Refining the Mungaroo Formation and Lower Barrow Group depositional models, Exmouth Plateau, North Carnarvon Basin: WA-390-P phase II exploration

2011 ◽  
Vol 51 (2) ◽  
pp. 713
Author(s):  
Jon Minken ◽  
Phil Cox ◽  
Sandy Buchanan ◽  
Dean Griffin ◽  
Yohan Kusumanegara ◽  
...  
Keyword(s):  
Depositional Environments ◽  
Sediment Supply ◽  
Late Triassic ◽  
3D Seismic ◽  
Composite Surface ◽  
Exmouth Plateau ◽  
Shelf Slope ◽  
Basin Floor ◽  
Sand Bodies ◽  
Depositional Models

Permit WA-390-P, in Australia’s Exmouth Plateau, has been the subject of an extensive exploration drilling campaign with gas discovered in the Late Triassic Mungaroo Formation and the Cretaceous Lower Barrow Group. Characterisation of these reservoirs with 3D seismic data, well logs, core and biostratigraphic information has allowed insight and refinement to the previously established depositional models. The Mungaroo Formation comprises a thick succession (more than 2 km) of delta plain deposits characterised on 3D seismic by channel morphologies of differing sizes and orientations. Well penetrations in the channels reveal sand-bodies that can be classified as either single-storey or multistorey. Single-storey sand-bodies are thin (less than 15 metres), narrow in planform (less than one kilometer), lack evidence of lateral accretion and occasionally exhibit a funnel geometry. Multistorey channels are characterised by relatively thick, vertically and laterally amalgamated sand-bodies (more than 15 metres), in a broad channel morphology (more than one kilometer) bounded at its base by a composite surface of erosion. Single-storey channels have been interpreted as distributary channels and multistorey channels as incised valleys. In contrast, the Lower Barrow Group is a contemporaneous wave-dominated delta and slope-to-basin-floor sediment gravity flow system. The depositional environments formed progradational clinoform seismic stratigraphic units that filled accommodation generated during rifting. The delta is organised into arcuate to cuspate lobes that show changes in the shelf-slope trajectory with variations in accommodation and sediment supply. During falling trajectories of the shelf-slope break, the slope is demarcated by gullies forming a line of feeder systems that transport sediment from the delta shoreface into the deep-water. The sediment gravity flows formed coalescing fans that blanket the toe-of-slope and basin floor.

Sedimentary System and Sand Bodies Distribution of the 2nd Member of Xujiahe Formation in Xinchang Area, Western Sichuan Depression, China

2021 ◽  
pp. 1-54
Author(s):  
Xiaofei Shang ◽  
Meng Li ◽  
Taizhong Duan
Keyword(s):  
Sediment Supply ◽  
Late Triassic ◽  
Gas Reservoirs ◽  
Xujiahe Formation ◽  
Western Sichuan ◽  
Sand Body ◽  
Sedimentary System ◽  
Western Sichuan Depression ◽  
Sand Bodies ◽  
Distributary Channel

The Xujiahe Formation of Late Triassic in the Western Sichuan Depression contains abundant gas reservoirs. Influenced by the thrust tectonic movement of foreland basin, the fluvial-delta sedimentary system supplied by multiple provenances formed the Xu2 Formation of the Xinchang area. We used detailed description of drilling wells and cores to define the sequence stratigraphic framework and sand body types. We used stratal slices through the seismic volume to map the evolution of the sedimentary system and the sand body distribution. The results show that the Xu2 Formation exhibits a complete long-term base-level cycle, and there are six sand body deposit types: distributary channel, inter-channel, subaqueous distributary channel, inter-distributary bay, mouth bar and sheet sand. Stratal slices through the seismic volume at different levels map the spatial variation of sand and mudstone, which we use to construct a sedimentary filling evolution model. This model indicates that during the time of deposition of the Lower Sub-member the main provenance supply came from the NW direction, resulting in the sand bodies mainly deposited in the west. During the time of depositon of the Central Sub-member, sediment supply was large and came from both the NW and NE directions, resulting in large, laterally extensive, thick sands. During the time of deposition of the Upper Sub-member, sediment supply was from the NE direction, with the sand bodies more developed in the east. The flow direction of the channels indicate that they migrated from northwest to northeast. There are differences in channel energy, sedimentary characteristics and reservoir physical properties in the three Sub-members, which cause differences in natural gas productivity of Xu2 Formation. We believe that detailed mapping the spatial distribution of sedimentary systems can provide critical guidance to not only explore, but also to develop in high-quality oil and gas reservoirs like Xu2 Foramtion.

