Widespread Marine Transgression Research Articles

Late Cretaceous Sevier Versus Laramide Orogenies in Wyoming‐Utah‐Colorado, USA: New Insights From Basin Subsidence History

AbstractVariability in subsidence rates within Upper Cretaceous strata of the Western Interior Basin offers crucial insights into the response of surface sedimentation styles to Sevier‐to‐Laramide tectonics and related deep mantle processes. The formation mechanisms of the Late Cretaceous Western Interior Basin in North America have long been a subject of debate. A re‐evaluation of the basin's subsidence history reveals rapid subsidence pulses lasting ca. 2 Myr within longer‐term (average 5.7 Myr) progradational or aggradational clastic wedges. The timing of these wedges, especially the widespread marine flooding resulting from subsidence, is constrained through the calibration of ammonite zonation with absolute dates. Sevier wedges exhibit a different architecture compared to the Laramide wedges. The former recorded initial rapid and widespread marine transgressions followed by long‐term coastal progradation, whereas the latter developed by initial erosional and progradational growth followed by aggradation and long‐term coastal transgression. The Sevier clastic wedges, initially accumulated within a N‐S elongated, long‐wavelength tectonic subsidence zone close to the thrust belt, gradually migrated cratonward. Starting in the early Campanian (ca. 82 Ma), the Laramide Orogeny developed along a NW‐SE trend and then migrated northeastward, roughly consistent with coeval long‐wavelength frontal basin subsidence. The spatio‐temporal variations in long‐wavelength tectonic subsidence indicate a shift in the dynamic subsidence's migration direction from eastward to northeastward, driven by changes in Farallon subduction direction and mode. Our work shows how repeated subsidence behavior in the Sevier‐to‐Laramide transition records evolving architectural responses and the trajectory of coeval dynamic topography.

Sedimentology and hydrocarbon potential of the Late Ordovician glacial deposits on the Arabian Platform and Southeastern Turkey

The Late Ordovician glacial deposits are widespread and constitute a significant portion of the Early Paleozoic stratigraphic sequence of the cover rocks of the Arabian and African platforms. The glaciation lasted less than one million years between the Late Ashgillian (445 Ma) and Early Silurian (444 Ma) but it had a strong impact on the whole area. It has been proven that the glaciofluvial sandstones form important oil and gas reservoirs in Saudi Arabia and in North African and other Middle Eastern countries, including SE Turkey, but their heterogeneity and internal lithofacies characteristics have not been fully understood yet. In Saudi Arabia the hydrocarbon-producing glacial paleovalley systems forming the Sarah Formation extend 70 km in the W-E direction. In southern Turkey, similar glacial paleovalleys, defined as the Yurteri Formation, extend in a NW-SE direction. It consists of massive, well-sorted, porous reservoir sandstones of good quality and produces significant amounts of oil and sweet gas in SE Turkey. When the glaciation ceased in the Early Silurian time, the ice mass melted and released large volumes of water into the oceans. Returning waters resulted in rapid sea-level rise and onlap relations across the platforms. This widespread marine transgression deposited organic-rich, potential source-rock hot shale facies directly on the good-quality glaciofluvial reservoir sandstones. This publication is based on intensive outcrop and subsurface studies on the core samples of the reservoir sandstones and the source-rock shale facies in every part of Saudi Arabia and SE Turkey. These studies clearly indicated the hydrocarbon potentials of the Late Ordovician glaciation formed on the Gondwana plate. The aim of this paper is to demonstrate the presence of a close genetic relationship between the glaciofluvial reservoir sandstones and overlying hot shale source-rock facies and downward migration of oil and gas into the underlying porous sandstones mainly due to hydrostatic pressure.

Middle to Late Devensian glaciation of north‐east Scotland: implications for the north‐eastern quadrant of the last British–Irish ice sheet

ABSTRACTWe present a review of over 175 years of research into the Middle to Late Devensian (Weichselian) glaciation of NE Scotland based crucially on both its lithostratigraphic and geomorphic records. The location of the region, and surrounding seabed, makes this unusually detailed record significant for deciphering the former interactions and dynamics of Scottish and Scandinavian ice within the North Sea Basin (NSB), which continue to be controversial. A 12‐stage event stratigraphy is proposed based on a parsimonious interpretation of stratigraphic relationships, till lithology and regional clast fabrics, striae, subglacial bedforms, ice‐marginal features and published geochronometry at critical sites. The record of regional glaciation supports converging evidence that the north‐eastern quadrant of the last British and Irish Ice Sheet reached its maximum spatial extent in the late Middle to early Late Devensian and later re‐expanded following widespread internal glacial reorganizations, marine transgression and partial retreat from the central NSB. Retreat was interrupted by several glacial readvances of limited extent. Field‐captured data help to identify important events that are not clearly resolved from remote sensing alone, particularly regarding growth phases of the last glaciation.

