Search

The Cenozoic topographic growth of the Tibetan Plateau is a pulsed, polyphase process that still requires more constraints. The Cenozoic sedimentary record of the Ningnan Basin, a continental basin located adjacent to the northeastern margin of the Tibetan Plateau, is a key archive for recording the surface evolution of the Tibetan Plateau. This work reports new provenance data (apatite fission‐track, apatite U–Pb dating, and trace element analysis on the same individual grains) from the Oligocene–Pliocene sedimentary sequence that filled the Ningnan Basin. The data set shows variations in provenance patterns through the Miocene which are related to the tectonic evolution of the northeastern margin of the Tibetan Plateau. In contrast to a primary provenance from the Western Ordos Block (WOB) during the Oligocene, the Miocene sediments were mostly derived from the recycling of Mesozoic successions that occur along the northwestern Haiyuan Fault, documenting it was active in the last ca. 15 Myr. These sediments, in turn, were derived from different orogenic blocks but mainly from different segments of the Qilian Mountains. We show that the Late Miocene–Pliocene sediments were primarily derived from transpressional uplift along the Haiyuan Fault, which affected regions such as the Liupan Mountains. Progressive northeastward migration of tectonic stress since the Middle Miocene has induced extensive regional deformation in the northeastern Tibetan Plateau, particularly along the Haiyuan Fault. The provenance record of the neighbouring Cenozoic basins is a key archive for deciphering this tectonic evolution. [ABSTRACT FROM AUTHOR]

The Zama discovery was identified off the coast of Tabasco, Mexico, in the Sureste Basin of the Gulf of Mexico and is hosted in a three‐way closure in the Upper Miocene. This study conducted a detailed detrital zircon (DZ) U–Pb and (U‐Th)/He provenance analyses on samples from sandstone reservoirs in the Zama‐3 and Zama‐2ST1 wells. A total of 22 sandstone samples (11 from each well) were collected for DZ U–Pb and (U‐Th)/He dating from different reservoir zones, testing the hypothesis that different zones were whether originally derived from varied sedimentary source terranes and associated transport pathways to the Zama mini‐basin depositional site. Additional objectives include determination of maximum depositional ages, reconstruction of paleofluvial systems, and exploring the temporal evolution of the drainage region and hinterland tectonics. The DZ U–Pb age spectra from both Zama wells have remarkably homogenous DZ signatures with very similar DZ age modes and modal percentages, displaying dominant Permian/Chiapas Batholith (ca. 35%–45%), Mesoproterozoic/Oaxaquian (ca. 20%–35%), Early Palaeozoic/Acatlán (ca. 8%–20%), and Cenozoic magmatic arc (ca. 15%–25%) age modes, as well as some subsidiary (<5%) early Proterozoic/Archean and Early Cretaceous DZ age components, linked to recycled lower Palaeozoic strata and the Guerrero Terrane and Alisitos arc, respectively. Despite differences in paleocurrent directions, deduced from image logs, there are no systematic differences in DZ spectra, indicating a consistent sediment provenance and no changes in source area. All Zama samples analysed in the study are characterized by abundant syn‐depositional Late Miocene DZ grains, clustering between 8.6 and 10.2 Ma, corroborating a Tortonian (Late Miocene) depositional age, and yield rapid sediment accumulation rates of ca. 200 m in <1.4 Ma (13 m/Myr). Doubled zircon U–Pb and (U‐Th)/He age pairs are indicative of recycling of early Mesozoic rift strata and Paleogene and younger Chiapas basement. These new DZ U–Pb and (U‐Th)/He data have a nearly invariant Tortonian sediment provenance that is similar to the modern Grijalva River flowing generally northward out of the Chiapas highlands. The paleo‐Grijalva drainage, providing sediment to the Late Miocene Zama mini‐basin, was likely drastically larger than the present catchment as it involved 10 Ma plutonic sources that were subsequently downfaulted along the Pacific coast in the latest Miocene. Importantly, DZ U–Pb age components are consistent with Oaxaquia, early Acatlán, and Guerrero/Alisitos signatures and point to sourcing from the Chortis block during its tectonic eastward translation. Such a scenario would allow for a substantially larger Miocene paleo‐drainage that would have encompassed both Chiapas and portions of Chortis. The Miocene tectonic translation of Chortis and erosion of a large and tectonically active hinterland would also reconcile the dramatically larger Middle to Late Miocene sediment supply, funnelling a large influx of sediment into the southern Gulf of Mexico. Rapid Late Miocene sediment accumulation in the salt‐defined Zama mini‐basin must have involved sustained sediment flux via the paleo‐Grijalva drainage and was likely facilitated and focused by continued salt deflation due to sediment loading, as described in Part II. Thus, our work provides new scientific insights into one of the largest hydrocarbon discoveries in Mexico in recent years. [ABSTRACT FROM AUTHOR]

Source‐to‐sink dynamics are subjected to complex interactions between erosion, sediment transfer and deposition, particularly in an evolving tectonic and climatic setting. Here we use stratigraphic forward modelling (SFM) to predict the basin‐fill architecture of a multi‐source‐to‐sink system based on a state‐of‐the‐art numerical approach. The modelling processes consider key source‐to‐sink parameters such as water discharge, sediment load and grain size to simulate various sedimentary processes and transport mechanisms reflecting the dynamic interplay between erosion in the catchment area, subsidence, deposition and filling of the basin. The Cenozoic succession along the SW Barents Shelf margin provides a key area to examine controls on source‐to‐sink systems along a transform margin that developed during the opening of the North Atlantic when Greenland and Eurasian plates were separated (ca. 55 Ma onwards). Moreover, the gradual cooling which culminated in major glaciations in the northern hemisphere during the Quaternary (ca. 2.7 Ma), has affected the spatio‐temporal evolution of the sediment routing along the western Barents Shelf margin. This study aims to characterize the relative importance of different source areas within the source‐to‐sink framework through SFM. In the early Eocene, the SW Barents Shelf experienced a relatively equal sediment delivery from three principal source areas: (i) Greenland to the north, (ii) the Stappen High to the east, representing a local source terrain, and (iii) a major southern source (Fennoscandia). In the middle Eocene, our best‐fit modelling scenario suggests that the northern and the local eastern sources dominated over the southern source, collectively supplying large amounts of sand into the basin as evidenced by the submarine fans in Sørvestsnaget Basin. In the Oligocene (ca. 33 Ma) and Miocene (ca. 23 Ma), significant amounts of sediments were sourced from the east due to shelf‐wide uplift. Finally, this study highlights the dynamic nature and controls of sediment transfer in multi‐source‐to‐sink systems and demonstrates the potential of SFM to unravel tectonic and climatic signals in the stratigraphic record. [ABSTRACT FROM AUTHOR]

