Regressive Surface Of Marine Erosion Research Articles

The regressive surface of marine erosion generated by tides: A case study from a Pleistocene tidal sand ridge sequence, Calabria, Southern Italy

AbstractThe regressive surface of marine erosion is a key stratigraphic discontinuity used to identify episodes of forced regression in marine strata. Typically, it marks the base of shallow‐marine (e.g. shoreface and deltaic) deposits eroding over relatively deeper‐water (e.g. shelf and prodelta) lithofacies. While well‐documented in marginal‐marine areas, its occurrence in offshore or strait settings dominated by tidal currents is less understood. This study investigates lower Pleistocene outcrops in the Plio‐Quaternary Siderno Basin, Calabria, southern Italy, where tidal sand ridges developed in a Mediterranean strait. High‐resolution drone images reveal a basinward‐dipping basal surface marking the onset of tidally dominated sedimentation. This discontinuity separates underlying shelf fines from overlying cross‐stratified, tidal bioclastic/siliciclastic arenites, indicating a prolonged period of marine regression in a strait setting. The stratal architecture of the ridges shows cross‐strata aggradation in up‐dip sections, transitioning down‐dip into balanced aggrading/prograding strata, and further basinward into markedly prograding deposits. These features are interpreted to reflect an initial phase of normal regression, evolving into forced regression. This latter stage is characterised by a progressive deepening of the basal discontinuity, causing more erosional effects on the underlying beds, with a vertical basinward fall of about 60 m over 2 km. Internal foreset geometry (two‐dimensional vs. three‐dimensional cross strata) and their vertical and lateral repetition indicate stages of equilibrium and disequilibrium for tidal bedforms, reflecting varying current speeds and water depth changes. The regressive surface of marine erosion here is formed by tidal currents, rather than waves, suggesting a new type of sequence stratigraphic discontinuity associated with tide‐dominated settings.

Unconformity generation and the shift from storm‐dominated to tide‐dominated processes in a Jurassic retroarc foreland basin: Insights from ichnology

AbstractAn enigmatic transition from the storm‐dominated, offshore to lower shoreface deposits of the Redwater Shale Member (Sundance Formation) to the overlying mixed tidal and aeolian Windy Hill Sandstone (Morrison Formation) in the Oxfordian of the North American Western Interior has long been a source of intrigue. Previously proposed drivers include the progradation of a large, tide‐dominated delta onto a storm‐dominated shelf, a complete reorganisation of the basin's hydrodynamics and climate, or the development of a regional unconformity (termed the J‐5). In south‐eastern Wyoming, the Redwater Shale is characterised as an offshore to distal shoreface deposit with glauconitic siltstones and sandstones punctuated by coquinoid and sandy tempestites and hosting a Cruziana Ichnofacies. The Windy Hill Sandstone, a time‐transgressive, sand‐rich, intertidal succession with classic Pteraichnus and stressed Skolithos Ichnofacies, sharply overlies the Redwater Shale and records an abrupt basinward shift in facies that accompanied at least tens of metres of sea‐level fall. New, detailed sedimentological, ichnological and architectural data collected across this transition in the study area provide fresh insights into the depositional history of these units and demonstrates the existence locally of a composite J‐5 unconformity. The unconformity developed as tectonically driven, prograding shoreline trajectories of the Redwater Shale gave way to degrading trajectories of the Windy Hill Sandstone, leading to a forced regression and formation of a regressive surface of marine erosion. The sharp juxtaposition of intertidal flat facies (Pteraichnus Ichnofacies) directly upon offshore to lower shoreface deposits (Cruziana Ichnofacies) is the key to recognising the unconformity and proves the value of the previously underutilised ichnological data.

Facies architecture and paleogeography evolution of regressive wave-dominated shorelines transitioning into tide-dominated estuaries: Early Devonian Subbat Member, Jauf Formation, Saudi Arabia

AbstractThe Paleozoic succession on the northern Arabian Plate was deposited during several regressive and transgressive events. The Early Devonian Subbat Member of the Jauf Formation comprises several smaller-scale intervals of the Paleozoic succession that were interpreted based on large-scale observations from outcrop and subsurface data. This study utilizes process-based sedimentology and investigates facies stacking, lateral continuity of sand bodies, and ichnofacies to interpret an open marine wave-dominated forced regressive system, that is followed by transgressive shorelines.This study integrates a total of 417 meters of the Devonian stratigraphy from four outcrops and two shallow cores. This dataset records a third-order sequence which developed through an extensive intra-plate siliciclastic influx in between two carbonate units during the deposition of the Subbat Member. This study illustrates the evolution of a falling-stage systems tract that is characterized by shoreface sand bodies and an erosional-based delta front in the lower Subbat Member. These sediments overlie a regressive surface of marine erosion (RSME), extending for hundreds of kilometers and transitioning to an overall transgression in the upper parts of the Subbat Member.This study interprets a total of seven facies associations (FAs): i) offshore, ii) wave-dominated delta, iii) shoreface to offshore transition, iv) fluvial channels, v) crevasse splays, vi) paleosol, and vii) estuarine facies associations. In the lower part of the Subbat Member, the wave-dominated delta and shoreface to offshore transitional FAs overlie the marine shelf strata of the offshore FA and develop a RSME. Fluvial channels and crevasse splays FAs are interpreted.Unique assemblages of trace fossils, in terms of intensity and diversity, ranging from the Nereites Ichnofacies to Skolithos Ichnofacies, play a major role in the understanding of the overall water depth and depositional setting. Distinctive terrestrial Prototaxites fossils are present in sheet-like bodies and are interpreted as part of extensive crevasse splays that formed during major river flooding events. This study provides a unique integrated approach using ichnology, sedimentology, and sequence stratigraphy to better understand the spatial and temporal facies distribution of a forced regressive sequence and refine the paleogeography of northern Arabia during Early Devonian time.