SEDIMENTARY FACIES AND DEPOSITIONAL ENVIRONMENTS OF DIVERSE EARLY PALEOCENE FLORAS, NORTH-CENTRAL SAN JORGE BASIN, PATAGONIA, ARGENTINA

We here investigate the sedimentology of the early Danian (ca. 66–64 Ma) Salamanca Formation in the north-central San Jorge Basin, southern Chubut Province, Patagonia, Argentina, in order to place the outstandingly diverse and well-preserved fossil floras it contains into specific environmental settings. These assemblages are among very few of Danian age from the entire Southern Hemisphere and thus provide critical data about geographic variation in recovery from the end-Cretaceous extinction. Understanding the depositional context of the Salamanca floras is necessary for comparison with other assemblages and for interpreting their exceptional preservation. The Salamanca Formation was deposited above a widespread erosional sequence boundary (SB-1) resulting from a relative base level rise and widespread marine transgression during the early Danian (Chron C29n). In response to this increase in accommodation space, a broad, shallow estuary formed that most likely extended westward at least as far as the San Bernardo belt. A transgressive systems tract was deposited in this estuary, consisting of bioturbated sand fining upwards to silt. The maximum marine flooding surface at the beginning of the highstand systems tract is defined by well laminated, unburrowed, clay deposits of a low energy, deep shelf. The Salamanca highstand systems tract (HST) consists of sandy and silty facies capped by accreting subtidal bars and sandy shoals containing an abundance of tidal indicators, suggesting deposition proximal to the San Jorge paleo-estuary head. A second sequence boundary (SB-2), formed during Chron C28r and early C28n, separates the older highstand deposits from younger lowstand and transgressive deposits. These consist of estuarine sand shoals, trough cross-bedded sands deposited in aggrading, fluvially influenced tidal channels, tidal flat muds, and bayhead deltas. The best preservation of compression floras and petrified trees occurred near the tops of subtidal bars below SB-2; at the end of the shallowing-upward cycle that caps the second HST; and in fluvially-influenced tidal channels, tidal flat mudstones, and bayhead deltas of the lowstand and transgressive systems tracts that lie above SB-2. These settings were proximal to the source forests and had rapid rates of burial. We interpret the dark muds of the Banco Negro Inferior, which cap the Salamanca Formation, as a late transgressive and highstand systems tract deposited during a time of rising groundwater table and declining river slopes in a widespread, lowland coastal forest.

Lithofacies architecture and palaeogeography of the Late Paleozoic glaciomarine Talchir Formation, Raniganj Basin, India

Talchir Formation (Permo–Carboniferous) of the Gondwana Supergroup records the Late Paleozoic glaciation in Peninsular India. Talchir sedimentary succession of the Raniganj Basin, Damodar Valley Coalfields, Peninsular India, bears ten facies types grouped under three facies associations, viz., the proglacial conglomerate–sandstone facies association (CS), the foreshore–shoreface conglomerate–sandstone–mudstone facies association (CSM) and the prodelta–shelf sandstone–mudstone facies association (SM). Overall facies architecture reflects initial ice–covered terrestrial subglacial sedimentation, which was subsequently reworked and emplaced subaqueously in front of the ice–grounding line, and finally overlapped by storm–laid prodelta–shelf sediments. Repeated glacial advance–retreats with shifts in the position of the ice–grounding line during phases of climatic amelioration led to multiple deglaciation– related fining–up cycles. Decoupled ice sheet and floating icebergs contributed icerafted debris (IRD) to these sediments. Gradual retreat of the ice sheet, however, restricted the supply of IRD towards top of the succession. Overlap of wave–agitated shoreface–shelf sediments on the glaciogenic sediments indicates widespread marine transgression caused by glacier melting during ice–house to green–house climatic transition, and crustal downsagging related to glacioisostasy. Subsequently, complete disappearance of the ice sheet caused basinal exhumation along with crustal uplift due to isostatic rebound, leading to multiple horst–graben bounded basinal systems, which received post–Talchir coal–bearing Gondwana sediments.