The distribution and timing of Neogene extensional structures along the offshore Tanzania margin and their influence on submarine sediment dispersal pathways remain poorly constrained. This knowledge gap limits understanding of the propagation of the East African Rift System (EARS) in the western Indian Ocean. In this study, we use 2D and 3D seismic reflection data to explore a portion of the upper slope region offshore the Rufiji River delta which led to the discovery of a new extensional structure. Horizon maps and seismic sections extracted from the 3D volume reveal that the slope was intersected by W‐E‐oriented turbidite channels during the Cenozoic until the early Pliocene (5.3 Ma). Since then, the opening of this graben, whose timing is also constrained by stratigraphic horizon flattening, has led to a southward reorientation of these channels, a pattern that persists today, as evidenced by the flow direction of the channels at the modern seafloor. 2D seismic profiles reaching depths of 10 s two‐way travel time (TWT) indicate that the formation of this graben is not related to the reactivation of Mesozoic structures. In detail, seismic data show that the acoustic basement is intersected by extensional faults, likely related to the Jurassic rift tectonics, which is reactivated during the middle Cretaceous forming a gentle monocline. The lack of deformation in the post‐Cretaceous suggests a period of tectonic quiescence which persists until the establishment of a new extensional regime responsible for the graben's opening, indicating a decoupling between Mesozoic and Neogene tectonics. Considering the similarity in kinematics, orientation and timing between the graben and other structures along the margin, onshore and offshore, we interpret this graben to be generated by a later tectonic phase of the EARS. These new results may indicate that tectonic stresses associated with the EARS migrated from the Tanzania craton, where the oldest rift structures are dated to ca. 25 Ma, to the western Indian Ocean, where the tectonic activity started during the middle‐late Miocene to Pliocene. [ABSTRACT FROM AUTHOR]

The Cenozoic India‐Asia collision has elevated the Tibetan Plateau and produced large strike‐slip faults in the interior and margins of the plateau, which profoundly influenced drainage reorganization and divide migration in Asia. Recent studies have revealed that the drainage divides between the major rivers in and around the Tibetan Plateau have been migrating for tens of millions of years, due to tectonic and/or climatic disturbance or river capture events. Drainage‐divide stability analysis can provide new, independent insights into the Cenozoic evolution of the river systems. In this study, we focus on the Hanzhong Basin and the adjacent Micang Shan (Shan means Mountain(s)) at the tail of the Qingchuan strike‐slip fault in the outskirts of eastern Tibet. We investigated the stability of the Micang Shan drainage divide, which separates the Han and Jialing rivers (two major tributaries of the Yangtze River), using two methods—χ‐plot and Gilbert metrics. The results show that most segments of the Micang Shan drainage divide are either moving south or stable. We further calculated the predicted stable divide location and identified the abandoned river channels and residual planation surfaces. Based on these analyses, we suggest that (1) the migration of the Micang Shan drainage divide is driven by the tectonic subsidence of the Hanzhong Basin; and (2) the upper reaches of the Han River flowed southward to the Sichuan Basin before basin subsidence. This study supports the hypothesis that the Palaeo‐Middle Yangtze River and its tributaries primarily flowed southward. Moreover, the flow direction of the Middle Yangtze River has been, and still is, transitioning from southward to eastward. The change in river network flow direction is driven by regional block tilting towards the east, surface deformation from strike‐slip faulting, regional extension east of the Tibetan Plateau and/or increased influence from the summer monsoon. [ABSTRACT FROM AUTHOR]

The northern South China Sea (SCS) margin evolved from the Mesozoic convergent to Cenozoic divergent continental margin, and thus, it developed on a heterogeneous crystalline basement with inherited Mesozoic structures. Pre-existing structures and their interactions with rift faults have historically not been described or interpreted in the intensely stretched Baiyun sub-basin. Large-scale 3D seismic reflection data allow us to identify four types of Mesozoic tectonic fabrics within the basement and explain their genesis: (1) Thin, isolated and north-dipping seismic reflections 1, interpreted as thrust faults representing orogenic processes. Tilted thick seismic reflections 2 are formed by reactivation of seismic reflections 1 during post-orogenic extension, which are all related to the NW-ward subduction of the palaeo-Pacific plate. (2) Thin, isolated and shallowly dipping seismic reflections 3 and low-amplitude, semi-transparent and chaotic seismic reflections 4 represent the low-angle thrust system and the associated nappe units, which are related to the shift from NW-to NNW-ward subduction of the paleo-Pacific plate. Subsequently, we investigate the structural interaction between Mesozoic intra-basement and Cenozoic rift structures. Syn-rift, post-rift and long-term faults are developed in Cenozoic strata, and quantitative statistical and qualitative analyses revealed two main types of structural interactions between them and underlying intra-basement structures: (1) Rift faults develop with inheritance of intra-basement structures, including fully and partially inherited faults. (2) Rift faults modify intra-basement structures, although they are controlled by intra-basement structures at an earlier stage. Finally, our results reveal the control of pre-existing structures on the geometry of the Baiyun sub-basin, especially the selective reactivation of NE-trending shear zones (SR2), which are influenced by the regional stress field and the width and dip of the shear zones. [ABSTRACT FROM AUTHOR]

Foreland basins are ideal laboratories to examine and quantify forces that contribute to Earth's topography. The interaction of these driving mechanisms (atmospheric, lithospheric and asthenospheric) affects the accumulation and preservation of strata in marine or terrestrial depocentres. For foreland basins that cover thousands of kilometres along orogens, geodynamic processes or lithospheric structure might differ and/or overlap differently along or across strike. The Magallanes-Austral basin in the southernmost Patagonia serves as a good analogue to analyse the interactions between subcrustal forces and foreland sedimentation. While to the northern part of southern Patagonia, Cenozoic basins were predominantly terrigenous and above sea level; at the southernmost end of Patagonia, sedimentation in the island of Tierra del Fuego was mostly submarine. We analysed in this contribution the southernmost foreland of Patagonia by combining backstripping with reconstruction of flexural and dynamic subsidence. These results were compared with terrestrial records exposed further north of southern Patagonia. We found that, in addition to crustal contributions (as deformation and sedimentation), subcrustal forces are required to accommodate the proximal and distal foreland strata and explain the palaeoenvironmental and subsidence discrepancies that resulted after our analysis. When our models are compared with dynamic topographic curves, strong correlations are observed during the Palaeogene, whereas strong topographic differences occurred in the Neogene. Dynamic topography models in the Neogene have reproduced clear uplift, whereas our residual topography results show equilibrium (close to the orogen) to subsidence values (to the distal foreland). We propose that changes in the lithospheric mantle had to work together with the rest of the tectonics and dynamic forces to match 1-D backstripping and flexural curves. This suggests that foreland basins in southern Patagonia were controlled differently along strike the southern Andes and that crustal deformation, asthenospheric flows and a heterogeneous lithospheric mantle structure affected the Cenozoic basin evolution. [ABSTRACT FROM AUTHOR]

The Eocene compressional phase is well known to have contributed to the construction of the Andes orogen at latitudes north of 30° S, but its extension to the south has not been fully studied. Moreover, synorogenic deposits of Eocene age across the foreland are scarce. The Cenozoic Manantiales Basin records the unroofing sequence of the Andes at 32° S. This study focuses on the basal infill of the Manantiales Basin, informally called the Areniscas Chocolate, which has received less attention than the upper infill until now. Sedimentological, geochronological and provenance studies were carried out on this unit. Here, we present the first ages for the Areniscas Chocolate sequence, of ca. 35–39 Ma (maximum depositional age, MDA). This MDA is interpreted as close to its depositional age, which together with their stratigraphic characteristics, allow us both to separate it from the overlying Miocene Chinches Formation and to propose it as an independent lithostratigraphic unit called Río de los Patos Formation (nov. den.). The provenance analysis of the Río delos Patos Formation indicates a sediment input from western sources located in the Coastal Cordillera and Western Principal Cordillera. Facies associations suggest that the Río de los Patos Formation represents the distal synorogenic deposits during the construction of an Eocene relief to the west. Therefore, the Manantiales Basin started during the late Eocene as a distal foreland basin, indicating that Eocene compression reached latitudes as far south as 32° S. Our results shed light into the characterization of the earliest infill of the Manantiales Basin, as well as into the tectonic evolution of the basin. [ABSTRACT FROM AUTHOR]