Sharp‐based shoreface successions reconsidered in three‐dimensions: A forward stratigraphic modelling perspective

AbstractSea‐level fall is commonly inferred to generate a sharp‐based shoreface succession that displays an abrupt vertical transition from heterolithic, lower shoreface to sandy, upper shoreface deposits across a marine erosion surface. Three‐dimensional, process physics‐based, coupled hydrodynamic‐morphodynamic models are constructed to compare bedding architecture and facies patterns of wave‐dominated delta deposits preserved during normal (static sea level) and forced (falling sea level) regression and then transgression during subsequent sea‐level rise. The models suggest that wave‐dominated deltas will develop a sandy shoreface inner clinoform dipping from the subaerial delta plain to a relatively flat wave‐scoured subaqueous delta top, which is laterally separated from a delta front outer clinoform that dips from the subaqueous delta top edge to the shelf floor. As these systems prograde, deposits of these dual‐clinoforms will become vertically stacked and will be separated by a regressive surface of marine erosion. Significant grain‐size contrasts between these vertically stacked clinoform deposits reflect differences in sediment‐transport directions and sorting under river and wave‐driven littoral currents along the coast, and cannot be related uniquely to sea‐level changes. The marine erosion surface under a sharp‐based shoreface deposit records abrupt facies shift across a kilometres‐wide, wave‐eroded surface and defines a discontinuity in the preserved vertical succession. The continuity of a regressive surface of marine erosion mapped over many tens to hundreds of kilometres across mid‐shelf regions of some stratigraphic sequences reflects a gradual lateral shift in the position of littoral current erosion on a subaqueous delta top. Timelines cross such vertical lithic discontinuities throughout the extent of a prograding deposit, and the regressive surface of marine erosion thus has little chronostratigraphic significance. The results of these models suggest caution in inferring sea‐level changes from the character of vertical facies changes observed in individual well logs and isolated outcrop exposures.

Episodes of seabed rise and rapid drowning controlling the development of regressive and transgressive rhodolithic limestones in a tectonically-active subduction setting (Early Miocene, Wairarapa region, New Zealand)

ABSTRACT Early Miocene limestones from the Wairarapa region of New Zealand were deposited on thrust-bounded margins of trench-slope basins, and consist of two superposed stratal units, namely units A and B, interpreted as forced regressive and forced transgressive foralgal and rhodolith-bearing deposits, respectively. Unit A is floored by a regressive surface of marine erosion cut into shelfal to bathyal siliciclastic successions, and is overlain across a transgressive surface of erosion by Unit B. A drowning surface abruptly places the latter deposits in contact with deeper hemipelagites and turbidites. The succession is explainable within a tectono-eustatic based framework as follows: (1) Structurally controlled rapid relative sea-level fall, (i.e. sea-bed rise), from upper bathyal to shelfal depths promoted development of regressive (‘lowstand’) mixed carbonate–siliciclastic deposits. Continuation of seabed rise resulted in deposition of pure carbonate sediments, which are represented by channel-fill rhodolithic rudstones; (2) early stage of relative sea-level rise (i.e. seabed drowning) caused emplacement of transgressive glauconitic limestones, consisting of either foralgal deposits, or incised rhodolithic limestones; (3) continued relative sea-level rise terminated carbonate production. The present study documents carbonate production and termination in a tectonically active and confined intra-slope setting, reflected in the development and distribution of unusual forced regressive, and transgressive rhodolithic-heterozoan carbonates.