Lower Permian fluvial cyclicity and stratigraphic evolution of the northern margin of Gondwanaland: Warchha Sandstone, Salt Range, Pakistan

During the Lower Permian (Artinskian), fluvial conditions prevailed in what is now the Salt Range of northern Pakistan. Deposits of the Warchha Sandstone are characterised by a range of fluvial facies and architectural elements that together record both the proximal and distal parts of a meandering river system that drained the northern margin of Gondwanaland. Stratigraphic units are arranged into vertically stacked fining-upward cycles represented by thin accumulations of channel-lag deposits at their bases, and sandstone-dominated channel fill and thicker accumulations of overbank mudstone at their tops. Sedimentary cyclicity records fluvial system development on a variety of spatial and temporal scales. Overall, the Warchha Sandstone preserves a series of three to ten vertically stacked fining-upward cycles that form part of a larger-scale, third-order sequence that is itself bounded by regionally extensive and laterally correlatable unconformities that were generated in response to combined tectonic and eustatic changes. The sequence-stratigraphic architecture reflects regional palaeogeographic development of the Salt Range region. The small-scale fluvial cycles originated through autogenic mechanisms, predominantly as a result of repeated channel avulsion processes that occurred concurrently with on-going subsidence and the progressive generation of accommodation. Each erosively based fining-upward fluvial cycle is divided into three parts: a lower part of trough cross-bedded conglomerate and coarse sandstone; a middle part of tabular cross-bedded, ripple cross-laminated and horizontally laminated sandstone; and an upper part of predominantly horizontally laminated and massive mudstone. Overall, the Warchha Sandstone records the progradation of a wedge of non-marine strata into a previously shallow-marine depositional setting. The underlying marine Dandot Formation is terminated by a major unconformity that represents a type-I sequence boundary associated with a regional relative sea-level fall and a significant regression of the Tethyan shoreline. The overlying Warchha Sandstone represents the onset of the subsequent lowstand systems tract in which a northward-flowing meandering river system redistributed clastic detritus derived from a tectonically-active source area (the Aravalli and Malani ranges) that lay to the south. This episode of fluvial sedimentation was terminated by a widespread marine transgression recorded by an abrupt upward transition to estuarine and shallow-marine deposits of the overlying Sardhai Formation. This change marks the transition from lowstand deposits to a transgressive system tract.

Evolution of Late Cretaceous–Palaeogene synorogenic basins in the Pieniny Klippen Belt and adjacent zones (Western Carpathians, Slovakia): tectonic controls over a growing orogenic wedge

The Pieniny Klippen Belt and neighbouring zones of the Western Carpathians represent an ancient accretionary wedge that developed during the meso-Alpidic (Coniacian–Eocene) tectonic epoch. After an overview of the extensive literature data, the authors present an interpretation of the synorogenic sedimentary record of these zones as being related to various environments of the foreland basin system consisting of the trench-foredeep and wedge-top depositional areas. The peripheral trench-foredeep depozones migrated from the South Penninic-Vahic oceanic realm towards the Oravic continental fragment in an intra-Penninic position, where the synorogenic deposits were laid down with coarsening- and thickening-upward trends before being overthrust by the propagating orogenic wedge tip. The development of wedge-top, piggyback basins (Gosau Supergroup) was controlled by the dynamics of the underlying wedge, composed of frontal elements of the Fatric and Hronic cover nappe systems of the Central Western Carpathians (Austroalpine units). Several compressional and extensional events are documented in the complex sedimentary and structural rock records within the wedge and related basins. The successive transgressive-regressive depositional cycles and corresponding deformation stages are interpreted in terms of a dynamic accretionary wedge that maintained the critical taper only transiently. The supercritical taper states are reflected in regression, shallowing and erosion in the wedge-top area, while the trench was supplied with large amounts of clastics by various gravity-flow types. On the other hand, the collapse stages tending to subcritical wedge taper are indicated by widespread marine transgressions or ingressions in the wedge-top area and a general deepening of all basins to bathyal conditions. Accordingly, the evolution of the entire trench-foredeep and wedge-top basin systems was principally controlled by the complex interplay of the regional tectonic evolution of the Alpine-Carpathian orogenic system, local wedge dynamics and eustatic sea-level fluctuations.