How seafloor spreading in marginal basins controls subsidence patterns in continental margins under rift propagation settings remains poorly understood. Herein, based on detailed geological interpretation and backstripping of 37 high‐resolution multichannel seismic reflection sections, we calculate the Cenozoic tectonic subsidence across the Dangerous Grounds (DG), South China Sea, in order to study interactions between seafloor spreading and the propagation of rift basins. Our results show that rapid subsidence occurred in the eastern Dangerous Grounds (EDG) from the Palaeocene to early Oligocene, then migrated westwards to the middle Dangerous Grounds (MDG) during the early Oligocene to early Miocene, and finally reached the western Dangerous Grounds (WDG) during the early to middle Miocene. We interpret this western migration of intensive subsidence as the response of the inherited pre‐Cenozoic heterogeneous lithospheric structure of South China. Thermal re‐equilibration of the lithosphere then dominated the rapid post‐spreading subsidence throughout the whole DG from the middle Miocene. An anomalous subsidence deficit occurred in the EDG during the early Oligocene to early Miocene, and in the MDG during the early to middle Miocene; this phenomenon might be related to small‐scale mantle convection associated with the propagation of seafloor spreading from east to southwest. [ABSTRACT FROM AUTHOR]

In rift basins with multiphase extension, the reactivation of pre‐existing faults plays an important role in the evolution and partitioning of deformation. The Liaohe Subbasin is located in the northeastern Bohai Bay Basin, and the Tanlu Fault Zone (TLFZ) runs through it and experienced extension and right‐lateral strike‐slip during the Cenozoic. Therefore, it is an ideal region for studying the deformation and evolution of rift basins. Based on 3D seismic data, we document the structure and fault characteristics of the Eastern and Western Depressions of the Liaohe Subbasin, identify periods of activity on normal and strike‐slip faults, and analyse the evolution and mechanisms of the Cenozoic evolution of this subbasin. Our main results show that (1) the main faults in the Western Depression exhibited extensional motion throughout the Palaeocene, while the Eastern Depression exhibited significant right‐lateral motion during the Oligocene following the early extension stage. (2) The Cenozoic evolution of the Liaohe Subbasin can be divided into four stages: (i) an initial extension stage (the Palaeocene to the Eocene), (ii) an extension stage with initial strike‐slip (Early Oligocene), (iii) a right‐lateral strike‐slip stage (Late Oligocene) and (iv) a postrift stage (after the Neogene). (3) The upwelling of mantle material caused by the subduction and rollback of the Pacific Plate led to the extension of the Liaohe Subbasin from the Palaeocene to the Eocene. The TLFZ began right‐lateral motion at 40 Ma and experienced strong right‐lateral deformation when rifting was weak in the Oligocene and enhanced deformation after 12 Ma. (4) In this multiphase rifting process, under moderate obliquity, strike‐slip deformation is obvious in the areas close to pre‐existing faults, while extensional deformation is obvious in areas farther away. (5) Cenozoic extension and strike‐slip deformation due to partitioning of strain are caused by obliquely reactivation of TLFZ. This study suggests that the reactivation of pre‐existing strike‐slip faults plays a major role in evolution and strain partitioning. Moreover, the results will contribute to future hydrocarbon exploration in multiphase rift basins. [ABSTRACT FROM AUTHOR]

Palustrine‐lacustrine carbonates of the well‐dated Xichagou section (ca. 43 to ca. 13 Ma) next to the active Altyn Tagh Fault (ATF) are investigated in terms of abundance, lithofacies, strontium, carbon and oxygen isotopes, to differentiate tectonic and climatic controls on the evolution of intermontane lakes in the Tibetan Plateau. Volumetrically dominant siliciclastic strata document five depositional stages: mid‐Eocene alluvial fan (onshore), late Eocene fan delta (nearshore), Oligocene semi‐deep lake (offshore), early Miocene braided fluvial delta (nearshore) and mid‐Miocene fluvial plain (onshore). Carbonates are most abundant in the middle three lacustrine stages and contain various lithofacies, including calcretes, microbialites, grainstones and marlstones. Oxygen isotopes show two positive excursions (−1.17‰ and −2.59‰) at the first nearshore and late offshore stages, indicating two relatively saline stages linked to the Eocene and late Oligocene global warming climates. Carbon isotopes show a positive excursion (from −4.0‰ to +2.9‰) at the middle semi‐deep lake stage and meanwhile strontium isotopes of carbonates show a large negative excursion (from 0.7120‰ to 0.7113‰), both in response to the early Oligocene global humid and cooling climate and resultant lake expansion at the Qaidam Basin. Except for this lake expansion event, the first‐order lake transgressing, shallowing and regressing evolution at the Xichagou section were not consistent with Cenozoic global climatic change trends. Instead, the two‐stage strike‐slip faulting of the ATF probably induced the northeastward and eastward migration of basin depocenter and resulted in the lake transgression‐regression at the Xichagou section. The widespread presence and relatively minor variation in oxygen isotopes (from −7.5‰ to −7.0‰) of early Miocene microbialites in the northern Tibetan Plateau suggest a warm climate and a low relief before ca. 15 Ma. [ABSTRACT FROM AUTHOR]

The Cenozoic strata of the Xining Basin, NE Tibet, have provided crucial records for understanding the tectonic and palaeo‐environmental evolution of the region. Yet, the age of the lower part of the sedimentary stratigraphy and, consequently, the early tectonic evolution of the basin remain debated. Here, we present the litho‐ and magnetostratigraphy of various early Eocene sections throughout the Xining Basin independently constrained by the U–Pb radiometric age of a carbonate bed. Our study extends the dated stratigraphy down to 53.0 Ma (C24n.1r) and reveals highly variable accumulation rates during the early Eocene ranging from 0.5 to 8 cm/ka. This is in stark contrast to the low but stable accumulation rates (2–3 cm/ka) observed throughout the overlying Palaeogene and Neogene strata. Such a pattern of basin infill is not characteristic of flexural subsidence as previously proposed, but rather supports an extensional origin of the Xining Basin with multiple depocentres, which subsequently coalesced into a more stable and slowly subsiding basin. Whether this extension was related to the far‐field effects of the subducting Pacific Plate or the India–Asia collision remains to be confirmed by future studies. [ABSTRACT FROM AUTHOR]

Unravelling early Cenozoic basin development in northern Tibetan Plateau remains crucial to understanding continental deformation mechanisms and to assessing models of plateau growth. We target coarse‐grained red beds from the Cenozoic basal Lulehe Formation in the Qaidam basin by combining conglomerate clast compositions, paleocurrent determinations, sandstone petrography, heavy mineral analysis and detrital zircon U–Pb geochronology to characterize sediment provenance and the relationship between deformation and deposition. The red beds are dominated by matrix‐supported, poorly sorted clastic rocks, implying low compositional and textural maturity and short transport distances. Although most sandstones have high (meta)sedimentary lithic fragment contents and abundant heavy minerals of metamorphic origin (e.g., garnet, epidote and chlorite), spatiotemporal differences in detrital compositions are evident. Detrital zircon grains mainly have Phanerozoic ages (210–280 Ma and 390–480 Ma), but Proterozoic ages (750–1000 Ma, 1700–2000 Ma and 2300–2500 Ma) are also prominent in some samples. Analysed strata display dissimilar (including south‐, north‐ and west‐directed) paleocurrent orientations. These results demonstrate that the Cenozoic basal deposits were derived from localized, spatially diverse sources with small drainage networks. We advocate that initial sedimentary filling in the northern Qaidam basin was fed by parent‐rocks from the North Qaidam‐South Qilian belts and the pre‐Cenozoic basement within the Qaidam terrane interior, rather than southern distant Eastern Kunlun regions. Seismic and drilling well stratigraphic data indicate the presence of paleohighs and syn‐sedimentary reverse faults and noteworthy diversity in sediment thickness of the Lulehe Formation, revealing that the Qaidam terrane exhibited as several isolated depocenters, rather than a coherent basin, in the early stage of the Cenozoic deposition. We suggest the Cenozoic Qaidam basin to have developed in a contractional deformation regime, which supports models with synchronous deformation throughout most of Tibet shortly after the India‐Eurasia collision. [ABSTRACT FROM AUTHOR]

