on 3D seismic data. We documented characteristics from four aspects of the faults in the study area: (a) fault arrangement; (b) fault segmentation; (c) flower structures; and (d) distribution of the depocenters along the faults. Based on the above data, we propose that the structures in the studied area were formed by a right-handed wrench. The principal shear for this model was caused by NNE- to NE-ward motion of the eastern part of the Eurasia plate due to the collision of the Indian-Australian and Eurasian plates starting approximately 49 Ma ago. The L13-L15 sub-sag area underwent early Eocene rifting, a late Eocene rifting-depression transition and an Oligocene-Quaternary thermal depression. The rift phase included three stages: the initial rifting, intensive rifting and late rifting. The deep lake mudstone deposited during the intensive rifting stage is the source rock with the most potential for oil generation. Shallow lake source rocks formed in the late rifting and transition stages are the secondary source rocks. Reservoir sweet spots were formed in the early period of the intensive rifting and late rifting stages. The junction sites between the front of the meandering river delta plain and fault steps are favorable places for good reservoirs. The sediments in the transition stage are rich in sandstone, making them perfect sites for prospecting reservoirs. [ABSTRACT FROM AUTHOR]

Cyclic sedimentation has varied at several timescales and this variability has been geologically well documented at Milankovitch timescales, controlled in part by climatically (insolation) driven sea-level changes. At the longer (tens of Myr) timescales connection between astronomical parameters and sedimentation via cyclic solar-system motions within the Milky Way has also been proposed, but this hypothesis remains controversial because of the lack of long geological records. In addition, the absence of a meaningful physical mechanism that could explain the connection between climate and astronomy at these longer timescales led to the more plausible explanation of plate motions as the main driver of climate and sedimentation through changes in ocean and continent mass distribution on Earth. Here we statistically show a prominent and persistent ~36 Myr sedimentary cyclicity superimposed on two megacycles (~250 Myr) in a relatively well-constrained sea-level (SL) record of the past 542 Myr (Phanerozoic eon). We also show two other significant ~9.3 and ~91 Myr periodicities, but with lower amplitudes. The ~9.3 Myr cyclicity was previously attributed to long-period Milankovitch band based on the Cenozoic record. However, the ~91 Myr cyclicity has never been observed before in the geologic record. The ~250 Myr cyclicity was attributed to the Wilson tectonic (supercontinent) cycle. The ~36 Myr periodicity, also detected for the first time in SL record, has previously been ascribed either to tectonics or to astronomical cyclicity. Given the possible link between amplitudes of the ~36 and ~250 Myr cyclicities in SL record and the potential that these periodicities fall into the frequency band of solar system motions, we suggest an astronomical origin, and model these periodicities as originating from the path of the solar system in the Milky Way as vertical and radial periods that modulate the flux of cosmic rays on Earth. Our finding of the ~36 Myr SL cyclicity lends credibility to the existing hypothesis about the imprint of solar-system vertical period on the geological record. The ~250 Myr megacycles are tentatively attributed to a radial period. However, tectonic causal mechanisms remain equally plausible. The potential existence of a correlation between the modeled astronomical signal and the geological record may offer an indirect proxy to understand the structure and history of the Milky Way by providing a 542 Myr long record of the path of the Sun in our Galaxy. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Pamir bears essential information for understanding intracontinental tectonic processes within the context of India-Asia convergence. However, it is unclear whether the arcuate shape of the Pamir is entirely the result of the India-Asia collision, or may have been in part an inherited, pre-Cenozoic feature. In this study, we address the evolution of the NE Chinese Pamir during the Paleogene by reviewing the stratigraphy of twelve sections in the western Tarim Basin and the establishment of sedimentary facies. The results indicate three episodes of deposition of alluvial coarse sediments in the foreland regions of NE Chinese Pamir during the (1) early Paleocene, (2) late Paleocene to early Eocene and (3) middle Eocene to Oligocene, respectively. These are correspondingly attributed to (1) retroarc deformation in an Andean-type margin of the southern Asia during subduction of the Neo-Tethys Ocean, (2) the immediate response in the Pamir to the India-Asia collision, and (3) continued India-Asia convergence. The alluvial conglomerates with grain-size up to 5–10 cm, imply a transport distance <60 km from the fan apex. This result, together with the 20–50 km northward thrust displacements, suggests that the orogen/basin boundary between the Pamir and the Tarim-Alai Basin was located less than ca. 80–110 km to the south from the present location of the Main Pamir Thrust during the Paleogene, indicating the arcuate shape of the Pamir was already largely established by the Paleogene, rather than entirely a result of the India-Asia continental collision. [ABSTRACT FROM AUTHOR]

Development of the rift-type North Croatian Basin located in the south-western Neogene Pannonian Basin System and belonging to the Central Paratethys realm, was controlled by tectonics, climate, volcanic activity and eustatic fluctuations. The extrabasinal controls produced a succession of depositional environments from terrestrial to marine, and back to terrestrial, and the deposits form a large-scale transgressive-regressive cycle. Basin evolution is subdivided into the syn-rift phase which lasted from the Early Miocene (Ottnangian) until the Middle Miocene (middle Badenian), and in the post-rift phase from the Middle Miocene (late Badenian) to the Quaternary. These complex controls on deposition generated the opening and closing of connections to the open sea that occasionally resulted in the formation of unfossiliferous continental deposits, or generated the radiation of endemic species, such that it has been necessary to use regional Neogene stages for stratigraphic analysis of the Central Paratethys history. Earlier stratigraphic studies of the North Croatian Basin, that had been primarily based on biostratigraphy and superposition, were improved by recent results yielded from radiometric dating, and integrated biostratigraphy. They have been focused mainly on the Early/Middle Miocene and the Miocene/Pliocene boundaries that separate intervals of the specific depositional evolution of the basin. Most important depositional and palaeogeographic differences concern a relatively long period of development of the early continental phase that lasted from the Ottnangian to the early Badenian. In contrast to parts of the Pannonian Basin System characterized by marine deposition in the early Badenian, the NCB was characterized by long-lived fresh-water lacustrine deposition. The fresh-water Lake Slavonia that developed from the middle Pliocene to the early Pleistocene, indicates an independent phase of evolution of the south Pannonian Basin System, so the Cernikian regional stage was introduced for the lacustrine succession. Those stratigraphic and palaeogeographic differences additionally support the complexity of the Pannonian Basin System within the Central Paratethys realm supporting heterogeneous depositional development of continental rift-type basins. [ABSTRACT FROM AUTHOR]

The main aim of this study is to explore the spatial patterns of the shelf-scale erosional unconformity related to the last glacial maximum (LGM), particularly in terms of the role of underlying geology and the presumed primary influence of sea-level changes. This involved a detailed mapping of the most recent and widespread erosional shelf surface in a sector of the northern margin of the Gulf of Cádiz (northeast Atlantic Ocean) located adjacent to a major fluvial source. A dense network of high-resolution seismic profiles collected in the 1990s and 2013 off the Guadiana River revealed two distinct geomorphological domains on the LGM shelf-scale subaerial surface. The outer domain exhibits a widespread occurrence of erosional truncations, with a rugged, erosional pattern over the most distal shelf setting that evolves landward into a planar unconformity. The inner domain is more extensive and is characterized by the common occurrence of highly reflective, localized mounded seismic facies that laterally evolve into an irregular surface and in places may develop a channelized morphology. Significant fluvial incision is limited to a major straight valley and a secondary distributary channel. A distinct partition of the lowstand surface is documented, and attributed to a well-marked lithological change. A coarse-grained inner shelf comprises underlying lithified coastal deposits, whereas a fine-grained outer shelf is regarded as the uppermost expression of regressive prodeltaic wedges. The influence of regional indurated surfaces is also expressed in (1) the pattern of erosion, this being more patchy on the inner shelf due to lateral changes of erodibility, whereas on the outer shelf it shows laterally continuous bands, owing to different modes of transgressive ravinement; (2) the spatial and temporal variability of fluvial incision. Inner shelf armoring by indurated deposits prevents reoccupation of previously incised valleys. [ABSTRACT FROM AUTHOR]

