New data broadly confirm current models of the formation of the Eurasia Basin. These involve formation of a continental rift system in the zone of the future Eurasia Basin in the Paleocene (66–56 Ma). This was followed by the first phase of opening of the Eurasia Basin with the formation of normal oceanic crust at 56–45 Ma, and ultra-slow spreading of the oceanic crust 45–0 Ma. The Eurasia Basin comprises two main segments: (1) the Eurasia Basin itself with volcano-tectonic ridges perpendicular to the rift axis; (2) the Peri-Laptev Sea Basin with a spreading rate < 7 mm/year and lacking perpendicular volcano-tectonic ridges. In the transition zone from the Gakkel Ridge to the Laptev Sea shelf, detailed bathymetry and seismic data reveal a thick layer of young sediments which include MTDs and channel systems. These sediments partially overlap the zone of continuation of the Gakkel-Sadko rift. Sediment transport originated from the distal parts of the Yana, Lena and Olenek river deltas. There are no transform faults or large shifts in the transition zone from the Gakkel Ridge to the shelf area. On the Eurasia Basin side, the spreading rate on the Gakkel Ridge (Sadko Rift) decreases significantly towards the continental slope. A zone can be preliminarily identified over which the spreading rate reduces to zero. This zone transforms into a wider continental rift in the upper part of the continental slope. This continental rift is then replaced on the shelf by a wide zone of scattered seismically active faults. Synchronous with ultra-slow spreading on the Gakkel Ridge were phases of intraplate extension forming normal faults in a strip about 1300 km wide reaching into the Amerasia Basin.

The Amerasian and Eurasian basins are distinguished in the Arctic Ocean and are separated by the Lomonosov Ridge. The Canadian Basin, with Cretaceous oceanic and transitional crust, is located in the southern part of the Amerasian Basin. The Alpha-Mendeleev Rise and its associated deep-sea basins (Podvodnikov, Makarov, Toll, Nautilus, and Stefansson) lie to the north of the Canadian Basin. The Alpha-Mendeleev Rise and associated basins have continental crust that has been altered to varying degrees. Their major formation occurred about 125–90 Ma. We discuss three models for the formation of the Canadian Basin. Model-1: the entire Amerasian Basin with the oceanic and transitional crust was formed first (before 125 Ma). The Alpha-Mendeleev Rise region was then formed on the earlier oceanic crust as a volcanic formation (125–90 Ma). Model-2: the Canadian Basin formed first (before 125 Ma). The Alpha-Mendeleev Rise area and associated basins were then formed due to the significant transtension of the continental crust and magmatism (125–90 Ma). Model-3: The Alpha-Mendeleev rise area and associated basins formed first above a mantle plume (125–100 Ma). Subsequently, along one of the branches of continental rifting, spreading of the transitional and oceanic crust began and the Canadian Basin was formed (100–70 Ma). We find Model-1 to be the least probable, because it is now proven that the Alpha-Mendeleev Rise is underlain by continental crust. Model-2 and Model-3 are both possible. According to these models, the Canadian Basin formed as a backarc basin of the Pacific subduction zone.

Recently-acquired, high-quality seismic reflection profiles document the presence of possible carbonate deposits on the Mendeleev Rise in the Arctic Ocean during the Paleocene-Eocene Thermal Maximum and the Early Eocene Climatic Optimum. These deposits are concentrated at the crests of bathymetric highs and consist of clusters of buildups comprising small patch reefs overlain by larger, coalesced platforms, followed by back-stepped higher-relief platforms. The small buildups commonly are similar to 100-500 m in diameter and 50-100 m in height. The larger platforms are up to 3-7 km wide and up to 400 m thick. Some of the larger buildups are characterized by internal horizontally layered architecture, whereas others are characterized internally by clinoforms suggesting progradational growth. A common characteristic of these buildups is that they tend to achieve a common height (i.e., their tops align along the same level), typical of buildups sensitive to growth within the photic zone, whose upward growth is limited by sea level. The succession of buildup styles indicates carbonate factories under the influence of accelerating relative sea-level rise, which culminated in drowning and ultimate abandonment.