The thick sequence of mid‐late Cenozoic sediments preserved within the Enderby Basin of the East Antarctica margin contains key information regarding glacial history and palaeo‐oceanographic conditions during the last 34 My. The interplay between glacial processes and ocean circulation can be reconstructed from seismic stratigraphic studies. Here, interpretation of seismic sequences and geomorphology from an extensive 2D seismic dataset (∼75,000 km) are correlated with lithological data of the ODP site 1165 drilled on the continental rise, and used to assess the age and origin of the sediment, and the possible influence of oceanic currents on its distribution. Mapping of seismic units and facies reveals that, in addition to glacial sediments derived from the Antarctic mainland, the upper Cenozoic succession includes drift units with prograding sequences building out from the Mac. Robertson Land margin, west of the Prydz Bay. Three contourite drifts grew on the western side of submarine channels and large sediment wave fields suggest a mixed system of turbidity currents influenced by west‐flowing bottom currents. The drifts are composed of four seismic units representing stages of onset (Lower Oligocene), main growth (Early‐Middle Miocene), maintenance (Middle‐Late Miocene) and burial (Pliocene). The internal geometry and reflection patterns of the drifts imply an intensified current activity from the Early to Middle Miocene. The results plausibly reflect that the formation of proto Antarctic Bottom Water (AABW) started around the Eocene–Oligocene boundary and intensified episodically from the early to middle Miocene. [ABSTRACT FROM AUTHOR]

Sediment accumulation rates in foreland basins result from a complex interplay between surface and deep processes in both the exhumed relief domain and sedimentary basins. The growth and decay of a mountain belt during orogenic and post‐orogenic phases have been largely studied, thanks to thermochronological and structural studies. The sedimentary response of the orogenic phases in the preserved sediments of the surrounding basins is well known in terms of sedimentary filling patterns and architecture, but much less better quantified. Here, we performed a measurement of the siliciclastic sediment volumes of the Pyrenean retro‐foreland basin—the Aquitaine Basin and the Bay of Biscay during Cenozoic times—for a better understanding of the erosion and the sediment transfer and deposition during the convergence (syn‐orogenic) to post‐convergence (post‐orogenic) periods of the Pyrenees Mountain. The measurement of the compacted siliciclastic sediment is based on sediment thickness (isopach) maps of known lithologies, derived from the interpretation of 40,000 kms of seismic profiles. Thanks to the siliciclastic sediment volumes quantification and a well‐known retro‐foreland basin tectono‐sedimentary evolution, we bring quantitative results as: The amount of preserved sediments is of 51,500 ± 16,800 km3 for the Cenozoic.The siliciclastic sediment rate curve during Cenozoic shows two major increases around 26.0 and 2.5 Ma. The 26.0 Ma increase is clearly related to the erosion of the Pyrenees of tectonic origin. The major 2.5 Ma one would be mainly related to a climatic forcing.The mass balance between the Aquitaine Platform and the deepest domains changes through time in favour of the deep domain. This might be explained by the ratio between subsidence that created accommodation space and the sediments feed by the mountain belt and stored in the Aquitaine Platform. [ABSTRACT FROM AUTHOR]

Quantitative assessment of terrigenous sediment flux to the deep basin has mainly been limited to the Cenozoic Era, given challenges with reconstruction of more ancient source to sink systems. Subsurface mapping in the northern Gulf of Mexico basin, where there is a robust database of wells and seismic data, allows estimation of sand‐size grain volumes within 12 chronostratigraphically defined Late Mesozoic supersequences. Five subsurface depocentres with thicknesses of >400 m are identified, revealing a history of sediment routing via major fluvial axes (paleo rivers) southward from a mid‐continent drainage divide. The interpreted paleo‐rivers are further confirmed by compilation and synthesis of published and novel detrital zircon provenance data showing combinations of age peak subsets that vary considerably between depocentres. This study quantifies sediment volumes within each depocentre by inverting porosity over defined gross rock volumes derived from subsurface well logs and 2D seismic mapping. Two temporal trends of progressively increasing grain volume can be related to climatic effects on fluvial discharge and sediment delivery to the depocentres: (1) Late Jurassic to Early Cretaceous (Oxfordian to early Aptian) and (2) Late Cretaceous (Late Aptian to Coniacian). The first temporal trend probably reflects the local climate becoming less arid with northward drift of the North American Plate into higher latitudes. The second trend mirrors increasing Cretaceous paleotemperatures and rising global sea levels. This second trend is also marked by increased shelf margin bypass of sand indicated by deep basin drilling. Partitioning of Late Mesozoic grain volume by fluvial axes shows that the Paleo‐Apalachicola and Paleo‐Mississippi rivers, sourced from Appalachian basement terranes, generated the largest and longest terrigenous sediment flux into the Gulf of Mexico basin in the Late Mesozoic. Overall, Late Mesozoic siliciclastic grain volumes are estimated to be an order of magnitude less than those previously documented for the Cenozoic Era. [ABSTRACT FROM AUTHOR]

The Late Cretaceous to Cenozoic is known for its multiple inversion events, which affected Central Europe's intracontinental sedimentary basins. Based on a 2D seismic profile network imaging the basin fill without gaps from the base Zechstein to the seafloor, we investigate the nature and impact of these inversion events on Zechstein salt structures in the Baltic sector of the North German Basin. These insights improve the understanding of salt structure evolution in the region and are of interest for any type of subsurface usage. We link stratigraphic interpretation to previous studies and nearby wells and present key seismic depth sections and thickness maps with a new stratigraphic subdivision for the Upper Cretaceous and Cenozoic covering the eastern Glückstadt Graben and the Bays of Kiel and Mecklenburg. Time‐depth conversion is based on velocity information derived from refraction travel‐time tomography. Our results show that minor salt movement in the eastern Glückstadt Graben and in the Bay of Mecklenburg started contemporaneous with Late Cretaceous inversion in the Coniacian‐Santonian. Minor salt movement continued until the end of the Late Cretaceous. Overlying upper Paleocene and lower Eocene deposits show constant thickness without indications for salt movement suggesting a phase of tectonic quiescence from the late Paleocene to middle Eocene. In the late Eocene to Oligocene, major salt movement recommenced in the eastern Glückstadt Graben. In the Bays of Kiel and Mecklenburg, late Neogene uplift removed much of the Eocene‐Miocene succession. Preserved deposits indicate major post‐middle Eocene salt movement, which likely occurred coeval with the revived activity in the Glückstadt Graben. Cenozoic salt structure growth critically exceeded salt flow during Late Cretaceous inversion. Cenozoic salt movement could have been triggered by Alpine/Pyrenean‐controlled thin‐skinned compression, but is more likely controlled by thin‐skinned extension, possibly related to the beginning development of the European Cenozoic Rift System. [ABSTRACT FROM AUTHOR]