While bedforms are increasingly being recognized and analyzed in bathymetric and seismic data sets, exact mechanisms for the formation of large bedforms are not well understood. This paper describes a suite of Paleocene to Miocene bedforms found along a series of contourite terraces that compose the Uruguayan continental slope. Results are compared with similar bedforms found along other continental margins. This study describes diagnostic, large-scale features associated with major discontinuities, including channels, scours, furrows, sand ribbons, and barchan dunes. These record periods of increased bottom current activity and thus represent distinct paleoceanographic markers within the basin. Sequences of layered, muddy two-dimensional dune-like bedforms also commonly occur between discontinuities. The vertical bedform distribution exhibits a repetitive pattern generated by bottom currents, with sediment supply from simultaneous downslope processes deposited primarily over discontinuous intervals. Sediment reworking and redistribution along slope by bottom currents generated thick, extensive sand-rich deposits concentrated at particular locations. These features raise fundamental questions concerning margin processes, morphologies, stratigraphic context, and bedform development in deep-marine environments. Given their role in paleoceanographic reconstructions and resource exploration, these deposits and the mechanisms that form them require more formal understanding. [ABSTRACT FROM AUTHOR]

This paper presents new results on zircon U-Pb dating of a two-mica schist from the Qinling Group in the core of the North Qinling Orogenic Belt (NQB), Central China, with the aim of constraining the formation time of the Qinling Group, and the tectonic affinity of the North Qinling Microcontinent. Zircon U-Pb dating indicates that the protolith of the metasedimentary rock in the Qinling Group was deposited later than ~1502 Ma. The Qinling Group in the NQB represents a long-lived unit, and its formation age can be constrained to the period between the Paleoproterozoic and early Neoproterozoic. The zircon age populations of the studied sample can be divided into two major populations of 1559-1642 and 1470-1548 Ma, and one subordinate population of 1717-1794 Ma, indicating their provenances were mainly attributed to the NQB and subordinately from the North China Craton (NCC) and the Yangtze Craton (YZC). And the distribution of the early Neoproterozoic magmatic events and the Nd-Pb whole-rock isotopes, zircon Hf isotopes, and trace element compositions of the Precambrian basement rocks in the NQB is significantly different from those in the NCC and YZC, indicating that the NQB cannot be a southern sector of the NCC, or a northern sector of the YZC, and was an independent microcontinent from the Paleoproterozoic to the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

This paper summarizes the main sedimentary sequences of major cratonic basins during the breakup of Rodinia and the assembly of Gondwana and extracts evolutionary stages of the Neoproterozoic basins around the Paleo-Pacific Ocean and Iapetus Ocean tracts. During the breakup of Rodinia, sedimentary sequences and evolutionary stages of the main basins in major cratonic blocks, such as Yangtze, Australia, Eastern American, Western American, and Western Africa cratons, mostly experienced intracratonic rifting, drifting or passive continental margin, carbonate platform construction, and foreland basin stages. The time of rifting to drifting transition in Congo-São-Francisco precisely marked the closure of the Adamastor Ocean between Congo-São-Francisco and Rio de la Plata and presaged the opening of the Iapetus Ocean. The time of rifting to drifting transition of Eastern American of Laurentia and West Africa initiated at ~580 Ma also signified the opening of the Iapetus Ocean. The time of drifting stage of the main basins around the Paleo-Pacific Ocean tracts is not only earlier than those of the Iapetus Ocean tracts but also is characterized by diachronism. The time of drifting onset of basins in the Yangtze Block is ~720 Ma, the time of drifting initiation of the Adelaide Fold Belt in South Australia is 680 Ma, and the time of drifting stage of the south-western margin of Laurentia occurred at 550 Ma. The different times of rifting to drifting transition of the Adelaide Fold Belt in South Australia, the Yangtze Craton, and Western American of Laurentia signified the nonisochronous opening of the Neoproterozoic Paleo-Pacific Ocean. [ABSTRACT FROM AUTHOR]

The Lower Cretaceous sedimentary strata in the Lhasa Terrane record the palaeogeographic and tectonic history of the Tibetan Plateau prior to the India-Asia collision. The Lower Cretaceous strata in the Coqen Basin of the northern Lhasa subterrane include the Duoni and Langshan Formations. The Duoni Formation is composed of conglomerates, sandstones, siltstones and mudstones in the south deposited in a fluvial environment and quartzose-lithic sandstones, siltstones and mudstones in the north deposited in a shelf-coastal environment. The overlying Langshan Formation is characterized by abundant Orbitolina - and rudist-bearing wackestones and packstones, which were deposited on a low-energy carbonate ramp. The Langshan Formation in the Coqen Basin was deposited between ~ 119–115 Ma and ~ 98 Ma based on its large benthic foraminiferal assemblages. Age constraints based on the interbedded tuff and conformably overlying Langshan Formation indicate that the Duoni Formation was deposited between ~ 123 and 115 Ma. Sandstone detrital modal compositions further indicate that the Duoni Formation was primarily derived from magmatic arc and recycled orogen sources. Detrital zircons from the Duoni Formation yield a primary age population of 160–110 Ma (peaking at ~ 130 Ma), with negative ε Hf ( t ) values (− 18.7 to − 2.7), and additional age ranges of 550–500, 1200–900, and 1600–1500 Ma, thereby indicating that the Zenong volcanic rocks and Palaeozoic sedimentary bedrocks in the northern Lhasa subterrane are the most likely sources. The palaeogeography of the northern Lhasa subterrane can be approximately described in two stages. During the Aptian (~ 123–115 Ma), with the eruption of the Zenong volcanic rocks, the Duoni Formation accumulated in fluvial and shelf-coastal environments and was sourced from the Zenong volcanic rocks and basement rocks from the southern region of the northern Lhasa subterrane. The enhanced magmatic activities in the northern Lhasa subterrane may have influenced the Duoni Formation deposition. During the Late Aptian-Early Cenomanian (~ 115–98 Ma), a north-south transgression occurred, causing the majority of the northern Lhasa region to be dominated by shallow-marine limestones of the Langshan Formation. [ABSTRACT FROM AUTHOR]

The New Siberian Islands archipelago is one of the few research objects accessible for direct study on the eastern Arctic shelf. There are several models that have different interpretations of the Paleozoic tectonic history and the structural affinity of the New Siberian Islands terrane. Some infer a direct relationship with the passive continental margin of the Siberian paleocontinent. Others connect it with the marginal basins of Baltica and Laurentia, or the Chukotka-Alaska microplate. Our paleomagnetic investigation led us to create an apparent polar wander path for the early Paleozoic interval of geological history. Based on it we can conclude that the New Siberian Islands terrane could not have been a part of these continental plates. This study considers the possible tectonic scenarios of the Paleozoic history of the Earth, presents and discusses the corresponding global reconstructions describing the paleogeography and probable mutual kinematics of the terranes of the Eastern Arctic. [ABSTRACT FROM AUTHOR]