Evolution of a complex early Permian coarse-grained shoreline along a rift basin margin

ABSTRACT Tectonic activity in extensional basins has a profound control on accommodation and sediment supply through the interplay between footwall uplift and hanging-wall subsidence, and thus largely influences the three-dimensional architecture of syn-rift sequences. This is emphasized in areas close to major rift-border faults, where steep coastal reliefs and fluvial gradients produce compound facies zonation and stratigraphic styles with strong lateral variability. The lower Permian High Cliff Sandstone was deposited in an array of shallow marine environments along the margin of the northern Perth Basin during a protracted late Paleozoic rifting episode in Western Australian basins. The formation is composed of fluvio-deltaic and nearshore strata sharply overlying a thick succession of offshore mudstone that was deposited during a phase of tectonic quiescence. This basal contact likely reflects submarine erosion and is, therefore, interpreted as a regressive surface of marine erosion generated in response to forced regression. The facies arrangement consisting of interbedded sandstone, conglomerate, and heterolithic facies chiefly records the evolution of a low- to high-gradient paleoshoreline punctuated by coastal streams, steep sea cliffs, and back-barrier lagoons. Extraformational outsized clasts were probably emplaced by the erosion of exhumed basement and older sedimentary rocks through fluvial incision, wave sapping, or landsliding. The along-strike variability between low- and high-gradient shoreline deposits indicates a dynamic depositional setting with a complex tectonic influence. The basal regressive surface of marine erosion is attributed to footwall uplift during the early reactivation stage of basin-bounding normal faults and, therefore, records the initiation of a new syn-rift phase in the northern Perth Basin.

Systems tracts and their bounding surfaces in the low- accommodation Upper Mannville group, Saskatchewan, Canada

Abstract Sequence stratigraphic interpretations of paralic successions can be challenging, because such settings are commonly controlled by a combination of allogenic controls and autogenic processes, leading to complex depositional architectures. In low-accommodation systems where parasequences are less than 15 m thick, the challenges in recognizing discrete stratigraphic surfaces are exacerbated by limited vertical separation between surfaces or their outright erosional amalgamation, requiring high-resolution facies analysis to resolve their geometries. Herein, we present criteria derived from core data and well logs to differentiate between allogenic and autogenic surfaces in a low-accommodation paralic setting, using the Lower Cretaceous Mannville Group of west-central Saskatchewan, Canada as a case study. The upper part of the Mannville Group (Sparky, Waseca and McLaren formations) displays complex stratigraphic relationships related to base-level changes. Marine flooding surfaces (MFS) and transgressive surfaces of erosion (TSE) of 3rd and 4th order record allogenic changes ( e.g., basin subsidence and/or eustatic changes in sea level), and are used to define parasequence boundaries of strandplain-shoreface successions. Deltaic deposits not only possess these allogenic transgressive surfaces, but autogenic 5th-order flooding surfaces, which are broadly similar in appearance, as well. These autogenic surfaces record responses to channel avulsion or lobe abandonment, separate discrete delta lobes, and display limited lateral extents. Shoreface-related flooding surfaces, by contrast, bound true allogenic parasequences and, therefore, have regional correlatability. The Waseca Formation also possesses surfaces related to base-level fall. To the north, a subtle regressive surface of marine erosion (RSME) marks the base of the falling stage systems tract. Elsewhere, a widespread subaerial unconformity (SU) separates the Waseca into lower and upper members. In most areas, the SU is amalgamated with surfaces generated by later base-level rise. Upper Mannville strata in the study area, therefore, can be separated into parts of two depositional sequences. The main deposits of the lower sequence comprise a highstand systems tracts (HST) in the Sparky Formation. The base of the Lower Waseca Member marks the onset of a transgressive systems tract (TST), associated with widespread shoreline retreat. A 3rd-order maximum flooding surface (MxFS) marks the end of transgression and resumption of normal progradational regression in a highstand systems tract associated with the Lower Waseca Member. Following highstand normal regression, a major base-level fall initiated a subaerial unconformity that marks the base of the upper sequence. Fluvial valley incision led to sediment bypass and deposition of forced regressive and lowstand shoreface and delta complexes of the falling stage systems tract (FSST) and lowstand systems tract (LST), respectively, in the northern part of the study area. Pedogenic modification of subaerially exposed sediment occurred in interfluve areas. Ensuing TST accumulation was initially confined to the tidal-fluvial estuarine infill of the incised valleys and transgressive bay deposits of the Upper Waseca Member. The Upper Waseca is capped by a 3rd-order maximum flooding surface (MxFS), which separates it from the overlying McLaren Formation. This marks the return to regional shoreline progradational regression and corresponds to the highstand systems tract (HST) of the upper sequence.