scholarly journals New approach to appraise non-structural Tyumen formation traps in the absence of high quality of data

2021 ◽  
Vol 6 (3) ◽  
pp. 43-51
Author(s):  
Evgeniia M. Viktorova ◽  
Daria I. Zhigulina ◽  
Pavel Y. Kiselev ◽  
Vladimir Y. Klimov
Keyword(s):  
Seismic Data ◽  
Depositional Environments ◽  
3D Seismic ◽  
Quality Of Data ◽  
Resource Base ◽  
High Quality ◽  
Blind Test ◽  
Sand Bodies ◽  
3D Seismic Data

Background. On the one hand, the focus of exploration works changes to the more difficult reserves side, which were basically accumulated in the non-structural traps of Achimov and Tyumen formations. On the other hand, there are two important questions. The first is how the volume of reserves should be estimated correctly and the second is which volume of reserves is enough for economic successfully development. Aim. The main aim is to create a new actual approach of non-structural traps appraisal is considered in the absence of high quality of seismic data which allows identify such types of traps, which allows identify such types of traps. Materials and methods. Presented at the article algorithm enables estimate resources of non-lithological traps as exemplified in Tyumen formation, which was formed during depositional changes from continental to transitional depositional environments. The algorithm consists of some steps. The first step is collection on numbers, sizes and areas potential sand bodies based on different seismic attributes from analogies data. On the next step the coefficient which shows what numbers of geological bodies can be found on the unit of area was defined. Based on these data the probability distribution function which shows what part of studied area could be covered by potential bodies was made. After these steps, the integral resource base without regard to geological chance of success (gCoS) can be estimated. In order to account for geological risks the numbers of potential traps (including also non-structural traps), which were formed by meandering rives, tidal channels and point-bars, have to be defined. As a result, the discrete mathematical distribution of expected numbers of traps was made based on analogies data. If the oil infl ow was obtained from wells which have already drilled on the studied area part of resource base transfer to reserves (without including gCoS). Results. Discussed method was applied for “blind-test” on the new studied block with 3D seismic data. The obtained results of potential sand bodies fraction is correspond to the initial distribution from analogy fields. The method can be used for resource base potential on any block where there are lithological traps, which are controlled by mainly the facies conditions instead of structural plan, and also the 3D seismic data is absent. Conclusions. The appliance of discussed method which based on the available statistical data helps improve the quality estimation of change resource base range and allows to map the new prospective areas containing reserves and resources. One more important thing is this method allows to resolve the problem of base potential estimation and as a result to put a price on asset and risk capital values needed to explore the potential areas by drilling before the key outlays in the exploration program will be invested.

Controls on the sedimentary characteristics of shelf-edge deltas in a source-to-sink context

2021 ◽  
Author(s):  
Laura Bührig ◽  
Luca Colombera ◽  
Nigel P. Mountney ◽  
William D. McCaffrey
Keyword(s):  
Late Quaternary ◽  
Depositional Environments ◽  
Late Triassic ◽  
Hydrodynamic Process ◽  
Shelf Edge ◽  
Sea Level Changes ◽  
Sedimentary Characteristics ◽  
Shelf Slope ◽  
Source To Sink ◽  
Shelf Margin