The tectonic evolution of the Arctic Ocean remains debated. We present a new interpretation of selected seismic profiles for the Amerasia Basin. We extend and correlate the seismic stratigraphy for the area from the AlphaMendeleev Rise to the Canada Basin. The seismic stratigraphy is tied to isotope ages of volcanic rocks. It shows that the Canada Basin postdates formation of the Alpha-Mendeleev Rise. We distinguish the following stages in the formation of the Amerasia Basin: Stage 1. Jurassic-Neocomian formation of continental rifts. Stage 2. Barremian (Aptian)-Albian (125-100 Ma) large-scale extensional tectonics and magmatism in the AlphaMendeleev Rise and adjacent basins, formation of SDR-type complexes and failed passive volcanic continental margins. Continental rifting occurs with local formation of SDR-type complexes in the future Canada Basin. Stage 3. Late Cretaceous (100-70 Ma) back-arc opening of the Canada Basin with rotation of Alaska toward the Pacific Ocean. Transitional crust and highly stretched (hyper-extended) continental crust formed first, followed by oceanic crust. Sea-floor spreading propagated toward the Nautilus Basin and the Alpha-Mendeleev Rise. Large submarine volcanoes formed during late stages of the opening. Stage 4. ca. 70-56 Ma formation of graben systems in the 78 & ring;N Basin, Stefansson Basin, north and east of the Chukchi Borderland. Stage 5. Cenozoic general subsidence of the basin and formation of normal faults north of the Chukchi Borderland. Amerasia Basin formation began just after the end of the Verkhoyansk-Chukotka collision orogeny and South Anyui Ocean closure, simultaneously with orogenic collapse.

The Arctic Cretaceous Tectonic and Igneous Mega-Province (Arctic TIMP) was active in the period 125-80 Ma. We define a TIMP as a region that is large on a global scale and experiences widespread magmatism and tectonic extension. This province has three main domains: (1) the North Atlantic with its continental rifting, (2) the High Arctic Large Igneous Province (HALIP – the Arctic Ocean and some islands), and (3) part of the Verkhoyansk-Chukotka Orogen where collapse, extension and magmatism occurred. The classical HALIP regional domain has three main elements: (1) intraplate basalt plateau traps (flood basalts), (2) areas of intraplate intrusive magmatism (dykes and sills), and (3) the Alpha-Mendeleev LIP magnetic domain. Nine magmatic seismic facies for the Alpha-Mendeleev LIP magnetic domain are recognized, including SDRs, half-grabens with SDR-like units, layered horizontal volcanic flows and large volcanic constructions. New data support the hypothesis that below all the magmatic seismic facies lies continental crust stretched on different scales and intruded by basalts. Three possible stages of HALIP-age magmatism and tectonics are recognized: (1) formation of basalt trap-type plateaus (±125-120 Ma); (2) synrift and postrift magmatism with SDR units containing both tholeiitic and alkali basalts in the Alpha-Mendeleev region along with conjugate basins (±120-100 Ma); and (3) formation of a number of large, Fedotov-type volcanic constructions in the Alpha-Mendeleev region (±100-80 Ma). At about 120 Ma orogenic collapse started in Verkhoyansk-Chukotka Orogen. The collapse was accompanied by regional uplift and magmatism. Granitoid syn-extension magmatism occurred commonly throughout the area. A large part of the land was covered by volcanics with variable compositions. Rift valleys were common. Orogenic collapse ended at about 100 Ma. The general timing of the orogenic collapse, extension, and magmatism in the Verkhoyansk-Chukotka region coincides with magmatic and tectonic events in the HALIP. The Arctic TIMP formed as a single, connected geodynamic system.