Tracking the isostatic and eustatic signals in an end Ordovician–early Silurian deglacial sedimentary record (Algeria – Libya border)

AbstractTo elucidate the signature of isostatic and eustatic signals during a deglaciation period in pre‐Pleistocene times is made difficult because very little dating can be done, and also because glacial erosion surfaces, subaerial unconformities and subsequent regressive or transgressive marine ravinement surfaces tend to amalgamate or erode the deglacial deposits. How and in what way can the rebound be interpreted from the stratigraphic record? This study proposes to examine deglacial deposits from Late‐Ordovician to Silurian outcrops at the Algeria–Libya border, in order to define the glacio–isostatic rebound and relative sea‐level changes during a deglaciation period. The studied succession developed at the edge and over a positive palaeo‐relief inherited from a prograding proglacial delta that forms a depocentre of glaciogenic deposits. The succession is divided into five subzones, which depend on the topography of this depocentre. Six facies associations were determined: restricted marine (Facies Association 1); tidal channels (Facies Association 2); tidal sand dunes (Facies Association 3); foreshore to upper shoreface (Facies Association 4); lower shoreface (Facies Association 5); and offshore shales (Facies Association 6). Stratigraphic correlations over the subzones support the understanding of the depositional chronology and associated sea‐level changes. Deepest marine domains record a forced regression of 40 m of sea‐level fall resulting from an uplift caused by a glacio‐isostatic rebound that outpaces the early transgression. The rebound is interpreted to result in a multi‐type surface, which is interpreted as a regressive surface of marine erosion in initially marine domains and as a subaerial unconformity surface in an initially subaerial domain. The transgressive deposits have developed above this surface, during the progressive flooding of the palaeo‐relief. Sedimentology and high‐resolution sequence stratigraphy allowed the delineation of a deglacial sequence and associated sea‐level changes curve for the studied succession. Estimates suggest a relatively short (<10 kyr) duration for the glacio‐isostatic uplift and a subsequent longer duration transgression (4 to 5 Myr).

Forced regressive wedge in the Mesoproterozoic Koldaha Shale, Vindhyan basin, Son valley, central India

The present paper highlights the sequence development within the Mesoproterozoic Koldaha Shale Member of the Kheinjua Formation, Vindhyan Supergroup which records the occurrence of a forced regressive wedge and associated discontinuity surfaces at the base of the wedge. Nine lithofacies have been identified within the study area that are grouped into three lithofacies associations varying in depositional setting from outer shelf, through shoreface-foreshore-beach to continental braidplain. The outer shelf sediments are aggradational to slightly progradational representing highstand systems tract. The rapidly progradational, wedge-shaped shoreface to foreshore-beach succession occurs sharply or erosively above the outer shelf sediments and is bounded by a regressive surface of marine erosion (RSME) at the base and by a subaerial unconformity at the top. This, along with its downstepping trajectory, supports deposition of this sedimentary wedge during falling sea level. A laterally extensive soft sediment deformation zone occurs at the base of the wedge.The forced regressive wedge is incised by fluvial braidplain deposits that rest on an erosive surface representing a sequence boundary. The thin braidplain deposits are the product of aggradation during a subsequent early rise in relative sea level, and thus, they are inferred to represent a lowstand systems tract. The constituent architectural elements that characterize the braidplain deposits are downstream accretion elements and small channel elements. Further landward, the base and top of the shoreface wedge merge to form an unconformity across deposits that rest directly on the outer shelf sediments. The identification of forced regressive wedges has significant economic importance in view of the potential occurrence of hydrocarbons within the Proterozoic formations.

Forced regression across the marine to continental transition in Jammu sub-basin: Implication to the Oligo-Miocene unconformity in the Himalayan foreland

Similar to the other sub-basins, marine to continental transition in Jammu foreland also shows the presence of a characteristic greenish gray, quartz arenite unit, locally termed as White Sandstone unit. Process based sedimentological and sequence stratigraphic work carried out across this White Sandstone unit suggest that this unit was deposited in a shoreface settings during a forced regression. The sharp base of the White Sandstone unit represents a surf diastem (a kind of regressive surface of marine erosion) and does not signify a >10Myr unconformity. The gradational top of the unit, showing various degree of exposure and soil development, has been interpreted as type 1 sequence boundary. The White Sandstone unit, present along the entire stretch of the western Sub-Himalaya, also shows forced regressive nature in the Subathu sub-basin situated ∼350km SE of Jammu. So, the forced regression across the marine to continental transition in the entire western Himalayan foreland is a regional phenomena and not a local one. Contrary to the earlier works, which proposed the presence of an unconformity spanning >10Myr encompassing the Oligo-Miocene period, the present study showed that the unconformity, if present, is of small duration possibly spanning <40kyr. These findings seriously question the earlier interpretations of accelerated exhumation and unloading of the mountain load in response to climate driven enhanced erosion or passage of the forebulge for the development of the Oligo-Miocene unconformity in the Himalayan foreland and its relation to Cenozoic tectonic–climate connection.