<p>Shelf-edge deltas constitute important components of source-to-sink (S2S) systems. They distribute sediment to continental slopes and basin floors from rivers that have prograded across shelves, and due to their scale they form significant sediment accumulations at shelf margins. Because of their intimate relationship with regressive conditions, several geological controls govern their evolution, including relative sea-level changes, sediment budgets, river hydrology, and hydrodynamic processes; these factors are themselves influenced by characteristics of terrestrial catchments and continental shelves, and by climate. Despite their important role in sediment dispersal to shallow- and deep-marine environments, shelf-edge deltas are commonly overlooked in models that describe S2S systems, perhaps because of their relative paucity during the present-day highstand conditions. In subsurface and outcrop, their recognition can be difficult in cases where information with which to constrain the physiographic environment is limited, such that the spatial position of a delta relative to the shelf margin cannot be determined unequivocally.</p><p>This study aims to improve our understanding of controls on the sedimentary characteristics of shelf-edge deltas. For this purpose, >40 shelf-edge deltas of Late Triassic to late Quaternary age from >30 globally-distributed shelf-margin successions have been investigated, utilising literature-derived seafloor-, subsurface- and outcrop data. Following a database approach, sedimentary records have been quantitatively analysed in terms of geometry (e.g. dimensions, thickness, gradients) and facies characteristics (e.g. lithology, sedimentary structures) of depositional environments (e.g. delta top, delta front) and architectural elements (e.g. delta lobes, distributary mouth bars). Specific consideration has been given to assessment of palaeoenvironmental setting (e.g. hydrodynamic process regime, margin type, bathymetric setting, palaeolatitude). Moreover, scaling relationships between these properties and attributes of the S2S system (e.g. fluvial-system and catchment attributes, shelf configuration, shelf-slope transition) have been evaluated. Accordingly, the relative importance of controls on the sedimentary characteristics of shelf-edge deltas has been assessed.</p><p>This analysis demonstrates that environmental factors influence the sedimentary record of shelf-edge deltas via a complex interplay of dynamic processes and physiography of the S2S segments catchment, shelf and slope. Based on these findings, new facies models for shelf-edge delta types are developed, which are placed in the context of S2S linkages. Outcomes of this study aid the identification and classification of shelf-edge deltas and their preserved deposits, as well as the reconstruction of associated environmental conditions from stratigraphic records.</p>

scholarly journals Multi-Proxy Provenance Analyses of the Kingriali and Datta Formations (Triassic—Jurassic Transition): Evidence for Westward Extension of the Neo-Tethys Passive Margin from the Salt Range (Pakistan)

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 573
Author(s):  
Shahid Iqbal ◽  
Michael Wagreich ◽  
Mehwish Bibi ◽  
Irfan U. Jan ◽  
Susanne Gier
Keyword(s):  
Lower Jurassic ◽  
Sediment Supply ◽  
Heavy Mineral ◽  
Passive Margin ◽  
Indian Plate ◽  
Late Triassic ◽  
Indian Shield ◽  
Margin Setting ◽  
Salt Range ◽  
Mineral Data