In this paper, we propose a high‐resolution (HR) sedimentary budget quantification at basin‐scale for the Cenozoic deposits of the Pelotas Basin (South Atlantic). A new workflow is implemented including five main steps: (1) basin‐scale analysis and characterization, (2) quality control and selection of reference 2D dip‐sections, (3) HR seismic stratigraphy analysis, (4) sediment supply estimation taking into account lithology and porosity corrections and then (5) the estimation of the sedimentary budget curve including 41 time‐intervals for the last 65 Myr. Variance ranges were determined considering the parameters of the method on the case study. The main uncertainties are related to the seismic velocities for the time‐to‐depth conversion (5%–22%), the method for lithological parameters quantification and associated porosity correction (4.4%–14.3%), the absolute ages of stratigraphic markers (1%–25%), and the proportion of in‐situ sediment production (0.3%–0.5%). For the very first time, this method allows the identification of several cycles from an entire sedimentary basin fill characterized by pulses of sediment supply (Qs) whose growth phase lasts less than 1 Myr, followed by a constant phase lasting 1–2 Myr, and finally an exponentially decreasing phase lasting 2–5 Myr. These pulses alternate with phases where the sediment supply was very low for intervals of ca. 1–5 Myr. Ten major pulses were recognized during the Cenozoic. We propose that the sediment supply dynamic in the Pelotas basin records the orogenic phases of the Andes located more than 2,000 km upstream. The recorded Qs pulses in the basin are out of phase with respect to the active tectonic phases of the Central Andes. Finally, by comparing the volume of preserved sediment and the production capacity of the catchment, we suggest that a source of sediment in addition to the Brazilian craton and the Andes should be envisaged, potentially associated with deep‐water oceanic circulation. [ABSTRACT FROM AUTHOR]

The evolution of the tectonic deformation of the northeastern Tibetan Plateau (TP) in the Cenozoic is significant for understanding plateau growth during India‐Asia convergence. However, when deformation began and how it has developed in this pivotal region remain controversial. We focus on the temporal progress of Cenozoic deformation in the Qilian Shan, a major tectonic belt of the northeastern TP. In the present study, detrital apatite fission‐track (AFT) thermochronological analysis was performed on Oligocene‐Quaternary synorogenic sediments in the northern Qaidam Basin, where detritus is sourced from the Qilian Shan. Age components of buried but unannealed detrital AFT samples reveal two static peaks (i.e., peak ages that are consistent upsection) at ca. 60–50 Ma and ca. 40–36 Ma and a moving peak (i.e., peak ages that are younger upsection) with increased lag time during ca. 30–8 Ma. These new detrital AFT ages, integrated with the analysis of sedimentary provenance and data from previously published studies, indicate that Cenozoic tectonic deformation began in the Qilian Shan in the late Paleocene‐early Eocene. Furthermore, the Qilian Shan experienced a subsequent episodic deformation event in the late Eocene and the deformation or erosion of some terranes in the Qilian Shan decelerated during the Oligocene‐Miocene. Our results suggest that the northeastern TP responded to the India‐Asia collision almost instantaneously. [ABSTRACT FROM AUTHOR]

The Greater Caucasus orogen on the southern margin of Eurasia is hypothesized to be a young collisional system and may present an opportunity to probe the structural, sedimentary and geodynamic effects of continental collision. We present detrital zircon U-Pb age data from the Caucasus region that constrain changes in sediment routing and source exposure during the late Cenozoic convergence and collision between the Greater Caucasus orogen and the Lesser Caucasus, an arc terrane on the lower plate of the system. During Oligocene to Middle Miocene time, following the initiation of deformation within the Greater Caucasus, marine sandstones and shales were deposited between the Greater and Lesser Caucasus, and detrital zircon age data suggest no mixing of Greater Caucasus and Lesser Caucasus detritus. During Middle to Late Miocene time, Greater Caucasus detritus was deposited onto the Lesser Caucasus basin margin, and terrestrial, largely conglomeratic, sedimentation began between the Greater and Lesser Caucasus. Around 5.3 Ma, upper plate exhumation rates increased and shortening migrated to pro- and retro-wedge fold-thrust belts, coinciding with the initiation of foreland basin erosion. Sediment composition, provenance and structural data from the orogen together suggest the existence of a wide (230-280 km) marine basin that was progressively closed during Oligocene to Late Miocene time, probably by subduction/lithospheric underthrusting beneath the Greater Caucasus, followed by initiation of collision between the Lesser Caucasus arc terrane and the Greater Caucasus in Late Miocene to Pliocene time. The pace of the transition from hypothesized subduction to collision in the Caucasus is consistent with predictions from numerical modeling for a system with moderate convergence rates (<13 mm/yr) and hot lower plate continental lithosphere. Basement crystallization histories implied by our detrital zircon age data suggest the presence of two pre-Jurassic sutures between stable Eurasia and the Lesser Caucasus, which likely guided later deformation. [ABSTRACT FROM AUTHOR]

The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13°S and 27°S) is part of the Andean Plateau, which is the world's second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the presentday transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts. [ABSTRACT FROM AUTHOR]

Abstract: The Danube Basin is situated between the Eastern Alps, Western Carpathians and Transdanubian mountain ranges and represents a classic petroleum prospection site. The basin fill is known from many 2D reflection seismic lines and deep wells with measured e‐logs which provided a good opportunity for theories about its evolution. New analyses of deep wells situated in the Danube Basin northeastern margin allowed us to refine stratigraphy and to interpret various depositional systems. This also allowed us to outline changes in provenance of sediment during the Cenozoic. The performed interpretation of the Palaeogene and Neogene depositional systems also confirmed the Oligocene–Early Miocene exhumation of the basin pre‐Neogene basement. Opening and development of the Middle to Late Miocene basin depocentres above the boundary between the Western Carpathians and Northern Pannonian domain was recognized. Our analysis contributed to a better understanding of the Hurbanovo–Diösjenő fault which acts as an inherited weakness zone along the boundary of two crustal fragments with different provenance. We document various basin types stacked one on another (retro‐arc, back‐arc and extensional hinterland basin). The analysis of sediment sources reveals intricate geodynamic processes during the Eastern Alpine–Western Carpathian orogenic system collision with European platform (formation of ALCAPA microplate) and its successive tectonics escape during the Pannonian Basin System origination. [ABSTRACT FROM AUTHOR]

The central and southern Perth Basin in southwestern Australia has a geological history involving multiple regional unconformity-forming events from the Permian to Recent. This study uses sonic transit time analysis to quantify the magnitudes of net and gross exhumation for four stratigraphic periods from 43 wells. Most importantly, we quantify gross exhumation of the Permian-Triassic, Triassic-Jurassic, Valanginian break-up and post-Early Cretaceous events. Post-Early Cretaceous gross exhumation averages 900-m offshore and 600-m onshore. Up to 200 m of this exhumation may be attributed to localized fault block rotation during extension in the Late Cretaceous and/or reverse fault re-activation due to the compressive stresses in Australia in the last 50 Ma. The remainder is attributed to regional exhumation caused by epeirogenic processes either during the Cenozoic or at the Aptian-Albian boundary. Maximum burial depths prior to the Valanginian unconformity-forming event were less than those reached subsequently, so that the magnitude of Valanginian break-up exhumation cannot be accurately quantified. Gross exhumation prior to the break-up of Gondwana was defined by large magnitude differences (up to 2500 m) between adjoining sub-basins. At the end of Triassic, exhumation is primarily attributed to reverse re-activation of faults that were driven by short-wavelength inversion and exhumation at the end Permian is likely caused by uplift of rotated fault blocks during extension. The evidence from quantitative exhumation analysis indicates a switch in regime, from locally heterogeneous before break-up to more regionally homogeneous after break-up. [ABSTRACT FROM AUTHOR]