Forced regressive tidal flats: response to falling sea level in tide-dominated settings

Abstract During forced regression, the coastline advances seaward irrespective of sediment supply and relocates to a topographically lower position. Forced-regressive deposits are a component of the falling-stage systems tract. They are recognized by a basal unconformity which records erosion during the seaward facies shift, and are in turn capped by another unconformity due to subaerial exposure or wave ravinement during subsequent transgression. In wave-dominated settings, the basal “regressive surface of marine erosion” is a scoured surface cut by wave action, because erosion is needed to maintain the seaward-sloping bathymetric profile in equilibrium with the wave energy. The response to falling sea level in tide-dominated settings has not been as thoroughly discussed. The stratal architecture of the Lower Cambrian Gog Group of the southern Canadian Rocky Mountains reveals a new mechanism for the formation of this surface landward of the lever point of balance between sedimentation and erosion in the subtidal environment. Subtidal parasequences of the Lake O’Hara Member are typically composed of thin-bedded mudstone and ripple cross-laminated sandstone, followed by Skolithos pipe rock and thin- to medium-bedded cross-stratified sandstone overlain by thick-bedded cross-stratified sandstone. However, at the top of the Lake O’Hara Member, an erosional surface truncates a pipe-rock interval and the expected capping cross-stratified sandstones are absent. Overlying this surface, the Lake Oesa Member comprises tidal-flat deposits composed mainly of thinly interbedded mudstone and sandstone. This jump in facies at the erosional surface can be explained as a response to a fall in sea level. As the shoreline is forced to regress, the laterally continuous tidal flats advance and the pre-existing shallow-subtidal compound dunes are scoured by strong tidal currents, along with waves, that gradually carve a new equilibrium profile. We argue that the accretion of intertidal flats on top of subtidal sands is an overlooked yet predictable component of falling-stage systems tracts in tide-dominated settings.

A review of the character and interpreted origins of thick, mudstone-encased sandstone bodies in the Middle Triassic Doig Formation of Western Canada

Abstract Within the Middle Triassic Doig Formation of Western Canada there are thick sandstone bodies encased in muddier sediment — “anomalously thick sandstone bodies” (ATSBs). Interpretations vary from incised valleys, deltaic, barrier islands, turbidites in slope slumps, to shallow-water gravity-flow beds overlain by shoreface deposits in a slump or growth fault. Several authors have interpreted the uppermost beds in the sandstone bodies as shoreface deposits. The thick sandstone bodies were deposited during a period of regression and transgression but authors disagree as to whether or not the ATSBs and enclosing strata were deposited contemporaneously. Abrupt basal contacts, apparently abrupt lateral contacts, and stratigraphic relationships favour the sandstone bodies to be post-mudstone, formed during late regression. The most probable explanation for the origin of ATSBs is that during late regression, structural depressions formed on a muddy, pre-existing shelf and were filled by sandy sediment. Initial deposits in the thicker sandstone bodies commonly are debris-flow and/or slump deposits that filled in the deeper parts of the depression. As the depression filled, sediment entered wave- and current-influenced water depths and more typical shoreface deposits began to form. As regression proceeded some sandstone bodies were truncated by a regressive surface of marine erosion. Finally, all ATSBs and adjacent sediment were capped by a thin veneer of transgressive sediment.

Detached forced-regressive shoreface wedges at the Southern Iberian continental palaeomargin (Early Cretaceous, Betic Cordillera, S Spain)

The Lower Cretaceous (Barremian to Early Aptian) Cerrajón Formation on the Southern Iberian Continental Palaeomargin is represented in the study area by five sharp-based shoreface sandstone wedges (5–15 m thick). The sandstone packages abruptly pinch out landwards onto outer-ramp limestones and marls (Los Villares Formation). Sandstone tongues are interpreted as prograding wave-dominated shorefaces distally evolving to thin micro-hummocky cross-stratified sandstone beds alternating with marls deposited in a storm-wave siliciclastic-dominated outer ramp. In the context of sequence stratigraphy, most of the characteristics in outcrops for detached forced-regressive deposits have been tested at the sandstone wedges. Sandstone bases are characterized by a regressive surface of marine erosion (RSME) underlying a calcarenite containing reworked inner-ramp fossils and glauconite from the preceding highstand carbonate-dominated outer ramp (Los Villares Formation). The shoreface sandstones are in turn cut by incised channels (e.g. 2nd sandstone wedge) and filled with Lithophaga-bored sandstone concretions. Lithophaga-bored sandstone concretions are interpreted as deriving from (1) concretion formation in the forced-regressive to lowstand shoreface sandstone during early diagenesis, (2) exhumation of sandstones hosting concretions along incised channels, and (3) coastal winnowing of poorly cemented sandstone host leaving the sandstone concretions which were bored and colonized by coastal fauna in situ. Incised channels truncating shoreface sandstones and sandstone concretions colonized by coastal fauna are interpreted as recognition criteria for a second sea-level fall that occurred after a lowstand sea-level stage. The term paired-forced-regressive is used for a systems tract resulting from a double sea-level dip (two sea-level falls occurring during a single sea-level change cycle). Repeated fourth-order fall-to-rise cycles of relative sea level controlled the architecture and facies distribution of system tracts on the South Iberian Continental Palaeomargin during the Barremian to Early Aptian (Early Cretaceous).