Detailed sedimentological investigations on numerous outcrops and drill-core sections in the 2.1-Ga-old Franceville basin, Gabon, provide evidence for a large-scale injectite network. The injectites were formed by the injection of sands through a thickness of about 150 m of the FB1 Member, and now cover a minimum area of 70 km 2 corresponding to the Bangombé plateau, but are also recognized close to Franceville 35 km farther south-east. The injectite lithology corresponds to a mud- or carbonate-supported sandstone characterized by a loose and uncompacted fabric contrasting with the host-rock. Because the injectites are often parallel to subparallel to the stratification, they were misinterpreted as depositional beds by previous authors. At outcrop, the injectite bodies exhibit sill, dyke, wing and protrusive geometries emplaced during early burial within poorly compacted material, with partial wall erosion and dissociation. The source of the sand material is attributed to a channel-levee turbidite depositional system located in the lower part of the FB1 Member. These deposits were buried by a thick biochemical muddy cap deposited during a starvation phase, which increased the seal capacity of the system. This type of architecture has a high potential to develop compaction disequilibrium during burial. Moreover, in the case of the Francevillian injectites, the abundance of microbial organic matter favoured early methane degassing and lateral charging of the sand reservoir. The overpressure in the channels was periodically released during early burial, through the effect of rapid sedimentary and tectonic loading, and possible seismic activity. The fluidized sand was injected according to a symmetrical wing pattern. Thus, the injected masses caused a local decrease in the grade of the lateritic manganese ore deposit of the Bangombé plateau. [ABSTRACT FROM AUTHOR]

Detrital zircon U-Pb and trace element data provide new information on the provenance of Permian--Triassic foreland basin deposits of the Gondwanide orogen that belong to the Beacon Supergroup in Antarctica. Zircon U/Th ratios primarily point to dominantly igneous parent rocks with subordinate contributions from metamorphic sources. All three samples (two Permian and one Triassic) analyzed in this study yielded 1200-1000 Ma and 635-490 Ma zircon U-Pb age populations. The Triassic sample also yielded younger 367 Ma and 238 Ma age peaks. The combination of age and trace element proxies for rock type provides important new evidence in support of the common assertion that granitoid parent rocks of the Terra Australis and Gondwanide orogens served as a major source for the siliciclastic sediments. The results also point to smaller, but significant, contributions from Triassic (236 Ma) and Cambrian (539 Ma) mafic rocks and Ediacaran (ca. 559 Ma) alkaline source rocks from these regions. [ABSTRACT FROM AUTHOR]

Observations of physical and chemical changes across strain gradients can provide information about the processes that lead to localization and therefore provide better tools for prediction of spatial and temporal strain patterns. In contrast to the many chemical and microstructural studies of natural shear zones in metapelites and mafic lithologies, few have described kilometer-scale granitic strain gradients despite the fact that granitoid bodies make up much of the orogenic crust. This study reports microstructural and compositional data across two amphibolite-facies strain gradients from middle crust of the Grenville orogen. The kilometer-scale gradients, defined by stretched enclaves and foliation intensity, form parts of the Boundary and Bad River shear zones, located along the east and west borders of the Bad River granite in the southwestern Grenville Front tectonic zone in Ontario, Canada. The granite is bounded on both sides by older orthogneiss (ca. 1720 Ma igneous crystallization age). Zircon U-Pb ages indicate that the granite crystallized from a magma at ca. 1465 Ma, with metamorphic growth at ca. 1020 Ma. Zircons in the orthogneiss record metamorphic growth during these two younger episodes. These age determinations are consistent with other regional dates and indicate that the strain gradients in the Bad River granite formed during the Grenville orogeny. Whole-rock analyses reveal minor heterogeneity in major-element distribution in the granite that can be attributed to igneous processes, and homogeneity in the trace elements, indicating that strain did not affect the bulk-rock composition. In contrast, microstructural and chemical analyses across the two strain gradients indicate some correlation with strain: slight changes in mineral compositions, development of crystallographic preferred orientations in quartz, an increase in recrystallized fraction, a reduction in recrystallized grain size, and the development of a mixed-phase matrix. However, most of these variations are subtle and occur at different positions across the gradients. The spatial distribution of the microscale changes suggests a change in deformation mechanisms toward the margin, accompanying increased localization. The rheological weakening at the Bad River granite margins was the product of microstructural, rather than mineralogical, change, in contrast to nearby shear zones in more mafic units. [ABSTRACT FROM AUTHOR]

The Tremp Group of the Tremp-Graus Basin (Southern Pyrenees, Spain) is a succession of predominantly continental origin that records the Paleocene-Eocene Thermal Maximum (PETM), a transient episode of extreme global warming that occurred across the Paleocene-Eocene boundary. For this succession, the stratigraphic position of the PETM is accurately determined, and histories of tectonic and sea-level controls are well constrained. Building upon previous studies, this work assesses changes in sedimentary architecture through the PETM in the Tremp Group, based on quantitative sedimentological analyses documented over a km-scale strike-oriented transect in the Arén area, with the scope to better understand the response of this alluvial system to the hyperthermal event. The analysed features represent a partial record of the geomorphic organization and processes of the system at the time of deposition, and are therefore interpretable in terms of geomorphic change in alluvial landscapes caused by the PETM. The record of the PETM, as previously recognized, begins at a time when erosional palaeotopographic relief was developed and deposition was confined in valleys. A shift between valley back-filling and widespread aggradation is observed at the onset of the PETM interval, which demonstrates uniquely the impact of the hyperthermal on both depositional loci and interfluves. Compared to underlying strata, the interval that embodies the onset and main phase of the PETM is characterized by: (i) higher proportion of channel deposits; (ii) channel complexes of greater average thickness and width; (iii) barforms and channel fills that are slightly thicker; (iv) increased thickness of sets of cross-stratified sandstones; (v) similar values of maximum extraclast size, by architectural element. An evident change in the facies organization of channel deposits is also seen through the stratigraphy, though this appears to predate the PETM. Increased channel-body density in the PETM interval can be explained in terms of increased channel mobility, which itself can be related to changes in the stream catchments (e.g., greater bedload delivery, increased water discharge or discharge variability), or to changes in the nature of the depositional basin that would permit the channels to be more mobile (e.g., increased bank erodibility due to variations in vegetation type and density). Interfluve planation is inferred to have occurred immediately prior to, or penecontemporaneously with, accumulation of PETM deposits, which is in accord with inferences of increased erodibility of the interfluves or increased stream erosive power. These observations offer insight into the potential geomorphic metamorphosis of river systems in mid-latitude regions experiencing conditions of rapid global warming. [ABSTRACT FROM AUTHOR]