Data collected by several expeditions to the Arctic Ocean have yielded a seismic stratigraphic framework and basin fill history for the Alpha-Mendeleev Rise (AMR) and adjacent Podvodnikov, Makarov, North Chukchi, Toll, Mendeleev, Nautilus and Stefansson basins. The AMR comprises a double-sided volcanic passive margin formed in Aptian-Albian time. The North Chukchi, Podvodnikov, Toll, Mendeleev, Nautilus, and Stefansson basins formed synchronously with the Alpha-Mendeleev Rise as failed micro-oceanic basins. Their formation started with rifting and volcanism at ti 125 Ma and ended at 100- 90 Ma. Ages are constrained by new isotope magmatic rock ages. The region now comprising the Amerasia Basin was in an intraplate tectonic setting during Aptian-Albian times. On the Mendeleev Rise seismic units interpreted as seaward-dipping reflectors (SDRs) form wedges separated by highs. We propose an axial line along the Mendeleev Rise that separates probable half-grabens of different polarity. On the western slope of the Rise, all bright reflections have westward dips, while on the eastern slope they have eastward dips. SDR-like seismic units are common within the adjacent basins as well. Gravity/magnetic crustal modelling for two regional seismic lines demonstrate that the Mendeleev Rise and adjacent basins are associated with stretched continental crust.& COPY; 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Abstract The Alpha-Mendeleev Rise is located in the Amerasia Basin. The work is based on a synthesis of interpretation of regional 2D MCS seismic profiles and data from rock sampling using special underwater vehicles on the slopes of seamounts. The Rise is represented by alternation of highs (horsts) and half-grabens. At the base of the horst cover, bright reflectors are distinguished, which are interpreted as volcanics. Half-graben sections are wedge-shaped and are similar in geometry to seaward-dipping reflectors (SDRs) of continental passive volcanic margins. Rock sampling has shown that the horsts are composed of sedimentary rocks of Paleozoic age, penetrated by intrusions. Aptian-Albian sections with volcanics (basalts, trachybasalts, trachyandesites) were identified on the horsts. U/Pb dating of igneous rocks showed that typical age of rocks is 110-114 Ma. Magmatic Cretaceous rocks contain zircons with ages ranging from pre-Barremian Mesozoic to Precambrian. The presence of these ancient zircons indicates that the Alpha-Mendeleev Rise is composed of continental crust. A model of the crustal structure of the Alpha-Mendeleev Rise is proposed. The upper and lower crust is approximately 20-30% saturated with intrusions of basic composition. At the base of the crust, a high-velocity layer up to 5 km thick is distinguished.

&lt;p&gt;We present an interpretation of the regional seismic lines for the Amerasia Basin, and new data from analyses of rocks from the Alpha-Mendeleev Rise. This report is based primarily on interpretation of 2D seismic lines and analysis of magnetic and gravity field anomalies, from data acquired through the Russian Arktika-2011, Arktika-2012, Arktika -2014, and Arktika-2020 projects. We use also open Canadian seismic data (Shimeld et al., 2021) and published data. We propose that the Alpha-Mendeleev Rise is a Eurasian aborted double-sided volcanic passive continental margin with stretched and hyper-extended continental crust intruded by basalts. This rise has a number of SDR-like seismic units. The age of volcanism is ~125-100 Ma. The Podvodnikov, Toll, Mendeleev, Nautilus, Stefansson basins have SDR-like seismic units. The top of SDR-like units has a similar age in all basins. The Alpha-Mendeleev Rise has an axis of symmetry. The East North Chukchi, Toll, Mendeleev, Nautilus, Stefansson basins are coeval basins with very stretched continental crust. They are connected by a long united axial line of hyperextension, subsidence and volcanism.&amp;#160; The Makarov, Podvodnikov, West North Chukchi basins are coeval basins with very stretched continental crust. They are connected by a long united axial line of hyperextension, subsidence and volcanism.&amp;#160; The Alpha-Mendeleev Rise and all mentioned basins originated simultaneously in the same geodynamic environment during the HALIP magmatic epoch at nearly 125-100 Ma. This study was supported by the Russian Science Foundation (Grant 22-27-00160).&lt;/p&gt;