Forced regressive shoreface sandstone from Himalayan foreland: Implications to early Himalayan tectonic evolution

Sedimentology and sequence stratigraphic analysis of the ∼ 31 Ma old marker White sandstone unit from the Subathu Sub-basin, NW Himalayan foreland, suggest it to be a forced regressive wedge (FRW) formed during the transition from the marine Subathu Formation to the continental Dagshai Formation. The FRW is bounded between the “Surf diastem” below and type 1 unconformity at the top and differs from RSME (regressive surface of marine erosion, occurring below) bounded FRWs described from other classical coastal/foreland settings. Correct identification of bounding surfaces of a FRW has an important implication to the estimation of rate of relative sea-level (RSL) fall. A faster rate of RSL fall, higher than the sedimentation rate, has been postulated for the erosion of the lower shoreface and RSME. Using the logged thickness of the Subathu/Dagshai transition zone including the White sandstone (bounded between the “Surf diastem” and unconformity), available chronology and eustatic sea-level fall (0.023 mm/year at 31 Ma), a higher RSL fall than the sedimentation rate (0.07 mm/year) has been inferred during the deposition of the White sandstone. Petrography of sandstones and their Sr and Nd isotopic compositions indicate a major provenance switch-over from dominant mafic/ultramafic to metamorphic source from White sandstone (∼ 31 Ma) onwards attesting the link between hinterland tectonics, provenance and forced regression. The provenance switch-over at 31 Ma was earlier inferred to be driven by proto-Himalayan thrust propagation in the foreland. Using a simple isostatic model, on the contrary, a mechanism of accelerated surface uplift (at a rate of > 0.10–0.15 mm/year) is suggested for both provenance change and forced regression.

Facies and Stratigraphic Anatomy of a Temperate Carbonate Sequence (Capo Colonna Terrace, Late Pleistocene, Southern Italy)

Abstract Accurate interpretation of ancient non-tropical carbonate systems requires the development of appropriate facies and sequence stratigraphic models. These models should account for the marked differences in sedimentation style among non-tropical carbonates formed under different energy settings. This paper presents data and a conceptual model of the sequence architecture of non-tropical carbonates of moderate energy environments based on the late Pleistocene deposits of Capo Colonna marine terrace (Calabria, southern Italy). These deposits have the advantage of being continuously exposed along a proximal–distal transect across the paleo-shelf and their geometry has not been disturbed by later tectonic activity. They consist of a transgressive–regressive (T–R) cycle whose genesis can confidently be related to one of the interstadial glacio-eustatic fluctuations of marine isotope stage (MIS) 5. Eight different mixed carbonate–siliciclastic and carbonate facies are present in the studied sequence. Of these, biogenic-dominated facies are invariably made up of skeletal remains of light-independent organisms plus or minus red calcareous algae (the heterozoan association). The relatively young age of the deposits allows calibration of the paleoecological significance of observed facies by direct comparison with modern analogues from the Mediterranean Sea. Four laterally persistent discontinuity surfaces were identified along the transect, and interpreted, from bottom to top, as (1) a basal ravinement surface, (2) a submarine hardground locally acting as a substrate for algal boundstones, (3) a regressive surface of marine erosion, and (4) a surface of subaerial exposure. Sequence stratigraphic analysis indicates that the preserved T–R cycle is asymmetric, with a thicker regressive portion. Highstand deposits can be subdivided into a shore-connected sandy prism and more distal autochthonous and parautochthonous skeletal accumulations and algal boundstones. During forced regression, a thin, sharp-based, strongly progradational unit of calcarenites was deposited above the regressive surface of marine erosion. The deposits of Capo Colonna terrace document the response of non-tropical, moderate-energy carbonate ramps to sea-level fluctuations during icehouse conditions. Their architecture can facilitate the interpretation of other successions from similar settings and provide an end member to be compared and contrasted with high-wave-energy cool-water carbonates.