The article presents new data on sedimentological structures, which have been discovered at the Ryadino archaeological excavation in the northeast of the Kaliningrad District of Russia (the Šešupė River Valley). Tongue-shaped and domeshaped diapir-like structures indicate liquefaction-induced features. As the most plausible reason, the earthquake-induced shaking is discussed. A preliminary estimation of the time interval for the seismic event covers the period from the early up to the late Holocene. The reasons for seismic activity in this region can be related to neotectonic movements (including glacio-isostatic rebound) as recorded in the southeastern Baltic Sea area of the Fennoscandian ice sheet margin zone. The relation between a palaeoseismic event and the essential changes in the hydrographic network in the region is also discussed. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Ampani Group of rocks, a structurally deformed sedimentary package hosted within the Bastar Craton in central India, was studied for process-based facies and paleoenvironmental analyses. Outcrop mapping on 1:1500 scale, deconvolution of deformation pattern, and process-based facies analyses have led to the identification of fifteen facies types, clubbed under four facies associations. A range of paleoenvironmental settings varying from continental fluvial to distal marine shelf is inferred. Deductive paleohydrology revealed poorly-efficient 'dirty river' character for the Ampani River system with low water discharge. However, at times of catastrophic sheet floods release of sediments trapped at the river mouth in form of hyperpycnal underflows triggered formation of river mouth delta. Reworking of delta front sediment in wave-dominated coastline resulted development of beach-foreshore and shoreface (proximal to distal). Variation in the relative proportion of bar and interbar products within the shoreface successions exposed at different studied sections is interpreted as signature of relative bathymetric variation. The pro-deltaic Ampani shelf was storm infested. Tectonic perturbance in the basin hinterland in course of Ampani sedimentation is inferred from occurrence of a disparately thick lobate high-density flow deposit towards the top of shoreface succession and increase in feldspar content upward within the shoreface succession. Addition of detritus from a ∼1600 Ma Mesoproterozoic provenance in upper part of shoreface also strengthen the contention. Deconvolution of deformation pattern and delineation of environmental products ranging between continental and deep marine allowed us to infer the Ampani sediment package as fining-upward in character evolved in a transgressive mode. [ABSTRACT FROM AUTHOR]

The Uitenhage Group represents the earliest deposits that filled Mesozoic rift basins in the southern Cape of South Africa during the fragmentation of the supercontinent Gondwana. The sedimentology of the Enon Formation records the development of alluvial systems that drained the region since the onset of Gondwanan rifting, and therefore plays an important role in our understanding of early landscape evolution along the southern African continental margin. The mostly coarse conglomeratic unit was deposited continuously in actively subsiding, but separated, rift basins. As a result, the deposits are diachronous between basins and display highly varied thicknesses of up towell over 2000 m. [ABSTRACT FROM AUTHOR]

The Argentine margin contains important sedimentological, paleontological and chemical records of regional and local tectonic evolution, sea level, climate evolution and ocean circulation since the opening of the South Atlantic in the Late Jurassic-Early Cretaceous as well as the present-day results of post-depositional chemical and biological alteration. Despite its important location, which underlies the exchange of southern- and northern-sourced water masses, the Argentine margin has not been investigated in detail using scientific drilling techniques, perhaps because the margin has the reputation of being erosional. However, a number of papers published since 2009 have reported new high-resolution and/or multichannel seismic surveys, often combined with multi-beam bathymetric data, which show the common occurrence of layered sediments and prominent sediment drifts on the Argentine and adjacent Uruguayan margins. There has also been significant progress in studying the climatic records in surficial and near-surface sediments recovered in sediment cores from the Argentine margin. Encouraged by these recent results, our 3.5-day IODP (International Ocean Discovery Program) workshop in Buenos Aires (8-11 September 2015) focused on opportunities for scientific drilling on the Atlantic margin of Argentina, which lies beneath a key portion of the global ocean conveyor belt of thermohaline circulation. Significant opportunities exist to study the tectonic evolution, paleoceanography and stratigraphy, sedimentology, and biosphere and geochemistry of this margin. [ABSTRACT FROM AUTHOR]

The Quaternary stratigraphic record of Jebel El Mida, composed of continental deposits, is a useful example of concomitant travertines and alluvial deposition in an extensional setting. Travertine deposition occurred in a faulted Pleistocene alluvial fan giving rise to seven (recognised) facies interfingering with five other alluvial ones. The travertine depositional events indicate a tectonically driven evolution from terraced slope (facies group FC1--FC6) to a travertine fissure ridge-type depositing phase (facies group of FC1--FC7). Interfingering between travertine and alluvial facies indicates the co-existence of adjacent and time-equivalent depositional environments. The travertine deposition resulted from deep origin hydrothermal fluids channelled along damaged rocks volumes associated to a regional fault system, named as the Gafsa Fault (GF). The travertine--terrigenous succession in Jebel El Mida highlights the major role played by the GF in controlling: (i) the hydrothermal fluid flow, still active as also indicated by the numerous thermal springs aligned along the fault zone; (ii) paleoflow directions, discharge locations, volume, rate and fluctuations of the water supply. The paleoclimatic correlation with adjacent localities reveals that, at that time, humid episodes could have contributed to the recharge of the hydrothermal system and to the deposition of alluvial sediments. [ABSTRACT FROM AUTHOR]

The seismic stratigraphy, evolution and depositional framework of a sheared-passive margin, the Durban Basin, of South East Africa are described. Based on single-channel 2D seismic reflection data, six seismic units (A-F) are revealed, separated by major sequence boundaries. These are compared to well logs associated with the seismic data set. Internal seismic reflector geometries and sedimentology suggest a range of depositional regimes from syn-rift to upper slope and outer shelf. Nearshore and continental facies are not preserved, with episodic shelf and slope sedimentation related to periods of tectonic-induced base level fall. The sedimentary architecture shows a change from a structurally defined shelf (shearing phase), to shallow ramp and then terminal passive margin sedimentary shelf settings. Sedimentation occurred predominantly during normal regressive conditions with the basin dominated by the progradation of a constructional submarine delta (Tugela Cone) during sea-level lowstands (LST). The earlier phases of sedimentation are tectonic-controlled, however later stages appear to be linked to global eustatic changes. [ABSTRACT FROM AUTHOR]

Using analyses of the lithology, sequences, paleoenvironment, and tectonic setting, the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified. The lithological characteristics of the Lower Member, Middle Member, and Upper Member were analyzed and classified. Before the use of carbon, oxygen, and strontium isotopes in the analysis, all of the geochemical data were tested for validity. On the basis of the Z values obtained from carbon and oxygen isotopes, the paleoenvironments of the three members were elucidated. Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea. Middle Member developed in a semi-enclosed to normal marine environment with many rivers. Upper Member was formed in a normal marine environment. The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation, forming a relatively enclosed depositional setting. Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks; these paleogullies can be identified. On the basis of a comprehensive analysis, we propose that the Huanglong Formation developed in a platform system. Four microfacies were identified: supratidal flat, dolostone flat, grain shoal, and shelf microfacies. The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation, while the supratidal flat and shelf microfacies developed very few high-quality reservoirs. The paleogullies, in which increased amounts of grain shoal microfacies developed, controlled the distribution of high-quality reservoirs. [ABSTRACT FROM AUTHOR]

The late Ediacaran Billy Springs Formation is a little-studied, mudstone-dominated unit deposited in the Adelaide Rift Complex of South Australia. Sediments are exposed in an approximately 11 km × 15 km synclinal structure interpreted as a salt-withdrawal minibasin. The stratigraphic succession is characterized by convolute-laminated slump deposits, rhythmically laminated silty mudstones, rare diamictites and fining-upward turbidite lithofacies. Lithofacies are the product of deposition in a deepwater slope or shelf setting, representing one of the few such examples preserved within the larger basin. Although exact correlations with other formations are unclear, the Billy Springs Formation probably represents the distal portion of a highstand systems tract, and is overlain by coarser sediments of the upper Pound Subgroup. Diamictite intervals are interpreted to be the product of mass flow processes originating from nearby emergent diapirs, in contrast to previous studies that suggest a glacial origin for extrabasinal clasts. Within the spectrum of outcropping minibasins around the world, the sediments described here are unique in their dominantly fine-grained nature and overall lithological homogeneity. Exposures such as these provide an opportunity to better understand the sedimentological processes that operate in these environments, and provide an analogue for similar settings in the subsurface that act as hydrocarbon reservoir-trap systems. [ABSTRACT FROM AUTHOR]