The Salt Range, in Pakistan, preserves an insightful sedimentary record of passive margin dynamics along the NW margin of the Indian Plate during the Mesozoic. This study develops provenance analyses of the Upper Triassic (Kingriali Formation) to Lower Jurassic (Datta Formation) siliciclastics from the Salt and Trans Indus ranges based on outcrop analysis, petrography, bulk sediment elemental geochemistry, and heavy-mineral data. The sandstones are texturally and compositionally mature quartz arenites and the conglomerates are quartz rich oligomictic conglomerates. Geochemical proxies support sediment derivation from acidic sources and deposition under a passive margin setting. The transparent heavy mineral suite consists of zircon, tourmaline, and rutile (ZTR) with minor staurolite in the Triassic strata that diminishes in the Jurassic strata. Together, these data indicate that the sediments were supplied by erosion of the older siliciclastics of the eastern Salt Range and adjoining areas of the Indian Plate. The proportion of recycled component exceeds the previous literature estimates for direct sediment derivation from the Indian Shield. A possible increase in detritus supply from the Salt Range itself indicates notably different conditions of sediment generation, during the Triassic–Jurassic transition. The present results suggest that, during the Triassic–Jurassic transition in the Salt Range, direct sediment supply from the Indian Shield was probably reduced and the Triassic and older siliciclastics were exhumed on an elevated passive margin and reworked by a locally established fluvio-deltaic system. The sediment transport had a north-northwestward trend parallel to the northwestern Tethyan margin of the Indian Plate and normal to its opening axis. During the Late Triassic, hot and arid hot-house palaeoclimate prevailed in the area that gave way to a hot and humid greenhouse palaeoclimate across the Triassic–Jurassic Boundary. Sedimentological similarity between the Salt Range succession and the Neo-Tethyan succession exposed to the east on the northern Indian passive Neo-Tethyan margin suggests a possible westward extension of this margin.

Depositional environments and paleogeography in the Albian Moosebar Formation and adjacent fluvial Gladstone and Beaver Mines formations, Alberta

1984 ◽  
Vol 21 (6) ◽  
pp. 698-714 ◽  
Author(s):  
David R. Taylor ◽  
Roger G. Walker
Keyword(s):  
Brackish Water ◽  
Late Jurassic ◽  
Major Change ◽  
Depositional Environments ◽  
Fluvial Deposits ◽  
Maximum Thickness ◽  
The North ◽  
Major Exception ◽  
Flow Directions ◽  
Sand Bodies

The marine Moosebar Formation (Albian) has a currently accepted southerly limit at Fall Creek (Ram River area). It consists of marine mudstones with some hummocky and swaley cross-stratified sandstones indicating a storm-dominated Moosebar (Clearwater) sea. We have traced a tongue of the Moosebar southward to the Elbow River area (150 km southeast of Fall Creek), where there is a brackish-water ostracod fauna. Paleoflow directions are essentially northwestward (vector mean 318°), roughly agreeing with turbidite sole marks (329°) in the Moosebar of northeastern British Columbia.The Moosebar sea transgressed southward over fluvial deposits of the Gladstone Formation. In the Gladstone, thick channel sands (4–8 m) are commonly multistorey (up to about 15 m), with well developed lateral accretion surfaces. The strike of the lateral accretion surfaces and the orientation of the walls of channels and scours indicate northwestward flow (various vector means in the range 307–339°). The Moosebar transgression was terminated by construction of the Beaver Mines floodplain, with thick, multistorey sand bodies up to about 35 m thick. Flow directions are variable, but various vector means roughly cluster in the north to northeast segment. This indicates a major change in dispersal direction from the Gladstone and Moosebar formations.A review of many Late Jurassic and Cretaceous units shows a dominant dispersal of sand parallel to regional strike. This flow is mostly north-northwestward (Passage beds, Cadomin, Gladstone, Moosebar, Gates, Chungo), with the southeasterly dispersal of the Cardium being the major exception. Only at times of maximum thickness of clastic input (Belly River and higher units, and possibly Kootenay but there are no published paleocurrent data) does the sediment disperse directly eastward or northeastward from the Cordillera toward the Plains.

scholarly journals New data on the Dogger - Cenomanian stratigraphy of Tripolitza series in Central Crete

2018 ◽  
Vol 34 (2) ◽  
pp. 565
Author(s):  
Α. ΖΑΜΠΕΤΑΚΗ - ΛΕΚΚΑ ◽  
Α. ΑΛΕΞΟΠΟΥΛΟΣ
Keyword(s):  
Early Cretaceous ◽  
Late Eocene ◽  
Depositional Environments ◽  
Late Triassic ◽  
Late Paleozoic ◽  
Carbonate Microfacies ◽  
Aegean Islands ◽  
Lower Aptian ◽  
Sedimentation Conditions