Marine to continental transition in Himalayan foreland

Research Article| September 01, 2008 Marine to continental transition in Himalayan foreland M.K. Bera; M.K. Bera 1Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India Search for other works by this author on: GSW Google Scholar A. Sarkar; A. Sarkar † 1Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India † E-mail: anindya@gg.iitkgp.ernet.in Search for other works by this author on: GSW Google Scholar P.P. Chakraborty; P.P. Chakraborty 2Department of Applied Geology, Indian School of Mines, Dhanbad 826 004, India Search for other works by this author on: GSW Google Scholar R.S. Loyal; R.S. Loyal 3Centre of Advanced Study in Geology, Panjab University, Chandigarh 160014, India Search for other works by this author on: GSW Google Scholar P. Sanyal P. Sanyal 4Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India Search for other works by this author on: GSW Google Scholar GSA Bulletin (2008) 120 (9-10): 1214–1232. https://doi.org/10.1130/B26265.1 Article history received: 22 May 2007 rev-recd: 17 Nov 2007 accepted: 07 Dec 2007 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation M.K. Bera, A. Sarkar, P.P. Chakraborty, R.S. Loyal, P. Sanyal; Marine to continental transition in Himalayan foreland. GSA Bulletin 2008;; 120 (9-10): 1214–1232. doi: https://doi.org/10.1130/B26265.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Mapping, sedimentological studies, and sequence stratigraphic analysis in parts of the Himalayan peripheral foreland basin of northwest India suggest that deposition of basinal turbidites, derived from both the orogenic and ramp sides, took place due to progressive uplift of the basin margin, causing forced regression. The forced regressive wedge of shoreface white sandstone, thus deposited throughout the foreland basin across the regressive surface of marine erosion, cannot be included in the alluvial sediments of Dagshai Formation. Contrary to earlier inferences, the unconformity between the Subathu and Dagshai Formations is found to occur at the top of the white sandstone marked by caliche development or erosion by Dagshai channel sand interpreted as a Type 1 sequence boundary. The reworked fossils in calciturbidite units suggest that the upper limit of the Subathu Formation must be significantly younger than ca. 44 Ma, and the proposition of a synchronous orogen-scale unconformity of >10 m.y. duration and early exhumation of Himalayan rocks should be reassessed. The duration of unconformity between Subathu and Dagshai Formations is interpreted to be ≤3 m.y. The sea-level fall and shoaling of Subathu Sea that was already set in by forced regression received tectonic enhancement only at the beginning of the Dagshai Formation, which resulted a total turnaround from a marine to a continental alluvial system. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A major unconformity at the base of the Upper Triassic Charlie Lake Formation in the Western Canada Sedimentary Basin

Abstract The Middle Triassic succession of the Western Canada Sedimentary Basin consists of a series of prograding offshore to shoreface sediment lenses of the Doig Formation, overlain by a widespread shoreface sandstone of the Halfway Formation, in turn overlain by lagoonal and supratidal deposits of the Upper Triassic Charlie Lake Formation. Two distinct erosion surfaces are present in the Halfway to lowermost Charlie Lake succession — within or at the base of the Halfway Formation, depending on geographic location, and at the base of the Charlie Lake Formation. Early studies interpreted the erosion surface associated with the Halfway Formation to be an unconformity. At least one author interpreted an unconformity at the base of the Charlie Lake Formation. Subsequently, a conformable facies interpretation became dominant, with the erosion surface associated with the Halfway Formation relegated to be the base of tidal channel deposits. In the conformable facies interpretation, the Doig to lowermost Charlie Lake succession consists of a series of prograding transgressive–regressive sequences. Recently the unconformity interpretation has been resurrected with regional correlations and facies analysis to support the interpretation. The distribution of facies and stratigraphic relationships do not fit the conformable facies interpretation particularly well and are better explained by the presence of a major unconformity. Of the two erosion surfaces in the Halfway to lower Charlie Lake succession, the one at the base of the Charlie Lake Formation is interpreted to be the unconformity, and the erosion surface associated with the Halfway Formation is interpreted to be a regressive surface of marine erosion.

Tectonic controls on sequence stacking pattern and along-strike architecture in the Pleistocene Mejillones Formation, northern Chile: Implications for sequence stratigraphic models

In the Mejillones Formation, a shallow-marine Pleistocene succession of northern Chile, the cyclic stratigraphic record is the result of the complex interaction of regional uplift, glacio-eustasy, local tectonics, sediment supply, and sedimentary processes. Stratal geometries, characteristics of sedimentary facies, and nature of sequence-bounding unconformities have been investigated to evaluate the influence of: (i) intrabasinal, short-term normal faulting on both along-strike variations in sequence architecture and genetic complexity of key stratal surfaces; and (ii) long-term regional uplift on sequence stacking pattern. The stratigraphic succession, dissected by small-displacement (few meters) normal faults striking obliquely with respect to the palaeo-shoreline trends, displays systematic variations in sequence architecture and the nature of bounding surfaces across them. Indeed, depending on position with respect to the fault plane, two basic types of internal organisation can be recognised in the examined shallow-marine, almost clastic-starved sequence. Within grabens it consists of a siliciclastic-rich transgressive systems tract (TST), which is bounded beneath by a transgressively modified, Glossifungites-demarcated sequence boundary (SB/RS), overlain by a mollusc-bearing falling-stage systems tract (FSST). The erosional downlap surface that separates the TST from the FSST is the regressive surface of marine erosion (RSME). On the footwall crests the combination of marine regressive erosion, during falls in relative sea-level, and uplift has resulted in complete removal of the sediments of the TST from these sites, leading to the formation of a tectonically enhanced basal unconformity composed of the RSME superimposed onto the previous SB/RS (SB/RS/RSME). The prominent lateral change in component units (systems tracts) and nature of bounding surfaces within the studied sequence is directly related to the presence of normal faults and indicates that fault activity had a major impact on the sequence stratigraphic evolution of the Mejillones Formation, enhancing subsidence within the grabens and promoting unconformities in the horsts. Overall, the Mejillones Formation records a long-term sea-level fall driven by the contemporaneous regional uplift, punctuated by repeated, high-frequency eustatic sea-level changes. The effect of this superimposition was that glacio-eustatic sequences were displaced progressively downward and basinward and stacked in a distinct downstepping, tectonically enhanced falling-stage sequence set, which reflects basin-wide loss in accommodation space. The sequence set is underlain by a composite RSME that becomes progressively younger basinward and is made up by the lateral and down-dip connection of a series of lower-rank sequence boundaries including hanging-wall SB/RSs and footwall SB/RS/RSMEs of successive sequences.