The extension-driven break-up of the Pangean Supercontinent in the present-day Central and North Atlantic domains commenced during Permo-Triassic times. Permian rift processes in this region are generally attributed to crustal collapse during the latter part of the Hercynian/Variscan orogeny, but the Triassic rifting style is more complex and the presence of a single over-riding first-order control is equivocal. Basement terrane structures and boundaries provide pre-existing zones of weakness that had significant influences on the location, timing, orientation and extent of Triassic rifting. The 201 Ma Central Atlantic Magmatic Province (CAMP), a Large Igneous Province (LIP), increased lithospheric heat flow at the end of rifting, produced uplift and doming, and also contributed to deformation and subsequent continental breakup. Analysis of the Triassic basin structures in the Central Atlantic and North Atlantic domains (respectively Georgia to Nova Scotia and conjugate margin, and Newfoundland-Iberia) shows that four main basin types are geographically distributed: 1) southern basins (Georgia to Virginia), small to medium size with limited growth-structures, 2) basins in the Central-East domain (New Jersey-Nova Scotia), wide basins with growth-structures along long-lived inherited bounding faults, 3) basins in the Central-West domain (offshore NS and Morocco) that comprise numerous half-graben sub-basins in a lower unit and an upper very wide tabular unit, and 4) northern basins (Newfoundland-Portugal), that are tabular and extremely wide. Basin architectures suggest that subsidence was regional in extent and not necessarily controlled by main faults. Variations in crustal characteristics are considered to have led to the development of the four main basin types. Stratigraphic data show that the onset of deposition in the Central and southern North Atlantic domain was restricted to a Central Segment between two main structural lineaments. Overall, crustal rheology and inheritance exhibited first-order controls on subsidence and basin development. Triassic basins in the Central and North Atlantic domain were all filled by continental deposits in various palaeo-environments such as alluvial-fan, mega-fluvial systems, terminal fluvial systems, fan-delta fluvial systems, permanent oxic and anoxic lakes, playa lakes, and saline lakes, some of them interbedded with aeolian and volcanic deposits. Most basins were far from any marine domain but marine ingressions from the Tethys domain are inferred from dolomite and marine fauna in Portugal and from thick salt deposits in Morocco and offshore Canada during the late Rhaetian. A series of palaeogeographic maps are presented utilising plate reconstructions based on Sahabi et al (2004), in order to summarize continental-scale palaeo-environment distribution. Our tectono-stratigraphic model suggests that initial strain was accommodated in a Central Segment by inherited faults during the Early and Middle Triassic. During the Carnian, the rift domain was increasingly extended with the development of half-graben basins in the Central Segment and some in the Northern Segment. In both segments, the initial strain re-activated inherited faults and later the rift zones evolved towards significantly wider basins marked by the presence of a major erosional truncation surface across the basins and followed by lacustrine sedimentation that eventually overlapped paleo-topographic highs. Subsidence of such regional extent is likely driven by thermal processes following a phase of extreme lithospheric thinning and lower crustal removal associated with mantle uplift. The architecture of the Triassic rifting has the characteristics of the wide rift mode (very large basins with some active faults) for which subsidence is driven by lower crustal flow within a high heat-flow region. Nevertheless some faults were active during Late Triassic sedimentation but accounted for a relatively minor part of the overall subsidence. Pulses of active subsidence and topographic rejuvenation led to fluvial dominated deposition within basins. Non-rejuvenation of hinterland led to more lacustrine dominated sedimentation and eventual connection of basins across topographic highs due to regional (thermal) subsidence. During the latest Rhaetian, basins with the lowest elevations were possibly “flooded” by marine waters resulting in precipitation of thick salt deposits. [ABSTRACT FROM AUTHOR]

The Orphan Basin, located offshore northeastern Newfoundland, Eastern Canada, is a Mesozoic rift basin formed during the disintegration of Pangaea and the concurrent opening of the North Atlantic Ocean. The majority of previous work has divided the basin into the East (EOB) and West Orphan (WOB) subbasins, separated by the Central Orphan High (COH). These subbasins share some similarities but have different opening kinematics, timings, and sedimentary histories. Despite its critical location at the termination of the Charlie-Gibbs Fracture Zone (CGFZ), and the transition from the main North Atlantic Ocean to the Labrador Sea, the Orphan Basin remains relatively poorly understood compared to other marginal rift basins in the North Atlantic region. Additionally, much of the public domain geoscientific literature on the basin has not undergone peer review (e.g., conference abstracts, industry reports, etc.). As such, the aim of this review is to critically scrutinize and synthesize the wealth of geoscientific information on the basin, present an overview of the complex structure of the basin and its sedimentary fill, identify knowledge gaps, and provide insights for future research directions. This review highlights that significantly more is known about the EOB than the WOB, largely due to data availability. Furthermore, structural inheritance appears to have strongly influenced the evolution and geometry of rift-related faults. Areas requiring further research include refining the timing and relationship between the opening kinematics of the EOB and WOB, particularly pertaining to the role of the Flemish Cap. Additionally, the continuation of sedimentary facies from the better constrained EOB into the WOB is currently poorly understood, especially for the syn -rift strata, which results in substantial exploration risk in the WOB. Understanding the WOB, including the magmatic rocks, is essential for understanding the wider southern North Atlantic region. [ABSTRACT FROM AUTHOR]

The Boucheville Basin is one of the easternmost Mesozoic basins of the North Pyrenean Zone (NPZ) that was opened during the Albian extension between the Iberian and European plates. During the extension, a HT/LP metamorphism event affected the Albian basins near the North Pyrenean Fault (NPF). Our aim is to better understand the evolution of the Boucheville Basin during the Albian–Cenomanian lithospheric thinning, which occurred under high thermal conditions. Sedimentological and structural data were collected in the basin and are used to produce synthetic stratigraphic columns of different portions of the basin and to restore selected cross-sections. North–south cross-sections show that the Boucheville Basin is a large and asymmetrical deformed syncline with inverted borders. Synthetic stratigraphic columns show that the sedimentation of the Boucheville Basin starts with carbonate platforms deposited under low bathymetric conditions showing slope deposits and evolves to deep bathymetric conditions of marls deposited without evidence of slopes. Raman spectroscopy on carbonaceous material (RSCM) was made on samples used to construct the sedimentological stratigraphic columns in order to obtain a temperature map of the Albian metamorphism. They reveal homogeneity in the temperatures between 500 and 600 °C. In situ LA–ICP–MS U–Pb dating of titanite grains found in a syn-deformation located in the Albian calcschists provided an age of ca. 97 Ma that gives a time constraint for both the deformation and metamorphism. These data are used collectively to propose a model for the tectono-sedimentary and metamorphic evolution of the Boucheville Basin during the Albian extension. [ABSTRACT FROM AUTHOR]