Tripolitza series represents the eastern part of the Gavrovo - Tripolitza platform. It outcrops in central and southeastern Peloponnesus, Crete and the Aegean islands. Its stratigraphie column starts with a volcano-sedimentary, clastic sequences (the Tyros beds), of Late Paleozoic to Late Triassic age, followed by a carbonate series of Late Triassic to Late Eocene age and a tertiary flysch. On account of intense dolomitisation as well as of rarity of fossils, the stratigraphy of Tripolitza series is not so well known as the Gavrovo series. Recent investigation attempts to complete the puzzle of Tripolitza's stratigraphie column and to reconstruct the paleogeographic sedimentation conditions. In this paper, we study some stratigraphie sections, which are taken in different places in northern – central Crete(Fig.l). New data about the stratigraphy and the sedimentation conditions of the Tripolitza series during Late Dogger to Cenomanian, complete older ones and provide information about the paleogeographic evolution of the platform. Late Dogger is determinated by Pfenderina salernitana. It is overlain by a carbonate series containing Cladocoropsis mirabilis and Macroporella sellii, dating Early Malm. Early Malm (Oxfordian - Early Kimmeridgian) is characterized by the presence of Cladocoropsis mirabilis, Kurnubia palastiniensis, Neokilianina rahonensis, Parurgonina caelinensis. Late Malm (Late Kimmeridgian - Portlandian) is characterized by Clypeina jurassica and Kurnubia palastiniensis. Early Cretaceous (Valanginian - Barremian) is determinated by Salpingoporella katzeri and Orbitolinopsis capuensis. Early Aptian is determinated by Palorbitolina lenticularis, Salpingoporella dinarica, Debarina hahounerensis, Pseudocyclammina hedbergi. Late(?) Aptian comprises Sabaudia minuta, Cuneolina hensoni, Cuneolina laurentii, Glomospira urgoniana. Albian is characterized by the disappearence of Cuneolina hensoni and Cuneolina laurentii, while Praechrysalidina infracretacea and Cretacicladus minervini are present. Late Albian is determined by the presence of "Coskinolina" bronnimanni. Early Cenomanian is not determinated by characteristic microfossils. Upper Cenomanian is overlain in comformity with upper Albian - lower Cenomanian carbonates. It is characterized by Chrysalidina gradata, Pseudorhapydionina dubia, Pseudorhapydionina laurinensis, Nummoloculina heimi, Broeckina balcanica, Nezzazata gyra, Biconcava bentori, Trochospira anvimelechi. Sedimentation took place in a peritidal environment. We observe alternations of subtidal and intratidal to supratidal conditions of sedimentation. Comparison between the carbonate microfacies of different sections representing synchronous deposits on different places of the platform, show lateral differentiation of depositional environments, from subtidal to supratidal, even supported short and local emersive episodes, (compare lower Aptian deposits of Profitis Ilias and Pinakianou sections, upper Albian deposits of Kythia and Karouzanos sections in present paper, as well as upper Cenomanian deposits of Karouzanos section in this paper, Louloudaki section (ZAMBETAKIS-LEKKAS et al. 1995 and Vitina section ZAMBETAKIS et al. 1988, Varassova section BERNIER & FLEURY 1980, Gavrovo mountain I.G.R.S. & I.F.P. 1966)(Fig.2). Similar sedimentation characterize the perimediterranean platforms during this period (SARTONI & CRESCENTI 1962, DE CASTRO 1962, FARINACCI & RADOICIC 1964, GUSIC 1969, GUSIC, NIKLER & SOKAC 1971, VELIC 1977, CHIOCCHINI et. al.1979, LUPERTO SINNI & MASSE 1993).