Stratigraphic and palaeoenvironmental framework of the Early Permian sequence in the Salt Range, Pakistan

The Early Permian Gondwana regime succession of the Nilawahan Group is exposed only in the Salt Range of Pakistan. After a prolonged episode of non-deposition that spanned much of the Palaeozoic, the 350 m thick predominantly clastic sequence of the Nilawahan Group records a late glacial and post-glacial episode in which a range of glacio-fluvial, marine and fluvial environments evolved and accumulated. The Early Permian succession of the Salt Range has been classified into four formations, which together indicates a changing climatic regime during the Early Permian in the Salt Range region. The lower-most, Tobra Formation unconformably overlies a Cambrian sequence and is composed of tillite, diamictite and fresh water facies, which contain a floral assemblage (Gangamopteris and Glossopteris) that confirms an Asselian age. The Tobra Formation is overlain by marginal marine deposits of the Dandot Formation (Sakmarian), which contain an abundant brachiopods assemblage (Eurydesma and Conularia). Accumulation of the Dandot Formation was terminated by a regional sea-level fall and a change to the deposition of the fluvial deposits of the Warchha Sandstone (Artinskian). The Warchha Sandstone was deposited by high sinuosity meandering, avulsion prone river with well developed floodplains. This episode of fluvial sedimentation was terminated by a widespread marine transgression, as represented by the abrupt upward transition to the overlying shallow marine Sardhai Formation (Kungurian). The Early Permian Gondwana sequence represented by the Nilawahan Group is capped by predominantly shallow shelf carbonate deposits of the Tethyan realm. The sedimentologic and stratigraphic relationship of these four lithostratigraphic units in the Salt Range reveals a complex stratigraphic history for the Early Permian, which is mainly controlled by eustatic sea-level change due to climatic variation associated with climatic amelioration at the end of the major Gondwana glacial episode, and the gradual regional northward drift to a lower latitude of the Indian plate.

Uppermost Lower Aptian transgressive records in Mexico and Spain: chronostratigraphic implications for the Tethyan sequences

Terra Nova, 24, 333–338, 2012AbstractA widespread marine transgression, which began at the very end of the Early Aptian, is well recorded in Mexico and Spain. In Mexico, this transgression was the most important Aptian transgressive event and its record begins in the Dufrenoyia justinae Zone, whereas in Spain the corresponding transgression is registered in the uppermost part of the Dufrenoyia furcata Zone. The basal age of this Tethyan transgression does not correspond exactly to any of the Lower Aptian third‐order sequences as reported in the literature. In Spain, the most important Aptian transgressive event was earlier, corresponding to the Tethyan sequence Ap3, which is well‐defined below this transgression reported herein. Consequently, it is possible to correlate this later transgressive event with the third‐order Ap4 sequence, which has commonly been attributed to the Upper Aptian. The available ammonoid data allow us to correct the basal age of the transgression, and to correlate the start of the ammonite record in Mexico with the Tethyan sequence Ap4.

A stratigraphical-geochemical study on the Chaco Paraná continental rift basin—An approach study based on regional sedimentology and drill-hole core analyses, South América

A stratigraphical-geochemical study on the Chaco Paraná continental rift basin—An approach study based on regional sedimentology and drill-hole core analyses, South América

Reworked miospores in the upper paleozoic and Lower Triassic of the northern circum‐polar area and selected localities

Reworking of Devonian, Carboniferous and Permian palynomorphs into the Lower Triassic of western Canada, Yukon, the Canadian Arctic Archipelago and Alaska has been documented by a number of workers. The phenomenon occurs in other northern circumpolar localities, such as East Greenland and the Barents Sea, and was probably widespread. Examples are given from western and eastern Europe, Russia, the Middle East, Pakistan, China, Brazil and Australia. The abundance and diversity of reworked palynomorphs from a number of stratigraphic units of different ages into the Lower Triassic is an important palynostratigraphic phenomenon of chronostratigraphic value. It may be the result of a major regional regression in the late Permian, followed by a widespread marine transgression in the Early Triassic, or it may be due to tectonic activity resulting in eustatic sea‐level rise. Whatever the mechanism, the advancing transgression resulted in erosion of exposed Devonian, Carboniferous and Permian rocks, but by Mid‐Triassic times most pre‐Triassic rocks had been covered by sediment, and the supply of reworked material much reduced. Reworked Devonian taxa belong to a variety of suprageneric groups including cavate trilete spores (lycopsids), acavate trilete spores (ferns) and monolete spores; Lower Carboniferous taxa include cingulate trilete spores. Possibly reworked Upper Carboniferous and Permian pollen includes that of Gymnosperms—Cordaites, conifers, pteridosperms (taeniate bisaccate and polyplicates), and cycads and gnetophytes. Lower Triassic palynomorphs, possibly in situ, may include (sometimes abundant) acanthomorph acritarchs such as Micrhystridium breve, M. setasessitante, M. fragile and Wilsonastrum colonicum. Lack of recognition of reworking has many implications concerning chronostratigraphy, palynostratigraphy, paleoenvironments, paleoclimates, coal petrography, thermal maturity, geochemistry, and chemostratigraphy. For example, if the Upper Permian and Lower Triassic Densoisporites playfordii, D. complicatus, D. nejburgii, Lundbladispora obsoleta and Aculeisporites variabilis are not in situ, but reworked specimens of the Devonian progymnosperm cavate morphon Geminospora lemurata, one has to question the commonly held view that a lycopsid dominated macroflora, with a large biomass, recolonised the land in the Early Triassic. Lower Triassic assemblages in which reworking occurred but has not been recognised may give the impression of palynofloral diversity, whereas low diversity and low abundance would be more consistent with the hostile arid environment of the Lower Triassic. One Upper Permian and Lower Triassic plant entity, well‐adapted to harsh conditions, was the algal cyst Chordecystia chalasta. Nevertheless, some higher plants must have survived the Permian‐Triassic crisis as witnessed by the presence of gymnosperm pollen in the Mesozoic. This is Geological Survey of Canada (Calgary), Contribution no. 2004237.