The Saishitang Cu deposit, located on the eastern area of the Eastern Kunlun Orogenic Belt (EKOB), and on the northern margin of the Tibetan Plateau, is one of the most important copper deposits in Qinghai Province, China. Skarn and Cu orebodies mainly occur as stratoids or lenses along the contact zone between the quartz diorite and Lower to Middle Triassic metamorphosed tuff and marble. In this study, we use new zircon U–Pb ages, molybdenite Re–Os ages, granitoid geochemical compositions, and zircon Hf isotope data to constrain the ore genesis and the tectonic setting of the Saishitang Cu deposit. The quartz diorite is composed of inner medium- to fine-grained quartz diorite phase and an outer porphyritic quartz diorite phase. U–Pb dating of zircons by laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) yield ages of 222.7 ± 2.3 Ma and 222.6 ± 2.4 Ma for the inner and outer phase of quartz diorite, respectively. Molybdenite separated from ore-bearing quartz veins yields a Re–Os isochron age of 223.4 ± 1.5 Ma, indicating a close temporal link between magmatism and mineralization. Geochemically, the quartz diorite shows high contents of SiO 2 (59.63–68.21 wt.%), Al 2 O 3 (15.57–18.13 wt.%) and Na 2 O (3.07–3.56 wt.%), with A/CNK values between 0.90 and 1.01 and Mg# between 46 and 52, classified as the calc-alkaline I-type granite. The trace element patterns are characterized by high LREE (LREE/HREE = 7.36–13.03), weak negative Eu anomalies (δEu = 0.69–0.86), relative enrichment of Rb, Th, K, and Pb, and depletion of Nb, Ta, P, and Ti. The quartz diorite has variable ε Hf (t) values (− 2.5 to 4.87) and Mesoproterozoic two-stage model ages (997 to 1387 Ma). Based on petrological and geochemical features, we infer that the quartz diorite is derived from the partial melting of thickened lower crust with an additional input of mantle components. According to the geological, geochemical, and mineralogical features, we propose that the Saishitang Cu deposit is a skarn deposit with minor porphyry-type mineralization and the porphyry–skarn mineral system is related to the crust–mantle interaction. Based on the tectonic evolution of the Paleo-Tethys Ocean during the Late Triassic, we infer that the intrusions and associated Cu mineralization were related to regional extension of the EKOB in a post-collision environment. The results also show that most porphyry–skarn Cu deposits in the EKOB have similar mineralization ages (240–220 Ma) and the Late Triassic granitoids in the EKOB present significant potential for the prospecting of porphyry–skarn Cu deposits. [ABSTRACT FROM AUTHOR]

The Holowilena Ironstone is a Neoproterozoic iron formation in South Australia associated with glacial deposits of the Sturtian glaciation. Through a comprehensive field study coupled with optical and scanning electron microscopy, X-ray fluorescence, and X-ray diffraction, a detailed description of the stratigraphy, sedimentology, mineralogy, and structure of the Holowilena Ironstone was obtained. The Holowilena Ironstone comprises ferruginous shales, siltstones, diamictites, and is largely made up of hematite and jasper, early diagenetic replacement minerals of precursor iron oxyhydroxides, and silica. These chemical precipitates are variably influenced by turbidites and debris flows contributing clastic detritus to the depositional system. Structural and stratigraphic evidence suggests deposition within a synsedimentary half-graben. A model for the Holowilena Ironstone is proposed, in which dense oxic fluids expelled during sea ice formation in the Cryogenian pool in the depression of the half-graben, allowing for long-lived mixing with the ferruginous seawater and the deposition of iron oxides. This combination of glacial dynamics, tectonism, and ocean chemistry may explain the return of iron formations in the Neoproterozoic. [ABSTRACT FROM AUTHOR]

Whether the formation of the isolated sand body deposition in the forebulge area of a foreland basin system is structure- or deposition-controlled has puzzled geologists for decades, although sand body deposition is generally believed to be indicative of the position of the flexural forebulge in a foreland basin. The formation of a modern sand body in the forebulge area is thus examined by multi-scale geophysical observations based on combined reflection seismic profiles and compressed high-intensity radar pulse (CHIRP) profiles across the sand deposition along the forebulge of the Western Taiwan Foreland Basin (WTFB), which is a Late Miocene-present foreland basin in the overfilled stage. These profiles suggest that the accumulation of the sand deposits along the forebulge of the WTFB is not directly associated with forebulge faultings. The relief map of the forebulge deposit substratum shows a northwestward tilting slope, and the isopach of the forebulge sand body indicates that a large part of the sand body accumulated along the axis of the Taiwan Strait and the subdued forebulge of the WTFB. The difference between the prevailing directions of tidal currents between the Taiwan Strait and the East China Sea reflects the probable sedimentary influence of the cratonward migrating fold-thrust belt within a foreland shelf. We suggest that the formation and distribution of the sand deposits along the forebulge of the WTFB are generally controlled not only by the transverse downslope sedimentation but also longitudinal hydrodynamic processes at distal parts of the foreland basin. Our explanation provides a plausible tectono-sedimentary cause of the sand body deposition in the forebulge area in an overfilled foreland basin. The sedimentary dynamics of the sand body in the Taiwan Strait may be applicable for understanding the formation of isolated sand bodies in the distal part of the Cretaceous Western Interior Foreland Basin. [ABSTRACT FROM AUTHOR]

The Oligocene sedimentary succession in the eastern North Sea is revised and re-interpreted by applying new state-of-the-art reflection seismic data integrated with new bio- and Sr-stratigraphy data from three key wells in the study area. The Oligocene succession in the eastern North Sea is divided into four transgressive–regressive (T-R) sequences, characterized by non-accretional and/or aggradational transgressive systems tracts and prograding regressive systems tracts. Detailed studies of three wells, including biostratigraphy and Sr analysis, constrain the age relationships between the T-R sequences. Internal clinoform geometry indicates that the sediments were sourced from the present southern Norwegian mainland to the north of the depositional area. The direction of progradation shifted from being SE-directed in the earliest Rupelian (early Oligocene) to S- and SW-directed during Chattian time (late Oligocene). Rapid basin subsidence is indicated by the development of non-accretionary transgressive systems tracts, with subsequent progradation into water depths of hundreds of metres. The creation of accommodation space was out of phase relative to eustatic sea-level changes, and mainly controlled by regional-scale differential vertical movements where uplift and exposure of landmasses of the hinterland (southern Norway) occurred concurrently with basin subsidence. Halokinesis had an intra-basinal influence on the main sediment transport direction, but probably did not contribute much in creation of accommodation space. [ABSTRACT FROM AUTHOR]

Palaeozoic (Devonian) outcrops in Afghanistan and neighbouring countries (Iran, Pakistan) are numerous but very sparsely distributed, and poorly known. The first interpretation, based on rare or poor data considered these North Gondwanan terranes as poorly connected and some authors have suggested the presence of large oceanic domains in palaeogeographical models. Increase in knowledge, especially of the distribution of main fossils groups, and also some lithological similarities, allow a review of the preliminary models and the identification of connections between the different terranes. For example the presence of Fistuliporid Bryozoan beds or rich Receptaculites levels in different sections of the three countries, especially in the Dasht-e Nawar and Central Iran areas, allows the preliminary models to be reviewed and the connections among the different terranes to be clarified. [ABSTRACT FROM AUTHOR]