After Mesozoic rifting, the Atlantic margin of Morocco has recorded the consequences of the continental collision between Africa and Europe and the relative northward motion of the African plate over the Canary Island hotspot during Cenozoic times. Interpretation of recently acquired 2D seismic reflection data ( MIRROR 2011 experiment) presents new insights into the Late Cretaceous to recent geodynamic evolution of this margin. Crustal uplift presumably started during the Late Cretaceous and triggered regional tilting in the deep-water margin west of Essaouira and the formation of the Base Tertiary Unconformity ( BTU). An associated hiatus in sedimentation is interpreted to have started earlier in the north (presumably in the Cenomanian at well location DSDP 416) and propagated to the south (presumably in the Coniacian at well location DSDP 415). The difference in the total duration of this hiatus is postulated to have controlled the extrusion of Late Triassic to Early Jurassic salt during the Late Cretaceous to Early Palaeocene non-depositional period, resulting in regional differences in the preservation of salt structures: the Agadir Basin in the south of the study area is dominated by salt diapirs, whereas massive canopies characterised the Ras Tafelnay Plateau farther north and salt-poor canopies and weld structures the northernmost offshore Essaouira and Safi Basins. Accompanied by volcanic intrusions, a presumably Early Palaeogene reactivation of previously existing basement faults is interpreted to have formed a series of deep-water anticlines with associated gravity deformation of shallow-seated sediments. The orientation of the fold axes is roughly perpendicular to the present day coast and the extensional fault direction; therefore, not a coast-line parallel pattern of extensional faults, related to the rifting and break-up of the margin, but rather a coast-line perpendicular oceanic fracture zone might have caused the basement faults associated with the deep-water folds. Both the volcanic intrusions and the formation of the deep-water anticlines show a comparable age trend which gets progressively younger towards the south. A potential tempo-spatial relationship of the BTU and the reactivation of basement faults can be explained by the relative northward motion of the African plate over the Canary Island hotspot. Regional uplift producing the BTU could have been the precursor of the approaching hotspot during the Late Cretaceous, followed during the Early Palaeogene by a locally more pronounced uplift above the hotspot centre. [ABSTRACT FROM AUTHOR]

The continuous Cenozoic strata in the Xining Basin record the growth and evolution of the northeastern Qinghai-Tibetan Plateau. Here, the mechanisms and evolution of the Xining Basin during the Cenozoic were investigated by studying the sedimentary facies of 22 Cenozoic sections across the basin and detrital zircon U-Pb ages of three Cenozoic sections located in the eastern, central and western basin, respectively. In the Eocene ( ca. 50-44 Ma), the India-Eurasia Collision affected the northeastern Qinghai-Tibetan Plateau. The Central Qilian Block rotated clockwise by ca. 24° to form the Xining Basin. The Triassic flysch sediments surrounding the basin were the primary sources of sediment. Between ca. 44-40 Ma, the basin enlarged and deepened, and sedimentation was dominated by saline lake sediments. Between ca. 40-25.5 Ma, the Xining Basin began to shrink and dry, resulting in the deposition of saline pan and saline mudflat sediments in the basin. After ca. 20 Ma, the Laji Shan to the south of the Xining Basin was uplifted due to the northward compression of the Guide Basin to the south. Clasts that eroded from this range dominated the sediments as the basin evolved from a lacustrine environment into a fluvial system. The Xining Basin was an extensional basin in the Early Cenozoic, but changed into a compressive one during the Late Cenozoic, it was not a foreland basin either to the Kunlun Shan or to the western Qinling Shan in the whole Cenozoic. The formation and deformation of the Xining Basin are the direct responses of the India-Eurasia Collision and the growth of the Qinghai-Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The Andean Orogen is the type-example of an active Cordilleran style margin with a long-lived retroarc fold-and-thrust belt and foreland basin. Timing of initial shortening and foreland basin development in Argentina is diachronous along-strike, with ages varying by 20-30 Myr. The Neuquén Basin (32°S to 40°S) contains a thick sedimentary sequence ranging in age from late Triassic to Cenozoic, which preserves a record of rift, back arc and foreland basin environments. As much of the primary evidence for initial uplift has been overprinted or covered by younger shortening and volcanic activity, basin strata provide the most complete record of early mountain building. Detailed sedimentology and new maximum depositional ages obtained from detrital zircon U-Pb analyses from the Malargüe fold-and-thrust belt (35°S) record a facies change between the marine evaporites of the Huitrín Formation ( ca. 122 Ma) and the fluvial sandstones and conglomerates of the Diamante Formation ( ca. 95 Ma). A 25-30 Myr unconformity between the Huitrín and Diamante formations represents the transition from post-rift thermal subsidence to forebulge erosion during initial flexural loading related to crustal shortening and uplift along the magmatic arc to the west by at least 97 ± 2 Ma. This change in basin style is not marked by any significant difference in provenance and detrital zircon signature. A distinct change in detrital zircons, sandstone composition and palaeocurrent direction from west-directed to east-directed occurs instead in the middle Diamante Formation and may reflect the Late Cretaceous transition from forebulge derived sediment in the distal foredeep to proximal foredeep material derived from the thrust belt to the west. This change in palaeoflow represents the migration of the forebulge, and therefore, of the foreland basin system between 80 and 90 Ma in the Malargüe area. [ABSTRACT FROM AUTHOR]

Located at the southern edge of the eastern Himalayan syntaxis, the Central Myanmar Basin ( CMB) is divided into several Tertiary sub-basins that have been almost continuously filled since the Indo-Asia collision. They are currently drained by the Irrawaddy River, which flows down the eastern Tibetan Plateau and the Sino-Burman Ranges. Tracing sediment provenance from the CMB is thus critical for reconstructing the past denudation of the Himalayan-Tibetan orogen; it is especially relevant since a popular drainage scenario involves the capture of the Tsangpo drainage system in Tibet by a precursor to the Irrawaddy River. Here, we document the provenance of sediment samples from the Minbu Sub-Basin at the southern edge of the CMB, which is traversed by the modern stream of the Irrawaddy River. Samples ranging in age from middle Eocene to Pleistocene were investigated using Nd isotopes, trace element geochemistry and sandstone modal compositions. Our data provide no evidence of a dramatic provenance shift; however, sandstone petrography, trace element ratios and isotopic values display long-term trends indicating a gradual decrease of the volcanic input and its replacement by a dominant supply from the Burmese basement. These trends are interpreted to reflect the progressive denudation of the Andean-type volcanic arc that extended onto the Burmese margin, along the flank of the modern Sino-Burman Ranges, where most of the post-collisional deformation of central Myanmar is located. Though our results do not exclude an ephemeral or diluted contribution from a past Tsangpo-Irrawaddy connection, sedimentation rates suggest that this hypothesis is unlikely before the development of a stable Tsangpo-Brahmaputra River in the Miocene. These results thus suggest that the central Myanmar drainage basin has remained restricted to the Sino-Burman Ranges since the beginning of the India-Asia collision. [ABSTRACT FROM AUTHOR]