REWORKED MIOSPORES IN THE UPPER PALEOZOIC AND LOWER TRIASSIC OF THE NORTHERN CIRCUM-POLAR AREA AND SELECTED LOCALITIES

Abstract Reworking of Devonian, Carboniferous and Permian palynomorphs into the Lower Triassic of western Canada, Yukon, the Canadian Arctic Archipelago and Alaska has been documented by a number of workers. The phenomenon occurs in other northern circumpolar localities, such as East Greenland and the Barents Sea, and was probably widespread. Examples are given from western and eastern Europe, Russia, the Middle East, Pakistan, China, Brazil and Australia. The abundance and diversity of reworked palynomorphs from a number of stratigraphic units of different ages into the Lower Triassic is an important palynostratigraphic phenomenon of chronostratigraphic value. It may be the result of a major regional regression in the late Permian, followed by a widespread marine transgression in the Early Triassic, or it may be due to tectonic activity resulting in eustatic sea-level rise. Whatever the mechanism, the advancing transgression resulted in erosion of exposed Devonian, Carboniferous and Permian rocks, but by...

Evolution of the Miocene-Recent Woodlark Rift Basin, SW Pacific, inferred from sediments drilled during Ocean Drilling Program Leg 180

Abstract The results of drilling during Ocean Drilling Program Leg 180 provide insights into fundamental processes of continental break-up, because rifting can be related to westward propagation of a spreading centre into continental crust. A generally north-south transect of holes was drilled across the Woodlark Rift on the uplifted northern rift margin on the Moresby Seamount (Sites 1114 and 1116), on the hanging wall of the low-angle (25–30°) extensional Moresby Detachment Fault (Sites 1108, 1110–1113 and 1117) and across the downflexed northern rift margin (Sites 1118, 1109 and 1115). The results, when placed in the regional tectonic context, document a history of Palaeogene ophiolite emplacement, followed by Miocene arc-related sedimentation. Regional uplift and emergence of the forearc area took place in Late Miocene time. Submergence to form the Woodlark Rift began in latest Miocene time, marked by widespread marine transgression and shallow-water deposition, accompanied by input of air-fall tephra and volcaniclastic sediments. During Pliocene time, deposition within the rift basin was dominated by deep-water turbidites, including high-density turbidites in the south. Strong extension along the north-dipping Moresby Detachment Fault was active during Pleistocene time, associated with uplift of the Moresby Seamount and shedding of fault-derived talus, mainly of meta-ophiolitic origin. During Pleistocene time, a carbonate platform was constructed to the NW, trapping clastic sediment and resulting in a switch to slower, more pelagic and hemipelagic deposition within the Woodlark Rift Basin. The marked change in rift basin configuration during Pleistocene time may relate to westward propagation of the Woodlark oceanic spreading centre at c. 2 Ma.

