Cretaceous Deep Marine Research Articles

Lower Cretaceous deep marine deposits in western Tibet: Implications for paleoceanographic evolution of the Mesotethyan Ocean

Cretaceous pelagic deposits in the Bangong-Nujiang Suture Zone are significant for understanding the last evolutionary stage of the Mesotethyan Ocean and constraining the timing of initial Lhasa-Qiangtang collision, however few existing studies present the necessary sedimentological and biostratigraphic data. Here, we present detailed lithostratigraphic and biostratigraphic surveys in the Rotug area. A total of 40 species belonging to 23 genera are identified in the pelagic siliceous sedimentary sequences and indicate an Early Cretaceous (Hauterivian–late Aptian) age based by correlation on Unitary Association Zones. These newly discovered radiolarians help to constrain the paleoceanography and paleogeography of the Mesotethyan Ocean and indicate a deep marine setting existed across western Tibet during the late Aptian. Faunal similarities across the entire Tethyan realm, suggest this ocean was connected with the Neotethyan Ocean during the Early Cretaceous. This study has implications for the paleoceanographic evolution of the post-collisional residual-sea and sedimentary characteristics of marginal basins adjacent to continents during the Late Mesozoic.

Santonian-Campanian planktonic foraminifera biostratigraphy of the northern Moghan area (NW Iran): implications for the timing of Cretaceous marine transgression

An Upper Cretaceous deep marine unit containing planktonic foraminifera was studied based on the material recovered from a subsurface section at the northern part of the Moghan area. The unit contains a relatively diverse assemblage of planktonic foraminifera, which allowed identifying a number of three biozones spanning the late Santonian to early late Campanian. These are Dicarinella asymetrica Zone, Globotruncanita elevata Zone, and Globotruncana ventricosa Zone. Based on the stratigraphic values of the identified planktonic foraminifera, a late Santonian to middle-late Campanian age is ascribed to the examined strata. The biostratigraphic results also point to the earlier marine transgression in the northern Moghan area starting in the late Santonian. Our biostratigraphic results indicate a prominent stratigraphic hiatus at the contact of Upper Cretaceous unit with the overlying Sarmatian strata, comprising the late Campanian to middle Serravallian.

Provenance investigation from sedimentary petrography of the Upper Cretaceous deep marine low density turbidites of the Tanjero Formation around Arbat, northeastern Iraq

Deep marine low density turbidites of the Upper Cretaceous Tanjero Formation were studied in terms of their petrographic composition to deduce the provenance of the unit around Arbat, northeastern Iraq. Petrographic works based on modal analysis of the clastic rock fragments and released single minerals in silt, fine to coarse grained sandstone, and, in very small quantities, pebbly sandstone show that these turbidites are mainly composed of sedimentary rock fragments such as carbonate, microcrystalline and cryptocrystalline quartz bearing siliceous sedimentary cherts, Radiolaria bearing cherts, and released Radiolaria fossils from the cherts during a short distance transportation. Quartz and feldspar ratios in the whole thin sections are below two percent. The turbidite siltstones and sandstones are litharenite (calclithite) in composition, indicating sedimentary source rocks mainly consisting of carbonate rocks, Radiolaria, and chert-rich limestone. There is no significant petrographic variation across the clastic succession of the area. The composition of the clastic rocks suggests a recycled sedimentary source. Likewise, the QtFL ternary diagram suggests that the sediments are derived from a lithic recycled provenance, which indicates not only the Lower Cretaceous deep marine Qulqula (radiolarian) Formation as in the previous provenance works but also another deep marine unit, the Lower Cretaceous Balambo Formation, and a shallow water Lower Cretaceous Qamchuqa formation.

Marine palynology and environmental interpretation of the Lower Cretaceous (Barremian?–Aptian) rock units in the Koppeh-Dagh Basin, NE Iran

The Sarcheshmeh and Sanganeh formations are the Lower Cretaceous deep marine sequences of the Koppeh-Dagh sedimentary basin, which revealed a diverse assemblage of dinoflagellates. The paper discusses palynostratigraphy, palynofacies and palaeoenvironment of these rock units in a borehole drilled in the eastern part of this basin. Ninety-five ditch-cutting samples were prepared and studied palynologically, which resulted in recognition of 76 species of dinoflagellate cysts belonging to 29 genera. The recorded assemblages are in accordance with the Odontochitina operculata Zone suggesting a Barremian?–Aptian age for the formations. Palynological data extracted led to identification of five palynofacies types based on the categories of Tyson (1995). These indicate a marginal, proximal and distal shelf environment of deposition. The obtained data from calculated palaeoecological factors revealed a gradual sea level rise during the deposition of these rock units, resulting in replacement of the oxic/dysoxic Sarcheshmeh Formation by the dysoxic/anoxic Sanganeh Formation.