With the advent of widely available 3D seismic data, numerous workflows focused on extracting subsurface stratigraphic information have been developed. We present here tools and rules that can maximize the amount of geologic information that can be extracted from seismic volumes. The fundamental principle enhancing the value of geologic insights extracted from seismic data is the integration of two disciplines: (1) seismic stratigraphy (i.e., images derived from section views that yield insights into stratigraphic architecture); and (2) seismic geo-morphology (i.e., images derived from plan views that yield insights into paleo-landscapes). Both disciplines leverage the possibility of generating subsurface images in 3D with the objective of interpreting depositional environments and better predict lithofacies distribution both spatially and temporally. A second principle is that interpretation of geologically meaningful patterns derived from these two disciplines must be in agreement with each other. That is, interpretations based on observations from the geomorphological domain must be corrob-orated by interpretations based on observations from the stratigraphic domain, and vice versa. To achieve this, the workflows presented here illustrate multiple analytical approaches, which include: (1) initial reconnaissance through 3D volumes in several observational domains (e.g., section, plan and perspective views) with various slicing techniques and animation tools; (2) detailed focus on features of geologic interest that have been iden-tified through reconnaissance, with further investigation through a combination of detailed slicing, horizon picking and seismic attributes calculation; and (3) comprehensive integration of seismic geomorphologic with seismic stratigraphic analyses to ensure consistent and reasonable interpretation of depositional environments and lithofacies. Context is highlighted as a critical underlying aspect of these workflows to help differentiate between reasonable and unreasonable interpretations, which constitutes a third principle of seismic stratigraphy and seismic geomorphology. It is not uncommon that a pattern observed in section or map view might be a non-unique indicator of a depositional environment; hence, knowing the context can be critical in making the correct geological interpretation of these non-unique patterns. From past to future, seismic stratigraphy and seismic geomorphology are two disciplines that, when integrated, play a fundamental role in resource exploration / production (e.g., hydrocarbon, water, hydrogen) and carbon storage, as well as providing enhanced under-standing of the past evolution of Earth and prediction of its future (e.g., sea level and climate). Hence, awareness of the broad range of workflows available to extract geologic insights from seismic data is critical for both applied and fundamental sciences.

Over a period of the past 15-20 years, the Russian Government implemented the Arctic Mega Project for geological and comprehensive study of the Arctic Ocean. In this paper we discuss the methods that were used in the implementation of this project. In the course of several expeditions, multiple types of data were acquired, which included: (1) seismic data of different types, (2) subbottom profiler data, (3) geological sampling on slopes of the Mendeleev Rise with the use of special equipment, (4) borehole drilling, (5) gravity and magnetic anomalies, (6) offshore geodetic data, (7) multi-beam bathymetry surveys, and (8) field surveys on multiple Arctic islands. Several nuclear icebreakers and a scientific research submarine were deployed in these operations. Specifically, more than 23,000 km of 2D multi-channel seismic lines and more than 4000 km of wide-angle refraction/reflection seismic lines were acquired, in addition to subbottom profiles for the Eurasia Basin and new bathymetric data of the Arctic Ocean. The new database is intended to facilitate the development of new insights into Arctic geology and geodynamics and contribute to a better understanding of the structure and tectonic evolution of the Arctic Ocean as a whole.

A seismic stratigraphic framework and basin fill geohistory for Arctic Ocean basins is presented based on data collected by several Russian Government organized expeditions to the Arctic Ocean. This analysis tied together seismic stratigraphic interpretations for the shelf and the deep-water part of the ocean. The stratigraphic framework is based on age data derived from linear magnetic anomalies in the Eurasia Basin, borehole data for the Lomonosov Ridge and Alaska Shelf, and correlations with various regional geological events. Six seismic boundaries were identified and traced regionally over large areas. We present as a hypothesis that the Arctic Ocean probably was formed during four phases with different kinematics: 133-125 Ma-Canada Basin opening, 125-80 Ma-superplume-related tectonics and magmatism in the Alpha-Mendeleev Rise area and adjacent basins, 80-56 Ma - strike-slip fault tectonics, and 56-0 Ma-Eurasia Basin opening. The time interval of 45-20 Ma appears to be a period of large-scale vertical intraplate movements and normal faulting. Climatic events are recorded in the sedimentary cover of the Arctic Ocean. The analyses were based on a comprehensive dataset that included more than 23,000 km of 2D seismic lines, which were acquired in the deep-water part of the ocean, supplemented by a large number of federal and commercial seismic lines, which were acquired for the Russian shelves during the past 10-15 years. In addition, special multiple Russian expeditions collected samples on scarps of the Mendeleev Rise that served as ground truth for the seismic interpretation.