The evolution of drainage systems in and around active orogens may be strongly affected by climatic or tectonic processes. Information on the drainage evolution is stored in the sediments of the foreland depocentres. We investigated the provenance of two key deposits adjacent to the Central Alps, the Pliocene Sundgau gravels and the Pleistocene Höhere Deckenschotter by applying detrital thermochronology. Combined with provenance information from Rhine Graben deposits, we propose a reconstruction of the north Alpine drainage system since the middle Pliocene and discuss potential controlling mechanisms. Our data show that the Rhine Graben received detritus from the Alpine realm already during the Pliocene, indicating two different river systems-the proto-Rhine and the Aare-Doubs-draining the Alpine realm toward the North Sea and Mediterranean Sea. The investigated sediments contain detritus from two central Alpine sources, one showing a regional exhumational equilibrium and the other characterized by increasing exhumation rates. Discharge of the latter source ceased after ~2 Ma, reflecting a northward shift of the main Alpine drainage divide. Between ~2.0 and 1.2 Ma, the drainage system was affected by a major change, which we explain as resulting from a change in the Alpine stress field leading to tectonic exhumation and topography reduction in the area of the southern Aar massif. Generally, it seems that between ~4 and 1.2 Ma, the drainage system was mainly controlled by tectonic processes, despite first glaciations that already affected the north-Alpine foreland by ~2 Ma. The drainage system only seems to have reacted to the late Cenozoic climate changes after ~1.2 Ma, i.e., at the time of the most intense Alpine glaciation. At that time, the course of the Rhine River shifted toward the area of the Hegau volcanics, and the size of the Rhine River catchment became strongly reduced. [ABSTRACT FROM AUTHOR]

Acoustic profiling methods are widely used to provide a rapid view into geological structures. For the interpretation of acoustic profiling results (single- and multi-beam), reliable geo-acoustic models are needed. Suitable geo-acoustic models covering a wide range of sediment types do not exist to date for the Baltic Sea. Based on surface sediment datasets, geo-acoustic models have been set up for the prediction of acoustical parameters derived from sedimentological data for south-western Baltic Sea surface sediments. Empirical relationships were created to predict key in situ parameters (p-wave velocity, wet bulk density) from sedimentological core data, notably grain density and water content. The Gassmann-Hamilton equations were used to set up a more generic physically based model. For the first time semi-empirical equations for the calculation of the elastic frame modulus and the solid sediment particle modulus were established by an iterative Gassmann-Hamilton fitting procedure. The resulting models have a remarkably good performance with, for example, a calculated sound velocity accuracy of about 17-32 m s depending on model input data. The acoustic impedance of seafloor sediments can be estimated from single-beam echosounding if the contribution of seafloor reflectivity is extracted from the total acoustic signal. The data reveal a strong linkage between acoustic impedance and selected sediment properties (e.g. grain size, water content). This underlines the potential for effective mapping of seafloor sediment properties (e.g. habitat mapping). Furthermore, these geo-acoustic models can be used by marine geologists for a precise linkage between sediment facies identified in longer cores and corresponding acoustic facies recorded by high-resolution seismic profiling in future work. [ABSTRACT FROM AUTHOR]

The sandstone-hosted Pb-Zn deposits worldwide, including those in the Middle Triassic series of the epicontinental basin in SE Germany, were targeted upon in a literature review by Bjørlykke and Sangster in 1981, treating each mineralization as a separate entity. A different approach based on structural geology, sediment mineralogy and geochemistry (major and trace elements, C-, O-, S- and Pb isotopes) has been taken to study a "metalliferous catena" from sandstone-hosted to unconformity-related Pb-Cu-Zn deposits. The resultant model encompasses five reference types of base metal mineralization lined up along a NW-SE transect perpendicular to the various facies zones of the basin and covering the entire sequence of mineralizing processes from marine-diagenetic processes in the basin center through the epigenetic mineralization finding an outlet in the unconformity-related vein-type deposits close to the basement boundary fault at the edge of the epicontinental basin. The stratiform "Bleiglanzbank-type" (stage I) is confined to the basin center of the Middle Triassic Keuper Basin. Galena derived from bacterial reduction of sulfate and from Pb originating from a marine source of strongly homogenized average basement Pb. The Pb ore evolved in an extensional geodynamic regime. The marine-diagenetic "Bleiglanzbank-type" mineralization can be characterized as a marker stage for a Pb-enriched basin fill. The sulfidic and non-sulfidic stratabound Zn-Cu-Pb mineralization named "Weiden-type" is still dominated by Pb sulfide with only subordinate amounts of cerussite. The ore developed more landward in the epicontinental basin, in a sabkha to alluvial-fluvial depositional environment. The Pb model ages are significantly higher than those of the "Bleiglanzbank-type "ore. The reason for the chemical and facial differences in the epicontinental basin are accounted for by a barrier resultant from synsedimentary faulting around 230 Ma. It is a true dia- (to epigenetic) mineralization whose fluid migration is explained by a flood recharge model. Basin dynamic and structural geology changed from extensional to moderately compressional. Two epigenetic, Pb-dominated sandstone-hosted ore types may be defined in the region, the flexurebound sulfidic and non-sulfidic Pb-(Cu-Zn) mineralization of "Eschenfelden-type" (stage III) is structure-related and superimposed on the afore-mentioned "Weiden-type" and the "Freihung-type" (stage IV). In the latter the flexure no longer existed and has turned into a reverse fault while the Pb mineralization became ore grade. The compressional regime dominated the block faulting in this ore type being located more landward. The maximum horizontal stress exerted from the basement onto the platform sediments was reached during the Lower Cretaceous resultant in a stacked pattern of Mesozoic beds and the development of an unconformity truncating the Jurassic beds. Intraformational recycling of Pb was at a maximum around the reverse faults later than 85 Ma when reverse faults conduced to an overstepping of Triassic sediments, containing "Weiden-type" Pb protore (Roll front-like intraformational recycling of Pb). The 206Pb/207Pb model ages of "Weiden-", "Eschenfeld- "and "Freihung-type" ore mineralization are almost identical. Investigations focused on the temperature of formation yielded 110° to 150 °C for the sulfides and 141° to 169 °C for the carbonate minerals. In this compressional regime, heat has been generated by friction along the fault planes as a function of dip angle and depth, reducing the grain size and delivering elements to the intrastratal solutions. The mineralized structures tend to strike NW-SE and in plan view are shaped concave towards the basement from which the maximum horizontal pressure was exerted onto the platform sediments. The unconformity-related sulfidic Pb-( Zn) mineralization of "Erbendorf-type" (stage V) formed in an extensional regime creating a strike-slip fault system at temperature between 132 °C and 200 °C. The Pb isotope signature is different from the ore types dealt with previously as far as the U series is concerned and closely resembles the sulfidic members from the sandstone-hosted Pb deposits which both have a common source for Th in monazite. Intraformational recycling in sandstone-hosted Pb deposits and concentration of Pb in unconformity -related vein-type deposits tapped the same element source and belong to the "metalliferous catena" of Pb ore crossing the basin-basement boundary or unconformity, respectively. Sandstone-hosted and unconformity-related mineral deposits are not separate entities but two sides of the same coin, the geodynamic evolution of an epicontinental basin. They are a function of the position within the "metalliferous catena" from the basin center to its edge. [ABSTRACT FROM AUTHOR]

