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Stephen Louwye - One of the best experts on this subject based on the ideXlab platform.
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dinoflagellate cyst stratigraphy and palaeoecology of the pliocene in northern belgium southern north sea basin
Geological Magazine, 2004Co-Authors: Stephen Louwye, Martin J Head, Stijn De SchepperAbstract:Dinoflagellate cysts and other palynomorphs from the Pliocene Kattendijk and Lillo formations, exposed in two temporary outcrops in northern Belgium, provide new information on the biostratigraphic position and Sequence stratigraphic interpretation of these units. Dinoflagellate cysts from the Kattendijk Formation indicate an age between about 5.0 Ma and 4.7–4.4 Ma (early Early Pliocene) in our sections, confirming a correlation with standard Sequence 3.4 and implying a slightly greater age than the Ramsholt Member of the Coralline Crag Formation of eastern England. The unconformity at the base of the Kattendijk Formation was not seen, but presumably correlates with Sequence Boundary Me2 at 5.73 Ma. The overlying Lillo Formation is late Early Pliocene or early Late Pliocene ( c . 4.2–2.6 Ma) in age, and the unconformity at its base may be correlated with Sequence Boundary Za2 at 4.04 Ma or Pia1 at 3.21 Ma. The Oorderen Sands and superjacent Kruisschans Sands members (Lillo Formation) are both part of the same depositional cycle. They were probably deposited before 2.74 Ma, and certainly before the onset of Northern Hemisphere cooling at c . 2.6 Ma. Evidence from dinoflagellate cysts indicates that both a shelly unit at the base of the Lillo Formation and the lower part of the overlying Oorderen Sands were deposited during a conspicuously cool climatic phase, with warmer temperatures returning during later deposition of the Oorderen Sands and Kruisschans Sands members. Many dinoflagellate cyst and acritarch species are reported here for the first time from the southern North Sea Basin. Selenopemphix conspicua (de Verteuil & Norris, 1992) stat. nov. is proposed.
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shallow marine lower and middle miocene deposits at the southern margin of the north sea basin northern belgium dinoflagellate cyst biostratigraphy and depositional history
Geological Magazine, 2000Co-Authors: Stephen Louwye, J De Coninck, Jacques VerniersAbstract:Detailed dinoflagellate cyst analysis of the Lower–Middle Miocene Berchem Formation at the southernmost margin of the North Sea Basin (northern Belgium) allowed a precise biostratigraphical positioning and a reconstruction of the depositional history. The two lower members of the formation (Edegem Sands and decalcified Kiel Sands) are biostratigraphically regarded as one unit since no significant break within the dinocyst assemblages is observed. The base of this late (or latest) Aquitanian–Burdigalian unit coincides with Sequence Boundary Aq3/Bur1 as defined by Hardenbol and others, in work published in 1998. A hiatus at the Lower–Middle Miocene transition separates the upper member (the Antwerpen Sands) from the underlying member. The greater part of the Antwerpen Sands were deposited in a Langhian (latest Burdigalian?)–middle Serravallian interval. The base of this unit coincides with Sequence Boundary Bur5/Lan1. Biostratigraphical correlation points to a diachronous post-depositional decalcification within the formation since parts of the decalcified Kiel Sands can be correlated with parts of the calcareous fossil-bearing section, up to now interpreted as Antwerpen Sands. The dinoflagellate cyst assemblages are dominated by species with a inner neritic preference, although higher numbers of oceanic taxa in the upper part of the formation indicate incursions of oceanic watermasses into the confined depositional environment of the southern North Sea Basin.
Claus Heilmannclausen - One of the best experts on this subject based on the ideXlab platform.
