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- Volume 35, Issue 1, 2023
Basin Research - Volume 35, Issue 1, 2023
Volume 35, Issue 1, 2023
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A song of volumes, surfaces and fluxes: The case study of the Central Mallorca Depression (Balearic Promontory) during the Messinian Salinity Crisis
[Building on paleo‐topographic reconstructions of the basin as well as seismic imaging of the Messinian Salinity Crisis (MSC) evaporites, the origin of the evaporite deposits of the Central Mallorca Depression (CMD) were put in context of a physical model that explores the dynamics of the basin with as little assumptions as possible. The authors find that the mechanisms leading to the gypsum and the halite deposits most likely differed, with the latter needing a high amplitude sea‐level drawdown.
The Central Mallorca Depression (CMD) located in the Balearic Promontory (Western Mediterranean) contains a well‐preserved evaporitic sequence belonging to the Messinian Salinity Crisis (MSC) salt giant, densely covered by high‐ and low‐resolution seismic reflection data. It has been proposed recently that the MSC evaporitic sequence in the CMD could be a non‐deformed analogue of the key MSC area represented by the Caltanissetta Basin in Sicily. This presumed similarity makes the CMD an interesting system to better understand the MSC events. Physics‐based box models of the water mixing between sub‐basins, built on conservation of mass of water and salt, help constrain the hydrological conditions under which evaporites formed during the MSC. Those models have been widely used in the literature of the MSC in the past two decades. They have been mostly applied to the Mediterranean Sea as a whole focusing on the Mediterranean–Atlantic connection, or focusing on the influence of the Sicily Sill connecting the Western and Eastern Mediterranean Sea. In this study, we apply a downscaled version of such modelling technique to the CMD. First, we quantify the present‐day volumes of the MSC units. We then use a reconstructed pre‐MSC paleo‐bathymetry to model salinity changes as a function of flux exchanges between the CMD and the Mediterranean. We show that a persistent connection between the CMD and the Mediterranean brine near gypsum saturation can explain volume of Primary Lower Gypsum under a sea level similar to the present. For the halite, on the contrary, we show that the observed halite volume cannot be deposited from a connected CMD‐Mediterranean scenario, suggesting a drawdown of at least 850 m (sill depth) is necessary. Comparison between the deep basin halite volume and that of the CMD shows that it is possible to obtain the observed halite volume in both basins from a disconnected Mediterranean basin undergoing drawdown, although determining the average salinity of the Western Mediterranean basin at the onset of drawdown requires further investigation.
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Tectonic evolution of the Triassic Songpan‐Ganzi basin as constrained by a synthesis of multi‐proxy provenance data
Authors Yan Tang, An Yin, Xi Xu, Kaixuan An and Yunpeng Zhang[DZmix modelling of the Songpan‐Ganzi detrital‐zircon age data supports the remnant ocean model.
The triangular Songpan‐Ganzi flysch terrane exposes a Triassic turbidite sequence with an average thickness of ca. 8 km. The sediments may have been accumulated in a remnant Paleo‐Tethyan ocean bounded by the converging North China, South China, and the Qiangtang terrane from three sides, or a back‐arc basin with an oceanic basement created during the Triassic closure of the Paleo‐Tethyan ocean. To differentiate the two competing models, we systematically reviewed the available provenance data that include U–Pb detrital zircon ages at the basin scale, paleocurrent directions, sandstone petrography, and heavy‐mineral assemblages from the Triassic Songpan‐Ganzi basin samples. We use the Kolmogorov–Smirnov tests to differentiate competing hypotheses for detrital‐zircon provenance interpretations and DZmix modelling to quantify relative contributions of detrital zircon from all potential source areas for the Triassic Songpan‐Ganzi deposits. The most important result of this work is that the Songpan‐Ganzi basin had a stable and locally derived source system: the western, central and eastern sub‐basins were mainly sourced from the north whereas the easternmost and southeastern sub‐basins were mainly sourced from westernmost South China (i.e., the Longmen Shan area) and the Qiangtang terrane. The stability of the source areas around the Songpan‐Ganzi basin throughout the Triassic is most compatible with the remnant ocean model that predicts a long‐lived marine basin with a pre‐Triassic oceanic/continental basement trapped between converging continental blocks during the Triassic.