The deep marine Crocker Formation in NW Sabah, Malaysia has been well studied in terms of sedimentology, stratigraphy and structural geology. However, not much is known about its potential as a petroleum source rock. This study partly addresses this subject by means of petrographic analysis to characterise the Crocker sediments in terms of its organic matter content and thermal maturity. Crushed rock samples mounted in resin blocks were examined under reflected white and ultraviolet light. Petrographic analysis indicates that the Crocker Formation samples have low phytoclast content (<2%). The mostly indigenous phytoclasts (microscopic plant fragments) can be divided into 4 groups based on their reflectance values; vitrinite with dark inclusions (lowest reflectance), vitrinite, oxidised vitrinite and inertinite (highest reflectance). These phytoclast groups exhibit a reflectance profile of 0.6, 0.8, 1.0 and 1.2%Ro respectively. Such an approach (measuring the reflectance of different phytoclast groups) can aid the petrographer to evaluate and validate vitrinite reflectance measurements in samples such as the Crocker that has a variable phytoclast assemblage. The average vitrinite reflectance is 0.82%Ro, which indicates that the Crocker sediments analysed were once buried to a depth of 4.1 km on average. Although its thermal maturity is within the oil generation window at present day, the Crocker Formation is considered a poor petroleum source rock because it is poor in phytoclast content (<2%) and appears to lack oil-prone liptinitic macerals. However, favourable source rock units could exist within the Crocker in the form of slump or masstransport units, if the organic or phytoclast content is high enough and oil-prone organic matter is sufficiently present. Further geochemical analysis and regional data need to be incorporated for a more comprehensive analysis and assessment of the Crocker as a petroleum source rock and/or an analogue for subsurface geological units. [ABSTRACT FROM AUTHOR]

The middle Oxfordian warming climate and sea-level rise initiated the development of vast carbonate platforms in some western European basins. At the same time, however, siliciclastics and siliceous sponges dominated certain marginal areas of the Iberian ramp. There, siliciclastic input was particularly prominent during the latest Oxfordian and may have been related to a global sea-level fall, synsedimentary tectonic activity, or humid climatic conditions in the hinterland. Field analyses and computer modelling have been previously used to determine the factors that controlled sedimentation. However, it is still unclear if the specific conditions that prevailed during the latest Oxfordian were due to eustasy, tectonics or climate, and when precisely they occurred. Here, we document major changes in sedimentological, micropalaeontological, and mineralogical records on the Iberian ramp during this interval. Detailed sedimentary facies and palynofacies analyses combined with sequence-stratigraphic and cyclostratigraphic analyses of the Ricla Barranco section enable the establishment of a high-resolution time frame. Based on the quartz and mica percentage fluctuations, one large- and seven small-scale sequences are defined. The large-scale sequence boundaries correlate with third-order sequence boundaries Ox 8 and Kim 1 defined by Hardenbol et al. (1998). The large-scale maximum-flooding surface corresponds to the base of the most calcareous interval and to the maximum abundance of marine phytoplankton and opaque, equidimensional phytoclasts. The small-scale sequences correspond to the 100-kyr orbital eccentricity cycle. Calcareous nannofossils and clay minerals were used as palaeoclimatic proxies. Nannofossil abundances and fluxes are lower in the upper part than in the lower part of the interval studied, suggesting a decrease in sea-surface trophic conditions, also shown by an increase in the relative abundance of oligotrophic taxa. This upper part is also characterised by an increase in smectite, which coincides with the base of the large-scale highstand deposit, and is interpreted as reflecting the establishment of dry conditions. A first increase in smectite occurs in the lower part of the succession, and coincides with high percentages of quartz and mica. This latter mineralogical assemblage is interpreted as recording the onset of the Late Jurassic to Early Cretaceous rifting stage, which occurred just before the Planula–Galar ammonite subzone transition. The present study points out a return toward optimum conditions for carbonate sedimentation only 300 kyr after the prominent increase in siliciclastic input due to tectonic activity. The recovery of carbonate production was accompanied by a global sea-level rise and by decreasing rainfall on nearby land. [ABSTRACT FROM AUTHOR]

Tufa deposits that can be fit into a single depositional model are restricted to relatively few publications in the geological literature. This paper presents a detailed sedimentological study of Quaternary (Early Holocene) paludal tufas partly exposed in the Ben Younes piedmont. Field data reveal five main paludal lithofacies: phytoherm framestones, sapropelitic tufa, microdetrital tufa, microbial laminites and lime muds. Radiocarbon dating of residual organic matter in tufa shows that the tufa ranges in age from 8790 ± 50 to 3230 ± 60 BP. Most tufa deposits appear to remain preserved during the different stages of their development. Lithification and diagenetic modifications of tufa show two major trends, an increase in the average carbonate grain size and non-selective dissolution of the fabric where deposits are exposed to meteoric diagenesis. The studied tufas are "water-limited" and the importance of climate in their formation is as major as implied in other Mediterranean equivalents. The predominance of paludal conditions in this area is controlled by the flat substrate, the spring locations, and the water supply. The Gafsa Strike-slip Fault, aside its tectonic role, acts as a major regional sill that controlled paleoflow directions, discharge locations, content, volume, rate and fluctuations of the water supply. [ABSTRACT FROM AUTHOR]

Imbricate structure is a common sedimentary structure and is well developed in sandy sediments. Here, we report a lamina-controlled fine-sand-particle imbricate structure in a set of very fine grained sedimentary rocks (fine sandstone, siltstone, and mudstone) at the Dockyard and Qianceng Cliff areas of Lingshan Island, Qingdao, Shandong, China. Sets of up to 300 laminae are found in stratigraphic profiles in these areas. The laminae are generally less than 1 mm thick, with most being 0.3-0.4 mm thick and the thinnest being <0.1 mm. The dip angle of the imbricate structure varies widely, between 0° and 90°, with an average dip angle of about 40°-50°, which is higher than that of imbricate riverbed gravels (about 34°). The dip angle is a function of the shape and sorting of the particles, as well as the hydrodynamic conditions under which these fine-grained sediments were deposited. Several profiles show well-developed multiscale, soft-sediment deformation structures. Flute casts, load casts, and groove casts are also common. Fragments of carbon remains occur widely and commonly constitute stringers several millimeters thick and up to 10 cm long, together with fine clasts. Vitrain lenticles are also common. Based on the imbricate structure of the Lingshan Island deposits, it is shown that in addition to paleocurrent analysis, the imbricate structure can be used to infer information about fluid properties, transport characteristics, and sedimentary processes of the depositional environment. A near-bottom underflow, either of authigenic origin or derived from cold river water in winter in a delta interdistributary bay or delta-front environment, is inferred to have provided the hydrodynamic setting in which this imbricate structure formed. The imbricate structure, together with other sedimentary structures and features, shows that the sedimentary rocks on Lingshan Island were deposited in an inland, shallow-water environment, such as a delta, and not in a deep-water or submarine continental-slope environment. [ABSTRACT FROM AUTHOR]

Abstract: The sedimentary succession of southeastern Jamaica preserves a depositional record of accommodation changes and tectonic events for the last 14 Ma. The depositional systems which occur in the area have been classified according to distinct tectono-stratigraphic packages based on the depositional environments, rapid facies changes, and or significant erosion surfaces. This paper places the sedimentology and geochemistry within a tectonic evolutionary framework for the northern margin of the Caribbean Plate over the last 14 Ma. This involves considering issues of changing accommodation; deformation episodes including folding and faulting and the subsequent cutting of unconformities. A model for the tectono-stratigraphic development of southeastern Jamaica is also proposed. The model incorporates critical surfaces, major faults, subsidence and uplift which later influence the depositional environments. [Copyright &y& Elsevier]