We present an atlas of paleogeographic and paleotectonic maps which documents major events in the Arctic for 0-157 Ma. We demonstrate that the Mendeleev Ridge has a continental basement. The following chronology of events in the history of the Arctic Ocean is proposed: (1) Jurassic: continental rifting in the area of the SverdrupBanks basins and in the area of the present-day Canada Basin; a system of continental-margin volcanic belts formed in the region of Chukotka and the Verkhoyansk-Omolon; (2) Berriasian-Barremian: formation of the continental-margin Verkhoyansk-Chukotka Orogen; fast opening of Canada Basin (similar to 133-125 Ma); (3) AptianAlbian: formation of continental igneous provinces, rifting and magmatism in the area of the AlphaMendeleev ridges; rifting in the Ust'-Lena, Anisin, North-Chukchi, Podvodnikov and Toll basins; (4) Cenomanian-Campanian: intraplate magmatism in the area of the Alpha-Mendeleev ridges; (5) CampanianMaastrichtian: a likely start of compressional deformations in the area of the Chukchi Sea; (6) Paleocene: formation of the continental-margin orogen; continental rifting along the present-day Eurasia Basin and the Ust'Lena Basin; (7) Early-Middle Eocene: onset of opening of the Eurasia Basin started; (8) Middle-Late Eocene: a major restructuring of paleogeography of the Arctic took place at ca. 45 Ma with subaerial emergence of the Barents and Kara Sea shelves and onset of ultra-slow spreading of the Gakkel Ridge, and start of the epoch of formation of normal and strike-slip faults on the Lomonosov and Alpha-Mendeleev ridges and on the shelves of the Chukchi and East Siberian seas. Paleoclimate is discussed in connection with changes in the paleogeography.

The paper by Teillet et al., 2020b constitutes a detailed sedimentological study of the upper part of the Yadana carbonate platform (offshore Myanmar). However, the limited consideration and integration of the 3D seismic data results in a study lacking critical context, with the authors concluding that the Yadana Platform developed under strict oligo-mesophotic conditions and presents a layer-cake architecture with laterally continuous lithofacies. We suggest that the interpretations of Teillet et al., 2020b are not adequately supported because: (1) lithostratigraphic principles are applied to correlate the main lithofacies from four wells using core data across a wide platform (10–20 km); (2) the core data presented are restricted spatially as well as in depth, and are not laterally and vertically representative of the entire platform, hence these core data cannot be solely used to justify the lateral continuity of lithofacies and absence of euphotic depositional environments in the Yadana Platform; (3) the study is not integrated within a comprehensive chronostratigraphic framework and sedimentological observations are not connected in a systematic way; and (4) information extracted from the analysis of seismic facies and seismic geomorphology are ignored, even though lateral variability is observable on seismic within the platform (i.e., variability in depositional features and geometries). Seismic stratigraphy and seismic geomorphology should be considered because they allow the integration of any paleogeographic study into a comprehensive chronostratigraphic framework where 3D seismic data are available. These comments aim at stimulating a discussion on the value of seismic stratigraphy and seismic geomorphology, which should not be dismissed, to better document the evolution of carbonate platforms through time and space, and accurately assess controls on platform architecture and evolution.