MAPPING THE PLATE TECTONIC RECONSTRUCTION OF SOUTHERN AND SOUTHEASTERN AUSTRALIA AND IMPLICATIONS FOR PETROLEUM SYSTEMS

Southern Australian breakup history is divisible into three phases. The first phase began with Callovian (c.159–165 Ma) rifting in the western Bight Basin. During the Tithonian (c.142–146 Ma), rifting extended eastwards into the Duntroon, Otway and Gippsland Basins. By the Valanginian (c.130–135 Ma), ocean crust formed between India and western Australia. Structural style in the western Bight changed to thermal subsidence. However, fluvio-lacustrine rift sedimentation continued in Duntroon, Otway and Gippsland until the Barremian (c.115–123 Ma) when these basins also changed to thermal subsidence. The diachronous progression of basin fill types produces a progressive shift in ages of potential source, seal and reservoir intervals along the margin.The second phase began during the Cenomanian (c.92–97.5 Ma) with uplift in eastern Australia, stress reorganisation and divergence of basin development. The Otway, Sorell and Great South Basins formed in a transtensional regime. These tectonics resulted in trap generation through faulting, inversion and wrenching. During the Santonian, oceanic spreading began in the southern Tasman Sea (c.85 Ma). Slow extension caused thinning of continental crust in the Bight and Otway Basins and subsidence into deeper water. Ocean crust formed south of the Bight Basin in the Early Campanian (c.83 Ma) and also started extending up the eastern Australian coast.The third stage in development was caused by Eocene changes to fast spreading in the Southern Ocean (c.44 Ma), final separation of Australia and Antarctica, and cessation of Tasman Sea spreading. These events caused collapse of continental margins and widespread marine transgression. The resultant loading, maturation and marine seal deposition are critical to petroleum prospectivity in the Gippsland Basin.

Mantle flow mechanisms of epeirogeny and their possible role in the evolution of the Western Canada Sedimentary Basin

Otherwise stable cratons periodically experience enigmatic episodes of large-scale uplift and subsidence that may result in widespread marine transgressions and the subsequent formation of sedimentary basins. Strata in the Western Canada Sedimentary Basin, for example, record flooding events that reached deep into the interior of the continent during the Devonian to Carboniferous. The epeirogenic motion which caused this deposition was contemporaneous with compressive tectonic events along the western plate margin of Laurussia. We propose that the long-wavelength component of inferred subsidence and uplift across the basin was the result of mantle flow-induced dynamic topography. In particular, we investigate the epeirogenic signals associated with the coupled mantle processes of near-surface subduction and later stage penetration of accumulated slab material through the endothermic phase change at 660 km depth. Numerical simulations of convection are presented to model the thermo-mechanical evolution of subduction in the mantle. The associated dynamic topography is initially characterized by tilting of the continental margin and submergence approximately 1000 km from the trench due to viscous effects associated with the subduction. A more extensive transgression onto the continental platform follows as accumulating slab material penetrates through the endothermic phase change. We argue that the predicted subsidence and uplift is broadly consistent with the inferred record of Devonian–Carboniferous epeirogeny across western Canada, and thus that the evolution of the Western Canada Sedimentary Basin may be intimately connected to mantle flow processes occurring contemporaneously beneath the craton.

Neogene Paratethyan Succession in Turkey and Its Implications for the Palaeogeography of the Eastern Paratethys

Abstract The Neogene marginal succession of the Eastern Paratethys (EP) crops out along the southern Black Sea coast and in the Marmara region of Turkey, and provides important clues to the tectono-sedimentary and palaeoceanographic conditions. In the Tarkhanian stage, the southern margin of the EP basin was largely a carbonate platform covered by warm, marine waters. From the end of the Tarkhanian to the Early Chokrakian there was an overall emergence throughout the basin, which is indicated by an influx of siliciclastic sediments. The fossil assemblage indicates that normal marine conditions persisted during most of this period, except for a salinity reduction towards the end due to an eustatic isolation of the basin, which in turn led to anoxic bottom water conditions. The Late Chokrakian isolation became even more severe during the Karaganian as indicated by the endemic fossil assemblage indicating brackish-marine conditions. Carbonate platform conditions prevailed in the northern Pontides during this time. In the Early Konkian, the basin was reconnected briefly with the world ocean by a transgression from the Indo-Pacific Ocean. In the Late Konkian there was a return to brackish-marine conditions. Lower Sarmatian sediments are absent in the southern margin of the EP, but elsewhere in the basin this stage is characterized by a widespread marine transgression. In the Middle-Late Sarmatian, the EP basin was partially isolated with freshening and anoxic bottom-water conditions. During this time there was a brief marine transgression from the Mediterranean into the Marmara region, but it did not reach the Paratethyan basin. The Pontian is characterized by an extensive transgression from the EP that inundated the Marmara and northeastern Aegean regions. The connection with the Marmara Basin was cut off during the Kimmerian and re-established during the Late Akchagylian, when the EP basin was inundated by the Mediterranean waters via the Sea of Marmara as a result of increased North Anatolian Fault activity and a short-term global sea level rise.