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The interplay between basement fabric, rifting, syn‐rift folding, and inversion in the Rio do Peixe Basin, NE Brazil
[AbstractThe Rio do Peixe Basin is part of a series of aborted Cretaceous rifts formed within the Proterozoic Borborema Province, onshore NE Brazil in response to rifting between Africa and South America. The basin is remarkably well‐imaged and comprises fault‐bounded depocentres, the main ones being the NE‐oriented Brejo das Freiras and the E–W‐oriented Sousa half‐grabens. These grabens and their bounding faults are influenced by Neoproterozoic basement shear zones and present a complex framework of secondary normal faults and folds. Recent workers also interpret large reverse faults and regional post‐rift shortening driven by far‐field stresses from the Andes. For those reasons, the basin represents an ideal setting to investigate the multiphase history of rift basins. We thus combine borehole‐calibrated 2D and 3D seismic and magnetic data with section restoration and numerical modelling to investigate the architecture and evolution of this basin. We aim to understand: (i) the controls of the basement fabric in 3D fault architecture and kinematics and (ii) how syn‐rift faults controlled the geometry and development of fault‐related folds. By doing this, we also investigate the timing, kinematics, and magnitude of inversion in the basin to explore its multiphase history. We demonstrate that (i) the basement fabric controlled not only the strike of faults but also their geometry and polarity at depth, (ii) folds in the syn‐rift sequence are attributed simply to syn‐rift extension along stepped and/or curved faults, and (iii) inverted and/or reverse faults occur within the basin, but these are minor and appear to have formed during rifting. We explain this minor inversion by a change in plate kinematics related to the onset of the nearby transform margin to the north. These results have implications for understanding the 3D evolution of oblique grabens, the role of structural inheritance, and the recognition of inversion‐ versus extension‐related folds in rift basins worldwide.
,3D evolutionay diagram showing the evolution of the Rio do Peixe Basin and the relationship between the Precambrian basement fabric (a) with the nucleation and orientation of the main syn‐rift normal faults (b) and the subsequent syn‐rift folding (c) over steps and/or curvatures in normal fault geometries.
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The Acre Basin basement (NW Brazil) and the transition from the intracratonic to retroarc foreland basin system
Authors Rick Souza de Oliveira and Roberta Mary Vidotti[AbstractThe understanding of the crustal transition between orogenic zones and cratonic portions in distal regions of foreland basins has received increasing attention, but the analysis is often hampered by the sedimentary cover. Despite the peculiar location of the Acre Basin, specifically between the Amazonian Craton and the sub‐Andean zone, local basement studies are still scarce due to lacking seismic data and exploratory wells. Therefore, this work aims to map basement depths, estimate crustal compositions and identify the main depocenters, structures and limits of Acre Basin using an integrated analysis to understand better the region lithospheric evolution, its relationship with the Amazonian Craton and its positioning within the Andean orogeny. For that, we used well, 2D seismic reflection, airborne and ground gravity and magnetic data as well as the EMG2008. Tilt Depth estimates indicate basement depths between 500 and 7800 m and larger sedimentary thicknesses in the northern portion. Additionally, we modelled groups of potential sources between 0.1 and 22 km and Moho depths between 26 and 37 km. Compositionally, the upper crust consists dominantly of meta‐sedimentary and low‐grade metamorphic rocks and granites, indicating that the sub‐Andean and Acre Basins share a similar basement. Thus, there are indications that the basement of the Acre Basin is essentially formed by the Sunsás province in the Amazonian Craton. However, local differences in basement depth, magnetic susceptibility and exploratory potential led to the subdivision into Divisor and Xapuri sub‐basins, north and south of the Fitzcarrald Arch, respectively. Finally, it was possible to establish the limits of the Andean orogeny influence in the Acre Basin and delimit the area of the Western Amazon Foredeep installed during the Neogene.
,The Western Amazon Foredeep, installed in the region as a result of the advance of the Andean orogeny from the Neogene, encompassing the Acre Basin with its updated boundaries and the Subandean Basins of Oriente, Marañon, Ucayali and Madre de Dios. Crustal subdivision and projection of Geochronological province Sunsas towards Acre Basin through joint geophysical analysis of potential field and seismic methods.