ABSTRACT Stratigraphic models typically predict accumulation of deep-water sands where coeval shelf-edge deltas are developed in reduced-accommodation and/or high-sediment-supply settings. On seismic data, these relationships are commonly investigated on a small number of clinothems, with a limited control on their lateral variability. Advanced full-volume seismic interpretation methods now offer the opportunity to identify high-order (i.e., 4th to 5th) seismic sequences (i.e., clinothems) and to evaluate the controls on shelf-to-basin sediment transfer mechanisms and deep-water sand accumulation at these high-frequency scales. This study focuses on the Lower Barrow Group (LBG), a shelf margin that prograded in the Northern Carnarvon Basin (North West Shelf, Australia) during the Early Cretaceous. Thanks to high-resolution 3D seismic data, 30 clinothems (average time span of ∼ 47,000 years) from the D. lobispinosum interval (142.3–140.9 Ma) are used to establish quantitative and statistical relationships between the shelf-margin architecture, paleoshoreline processes, and deep-water system types (i.e., quantitative 3D seismic stratigraphy). The results confirm that low values of rate of accommodation/rate of sediment supply (δA/δS) conditions on the shelf are associated with sediment bypass, whereas high δA/δS conditions are linked to increasing sediment storage on the shelf. However, coastal process regimes at the shelf edge play a more important role in the behavior of deep-water sand delivery. Fluvial-dominated coastlines are typically associated with steep slope gradients and more mature, longer run-out turbidite systems. In contrast, wave-dominated shorelines are linked to gentle slope gradients, with limited development of turbidite systems (except rare sheet sands and mass-transport deposits), where longshore drift currents contributed to shelf-margin accretion through the formation of extensive strandplains. In this context, reduced volumes of sand were transported offshore and mud belts were accumulated locally. This study highlights that variations from fluvial- to wave-dominated systems can result in significant lateral changes in shelf-margin architecture (i.e., slope gradient) and impact the coeval development of deep-water systems (i.e., architectural maturity). By integrating advanced tools in seismic interpretation, quantitative 3D seismic stratigraphy represents a novel approach in assessing at high resolution the controls on deep-water sand delivery, and potentially predicting the type and location of reservoirs in deep water based on the shelf-margin architecture and depositional process regime.

Seismic amplitude has played a critical role in the exploration and exploitation of hydrocarbon in West Africa. Class 3 and 2 amplitude variation with offset (AVO) was extensively used as a direct hydrocarbon indicator and reservoir prediction tool in Neogene assets. As exploration advanced to deeper targets with class 1 AVO seismic character, the usage of seismic amplitude for reservoir presence and quality prediction became challenged. To overcome this obstacle, (1) we used seismic geomorphology to infer reservoir presence and precisely target geophysical analysis on reservoir prone intervals, (2) we applied rigorous prestack data preparation to ensure the accuracy and precision of AVO simultaneous inversion for reservoir quality prediction, and (3) we used lateral statistic method to sum up AVO behavior in regions of contrasts to infer reservoir quality changes. We have evaluated a case study in which the use of the above three techniques resulted in confident prediction of reservoir presence and quality. Our results reduced the uncertainty around the biggest risk element in reservoir among the source, charge, and trap mechanism in the prospecting area. This work ultimately made a significant contribution toward a confident resource booking.

The Vaca Muerta Formation consist of outer ramp to basinal facies in a mixed siliciclastic–carbonate creating an organic-rich section up to 500 m thick. This chapter documents stratal terminations, main bounding surfaces, and stacking patterns of the Vaca Muerta–Quintuco system as a means to establish a new sequence stratigraphic framework. The data set comprises more than 500 wells and a basin-scale seismic coverage that spans 30,000 km2 (11,583 mi2). Regional seismic interpretations and well correlations were calibrated with well geochemical data and acoustic impedance seismic sections. Twelve high-frequency depositional sequences (HFS) with variable combinations of systems tracts were defined and grouped in three low-frequency depositional sequences (LFS). Within this sequence stratigraphic framework, the Vaca Muerta Formation includes organic-rich (total organic carbon, TOC > 2wt. %) and organic-poor intervals (TOC < 2wt. %). At a high- frequency scale, the organic-rich intervals with the highest concentration of TOC belong to transgressive systems tracts and the lower sections within clinoform bottomset and foreset of highstand systems tracts. These condensed sections usually show the best reservoir properties in the self-sourced unconventional play. Conversely, organic-poor intervals are found in the foresets of falling-stage systems tracts and lowstand systems tracts. Condensed sections of each sequence allow subdivide the unconventional play in a stacking of 12 organic-rich Vaca Muerta units (OVM, TOC ≥ 2wt. %). The lowermost eight OVM units correspond to the main tested landing zones. Moreover, a detailed map of shelf breaks reveals a strong three-dimensional (3-D) spatial variability, which is summarized in four groups of plan-view geometries. The 3-D spatial variability of the organic-rich intervals is analyzed at local scale in two cases with different plan-view geometries. At regional scale, thickness maps of the main OVM units allow infer stratigraphic controls (e.g., systems tracts, previous clinoform paleo-topography) and tectonic controls, both regional (morphostructural domains) and local (subsidence axes and paleo-highs), active during the deposition of the Vaca Muerta Formation. The proposed sequence stratigraphic framework provides a predictive understanding of 3-D spatial distribution of the organic-rich intervals in subsurface assessments for the Vaca Muerta play and is applicable to the exploration of other analogous (mixed siliciclastic-carbonate systems) self-sourced unconventional resources.