The main source of siliciclastic sediment in the Barbados accretionary prism is off-scraped quartzose to feldspatho-litho-quartzose metasedimentaclastic turbidites, ultimately supplied from South America chiefly via the Orinoco fluvio-deltaic system. Modern sand on Barbados island is either quartzose with depleted heavy-mineral suites recycled from Cenozoic turbidites and including epidote, zircon, tourmaline, andalusite, garnet, staurolite and chloritoid, or calcareous and derived from Pleistocene coral reefs. The ubiquitous occurrence of clinopyroxene and hypersthene, associated with green-brown kaersutitic hornblende in the north or olivine in the south, points to reworking of ash-fall tephra erupted from andesitic (St Lucia) and basaltic (St Vincent) volcanic centres in the Lesser Antilles arc. Modern sediments on Barbados island and those shed by larger accretionary prisms such as the Indo-Burman Ranges and Andaman-Nicobar Ridge define the distinctive mineralogical signature of Subduction Complex Provenance, which is invariably composite. Detritus recycled from accreted turbidites and oceanic mudrocks is mixed in various proportions with detritus from the adjacent volcanic arc or carbonate reefs widely developed at tropical latitudes. Ophiolitic detritus, locally prominent on the Andaman Islands, is absent on Barbados, where the prism formed above a westward subduction zone with a shallow décollement plane. The four-dimensional complexities inherent with multicyclic sediment dispersal along and across convergent plate boundaries require quantitative provenance analysis as a basic tool in paleogeographic reconstructions. Such analysis provides the link between faraway factories of detritus and depositional sinks, as well as clues on subduction geometry and the nature of associated growing orogenic belts, and even information on climate, atmospheric circulation and weathering intensity in source regions. [ABSTRACT FROM AUTHOR]

The Patagonian Magallanes retroarc foreland basin affords an excellent case study of sediment burial recycling within a thrust belt setting. We report combined detrital zircon U-Pb geochronology and (U-Th)/He thermochronology data and thermal modelling results that confirm delivery of both rapidly cooled, first-cycle volcanogenic sediments from the Patagonian magmatic arc and recycled sediment from deeply buried and exhumed Cretaceous foredeep strata to the Cenozoic depocentre of the Patagonian Magallanes basin. We have quantified the magnitude of Eocene heating with thermal models that simultaneously forward model detrital zircon (U-Th)/He dates for best-fit thermal histories. Our results indicate that 54-45 Ma burial of the Maastrichtian Dorotea Formation produced 164-180 °C conditions and heating to within the zircon He partial retention zone. Such deep burial is unusual for Andean foreland basins and may have resulted from combined effects of high basal heat flow and high sediment accumulation within a rapidly subsiding foredeep that was floored by basement weakened by previous Late Jurassic rifting. In this interpretation, Cenozoic thrust-related deformation deeply eroded the Dorotea Formation from ca. 5 km burial depths and may be responsible for the development of a basin-wide Palaeogene unconformity. Results from the Cenozoic Río Turbio and Santa Cruz formations confirm that they contain both Cenozoic first-cycle zircon from the Patagonian magmatic arc and highly outgassed zircon recycled from older basin strata that experienced burial histories similar to those of the Dorotea Formation. [ABSTRACT FROM AUTHOR]

Stratigraphic data from petroleum wells and seismic reflection analysis reveal two distinct episodes of subsidence in the southern New Caledonia Trough and deep-water Taranaki Basin. Tectonic subsidence of ~2.5 km was related to Cretaceous rift faulting and post-rift thermal subsidence, and ~1.5 km of anomalous passive tectonic subsidence occurred during Cenozoic time. Pure-shear stretching by factors of up to 2 is estimated for the first phase of subsidence from the exponential decay of post-rift subsidence. The second subsidence event occured ~40 Ma after rifting ceased, and was not associated with faulting in the upper crust. Eocene subsidence patterns indicate northward tilting of the basin, followed by rapid regional subsidence during the Oligocene and Early Miocene. The resulting basin is 300-500 km wide and over 2000 km long, includes part of Taranaki Basin, and is not easily explained by any classic model of lithosphere deformation or cooling. The spatial scale of the basin, paucity of Cenozoic crustal faulting, and magnitudes of subsidence suggest a regional process that acted from below, probably originating within the upper mantle. This process was likely associated with inception of nearby Australia-Pacific plate convergence, which ultimately formed the Tonga-Kermadec subduction zone. Our study demonstrates that shallow-water environments persisted for longer and their associated sedimentary sequences are hence thicker than would be predicted by any rift basin model that produces such large values of subsidence and an equivalent water depth. We suggest that convective processes within the upper mantle can influence the sedimentary facies distribution and thermal architecture of deep-water basins, and that not all deep-water basins are simply the evolved products of the same processes that produce shallow-water sedimentary basins. This may be particularly true during the inception of subduction zones, and we suggest the term 'prearc' basin to describe this tectonic setting. [ABSTRACT FROM AUTHOR]

A response from the authors of the article "Patterns of Cenozoic sediment flux from western Scandinavia" in the 2012 issue.

The recent paper by Gołędowski et al. (2012) is a contribution to the ongoing debate regarding the possible processes involved in the geological evolution of the North Sea basin and adjacent hinterlands during the Cenozoic. Their major conclusions state (1) that the prominent seismic feature called the 'mid-Miocene unconformity' ( MMU) is a diachroneous surface in the North Sea basin and forms a regional hiatus and (2) that sediment flux from western Scandinavia was primarily controlled by climate and vegetation cover from the Late Eocene and onwards. We believe, however, that regarding the eastern North Sea basin, which was the depocentre for sediments sourced from southwestern Scandinavia, these conclusions are not supported by the geological record. The so-called 'mid-Miocene unconformity' is not a regional hiatus in the Danish and Norwegian sectors of the North Sea basin, but represents a distinct shift from prograding delta/slope systems to deposition of deeper marine hemipelagic mud, and thus provides a distinct seismic marker horizon. However, detailed studies show that there is a continuous sedimentation dominated by glacony-rich mud where a ca. 3 m thick mudlayer spans several millions years and thus are below seismic resolution. Consequently, seismic stratigraphy is not applicable for this condensed section. (1) Warm climate and dense vegetation cover in southern Scandinavia during the mid-Miocene Climatic Optimum were not able to hinder the progradation of a major siliciclastic wedge from Scandinavia into the North Sea basin. (2) The distinct temperature decrease in the Serravallian does not correlate with the aforementioned progradation, but on the contrary, correlate with the culmination of a major flooding event and deposition of a condensed succession of marine glaucony-rich clay. [ABSTRACT FROM AUTHOR]