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Location, extent, and magnitude of dynamic topography in the Late Cretaceous Cordilleran Foreland Basin, USA: New insights from 3D flexural backstripping
Authors Zhiyang Li and Jennifer Aschoff[AbstractMantle‐induced dynamic topography (i.e., subsidence and uplift) has been increasingly recognized as an important process in foreland basin development. However, characterizing and distinguishing the effects (i.e., location, extent and magnitude) of dynamic topography in ancient foreland basins remains challenging because the spatio‐temporal footprint of dynamic topography and flexural topography (i.e., generated by topographic loading) can overlap. This study employs 3D flexural backstripping of Upper Cretaceous strata in the central part of the North American Cordilleran foreland basin (CFB) to better quantify the effects of dynamic topography. The extensive stratigraphic database and good age control of the CFB permit the regional application of 3D flexural backstripping in this basin for the first time. Dynamic topography started to influence the development of the CFB during the late Turonian to middle Campanian (90.2–80.2 Ma) and became the dominant subsidence mechanism during the middle to late Campanian (80.2–74.6 Ma). The area influenced by >100 m dynamic subsidence is approximately 400 by 500 km, within which significant (>200 m) dynamic subsidence occurs in an irregular‐shaped (i.e., lunate) subregion. The maximum magnitude of dynamic subsidence is 300 ± 100 m based on the 80.2–74.6 Ma tectonic subsidence maps. With the maximum magnitude of dynamic uplift being constrained to be 200–300 m, the gross amount of dynamic topography in the Late Cretaceous CFB is 500–600 m. Although the location of dynamic subsidence revealed by tectonic subsidence maps is generally consistent with isopach map trends, tectonic subsidence maps developed through 3D flexural backstripping provide more accurate constraints of the areal extent, magnitude and rate of dynamic topography (as well as flexural topography) in the CFB through the Late Cretaceous. This improved understanding of dynamic topography in the CFB is critical for refining current geodynamic models of foreland basins and understanding the surface expression of mantle processes.
,Dynamic topography became the dominant subsidence mechanism in the Cordilleran foreland basin during the middle to late Campanian (80.2–74.6 Ma). The footprint of dynamic subsidence is approximately 400 by 500 km, within which significant dynamic subsidence (>200 m) occurs in an irregular‐shaped (i.e., lunate) subregion (ca. 450 by 150 km).
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Structural controls on the pathways and sedimentary architecture of submarine channels: New constraints from the Niger Delta
Authors Marco Pizzi, Alexander C. Whittaker, Mike Mayall and Lidia Lonergan[AbstractIn submarine settings, the growth of structurally influenced topography can play a decisive role in controlling the routing of sediments from shelf‐edge to deep water, and can determine depositional architectures and sediment characteristics. Here we use well‐constrained examples from the deep water Niger Delta, where gravity‐driven deformation has resulted in the development of a large fold and thrust belt, to illustrate how spatial and temporal variations in the rate of deformation have controlled the nature and locus of contrasting depositional styles. Published work in the study area using 3D seismic data has quantified the growth history of the thrust‐related folds at multiple locations using line‐length‐balancing, enabling cumulative strain for individual structures over time and along‐strike to be obtained. We integrate this information with seismic interpretation and facies analysis, focusing on the interval of maximum deformation (15 to 3.7 Ma), where maximum strain rates reached 7%/Ma. Within this interval, we observe a vertical change in depositional architecture where: (1) leveed‐confined and linear channels pass upward in to (2) ponded lobes with erosionally confined channels and finally (3) channelised sheets. Our analysis demonstrate that this change is tectonically induced and diachronous across the fault array, and we characterise the extent to which structural growth controls both the distribution and the architecture of the turbidite deposits in such settings. In particular, we show that leveed‐confined channels exist when they can exploit strain minima between growing faults or at their lateral tips. Conversely, as a result of fault linkage and increased strain rates submarine channels become erosional and may be forced to cross folds at their strain maxima (crests), where their pathways are influenced by across‐strike variations in shortening for individual structures. Our results enable us to propose new conceptual models of submarine channel deposition in structurally complex margins, and provide new insights into the magnitude of fault interaction needed to alter depositional style from leveed to erosionally confined channels, or to deflect seabed systems around growing structures.
,As thrust faults grow and link, strain rate on centrally located fault segments increases. This leads to submarine channels being deflected and focused through strain rate minima, controlling their locus and depositional expression. A reduction in deformation subsequently leads to the blanketing of topography and the development of basins filled with channelised sheets.
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Hydrostatic pore water pressure revisited
Authors Simon A. Stewart and Markus Albertz[AbstractHydrostatic or “normal” pressure can be easily visualized as a water column with pressure given by ρgh and any departures classified as abnormal pressure. This is the basis for commonly used hydrostatic pressure depth trends in sedimentary basins that are constructed on assumptions of constant gradients and are datumed at mean sea level or ground level. But the straightforward water column concept does not upscale in a simple way to sedimentary basins where the zones of interest are several thousands of metres below the land or sea surface. Sedimentary basins are heterogeneous, including stacked, confined reservoirs and variations in pore water composition. It is possible to construct pressure‐depth profiles that honour the geology and hydrostratigraphy of a basin and these give different hydrostatic baselines from simple constant gradients hung from familiar local datums such as ground level. Key steps are using a reservoir‐specific datums such as the water table or potentiometric surface relevant to that unit, then building a pressure‐depth trend that represents the pore fluid salinity variation and density profile throughout the reservoir unit. At a given depth, this version of hydrostatic may predict pressures several hundred psi different from a single density gradient hung from a datum local to the well, and exhibit a notched profile reflecting the geological and hydrological stratigraphy. This construct redefines normal and abnormal pore fluid pressures in sedimentary basins. The impacts of this alternative approach to sedimentary basin hydrostatics, even if data are limited and pressure profiles have to be framed probabilistically, extend to many aspects of studying and interacting with fluid systems in sedimentary basins including basin modelling, petroleum systems analysis, well planning and well operations.
