Continental Cretaceous Research Articles

Late Cretaceous (Santonian) Atractosteus (Actinopterygii, Lepisosteidae) remains from Hungary (Iharkút, Bakony Mountains)

Lepisosteid fishes are well known from the Upper Cretaceous of Europe, but only by fragmentary remains from some Cenomanian and Campanian–Maastrichtian deposits. Here we report various cranial and postcranial remains of gars, discovered in the Upper Cretaceous (Santonian) Csehbánya Formation of Iharkút (Bakony Mountains, Hungary). These remains represent one of the most diverse assemblages of lepisosteid fish material from Upper Cretaceous continental deposits of Europe. Based on tooth morphology, scale-microstructure and the features of the supracleithrum we refer these remains to the genus Atractosteus. Besides some uncertain remains from the Cenomanian of France and Spain, the Santonian aged fossils from Iharkút represent the oldest undisputable occurrence of the family Lepisosteidae in the European continental Cretaceous. Using tooth crown morphology, the surface microstructure of the ganoid scales and the anatomy of the supracleithrum a review of the Late Cretaceous lepisosteid record suggests the occurrence of both Atractosteus and Lepisosteus in the European archipelago.

Campinasuchus dinizi gen. et sp. nov., a new Late Cretaceous baurusuchid (Crocodyliformes) from the Bauru Basin, Brazil

A remarkably diverse terrestrial mesoeucrocodylian fauna has been recovered from the continental Cretaceous of the Bauru Basin in fluvial and lacustrine deposits. Members of at least six distinct groups are now recognized, including notosuchids, sphagesaurids, candidodontids, peirosaurids, trematochampsids, and baurusuchids. These mostly terrestrial crocodyliforms potentially developed ecological strategies that allowed them to live in a hot and arid climate during the Cretaceous. A new genus and species of Baurusuchidae, Campinasuchus dinizi gen. et sp. nov., is established on the basis of several partial skulls and skeletons from the Turonian-Santonian Adamantina Formation. This taxon is notable for its relatively short, anteriorly tapering snout, marked maxillary heterodonty with third maxillary and fourth dentary teeth extremely enlarged relative to other teeth, and the presence of a large anteroposterior depression on each palatine between the palatal fenestrae. The presence of yet another crocodyliform from the Adamantina Formation reinforces the idea that aridity, or maybe a seasonally warm and dry climate alternating with periods of higher rainfall, drove the diversification of terrestrial crocodyliforms throughout the Late Cretaceous.

Integrated stratigraphy from the Vallcebre Basin (southeastern Pyrenees, Spain): New insights on the continental Cretaceous−Tertiary transition in southwest Europe

An integrated sedimentological, magnetostratigraphic, and paleontological study of the Vallcebre section (south eastern Pyrenees, Spain) is carried out in order to define and portray the transition from the Cretaceous to the Tertiary in a continental setting. A robust magnetostratigraphy is correlated to the standard polarity scale in light of known biochronological constraints (charophyte, marine invertebrates, eggshells and other dinosaur remains). Our results show that this section is among the thickest stratigraphic records for the continental Maastrichtian in the Old World. Sedimentology indicates a progressive regression from marine through lagoonal to entirely continental environments. The section is dominated by mudstones deposited under low energy conditions. Exceptionally, a basin-wide regression maximum is recorded some time before the Cretaceous–Tertiary boundary (K/T). This regression maximum is marked by the input of coarse-grained (alluvial) sediments that record a dramatic change in the landscape (quiet mud plains changed to sandy floodplains deposited by high-energy currents). After a period of renewed quiescence following the regression maximum, a Cenozoic flooding took place. Such terminal Cretaceous sequence of events has been recorded in shorter sections in several other basins from southwestern Europe. This energetic sediment input suggests that some time before the K/T event, a sudden paleoenvironmental reorganization took place in the continental basins of south western Europe.

Carbon isotopic compositions of organic matter across continental Cretaceous–Tertiary (K–T) boundary sections: Implications for paleoenvironment after the K–T impact event