Sedimentology and Evolution of the Fluvial-Deltaic System: A Modern Depositional Model Analog from the Red Sea Coastal Region, Saudi Arabia

2021 ◽  
Author(s):  
Osman Abdullatif ◽  
Mutasim Osman ◽  
Mazin Bashri ◽  
Ammar Abdlmutalib ◽  
Mohamed Yassin
Keyword(s):  
Red Sea ◽  
Coastal Plain ◽  
Depositional Environments ◽  
Hydrocarbon Reservoirs ◽  
Sediment Supply ◽  
Arabian Shield ◽  
Space And Time ◽  
Groundwater Aquifers ◽  
Coastal Sabkha ◽  
Lithofacies Association

Abstract Siliciclastic sediments represent important lithological unit of the Red Sea coastal plain. Their subsurface equivalents are important targets of groundwater aquifer and hydrocarbon reservoirs in the region. The lithofacies of the modern fluvial deltaic system has several distinct geomorphic units and sub-environments such as alluvial, fluvial, delta plain, aeolian, intertidal, coastal sabkha and eustuarine sediments. This study intends to characterize the lithofacies and the depositional environments and to produce an integrated facies model for this modern fluvial-deltaic system. The study might provide a valuable modern analog to several important subsurface Neogene formations that act as important hydrocarbon reservoirs and groundwater aquifers. The study integrates information and data obtained from landsats, maps and detailed field observation and measurements of facies analysis of the fluvial and deltaic along traveses from the Arabian Shield to the Red Sea coast. The lithofacies sediment analysis revealed four main lithofacies associations namely lithofacies A,B,C ad D. Lithoacies Associations A, which represents the oldest unit is dominated by coarse gravel with minor sands facies. While the lithofacies B is dominated byfine gravel and sand lithofacies, occasionally pebbly, vary from horizontal, planar to massive sands with minor laminated to massive silts and mud facies. The lithofacies in A and B show lateral proximal to distal variation as well as characteristic vertical stacking patterns. The Facies Association A and B indicates a change in fluvial depositional styles from gravelly alluvial fans to gravelly sandy fluvial systems. The lithofacies association C represents the recent fluvial system which consists of minor gravel lag deposits associated maily with various sand lithofacies of planner, horizontal and massive sand associated with massive and limainted sand and mud lithofacies. The lithofacies Association D is dominated with Barchan sand dunes local interfigger with muddy iinterdunes and sand sheets. Lithofacies D occupies rather more distal geomporphic position of the fluvial deltaic system that is adjace to coastal sabkha. The lithofacies associations described here document the evolution and development of the coastal plain sediments through space and time under various autocyclic and allocyclic controls. This included the tectonics and structural development associated with the Red Sea rifting and opening since the Oligocene – Miocene time. Others controls include the evolution of the Arabian shield (provenance) and the coastal plain through space and time as controlled by tectonics, sediment supply, climate and locally by autocyclic environmental This study might be beneficial for understanding the controls and stratigraphic evolution of the Red Sea region and will be of great value for reservoir and aquifer characterization, development and management. This modern analog model can also help in providing geological baseline information that would be beneficial for understanding similar ancient fluvial deltaic sediments. The study might provide guides and leads to understand the subsurface facies, stratigraphic architecture and heterogeneity of any potential groundwater aquifers and hydrocarbon reservoirs.

The Characterization of Stratigraphic Play in Middle Baong Sand for Hydrocarbon Prospecting in Offshore North Sumatera Basin

2021 ◽  
Author(s):  
A. Nurhasan
Keyword(s):  
Depositional Environment ◽  
Hydrocarbon Exploration ◽  
Ratio Distribution ◽  
Basin Floor ◽  
Distinct Character ◽  
Net To Gross ◽  
And Migration ◽  
Sand Bodies ◽  
Malacca Strait