Deep-water turbidites commonly are deposited in water depths below storm wave base. These depths range from a few tens of meters to thousands of meters. Turbidite systems tend to be most active when depocenters lie at or near shelf margins,and this proximity of depocenters to shelf margins tends to be associated most commonly with times of relative sea level lowstand. Deep water depositional episodes can be divided into early and late lowstand time. Deposition during early lowstand is characterized by progressively larger and more frequent flow events,whereas deposition during late lowstand is characterized by progressively smaller and less frequent flow events. Consequently,during early lowstand time,erosion of channels tends to dominate such that channels tend to become progressively deeper with minimal preservation of deposits within feeder channels;successive flows are overfit. Subsequently during late lowstand progressively smaller flows tend to be underfit resulting in preservation of channel fill deposits. Turbidite systems tend to be characterized by three discrete regions:Region 1 corresponds to the most proximal reaches of turbidite systems dominated by canyons that commonly are tributive. Region 2 corresponds to that part of the turbidite system characterized by a single feeder channel complex that was characterized by flows with heights greater than confining walls,hence associated with levees. Region 3 corresponds to that part of the system distally, that is characterized by frequent avulsions and sand-prone overbank as well as channel-fill deposits,which can be described geomorphologically as a terminal fan. From a process perspective,Region 3 can be described as a frontal splay. From a sequence stratigraphic perspective,lowstand deposits commonly are bracketed by mud prone distal highstand and transgressive systems tract deposits. The succession of early to late lowstand deposition commonly is characterized by sand-rich Region 3 fan deposits overlain by leveed channel deposits of region 2.

The Barrow Group was deposited in the Northern Carnarvon Basin from the latest Tithonian to the Late Valanginian. This moderately deep-water shelf-margin is composed of ~100–500m high clinoforms that prograded during a syn-rift to post-rift transition. Integration of well data with extensive 2D and 3D seismic data was used to constrain the stratigraphic evolution of the Barrow Group in seven 3rd order seismic sequences (calibrated to dinocyst zones) across four main depocentres. Five shelf-margin categories were recognized based on stratal stacking patterns, the trajectory styles and angles (Tse), and the progradation/aggradation ratios (Pse/Ase) that were interpreted in terms of rates of accommodation creation and sediment supply (A/S ratio). Following the uplift of the Southern Carnarvon Basin (sediment source), the stratigraphic evolution of the Barrow Group developed in three stages. During the first stage (late syn-rift I; 148–143.5Ma), the shelf-margin prograded in a period of tectonic quiescence with relatively limited subsidence. During the second stage (late syn-rift II; 143.5–138.2Ma), the shelf-margin was affected by increasing rates of accommodation and high sediment supply, which reflects an active period of rifting triggering both tectonic subsidence in the basin, and active uplift in the hinterland. During the third stage (early post-rift I; 138.2–135.4Ma), the uplift of the continental shelf, following continental break-up, provided a new local source of sediment supply to the Barrow Group that then developed as a passive margin. The Lower Barrow Group (late syn-rift I and II) mainly developed under supply-dominated conditions. However, lateral variations in subsidence regime and shifts in sediment supply led to significant variations in shelf-margin architecture along-strike, directly impacting sediment partitioning between the shelf and the deep-water areas. Flat shelf-edge trajectories were associated with sediment bypass and increase in bottomset thicknesses, whereas rising shelf-edge trajectories were linked with sediment storage on the shelf. In contrast, the Upper Barrow Group (early post-rift I) developed in low-supply conditions with slow thermal subsidence, reflecting the passive context of the margin at this time. The Barrow Group provides a unique example of how rift tectonics can control the stratigraphic architecture of a regressive margin and reciprocally, how studying shelf-margin architecture can help constraining the dynamics and timing of rifting around the break-up stage.