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a mid oligocene cooling oi 2b reflected in the dinoflagellate record and in depositional Sequence architecture an integrated study from the eastern north sea basin
Marine and Petroleum Geology, 2010Co-Authors: Kasia K śliwinska, O R Clausen, Claus HeilmannclausenAbstract:Abstract Integrated micropaleontological (dinoflagellate and foraminifera) and 3D seismic studies of Oligocene surfaces were carried out in the eastern North Sea in order to investigate the influence of the climate on the evolution of depositional geometries and surface morphologies. Age-indicative dinoflagellates allowed a correlation of the succession with the global time scale and thereby with published oxygen isotope curves. Temperature-indicative dinoflagellate taxa furthermore allowed to infer paleoclimatic changes during the mid-Oligocene. One of the surfaces studied on 3D seismic datasets shows features such as low-angle landward directed onlaps, incised valleys and pockmarks, indicating a prominent, relative sea-level fall. The cold-water dinoflagellate Svalbardella was recorded immediately above this surface. The coincidence of a cold-water indicator with this distinctive Sequence Boundary shows that deposition of this Sequence was controlled by climatically induced sea-level changes, and that 3D seismic analysis combined with high-resolution dinoflagellate analysis substantially improves the understanding of the depositional history and processes within the North Sea Basin. The Svalbardella event represents the Oi-2b glaciation and coincides with the onshore NW European Rupelian/Chattian Boundary.
Gennari Valerio - One of the best experts on this subject based on the ideXlab platform.
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Lower Triassic (Induan to Olenekian) condonts, foraminifera and bivalves from the Al Mamalih area, Dead Sea, Jordan: constraints on the P-T Boundary
2019Co-Authors: Powell, John H., Nicora Alda, Perri, Maria Cristina, Rettori Roberto, Posenato Renato, Stephenson, Michael H., Masri Ahmed, Borlenghi, Letizia M., Gennari ValerioAbstract:Upper Permian to Lower Triassic successions exposed in the Al Mamalih area, east of the Dead Sea, Jordan record the transition between the alluvial Umm Irna Formation (Upper Permian) and the overlying shallow marine Ma’in Formation (Lower Triassic). The Permian-Triassic Boundary is constrained either within a hiatus represented by a Sequence Boundary between these formations or within ca 15 m of shallow marine beds overlying the Boundary. Above the Sequence Boundary reddened, shallow-marine beds (Himara Member) mark the initial Triassic (presumed early Induan) marine transgression (Himara Member). Absence of both body fossils and vertical infaunal burrows indicates low-diversity ecosystems following the Permian-Triassic extinction event. A gradational upward increase in grey, green and yellow siltstones beds (Nimra Member), accompanied by a concomitant increase in bioturbation (surface traces and infaunal vertical burrows), bivalves and brachiopods, stromatolites, conchostracans and lingulids in the lower part of the Nimra Member indicates colonisation of the substrate under shallow marine conditions during the recovery phase. Shallow-water carbonates in the Nimra Member yielded an abundant, low diversity assemblage of conodonts (e.g. Hd. aequabilis and H. agordina) and a foraminifera assemblage (Postcladella gr. kalhori-Earlandia spp.-Ammodiscus jordanensis n. sp.) that are interpreted as euryhaline recovery taxa that characterise the mid-late Induan. Abundant new material has allowed revision of the conodont apparatus and the foraminifera include a new species Ammodiscus jordanensis n. sp. of Induan age. The discovery of the bivalves Claraia bittneri (C. aurita group) and Eumorphotis multiformis is worthy of note. Upper Permian alluvial lithofacies (Jordan) pass basinwards, about 50 km to the northwest, to coeval shallow marine siliciclastic and carbonates in the Negev and Mediterranean coast of Israel
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LOWER TRIASSIC (INDUAN TO OLENEKIAN) CONODONTS, FORAMINIFERA AND BIVALVES FROM THE AL MAMALIH AREA, DEAD SEA, JORDAN: CONSTRAINTS ON THE P-T Boundary