Glacigenic rafting at Castle Hill, Gardenstown, and its significance for the glacial history of northern Banffshire, Scotland

Reinvestigation of the lower part of the key Quaternary section at Castle Hill, Gardenstown, has shown that the sediments are not in stratigraphical order, but consist chiefly of glaciotectonites, including rafts of soft sediments, which were deposited by ice moving southeastwards from the Moray Firth. Sedimentary structures are preserved in some of the rafts, which are separated by subhorizontal shears. The rafts accreted subglacially under conditions of moderate to high strain, the final glacial event being the deposition of a thin, discontinuous sheet of till, probably derived from a more westerly direction. It is proposed that interbedded dark grey shelly clay, till and sand elsewhere in northern Banffshire were emplaced, at least in part, by a similar mechanism during either the Middle Devensian, or more likely, the Late Devensian. Sand and clay with paired bivalve shells, which were formerly exposed within the Quaternary successions at Castle Hill and inland at King Edward, some 12 km to the south, are interpreted to be within glacigenic rafts, and are not in situ deposits formed during a widespread marine transgression. It is suggested that the alternation of phases of constructional and excavational deformation within a single glacial event rather than discrete glaciations provides a useful model for glacial deposition in northern Banffshire, and more generally in northeast Scotland. © 1997 John Wiley & Sons, Ltd.

Isolated carbonate platform of Caniego, Spain: A test of the latest Albian worldwide sea-level changes

Research Article| February 01, 1997 Isolated carbonate platform of Caniego, Spain: A test of the latest Albian worldwide sea-level changes P. A. Fernández-Mendiola; P. A. Fernández-Mendiola 1Universidad del País Vasco, Estratigrafía, Facultad de Ciencias, Apartado 644, 48080 Bilbao, Spain Search for other works by this author on: GSW Google Scholar J. García-Mondéjar J. García-Mondéjar 1Universidad del País Vasco, Estratigrafía, Facultad de Ciencias, Apartado 644, 48080 Bilbao, Spain Search for other works by this author on: GSW Google Scholar Author and Article Information P. A. Fernández-Mendiola 1Universidad del País Vasco, Estratigrafía, Facultad de Ciencias, Apartado 644, 48080 Bilbao, Spain J. García-Mondéjar 1Universidad del País Vasco, Estratigrafía, Facultad de Ciencias, Apartado 644, 48080 Bilbao, Spain Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1997) 109 (2): 176–194. https://doi.org/10.1130/0016-7606(1997)109<0176:ICPOCS>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation P. A. Fernández-Mendiola, J. García-Mondéjar; Isolated carbonate platform of Caniego, Spain: A test of the latest Albian worldwide sea-level changes. GSA Bulletin 1997;; 109 (2): 176–194. doi: https://doi.org/10.1130/0016-7606(1997)109<0176:ICPOCS>2.3.CO;2 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 The upper Albian Caniego carbonate platform consists of a 20-m-thick unit of rudist- and coral-bearing limestones that crops out at the northern margin of the Mena diapir in northern Spain. The limestones were deposited on top of a slowly subsiding area, the Mena paleohigh, a diapiric-induced horst bounded by synsedimentary faults. The Caniego limestones originated in shallow warm tropical waters following a widespread marine transgression at the base of the foraminifera Rotalipora appenninica zone (ammonite Stoliczkaia dispar zone). Around the middle part of the appenninica zone the Caniego limestones underwent subaerial exposure and karst development. Fibrous calcite cements filled the bulk of the fissure-dike and dissolution cavities. Field, petrological, and geochemical data indicate that the fibrous calcites are meteoric flowstones. δ18O values in these cements range from −3‰ to −4.5‰ and δ13C values range from −7‰ to −14‰ (relative to the Peedee belemnite [PDB] standard). Thick wedges of nearshore shallow-marine siliciclastic sediments were deposited in paleotrough areas surrounding the Caniego paleohigh while the platform was subaerially exposed. The carbonate platform was drowned in early Cenomanian time and hardground-condensed facies developed during this period (Rotalipora brotzeni zone). Deeper water noncondensed marly sedimentation was reestablished in the mid-Cenomanian (Rotalipora reicheli zone). Comparison of the Iberian Caniego limestones with worldwide successions suggests a coincidence in the timing of platform formation emergence and drowning in several basins of different lithospheric plates. Nevertheless, an overall lack of coordination of sea-level histories from different basins may be related to tectonic movements of the lithospheric plates. Plate rearrangement is invoked as the primary control on relative sea-level changes and sequence development. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The biogeography of the late Paleozoic floras of India