Pertamina EP is operating a small block in Offshore North Sumatera Basin where a couple of the fields are producing gas and condensate from the Belumai Carbonate. However, the wells production is depleting and several delineation wells are unable to find additional reserves, it is important to find a new play within the block. Few discoveries in the Middle Baong Sand (MBS) reservoir suggested a promising stratigraphic play to be explored, but it requires more detailed characterization of the reservoir extent. The Malacca strait-sourced MBS consists of several deposited sand packages during a mega sequence. The term MBS might represent a deltaic environment from a transgressive system tract of some marine shore bar or a basin floor fan. Each system has a distinct character (thickness, net to gross ratio, distribution) that must be evaluated before proposing an exploration well. The depositional environment and reservoir distribution are interpreted and modeled using regional 2D seismic and high-quality 3D seismic. Paleo-bathymetric interpretation from well samples shows a good correlation with the palinspastic reconstruction. The result shows that the Pertamia EP working area is located in the shore bar depositional environment. Seismic attributes are used to delineate reservoir distribution within the working block and well logs are used to constrain prospective sand bodies and water zones identification. Furthermore, source rock maturation and migration path and hydrocarbon occurrence from the discovery wells have been evaluated for hydrocarbon prospecting and risking. This study suggests a promising lead for hydrocarbon exploration in the study area and opens up a new opportunity for an underexplored play.

scholarly journals Deciphering tectonic, eustatic and surface controls on the 20 Ma-old Burdigalian transgression recorded in the Upper Marine Molasse in Switzerland

2019 ◽  
Author(s):  
Philippos Garefalakis ◽  
Fritz Schlunegger
Keyword(s):  
Sea Level ◽  
Depositional Environments ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Crustal Material ◽  
Molasse Basin ◽  
Shallow Marine ◽  
Depositional Settings ◽  
Stratigraphic Architecture ◽  
Aar Massif

Abstract. The stratigraphic architecture of the Swiss Molasse basin reveals crucial information about the basin’s geometry, its evolution and the processes leading to the deposition of the clastic material. Nevertheless, the formation of the Upper Marine Molasse (OMM) and the controls on the related Burdigalian transgression are not fully understood yet. During these times, from c. 20 to 17 Ma, the Swiss Molasse basin was partly flooded by a peripheral shallow marine sea, striking SW – NE. We proceeded through detailed sedimentological and stratigraphic examinations of several sites across the entire Swiss Molasse basin in order to deconvolve the stratigraphic signals related surface and tectonic controls. Surface-related signals include stratigraphic responses to changes in eustatic sea level and sediment fluxes, while the focus on crustal-scale processes lies on the uplift of the Aar-massif at c. 20 Ma. Field examinations show, that the evolution of the Burdigalian seaway was characterized by (i) shifts in the depositional settings, (ii) changes in discharge directions, a deepening and widening of the basin, and (iv) phases of erosion and non-deposition. We relate these changes in the stratigraphic records to a combination of surface and tectonic controls at various scales. In particular, roll-back subduction of the European mantle lithosphere, delamination of crustal material and the associated rise of the Aar-massif most likely explain the widening of the basin particular at distal sites. In addition, the uplift of the Aar-massif was likely to have shifted the patterns of surface loads. These mechanisms could have caused a flexural adjustment of the foreland plate underneath the Molasse basin, which we use as mechanism to explain the establishment of distinct depositional environments and particularly the formation of subtidal-shoals where a lateral bulge is expected. In the Alpine hinterland, these processes occurred simultaneously with a period of fast tectonic exhumation accomplished through slip along the Simplon detachment fault, with the consequence that sediment flux to the basin decreased. It is possible that this reduction in sediment supply contributed to the establishment of marine conditions in the Swiss Molasse basin and thus amplified the effect related to the tectonically controlled widening of the basin. Because of the formation of shallow marine conditions, subtle changes in the eustatic sea level contributed to the occurrence several hiatus that chronicle periods of erosion and non-sedimentation. While these mechanisms are capable of explaining the establishment of the Burdigalian seaway and the formation of distinct sedimentological niches in the Swiss Molasse basin, the drainage reversal during OMM-times possibly requires a change in the tectonic processes at the slab scale. We conclude that sedimentological records can be used to decipher surface controls and lithospheric-scale processes in orogens from the stratigraphic record, provided that a detailed sedimentological and chronological database is available.

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