Abstract: Controls on Early Cretaceous Deep-Marine Sandstones, Outer Moray Firth, UK North Sea.

Abstract: Controls on Early Cretaceous Deep-Marine Sandstones, Outer Moray Firth, UK North Sea.

A Reservoir Model for the Lower Cretaceous Deep Marine Sandstones in the Maloy Fault Block Area, Norwegian North Sea: ABSTRACT

The Maloy Fault Block area of the North Viking Graben forms a platform to the east of the Sogn Graben next to the coast of Norway. This area is characterized by an unusual and thick Lower Cretaceous section containing a number of discrete sandstone packages. Wells drilled elsewhere in the Norwegian North Sea are in contrast dominated by a relatively thin mud and marl dominated section in the Lower Cretaceous. Two wells in block 35/3 (the Agat field) encountered gas bearing sandstones of Albian age interpreted to represent deposition in a deep marine environment. An integrated sequence stratigraphic approach to the Lower Cretaceous stratigraphy in the Maloy Fault Block area has led to a new and more detailed understanding of controls on deposition in this area. This is based both on a regional dataset and good quality 3D seismic data. A Valanginian-Hauterivian relict slope/shelf system is present along the eastern basin margin. It formed a long-lasting topographic feature and in some areas was not onlapped until the Campanian time. A dramatic change in the basin configuration took place most likely in the Aptian time. This was initiated by erosion of the slope/shelf system which cut multiple huge canyons along themore » basin-margin. The canyons focused sediment input to the basin along discrete and mappable transport routes, some of which are controlled by erosion features inherited from the Late Jurassic. A complex history of deposition and filling followed. This was controlled by a constantly changing basin floor topography and left a complex pattern of partly constrained fan deposition.« less

Optimum microfossil sequences and cyclic sediment patterns in Early Cretaceous pelagic strata

Three sequencing methods were used to calculate the most likely biozonation and the periodicity of sedimentary cycles in Lower Cretaceous pelagic strata of the Atlantic and Indian oceans.A database was built of 378 first and last stratigraphic occurrences of calcareous nannofossils, dinocysts, foraminifers, and geomagnetic reversals in highest Jurassic through Lower Cretaceous deep marine strata at 10 Atlantic Ocean and 3 Indian Ocean drilling sites. There are 135 different events in total, about one third of which are unique to either ocean. Using the complete data set, the quantitative stratigraphy methods STRATCOR and RASC calculated closely comparable optimum sequences of average first- and last-occurrence positions. The preferred zonal solution, based on the STRATCOR method, includes 56 events, each of which occurs at three or more sites. The events comprise 6 geomagnetic reversals, 25 nannofossils, 5 planktonic foraminifera, 8 benthic foraminifera, and 12 dinocysts occurrences. Nine assemblage zones have been recognized of Tithonian through Albian age. All but 2 of 18 nannofossil events in the Atlantic Ocean optimum sequence were reported in the same stratigraphic order in a standard Mesozoic nannofossil zonation.Our quantitative examination, using Walsh spectral analysis, of the Lower Cretaceous cyclic sequences at three Deep Sea Drilling Project (DSDP) sites in the Atlantic Ocean generally supports the hypothesis that they are the product of cyclic climatic changes controlled by the Milankovitch orbital cycles. The peaks in the power spectra usually can be related to obliquity and precession cycles; some peaks seem to correspond to the eccentricity cycle. Obliquity seems to be the most important and persistent orbital element responsible for cyclic sedimentation in the Early Cretaceous Atlantic Ocean.The actual pelagic sedimentation rates were calculated for some cores using the results of spectral analysis. The correlation of the actual pelagic sedimentation rate with cyclic patterns and the occurrence of calcareous turbidites indicate that the changes in cycle pattern are the reflection of changes in the oceanographic setting. The changes in oceanographic setting are related to relative-sea-level fluctuations. The intervals dominated by laminated limestone were deposited during higher sea-level periods.

The Bottom Current Sediments (Contourites) in the Upper Cretaceus Deep-Water Deposits in the Northeeastern Part of Žumberak (Croatia)

The Upper Cretaceous deep marine deposits in NE parts of Žumberak contain sediments deposited by bottom currents - muddy, sandy and sandy-gravelly contourites. The complete (negative-positive) sequences and incomplete (negative-positive) sequences have been observed. Apart from the sediments that have been deposited by bottom currents, several turbidite layers reworked by bottom currents occur.