Università degli Studi di Milano, 2018Co-Authors: Powell, John H., Nicora Alda, Perri, Maria Cristina, Rettori Roberto, Posenato Renato, Stephenson, Michael H., Masri Ahmed, Borlenghi, Letizia M., Gennari ValerioAbstract:Upper Permian to Lower Triassic successions exposed in the Al Mamalih area, east of the Dead Sea, Jordan record the transition between the alluvial Umm Irna Formation (Upper Permian) and the overlying shallow marine Ma’in Formation (Lower Triassic). The Permian-Triassic Boundary is constrained either within a hiatus represented by a Sequence Boundary between these formations or within ca 15 m of shallow marine beds overlying the Boundary. Above the Sequence Boundary reddened, shallow-marine beds (Himara Member) mark the initial Triassic (presumed early Induan) marine transgression (Himara Member). Absence of both body fossils and vertical infaunal burrows indicates low-diversity, ecosystems following the Permian-Triassic extinction event. A gradational upward increase in grey, green and yellow siltstones beds (Nimra Member), accompanied by a concomitant increase in bioturbation (surface traces and infaunal vertical burrows), bivalves and brachiopods, stromatolites, conchostracans and lingulids in the lower part of the Nimra Member indicates colonisation of the substrate under shallow marine conditions during the recovery phase. Shallow-water carbonates in the Nimra Member yielded an abundant, low diversity assemblage of conodonts (e.g. Hd. aequabilis and H. agordina) and a foraminifera assemblage (Postcladella gr. kalhori-Earlandia spp.-Ammodiscus jordanensis n. sp.) that are interpreted as euryhaline recovery taxa that characterise the the mid-late Induan. Abundant new material has allowed revision of the conodont apparatus and the foraminifera include a new species Ammodiscus jordanensis n. sp. of Induan age. The discovery of the bivalves Claraia bittneri (C. aurita group) and Eumorphotis multiformis is worthy to note. Upper Permian alluvial lithofacies (Jordan) pass basinwards, about 50 km to the northwest, to coeval shallow marine siliciclastic and carbonates in the Negev and Mediterranean coast of Israel
Cong Liu - One of the best experts on this subject based on the ideXlab platform.
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geomorphologic indicators of sea level and lowstand paleo shelf exposure on early middle miocene Sequence boundaries
Marine Geology, 2011Co-Authors: Cong Liu, Craig S Fulthorpe, James A Austin, Carla M SanchezAbstract:Abstract Relationships between clinoformal Sequence boundaries and relative sea level change, in particular locations of lowstand shorelines and amounts of paleo-shelf exposure, represent a key topic in Sequence stratigraphy. This paper uses 3D seismic data to analyze morphologies of two Sequence boundaries in the early–middle Miocene section of the Northern Carnarvon Basin of the Australian Northwest Shelf. A step-like discontinuity is recognized on the outer paleo-shelf of Sequence Boundary DLS4 based on reflection truncation and seismic facies change. Vertical offset at this step varies from ~ 7 to 65 m, increasing along strike from SW to NE. The trace of this discontinuity comprises both linear and arcuate segments in coherence time slices. Isolated mounds and small platforms also occur on this Sequence Boundary, basinward of the discontinuity. Underlying sub-Sequence Boundary DLS3.1 displays a smaller step-like discontinuity, together with U- and V-shaped incisions as well as numerous, isolated depressions, the latter occurring within two large arcuate, concave-basinward features on coherence slices. We discuss several possible origins for these discontinuities. We conclude that step-like discontinuities on DLS4 and DLS3.1 represent buried wave-cut terraces or sea cliffs. Erosion is presumed to have occurred at or near ambient sea level. The incisions of DLS3.1 are karst. Together, these interpretations imply significant lowstand paleo-shelf exposure of early–middle Miocene Sequence boundaries.
Mads Huuse - One of the best experts on this subject based on the ideXlab platform.
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3D Seismic Analysis Reveals the Origin of Ambiguous Erosional Features at a Major Sequence Boundary in the Eastern North Sea: near Top Oligocene
Geological Society London Memoirs, 2004Co-Authors: J. P. V. Hansen, Ole R. Clausen, Mads HuuseAbstract:Abstract The near top Oligocene unconformity is a major Sequence Boundary in the eastern North Sea Basin. It is characterized by erosional scarps below the Boundary and a pronounced basinward shift in onlap above. The shift in onlap has previously been interpreted as caused by a major fall in sea level. Detailed 3D seismic analysis of a 20 by 20 km area at and basinward of the uppermost Oligocene clinoform breakpoint reveals that the erosional scarps were caused by undercutting of steep clinoforms by contour-parallel currents and resulting mass wasting whilst the lowermost onlap package consists of a contour-parallel drift deposited as the erosive currents waned. The 3D seismic analysis corroborates a recent analysis based on regional 2D seismic data, which found that the erosional scarps and the geometry of the onlap Sequence were indicative of a major shift in sediment input directions and not necessarily associated with any change of sea level. The paper thus demonstrates the utility of local 3D seismic analyses as a form of 9ground truthing9 regional basin analyses based on widely spaced 2D seismic grids.