,Hydrostatic (normal) pressure gradients are over‐simplified in most geoscience applications. Potentiometric surfaces are appropriate datums for confined reservoirs and non‐linear gradients are required where salinity varies with depth. Vertical wells through stacked reservoirs are expected to encounter hydrostatic pore pressure profiles that are notched according to hydrostratigraphy.
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‘I hate sand … it gets everywhere’—Phanerozoic sedimentary recycling from NW Africa
Authors James Lovell‐Kennedy, Emmanuel Roquette, Stefan Schröder and Jonathan Redfern[AbstractOver 10,000 published detrital zircon ages have been reprocessed (applying a +10% normal and reverse concordance range) and analysed to understand the evolution of the detrital zircon record of north‐west Africa during the Phanerozoic. Using dissimilarity and clustering analysis, shifts in detrital zircon populations allow interpretation of the evolution of source regions and source to sink systems throughout the Phanerozoic within the West Gondwana superfan. Previous thermochronology and field studies conducted across north‐west Africa indicate significant and sustained shifts in source regions in Meso‐Cenozoic times which are not recorded in the detrital zircon geochronology record. This discrepancy is most notable for Mesozoic to modern source to sink studies focused on the evolution of the Atlasic rift and opening of the Atlantic and Tethyan Oceans to the west and north respectively. Our results indicate a high degree of similarity between samples from Cambrian times onwards due to successive phases of sediment recycling. This highlights the need to integrate detrital zircon analysis with other techniques to provide confident reconstruction of sediment routing systems across Morocco. This systematic review also reveals the ubiquitous occurrence of Mesoproterozoic zircons within Moroccan sediment. No basement of this age is known from north‐west Africa—often described as the ‘Mesoproterozoic Gap’, which was thought to be a diagnostic feature of sediment derived from the West African Craton. However, zircons of this age form 7% of all analysed zircons and are present in sediments from at least 700 Ma. The presence of this population is interpreted as strongly diagnostic of provenance from either the Amazonian Craton or the Eastern Gondwana Orogen within Central Africa. Their presence in the Moroccan detrital record from the Neoproterozoic onwards raises questions about the position of the West African Craton in the Proterozoic, and for the spatial extent of Mesoproterozoic orogeny within north Africa.
,Key episodes of zircon formation and sedimentary recycling along the North Gondwana margin since Neoproterozoic times.
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Basin analysis palaeo‐landscape modelling: Testing the critical controls using experimental design constrained by a real 3D geological model, Gippsland Basin, Australia
Authors Xuemei Yang, Gregory Smith and Ritu Gupta[Investigate the main controlling variables and assess their relative importance for palaeo‐landscape evolution (e.g. climate, uplift and subsidence control sediment supply) by Paleolandscape basin modelling through deep time.
The main controlling variables for palaeo‐landscape evolution are investigated to assess their relative importance using the Gippsland Basin geological history. Palaeo‐landscape reconstruction is a complicated process controlled and affected by multiple variables, including tectonic, palaeo‐environment, sea‐level change, rainfall, sediment erosion, transportation, deposition, etc. The Basin and Landscape Dynamics software (Badlands) software was used with an efficient experimental design (ED) to guide the selected scenarios, process the results, and generate the multi‐variate equations that define and identify the important controlling variables. The ED was used to test and identify the main uncertainties and their possible ranges, based on actual field data, while at the same time ensuring that the full multi‐dimensional space for those variables was covered to enable the computation of multivariate equations from the minimum number of scenario runs. A full suite of 3D forward palaeo‐landscape models of the Gippsland Basin was built to reconstruct the basin history from its formation to the present (Early Cretaceous to Holocene, 137‐0 Ma). The models are compared to the corresponding full 3D realistic structural and stratigraphic model of the basin that has been built in Petrel (Schlumberger software). This constrains the sedimentary, stratigraphic, burial and thermal histories to the relative subsidence rates and basin‐fill for each geological sequence by using the model isopachs input to the Badlands modelling. The ED required only 22 scenarios to fit 12 identified variables and test for possible interactions with each other. The most significant variables are those that control sediment supply including non‐marine erodibility, rainfall, (Rainfall × Area) exponent m, Slope and critical slope while maximum % Marine Deposition and marine dispersal are also required to fill the marine accommodation space. Sea Level and subsidence only become significant when rapid enough to outpace sediment supply. The controlling factors change over time with basin development from rift to post‐rift phases and interactions are highly significant.