This paper reviews the biogeography of Paleozoic floras in India and addresses some of the important biogeographic questions that have been raised regarding the distribution of floras and faunas on the subcontinent. Little is known about the Silurian and Devonian floras. Plants of this age have been reported sparingly from the extra-peninsular Panjab-Kashmir Himalaya region. On the basis of the available evidence, land plants comprised a cosmopolitan world flora until the end of the Early Carboniferous. The beds above the Lower Carboniferous strata of Gondwanaland record a sudden large-scale extinction of plants due to widespread glaciation. The Gondwana glaciation is believed to have ranged from the Upper Carboniferous to the Upper Permian in different parts of the supercontinent. The earliest post-glacial fossiliferous strata of Upper Carboniferous/Lower Permian age in India are found in the Talchir Series which has been divided into two stages, the Talchir and the Karharbari. Talchir floras are depauperate and appear to have lived under unfavorably cold conditions. Approximately 20 Talchir taxa are reported. The floras are dominated by Gangamopteris. Conditions during the Karharbari in peninsular India favoured the development of diverse floras and extensive, thick peat accumulations. On the basis of floral evidence, climatic conditions are interpreted to have been milder and warmer than during the Talchir Stage. Gangamopteris still dominated but other glossopterids were becoming abundant and the pre-conifers first emerged. The Talchir series is overlain by the Damuda Series. The time during which the Damuda strata were being deposited is divided into three stages, the Barakar, Barren Measures (Kulti or Ironstone Shales), and the Raniganj. These stages are characterized by the increased diversification of Glossopteris and the waning of Gangamopteris. The tectonic movement of Gondwanaland northward away from its southern polar position resulted in gradually ameliorating temperatures during the Permian period. By the beginning of the Triassic, northward plate movement had positioned the subcontinent within an arid realm. Except for some rare occurrences of Glossopteris and Sphenophyllum, the glossopterids became extinct by the Triassic and were replaced by the Dicroidium floras. Some of the important biogeographic problems relating to the distribution of the late Paleozoic floras of India are concerned with the location of the northern, northeastern, and northwestern boundaries of Gondwanaland. The occurrence of non-Gondwanan forms at these localities could be interpreted as an indication that paleoecotones developed in the border areas between biogeographic provinces. However, an alternative hypothesis suggests that the areas of mixed floras constitute evidence that a microcontinent lay between the Eurasian plate and Gondwanaland. The occurrence of marine strata in the middle peri-Tethys region in the Salt Range and the Himalayan localities in Kashmir has long been established. However, the discovery of shelled faunas and smooth-walled acritarchs interpreted to be of marine origin throughout peninsular India indicates that the possibility of widespread marine transgressions into Lower Gondwana strata situated far from the Tethys will have to be considered.

Fossil vertebrate faunas of the British Rhaetian (latest Triassic)

Rhaetian fossil vertebrate faunas of Britain represent rich but biased samples of taxonomic diversity during uppermost Triassic time. Review of the Westbury Formation, Penarth Group, in particular, reveals a combination of marine, littoral, and terrestrial elements. Minimally, six species of shark are preserved along with a myriacanthid holocephalan, at least four actinopterygian taxa, a characteristic lungfish, ichthyosaurs, plesiosaurs, dinosaurs, and potentially the earliest representative of the Choristodera. Rare mammalian occurrences in the Westbury beds are also possible. Severnichthys gen. nov. is a large ostcichthyan, probably a palaeonisciform chondrostean, which historically has been mistaken for a labyrinthodont amphibian. At least two additional actinopterygian species and a holocephalan are known from the Lilstock Formation, and a mammal or mammal-like reptile is recorded from the uppermost Blue Anchor Formation. Analysis of element abundance in the disarticulated Westbury Formation assemblage indicates that many parts of some taxa are never preserved while other elements of the same form are common. Such preservational bias suggests that many species may be missing entirely from this long-studied but poorly understood taphocoenosis. Possibly contemporaneous cave faunas from nearby upland areas give a similarly biased picture of the terrestrial fauna during this time of widespread marine transgression.