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<jats:title>Abstract</jats:title> <jats:p>Until recently, information about the end of the Cretaceous was based upon investigation of global outcrop sections. New subsurface drilling and characterization from well cores and logs in the Gulf of Mexico Basin have greatly illuminated the end Cretaceous event. However, the paleogeography of the late Maastrichtian just prior to bolide impact is less well understood and is of great importance in terms of modeling the resulting distribution and composition of the Chicxulub impact material as well as tsunami and seiche wave height. Here we examine the Maastrichtian strata in the basin, synthesizing lithostratigraphic and chronostratigraphy, tectonic plate reconstructions, global and local sea level history, paleoclimate, and depositional systems. Our new Maastrichtian paleogeographic reconstruction shows the basin prior to the Chicxulub impact at a time of globally high sea level, with widespread deposition of deepwater chalks and shallow marine carbonates and local siliciclastic shorelines fed by the nascent Cordilleran belt. Stratigraphic correlations of wells and outcrops illustrate the range of paleoenvironments from coastal plain to deep marine. As much as 610 m (2000 ft) of Maastrichtian and Campanian section is mapped around the basin, reflecting accommodation provided by basin subsidence, salt deflation, and paleo-physiography. A large thickness of carbonates accumulated in the basin center, with steep shoreline to basin gradients particularly in Mexico. At the end of the Cretaceous, carbonate paleoenvironments probably covered 96% of the Gulf of Mexico basin, with less than 4% of the area likely occupied by siliciclastic systems, a distribution that evolved from the early Cretaceous. Our maps thus explain dominance of carbonate breccia and chalks in K/Pg boundary units deposited over the basin sites proximal or distal to the Chicxulub impact crater. This also elucidates the large impedance contrast and high amplitude seismic response of the K/Pg boundary horizon, mappable over vast portions of the basin.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Since the creation of the Cretaceous system by Jean-Baptiste d'Omalius d'Halloy, numerous analyses have provided details about the Cretaceous sedimentary successions of the Paris Basin, where many boreholes have been drilled. We attempt to present a synthesis of the Cretaceous deposits using drillings carried out in the central and eastern parts of the basin which, during the lower Cretaceous, corresponded to a continental environment highlighted by the Wealden facies. However, from the Berriasian to the Barremian, the south-eastern part of the basin was occasionally invaded by a shallow sea during transgressions originating from the Tethys Ocean. The sedimentary successions of this age presented in this article have been studied thanks to drilling carried out by Andra (French Agency for Nuclear Waste Disposal). Several new results are thus presented here: a discussion on the age of the Argiles ostréennes, the identification of an equivalent of the oceanic anoxic event OAE1a, and a build-up of a continuous section of the Albian Clays in their type locality. Regarding the Upper Cretaceous chalk, the Cenomanian to Maastrichtian stages are successively presented over the entire basin and correlations are proposed based on biostratigraphic data and various marker beds including marly levels, bentonites, hardgrounds or eco-events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Neuquén Basin, located at the foothills of the Central Andes of Argentina, with superb and extended exposures is a natural laboratory. It is important not only for its continuous sedimentary record and superb palaeontological biota but also for its significant economic hydrocarbon resources. This synthesis is intended to provide an update only on the Cretaceous timespan in the basin development. It is characterized by a succession of sedimentary rocks that were deposited in different environments over time, interspersed with volcanic rocks associated with an active volcanic arc. High-precision geochronology dating on the tuffs establishes robust chronological ages to constrain the different stages. As this brief review only shows a fragment of the information presently available, an effort has been made to compile a comprehensive and up-to-date bibliography to compensate for the brevity of the text.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> This contribution outlines the methodology of strontium-isotope stratigraphy, and reviews the information that underpins the calibration curve of <jats:sup>87</jats:sup> Sr/ <jats:sup>86</jats:sup> Sr against time for the Cretaceous. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper summarizes the data on the Early Cretaceous palaeogeography of the Russian Platform (RP) in a context of the development of North-eastern Peritethys. One of the main features of the region is the constant mutual influence of the Tethyan and Boreal water masses through the system of straits. The latest Volgian to Barremian development of the RP basin was under the major influence of Boreal water mass (WM). It differs from the Aptian-Albian interval, which formed under major influence of Tethyan and Peritethyan WM. Zonal biostratigraphy reflects the type of marine biota related to the type of the WM. The WM movement interrupted by several episodes of exposition of the southern margin of the RP the Berriasian - Barremian or the almost the whole Platform in late Middle to late Aptian.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Ilek Formation was distinguished by Ragozin in 1936 in the southeast of Western Siberia, as a sequence of continental deposits accumulated in the alluvial and lacustrine environments, dating Barremian-Early Albian. In the end of XX century a series of sites, comprising a rich and diverse Early Cretaceous vertebrates were discovered, that forced an intensive comprehensive research of the Ilek Formation. The stratotype section of the Bolshoi Ilek represents the abnormal section of the Ilek Formation, comprising the deposits of prodelta, delta front, and mouth bars. Three regions within the area of the Ilek Formation reflect the evolution of the fluvial system. The eastern region represents the oldest part of the section, preliminary dated to the Barremian based on spore and pollen analysis in addition to lithological characteristics. The western region was probably deposited during OAE-1a. The central region represents the final stage of the tectonic cycle, deposited within the environments of the calm plain river and fluvial delta. The vertebrate assemblages distinguished for the Kiya and Bolshoi Kemchug basins have specific features, which can support the heterochrony of the Ilekian deposits.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The late Maastrichtian Rørdal Member of the Møns Klint Formation is a remarkable lithological unit of the Danish Basin, characterised by chalk-marl cyclicity, standing out of pure Maastrichtian white chalk within the Chalk Group. A cyclostratigraphic analysis across this unit suggests a control by orbital precession and a strong amplitude modulation of the precession by the 405 kyr eccentricity cycle. Oxygen isotope data from bulk carbonate, benthic foraminifera and brachiopods indicate a prominent cooling commencing at the base of the unit with maximum cooling aligned with a 405 kyr amplitude modulation maximum. This unit thus represents a rare example of a climatic cooling associated with a 405 kyr insolation maximum. However, geochemical and calcareous nannofossil data support lower productivity levels across the unit, in contradiction with an expected ocean fertilization accompanying enhanced continental weathering as source of the clay material. An alternative model of deposition for this lithological unit is thus proposed via dense water cascading favored by sea level low, subsequent restriction of the Chalk Sea and associated gravity currents responsible for the resuspension of fine clastic deposits from the margins of the Baltic Shield.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> The Lower Cretaceous (upper Hauterivian - Albian) pelagic and hemipelagic carbonates of the Tuxen and Sola Formations in the Danish Central Graben, North Sea, constitute one of the oldest chalk successions recorded globally, but have received less attention than the Upper Cretaceous - Danian Chalk Group. This paper presents an updated depositional model for the succession drawn from synthesis of the latest published sedimentological and stratigraphic results and correlation of 11 wells in the Valdemar, Boje, Adda and Tyra Fields. Four depositional sequences, deposited on a relatively deep subphotic shelf, record <jats:italic>c.</jats:italic> 20 Myr of transgressive-regressive cycles, including: (i) late Hauterivian - earliest Barremian highstand and differential subsidence, resulting in aggradation across a westward-dipping ramp; (ii) early Barremian eastern (Adda Field) inversion causing plateau condensation, sediment bypass and sourcing of gravity flows, followed by lowstand-controlled basin isolation and associated anoxia (Munk Marl Bed), and finally late Barremian tectonic quiescence and highstand with deposition of clean reservoir chalk; (iii) latest Barremian lowstand causing filling of local depocentres, interrupted by early Aptian transgression-controlled anoxia during the global Oceanic Anoxic Event 1a (Fischschiefer Member), and finally late Aptian highstand; and (iv) latest Aptian - earliest Albian lowstand causing local erosion and heightened influx of clay. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> The Cretaceous Period ( <jats:italic>ca</jats:italic> . 143-66 Ma) attested to successive phases of regional tectonic activities and large-scale submarine volcanism resulting in increased atmospheric CO <jats:sub>2</jats:sub> ( <jats:italic>p</jats:italic> CO <jats:sub>2</jats:sub> ) concentrations, enhanced greenhouse climate and global warming, surface water bioproductivity, and well-developed pore and bottom water anoxia, especially during the mid-Cretaceous (Aptian to Turonian). These conditions triggered widespread deposition of organic carbon (OC)-rich black shales during episodes of severe oxygen exhaustion, commonly known as Oceanic Anoxic Events (OAEs). OAEs had many important consequences, including widespread mass extinction of marine and terrestrial organisms. Several intervals of enhanced oxic ventilation and deposition of OC-poor pelagic-hemipelagic red carbonates and claystone interrupted Cretaceous OAEs, which are commonly known as Cretaceous Oceanic Red Beds (CORBs). The mid-Cretaceous black shales from many parts of the world and the corresponding global carbon cycle changes indicated that OAE1 (Selli Level) and OAE2 (Bonarelli Event) are the most widespread and well-defined OAEs compared to the more regional OAE3 and Valanginian-Hauterivian black shales (Weissert Event). These appear to have been more restricted to the Atlantic and adjacent areas, a result of more regional conditions rather than being forced by global environmental perturbations. </jats:p> <jats:p> In the course of this review, the Egyptian territory in the southern Tethys shelf is taken as a case study area for the development, evolution, and regional expression of mid-Cretaceous OAEs. The region is characterized by a thick Cretaceous sedimentary succession of OC-rich black shale and OC-poor carbonates and mudstone interbeds. The late Albian OAE1d was reported in the North Western Desert (upper Kharita Formation) based on a positive carbon isotope excursion and moderate total sulfur (TS), total organic carbon (TOC), and redox-sensitive elements. The end-Cenomanian OAE2 was reported in several regions of Egypt based on positive δ <jats:sup>13</jats:sup> C excursions. However, differential deposition between OC-rich and OC-poor facies took place, especially in marginal to shallow marine settings where black shales are absent such as in the Eastern Desert and Sinai. During the Coniacian-Santonian, OC-poor limestone, calcareous shale, and red claystone were deposited under enhanced water column respiration in Egypt. This indicates that enhanced oxygenated ocean circulation controlled organic matter decomposition during weak continental weathering and enhanced carbonate production, all of which led to the deposition of OC-poor CORBs in this region. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Abstract</jats:p> <jats:p>The lithostratigraphy, biostratigraphy and depositional environments of the Cretaceous successions Pakistan were investigated to reveal the major geological events, including local, regional and global scale tectonics, phases of volcanism, basin condensation, emergence of structural highs and episodes of non-deposition. The succession is entirely missing at Salt Range, but were excellently exposed in Kirthar-Sulaiman Fold-Thrust belts. Such deviating nature (e.g., Hazara, Kalla Chitta, Surghar &amp; Kohat) suggesting episodical tectonic activities were associated with inter-intra rifting and drifting of the India-Madagascar-Seychelles and Antarctica-Australian Plates during Cretaceous time. Correspondingly, several unconformities within the Cretaceous succession at numerous stratigraphic intervals consistently attest the effect of tectonics throughout the period. The recognized unconformities over Kawagarh, Lumshiwal, Parh and Fort Munro formations testify episodic uplifts on local and/or regional scales during the Coniacian-Santonian, Coniacian-Maastrichtian, Campanian and Maastrichtian in response to the separation of Madagascar from the India-Seychelles plate. In contrast, there was continuous sedimentation of carbonate, clastic and/or submarine volcanics in the Kirthar and Indian-Eurasian suture zone. Significant geological events in the restricted regions e.g., local scale submarine volcanism (Bibai Formation), ironstone deposition (Dilband Formation) and basin condensation (Khuzdar) were also associated with such rifting-drifting phases along the WNW margin of the Indian Plate.</jats:p>