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Provenance of Oligocene lithic and quartz arenites of the East Carpathians: Understanding sediment routing systems on compressional basin margins
[Palaeogeographical reconstruction of the Moldavides Basin during Oligocene, depicting the drainage routes associated with the marine depositional systems (a); the cross‐section illustrating the advancing of the Carpathian indenter and the interfingering of the two turbidite systems supplied from opposite margins of the foreland basin (b).
We present new sedimentological, petrographical, palaeontological and detrital zircon U–Pb data on late Oligocene–early Miocene sedimentary rocks of the thin‐skinned thrust belt of East Carpathians. These data were acquired to reconstruct the sedimentary routing system for two compositionally different turbidite fans made of the regionally extensive Kliwa and Fusaru formations. On the eastern margin of the Moldavides foreland basin, large low‐gradient river systems draining the East European Platform provided well‐sorted quartz‐rich sand forming deltas on wide shallow shelves and thick Kliwa submarine fans. Due to the westward subduction of a thinned continental plate, the western basin margin was characterized by short, steep‐gradient routing systems where sediment transport to deep water was mainly through hyperpycnal flows. The Getic and Bucovinian nappes of the East Carpathians and the exhumed Cretaceous–Early Palaeogene orogenic wedge fed Fusaru fans with poorly sorted lithic sand. The Fusaru fans trend northwards in the foredeep basin having an elongate depocentre, interfingering and then overlapping on the distal part of the Kliwa depositional system due to the eastward advance of the Carpathian fold‐and‐thrust belt. A smaller sediment input is supplied by southern continental areas (i.e. Moesian Platform, North Dobrogea and potentially the Balkans). In general, the sandstone interfingering between distinct basin floor fan systems is less well documented because the facies would be similar and there are not many systems that have a distinct sediment provenance like Kliwa and Fusaru systems. This case study improves the understanding of regional palaeogeography and sedimentary routing systems and provides observations relevant here or elsewhere on the interfingering turbidite fan systems.
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Sediment provenance of the Lulehe Formation in the Qaidam basin: Insight to initial Cenozoic deposition and deformation in northern Tibetan plateau
Authors Xing Jian, Ling Fu, Ping Wang, Ping Guan, Wei Zhang, Hanjing Fu and Haowei Mei[AbstractUnravelling 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.
,Two‐stage sedimentary filling model for deposition of the Lulehe Formation in the Qaidam basin. The Lulehe Formation coarse‐grained red beds accumulated separately and the Qaidam terrane exhibited as several isolated depocenters, rather than a coherent basin, in the early stage of the Cenozoic deposition. The Cenozoic basal deposits were derived from localized, spatially diverse sources with small drainage network.
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Salt tectonics vs. inversion tectonics: The anticlines of the western Maestrazgo revisited (eastern Iberian Chain, Spain)
Authors Carlos L. Liesa, Antonio M. Casas‐Sainz, Marcos Aurell, José L. Simón and Ana R. Soria[AbstractMany works in the last decades underline the role of evaporites, not just as a conditioning factor but as the engine for subsidence and eventually basin inversion. The western Mediterranean alpine ranges are being investigated in this regard because of the presence of discontinuous units of Permian to Triassic evaporites, deposited in the western Tethys basins. This work presents a thorough analysis of two particular structures (Cañada Vellida and Miravete anticlines) in the intraplate Maestrazgo basin (eastern Iberian Chain, Spain) in which evidence to support their reinterpretation as salt‐driven structures have been recently reported. Our analysis includes (i) a comprehensive stratigraphic and structural study of the folds along their entire trace, (ii) the compilation of thickness and distribution of evaporite–bearing and supraevaporite units, paying special attention to changes in the thickness of units in relation to anticlines, and (iii) the study of fault patterns, sometimes in relation to the mechanical stratigraphy. All three aspects are also documented and discussed on a regional scale. The new data and interpretations reported here reinforce the extensional origin of the Late Jurassic–Early Cretaceous basins, and the role of regional extensional tectonics as the responsible for the development of first‐order syn‐sedimentary normal fault zones driving the formation and evolution of sub‐basins. These basins were subsequently inverted and deformed, including the formation of complex, box‐geometry anticlines that, in their turn, controlled deposition in Cenozoic basins. The review of the arguments that support the alternative of salt tectonics for the origin of such anticlines has allowed us to delve into the sedimentary and tectonic evolution of the inverted extensional basins and to propose a specific model for the development of these faulted anticlines. The role of salt levels and other interlayered detachments in the structuring of sedimentary basins and their inversion is also pondered. The observations in the eastern Iberian Chain reported here have implications to assess ongoing reinterpretations in terms of salt tectonics in other alpine basins and ranges of the western Mediterranean.