Facies succession, stratigraphic occurrence, and paleogeographic context of conglomeratic shorelines within the Falher "C", Spirit River Formation, Deep Basin, west-central Alberta

The Falher “C” is a Lower Cretaceous transgressive-regressive sequence that contains mixed coarse-grained sandstone and conglomerate gas reservoirs in the Deep Basin of west-central Alberta. A total of 11 facies were identified in cored intervals of the Falher “C” and are further grouped into five facies associations representative of deposition in an offshore-marine through continental spectrum. Coarse-grained sandstone and conglomerate facies of high reservoir potential comprise facies association two (FA2), and were deposited within wave-dominated upper shoreface and foreshore settings. Finer grained non-reservoir facies (mudstone, siltstone, and fine-grained sandstone) were deposited within storm-dominated lower shoreface (FA1), tidal inlet (FA3), back-barrier (FA4), and coastal plain (FA5) environments. Several significant stratigraphic surfaces have been utilized to further sub-divide the Falher “C” into three parasequences termed C1, C2, and C3. In ascending order of stratigraphic occurrence these surfaces are defined as i) TSE1, ii) RSE, and iii) TSE2. The lower and upper contacts of conglomerate-rich parasequence C2 correspond to a regressive surface of marine erosion (RSE), and the youngest transgressive surface of marine erosion (TSE2). From correlations made between cored intervals and calibrated well logs, it can be recognized that reservoir-quality conglomerates are stratigraphically restricted to Twp. 67. A paleogeographic model constructed for the Falher “C” demonstrates the distribution of important environments of deposition at four consecutive depositional intervals corresponding to distinct changes in sea level and sediment supply to the Falher shoreline. Initially, the shoreline underwent transgression in response to a relative rise of sea level whereupon parasequence C1 began to prograde northward. Transgression and progradation was followed by a relative fall of sea level and increased sediment supply that brought about a forced regression and deposition of the reservoir-bearing conglomeratic parasequence C2. Progradation of parasequence C3 was established shortly after a second period of transgression across the study area. Continued normal regression in response to progradation of parasequence C3 northward of the study area maintained aggradation of coastal-plain and deposition of the capping nonmarine C4 unit. The results of this study serve to enhance our present understanding of the scale, distribution, and three-dimensional predictability of conglomerate gas reservoirs in the Deep Basin of Alberta.

Sequence response to syndepositional regional uplift: insights from high-resolution sequence stratigraphy of late Early Pleistocene strata, Periadriatic Basin, central Italy

This paper deals with the depositional sequences that occur within the uppermost part of the Plio–Pleistocene Periadriatic basin fill in the southern Marche region, central Italy. The succession is an Early Pleistocene, easterly dipping clastic wedge showing an overall shallowing trend from slope clays to shallow-marine and non-marine deposits comprising two major sequences, namely Q mb and Q mc. Analysis has provided new insights into: (i) the nature of sedimentary facies and facies associations occurring within the upper part of Q mb and Q mc; (ii) the gradual contact within Q mb between regressive littoral deposits (RLD) and underlying deep-marine blue clays; (iii) the composite origin of the Emilian surface, which is a widespread erosional unconformity separating Q mb from Q mc; (iv) the cyclothemic pattern of Q mc, composed of downstepping, small-scale depositional sequences; (v) the role played by synsedimentary uplift on the stacking pattern of small-scale sequences and their internal architecture. Up to three small-scale depositional sequences have been recognised within Q mc (Q mc1, Q mc2 and Q mc3). They are up to 50 m thick and defined by previously unrecorded, lower-rank, regionally extensive surfaces. Facies organization indicates that, as a rule, in ascending stratigraphic order each small-scale sequence may includes a distinctive basal unconformity surface that can be traced from incised valleys to associated interfluves, an incised-valley fill, a transgressive surface of marine erosion, a transgressive systems tract, a highstand systems tract, a regressive surface of marine erosion and an attached falling stage systems tract. In proximal positions, the small-scale sequences are dominated by transgressive and highstand systems tracts with incised-valley fills and falling stage systems tracts absent or volumetrically much less significant. In relatively basinward locations, where the regressive surfaces of marine erosion converge with the lower sequence boundary, the falling stage systems tract may represent the entire depositional sequence. High-frequency sequences display a distinctive stacking pattern and form a tectonically induced forced regressive sequence set underlain by a composite, tectonically enhanced regressive surface of marine erosion formed by the lateral connection of lower-rank sequence boundaries.