The Mesozoic-Cenozoic basins located between the Faroe, Orkney and Shetland Islands along the NE Atlantic Margin are actively explored oil and gas provinces whose subsidence histories are complicated by multiple tectonic factors, including magmatism, inversion and regional-scale uplift and tilting, that have resulted in spatially variable exhumation. These basins also exhibit nonburial related, transient Cenozoic heating anomalies that make thermal history interpretation and burial history reconstructions problematic. In this study, we have applied a compaction-based approach, which is less susceptible to distortions from transient heating, to provide new constraints on Cenozoic burial and exhumation magnitudes in the UK sector of the Faroe-Shetland region using sonic transit time data from Upper Cretaceous marine shales of the Shetland Group in 37 wells. As estimates of exhumation magnitude depend critically on the form of the normal sonic transit time-depth trend, a new marine shale baseline trend was firstly constructed from shales presently at maximum burial, consistent with other marine shale baseline trends of different ages from nearby basins. Our results indicate that Upper Cretaceous marine shales are presently at or near (i.e. within ≤100 m net exhumation) maximum burial depths in the Møre and Magnus basins in the northeast of the study area as well as in the deeper water Faroe-Shetland Basin (i.e. Flett and Foula sub-basins). However, Upper Cretaceous strata penetrated by wells in the southwest have been more deeply buried, with the difference between maximum burial depth and present-day values (net exhumation) increasing from ca. 200 to 350 m along the central and northeastern parts of the Rona High to ca. 400-1000 m for wells located in the West Shetland Basin, North Rona Basin and southwestern parts of the Rona High. Although the precise timing of exhumation is difficult to constrain due to the complex syn- to post-rift tectonostratigraphic history of vertical movements within the Faroe-Shetland region, our estimates of missing section, together with available thermal history constraints and seismic-stratigraphic evidence, implies that maximum burial and subsequent exhumation most likely occurred during an Oligocene to Mid-Miocene tectonic phase. This was probably in response to major post-breakup tectonic reshaping of this segment of the NE Atlantic Margin linked to a coeval and significant reorganization of the northern North Atlantic spreading system, suggesting that fluctuations in intraplate stress magnitude and orientation governed by the dynamics of plate-boundary forces exert a major control on the spatial and temporal variations in differential movements along complexly structured continental margin. [ABSTRACT FROM AUTHOR]

There is growing recognition that pulses of compressive tectonic structuring punctuate the post-breakup subsidence histories of many 'passive' rifted continental margins. To obtain new insights into the nature and origin of compression at passive margins, we have conducted a comprehensive analysis of the post-breakup (<43 Ma) deformation history of the offshore Otway Basin, southern Australian margin, using a regional seismic database tied to multiple wells. Through mapping of a number of regional intra-Cenozoic unconformities we have determined growth chronologies for a number of major anticlinal structures, most of which are ˜ NE- SW-trending folds that developed during mild inversion of syn-rift normal faults or through buckling of the post-rift succession. These chronologies are supplemented by onshore structural evidence and by thermochronological data from key wells. Whilst our analysis confirms the occurrence of a well-documented pulse of late Miocene-early Pliocene compression, post-breakup deformation is not restricted to this time interval. We highlight the growth of a number of structures during the mid-late Eocene and the Oligocene-early Miocene, with evidence for considerable temporal and spatial migration of strain within the basin. Our results indicate a long-lived ˜ NW- SE maximum horizontal stress orientation since the mid-late Eocene, consistent with contemporary stress observations but at variance with previous suggestions that this stress orientation was initiated in the late Miocene by increased coupling of the Australian-Pacific plate boundary. We attribute the observed record of deformation to a compressional intraplate stress field, coupled to the progressive evolution of the boundaries of the Indo-Australian Plate, ensuring that this margin has been subject to ongoing compressional forcing since mid-Eocene breakup. Our results indicate that compressional deformation at passive margins may be more common than is generally assumed, and that passive margin basins with evidence for protracted post-breakup deformation histories can provide useful natural laboratories for obtaining improved understanding of the evolution of intraplate stress fields over geological timescales. [ABSTRACT FROM AUTHOR]

Multichannel high-resolution seismic and multibeam data were acquired from the Maldives-isolated carbonate platform in the Indian Ocean for a detailed characterization of the Neogene bank architecture of this edifice. The goal of the research is to decipher the controlling factors of platform evolution, with a special emphasis on sea-level changes and changes of the oceanic currents. The stacking pattern of Lower to Middle Miocene depositional sequences, with an evolution of a ramp geometry to a flat-topped platform, reflects variations of accommodation, which here are proposed to be primarily governed by fluctuations of relative sea level. Easterly currents during this stage of bank growth controlled an asymmetric east-directed progradation of the bank edge. During the late middle Miocene, this system was replaced by a twofold configuration of bank development. Bank growth continued synchronously with partial bank demise and associated sediment-drift deposition. This turnover is attributed to the onset and/or intensification of the Indian monsoon and related upwelling and occurrence of currents, locally changing environmental conditions and impinging upon the carbonate system. Mega spill over lobes, shaped by reversing currents, formed as large-scale prograding complexes, which have previously been interpreted as deposits formed during a forced regression. On a regional scale, a complex carbonate-platform growth can occur, with a coexistence of bank-margin progradation and aggradation, as well as partial drowning. It is further shown that a downward shift of clinoforms and offlapping geometries in carbonate platforms are not necessarily indicative for a sea-level driven forced regression. Findings are expected to be applicable to other examples of Cenozoic platforms in the Indo- Pacific region. [ABSTRACT FROM AUTHOR]

The Crotone Basin was generated in the late Cenozoic as a forearc basin of the Ionian arc-trench system. New data are gained through detailed field mapping, high-resolution stratigraphic analysis of a key area and examination of offshore well data and seismic reflection profiles. Major unconformities divide the basin fill into major sequences, which reveal a three-stage internal organization thought to reflect geodynamic events of the Calabrian arc and backarc area closely. The first stage is characterized by extensional block faulting and uplift followed by rapid drowning during high subsidence and transtension in the basin along a major NNW- to NW-striking fault system. This stage is interpreted to reflect resumption of rollback after an episode of slab tearing triggered by transitory docking of continental lithosphere in the trench. The initial uplift is inferred to reflect decoupling and rebound after the transitory coupling phase. The second stage is characterized by increased subsidence and continued extension/transtension. This trend presumably reflects a decreasing rate of rollback resulting from a tendency towards viscous coupling after acceleration of slab downwelling. The third stage is characterized by short-lived transpression along major shear zones and local inversion of former basins. This is inferred to reflect entrance into the trench of buoyant continental lithosphere, resulting in significant deceleration of slab rollback and consequently a break in, or slowing of, backarc extension, and predominance of the effects of compression related to Africa- Europe convergence. Overall, the above evolution resulted in the formation of a progressively narrower and rapidly retreating slab, inducing extreme rates of backarc extension, and may have played a critical role in determining the intermittent nature of the backarc rifting. [ABSTRACT FROM AUTHOR]

The significance of variations in the sediment flux from western Scandinavia during the Cenozoic has been a matter of debate for decades. Here we compile the sediment flux using seismic data, boreholes and results from other publications and discuss the relative importance of causal agents such as tectonism, climate and climate change. Western Scandinavia, the northern British Isles and the Faeroe- Shetland Platform were significant sediment sources during the Paleocene, which is well founded in tectonic causes related to the opening of the North Atlantic. From the Eocene and onward, variations in the sediment flux from western Scandinavia correlate better with climate and climate change. During the Eocene, sediment production was low. From the late Eocene onward, increased seasonality may have contributed to stimulating the sediment flux. Significant climatic cooling episodes correlate with Oligocene deposits in the North Sea, the post-mid- Miocene Molo and Kai Formations of the Norwegian Shelf, the southern North Sea delta system and large volumes of the Late Pliocene- Holocene Naust Formation. The sediment flux from Scandinavia during the Cenozoic is in general agreement with the detrital flux to the world's oceans. Furthermore, the large variations in the size of sediment catchment areas as well as the possibility of submarine and glacial erosion must be incorporated to understand regional variations in climate driven sediment flux. [ABSTRACT FROM AUTHOR]