,Despite the existence of Triassic salt layers, we question the diapiric origin of anticlines in the Iberian Chain and the role of salt in basin formation. Thickness changes are related to faults and extensional tectonics. Observations along the structures allow us to recognize different milestones in their evolution. Regional information and frequent drag folds indicate kinematics not compatible with salt extrusion.
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Ordovician tectonic transition from passive margin into peripheral foreland in the southern Ordos: A diagnostic insight into the closure of Erlangping Ocean between the North Qinling Arc and North China Block
Authors Jiaopeng Sun, Yunpeng Dong, Qiang Chen, Lei Yang, Wenhou Li, Dongdong Zhang and Qian Zhang[AbstractAchieving a reliable closure time of a back‐arc ocean is an essential aspect in studies on detailed tectonic processes of an active continental margin and arc–continent collision. This is particularly the case for the northern Qinling Orogen, which records the accretion of the North Qinling Arc (NQA) onto the North China Block (NCB) after the Erlangping back‐arc ocean closure. Sedimentological, petrological and geochronological signatures from the Ordovician successions in the southern Ordos reveal a tectonic transition from passive continental margin to peripheral foreland in the southern NCB at the beginning of Katian. Sedimentological and geochronological investigations reveal an abrupt shift of accelerating basin subsidence and deepening at the earliest Katian, separating ca. 300‐m‐thick shallow‐marine carbonate shelf assemblages from overlying ca. 2000‐m‐thick deep‐water carbonate slope and turbidite associations. Zircon age spectra of the Katian turbidites are characterized by early‐Palaeozoic and Neoproterozoic age clusters, which are different from those of the Middle Ordovician quartz arenites sourced merely from the NCB basement. Instead, these age patterns match well with those of the coeval successions in the northern NQA, indicating a spatially linked abyssal deposystem. Stratigraphic architecture deciphers a typical foreland basin geometry, involving, from south to north, northward‐propagating turbiditic wedge, northward‐backstepping carbonate slope and progressively shoaling carbonate platform, embodying foredeep, forebulge and backbulge, respectively. These characteristics of basin‐fill evolution reflect the northward migration of the flexural wave as a dynamic response to the northward expansion of the thickened NQA thrust wedge. Together with the other geological and geochronological data, our new insights indicate a southward subduction polarity of the Erlangping back‐arc oceanic crust followed by its termination at ca. 450 Ma, which was earlier than that of the main Proto‐Tethyan Shangdan Ocean between the NCB and South China Block. Our new data provide an updated view of the complex history of the Proto‐Tethys closure during the Gondwana assembly.
,Birth and evolution of the Ordovician southern Ordos peripheral foreland: a diagnostic insight into the closure of Erlangping back‐arc Ocean and the accretion of North Qinling Arc onto North China Block.
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Reorganization of continent‐scale sediment routing based on detrital zircon and rutile multi‐proxy analysis
Authors Maximilian Dröllner, Milo Barham and Christopher L. Kirkland[AbstractThe duration and extent of sediment routing systems are intrinsically linked to crustal‐ to mantle‐scale processes. Therefore, distinct changes in the geodynamic regime may be captured in the detrital record. This study attempts to reconstruct the sediment routing system of the Canning Basin (Western Australia) during the Early Cretaceous to decipher its depositional response to Mesozoic‐Cenozoic supercontinent dispersal. Specifically, we reconstruct source‐to‐sink relationships for the Broome Sandstone (Dampier Peninsula) and proximal modern sediments through multi‐proxy analysis of detrital zircon (U–Pb, Lu–Hf and trace elements) and detrital rutile (U–Pb and trace elements). Multi‐proxy comparison of detrital signatures and potential sources reveals that the majority of the detrital zircon and rutile grains are ultimately sourced from crystalline basement in central Australia (Musgrave Province and Arunta region) and that proximal sediment supply (i.e., Kimberley region) is negligible. However, a significant proportion of detritus might be derived from intermediate sedimentary sources in central Australia (e.g., Amadeus Basin) rather than directly from erosion of crystalline basement. Broome Sandstone data are consistent with a large‐scale drainage system with headwaters in central Australia. Contextualization with other broadly coeval drainage systems suggests that central Australia acted as a major drainage divide during the Early Cretaceous. Importantly, reorganization after supercontinent dispersal is characterized by the continuation of a sediment pathway remnant of an earlier transcontinental routing system originating in Antarctica that provided a template for Early Cretaceous drainage. Review of older Canning Basin strata implies a prolonged denudation history of central Australian lithologies. These observations are consistent with the long‐lived intracontinental tectonic activity of central Australia governing punctuated sediment generation and dispersion more broadly across Australia and emphasize the impact of deep Earth processes on sediment routing systems.
,- Integration of U‐Pb, Hf isotope and trace element analyses of detrital zircon and rutile decipher provenance.
- Potential source areas of broadly coeval formation are discriminated by multi‐proxy analysis.
- Integrated analysis of the detrital record after major geodynamic changes captures sedimentary reorganization.
- Source‐to‐sink correlation implies an Early Cretaceous sediment routing system originating in central Australia.
- Pre‐existing Gondwanan sediment pathways provided a template for Early Cretaceous drainage.
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Architecture, structural and tectonic significance of the Seagap fault (offshore Tanzania) in the framework of the East African Rift
[Seagap fault zone, is a 400‐km‐long crustal structure affecting the Tanzania margin probably since the mid Jurassic. By the late Eocene till early Neogene, the Seagap fault acted as a sinistral strike slip fault producing releasing and restraining bend structures. Seafloor seismic maps suggest by the late Neogene, the Seagap fault zone switched to normal fault behaviour.
The Southeastern portion of the East African Rift System reactivates Mesozoic transform faults marking the separation of Madagascar from Africa in the Western Indian Ocean. Earlier studies noted the reactivation of the Davie Fracture Zone in oceanic lithosphere as a seismically active extensional fault, and new 3D seismic reflection data and exploration wells provide unprecedented detail on the kinematics of the sub‐parallel Seagap fault zone in continental/transitional crust landward of the ocean‐continent transition. We reconstruct the evolution of the seismically active Seagap fault zone, a 400‐km‐long crustal structure affecting the Tanzania margin, from the late Eocene to the present day. The Seagap fault zone is represented by large‐scale localized structures affecting the seafloor and displaying growth geometries across most of the Miocene sediments. The continuous tectonic activity evident by our seismic mapping, as well as 2D deep seismic data from literature, suggests that from the Middle‐Late Jurassic until 125 Ma, the Seagap fault acted as a regional structure parallel to, and coeval with, the dextral Davie Fracture Zone. The Seagap fault then remained active after the cessation of both seafloor spreading in the Somali basin and strike‐slip activity on the Davie Fracture Zone, till nowaday. Its architecture is structurally expressed through the sequence of releasing and restraining bends dating back at least to the early Neogene. Seismic sections and horizon maps indicate that those restraining bends are generated by strike‐slip reactivation of Cretaceous structures till the Miocene. Finally based on the interpretation of edge‐enhanced reflection seismic surfaces and seafloor data, we shows that, by the late Neogene, the Seagap fault zone switched to normal fault behaviour. We discuss the Seagap fault's geological and kinematic significance through time and its current role within the microplate system in the framework of the East African rift, as well as implications for the evolution and re‐activation of structures along sheared margins. The newly integrated datasets reveal the polyphase deformation of this margin, highlighting its complex evolution and the implications for depositional fairways and structural trap and seal changes through time, as well as potential hazards.
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Origin of Lower Cretaceous quartzose arenites in northern India and the Indus Basins of Pakistan—The result of provenance composition, weathering or diagenesis?
Authors Hazel Beaumont, Stuart D. Burley, Tim Breitfeld, Thomas Gould and Stuart M. Clarke[Palaeogeographical reconstruction displaying the provenance terrains exposed across the northern Indian Plate in the Lower Cretaceous Epoch able to provide sediment detritus delivered to the Barmer and Cambay basins. Variations in detrital mineralogy across the WIRS and LMIB result from fluvial transport systems sourced from multiple highs and controlled by the rift palaeogeographies. It’s like the failed rifts of the Barmer and Cambay basins form a natural transport barrier that precluded the transport of detritus from the Aravalli Mountain Range across these deep rifts into the more westerly rift basins of the Kachchh and South Indus basins.
Lower Cretaceous (Aptian‐Albian) sandstones of the Ghaggar‐Hakra Formation in the Barmer Basin of northwest Rajasthan, India, have a complex depositional history which is confusing given they are quartzose arenites. The heavy mineral grains are very well‐rounded, and the assemblage is dominated by zircon and rutile grains suggesting that the sediments have been recycled multiple times, whilst the presence of staurolite indicates a metapelite provenance component. Petrographical analysis suggests that extreme diagenesis cannot account for the quartzose arenite composition, despite Early Cretaceous soil formation and at least two periods of subsequent telogenetic modification. An alternative explanation to extreme chemical weathering in the provenance area is that the Ghaggar‐Hakra sandstones are multi‐cycle sediments derived, at least in part, from the quartzose arenites of the Cambrian Jodhpur Group. This analysis suggests that variations in detrital mineralogy across the Western India Rift System and Indus Basins are the result of transcontinental fluvial transport systems sourcing sediment from specific basement highs (Nagar Parker High, Devikot High, Deodar Ridge and Aravalli Mountain Range) mixed with varying proportions of sediment derived from sandstones of the Jodhpur Group. Consequently, we suggest that Cretaceous fluvial systems were controlled by the local palaeogeographies within the failed rifts of the Barmer and Cambay Basins and that both basins formed barriers to sediment transport from the Aravalli Mountain Range across the northwest Indian plate and into surrounding basins.
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Joint inversion of temperature, vitrinite reflectance and fission tracks in apatite with examples from the eastern North Sea area
Authors Søren B. Nielsen and Niels Balling[AbstractAs sediment accumulation indicates basin subsidence, erosion often is understood as tectonic uplift, but the amplitude and timing may be difficult to determine because the sedimentary record is missing. Quantification of erosion therefore requires indirect evidence, for example thermal indicators such as temperature, vitrinite reflectance and fission tracks in apatite. However, as always, the types and quality of data and the choice of models are important to the results. For example, considering only the thermal evolution of the sedimentary section discards the thermal time constant of the lithosphere and essentially ignores the temporal continuity of the thermal structure. Furthermore, the types and density of thermal indicators determine the solution space of deposition and erosion, the quantification of which calls for the use of inverse methods, which can only be successful when all models are mutually consistent. Here, we use integrated basin modelling and Markov Chain Monte Carlo inversion of four deep boreholes to show that the erosional pattern along the Sorgenfrei–Tornquist Zone (STZ) in the eastern North Sea is consistent with a tectonic model of tectonic inversion based on compression and relaxation of an elastic plate. Three wells in close proximity SW of the STZ have different data and exhibit characteristic differences in erosion estimates but are consistent with the formation of a thick chalk sequence, followed by minor Cenozoic erosion during relaxation inversion. The well on the inversion ridge requires ca. 1.7 km Jurassic‐Early Cretaceous sedimentation followed by Late Cretaceous–Palaeocene erosion during inversion. No well demands thick Cenozoic sedimentation followed by equivalent significant Neogene exhumation. When data are of high quality and models are consistent, the thermal indicator method yields significant results with important tectonic and geodynamic implications.
,Thermal model of Danish well Aars‐1.
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Stratigraphic record of continental breakup, offshore NW Australia—Discussion
Authors Tiago M. Alves, Marcos Fetter, Cathy Busby, Tiago A. Cunha and Nathalia H. Mattos[AbstractReeve et al. (2022) address the stratigraphic record of continental breakup by focusing on a set of stratigraphic unconformities from a proximal sector of the NW Australian continental margin, inboard from the Exmouth Plateau. They suggest that such unconformities can potentially document a well‐defined three‐stage process: end of the syn‐rift phase, formation of a wide continent‐ocean transition zone (COTZ) and generation of ‘true’ Penrose‐type oceanic crust. We counterargue that continental breakup is a protracted event that can only be understood via seismic‐ and chronostratigraphic correlations of strata, and their composing sequences, across and along rifted margins. Tying proximal stratigraphic unconformities to magnetic anomalies outboard from the study area in Reeve et al. (2022) is open to question. In parallel, we suggest that age resolutions of ca. 1 Ma are not achievable using the micropaleontological data presented in Reeve et al. (2022), with an important reworking of microfossil assemblages potentially occurring during the erosional process forming local and regional unconformities. Our discussion addresses these points in more detail.
,Seismic profile from Northwest Iberia showing an older Breakup Sequence A, which relates to continental breakup in the Tagus Abyssal Plain, and Breakup Sequence B above, correlated with continental breakup in the Iberia Abyssal Plain.
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Volumes & issues
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Volume 36 (2024)
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Volume 35 (2023)
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Volume 34 (2022)
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Volume 33 (2021)
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Volume 32 (2020)
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Volume 31 (2019)
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Volume 30 (2018)
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Volume 29 (2017)
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Volume 28 (2016)
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Volume 27 (2015)
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Volume 26 (2014)
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Volume 25 (2013)
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Volume 24 (2012)
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Volume 23 (2011)
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Volume 22 (2010)
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Volume 21 (2009)
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