To assess the environmental perturbation induced by the impact event that marks the Cretaceous–Tertiary (K–T) boundary, concentrations and isotopic compositions of bulk organic carbon were determined in sedimentary rocks that span the terrestrial K–T boundary at Dogie Creek, Montana, and Brownie Butte, Wyoming in the Western Interior of the United States. The boundary clays at both sites are not bounded by coals. Although coals consist mainly of organic matter derived from plant tissue, siliceous sedimentary rocks, such as shale and clay, may contain organic matter derived from microbiota as well as plants. Coals record δ 13C values of plant-derived organic matter, reflecting the δ 13C value of atmospheric CO 2, whereas siliceous sedimentary rocks record the δ 13C values of organic matter derived from plants and microbiota. The microbiota δ 13C value reflects not only the δ 13C value of atmospheric CO 2, but also biological productivity. Therefore, the siliceous rocks from these sites yields information that differs from that obtained previously from coal beds. Across the freshwater K–T boundary at Brownie Butte, the δ 13C values decrease by 2.6‰ (from − 26.15‰ below the boundary clay to − 28.78‰ above the boundary clay), similar to the trend in carbonate at marine K–T sites. This means that the organic δ 13C values reflect the variation of δ 13C of atmospheric CO 2, which is in equilibrium with carbon isotopes at the ocean surface. Although a decrease in δ 13C values is observed across the K–T boundary at Dogie Creek (from − 25.32‰ below the boundary clay to − 26.11‰ above the boundary clay), the degree of δ 13C-decrease at Dogie Creek is smaller than that at Brownie Butte and that for marine carbonate. About 2‰ decrease in δ 13C of atmospheric CO 2 was expected from the δ 13C variation of marine carbonate at the K–T boundary. This δ 13C-decrease of atmospheric CO 2 should affect the δ 13C values of organic matter derived from plant tissue. As such a decrease in δ 13C value was not observed at Dogie Creek, a process that compensates the δ 13C-decrease of atmospheric CO 2 should be involved. For example, the enhanced contribution of 13C-enriched organic matter derived from algae in a high-productivity environment could be responsible. The δ 13C values of algal organic matter become higher than, and thus distinguishable from, those of plant organic matter in situations with high productivity, where dissolved HCO 3 − becomes an important carbon source, as well as dissolved CO 2. As the δ 13C-decrease of atmospheric CO 2 reflected a reduction of marine productivity, the compensation of the δ 13C decrease by the enhanced activity of the terrestrial microbiota means that the microbiota at freshwater environment recovered more rapidly than those in the marine environment. A distinct positive δ 13C excursion of 2‰ in the K–T boundary clays is superimposed on the overall decreasing trend at Dogie Creek; this coincides with an increase in the content of organic carbon. We conclude that the K–T boundary clays include 13C-enriched organic matter derived from highly productive algae. Such a high biological productivity was induced by phenomena resulting from the K–T impact, such as nitrogen fertilization and/or eutrophication induced by enhanced sulfide formation. The high productivity recorded in the K–T boundary clays means that the freshwater environments (in contrast to marine environments) recovered rapidly enough to almost immediately (within 10 yr) respond to the impact-related environmental perturbations.

Palynological zonation of the continental Cretaceous and lower Tertiary of eastern Russia

Fourteen palynological zones are recognized in the Cretaceous and Palaeocene exposed along the Pacific coast of Russia, from Primorye in the south to Chukotka in the extreme north-east. Each palynozone corresponds to a distinct stage of floristic evolution. The palynological correlation scheme incorporates all data from marine faunas, macroflora, and continental faunas (e.g., dinosaurs). Comparisons with palynological zonations for other parts of Asia, North America, and Australia reveal a potential for inletcontinental palynological correlation of Cretaceous and Palaeocene rocks.

Time and space distribution of Palaeozoic oolitic ironstones in the Tindouf Basin, Algerian Sahara

Summary The Tindouf Basin is located, mainly in Algeria, in the SW part of the Saharan Platform. It comprises Cambro-Ordovician to Carboniferous marine formations overlain by the continental Cretaceous and Pliocene Hamada cover. On the southern limb of the Tindouf Basin several oolitic ironstone deposits occur within Silurian and Devonian sediments. They occupy an area of 500 × 40 km and have an east — west trend. These oolitic ironstone deposits are part of the major North African oolitic ironstone belt, extending more than 3000 km, from Zemmour to Libya. These occurrences are of the LOID type (Local Ironstone Deposition), and contain more than 10000 million tonnes of ironstone reserves (1500 million tonnes in the Silurian and 9200 million tonnes in the Devonian). The various ironstones were formed in shallow marine environments such as barriers and deltas. The major features of these deposits are: (i) a palaeogeographical control of the sediment which was mainly formed on the flanks of uplifts; (ii) the occurrence of the ironstones at the top of coarsening-upward sequences, mostly located towards the end of major regressive cycles, particularly in the Pragian and Famennian; (iii) ooids developed in quiet environments such as lagoons or embayments, within an iron-rich mud; (iv) a southern, relatively close, iron source area and; (v) a palaeolatitudinal distribution giving successively cold and temperate climates. The Palaeozoic history of the basin involved pericratonic sedimentation on the borders of a large epicontinental sea.

Brazilian continental cretaceous

Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

Magnetostratigraphy, biostratigraphy and geochronology of Cretaceous–Tertiary boundary sediments, Red Deer Valley

Integrated magnetostratigraphic and biostratigraphic data for continental Cretaceous–Tertiary boundary sediments in Alberta allow a correlation with recognised sea floor magnetic anomalies 29 and 30. When compared with data from the marine Gubbio section in Italy, the correlation indicates that extinction of the dinosaurs on land was synchronous with foraminiferal extinctions in the sea which are equated with the Cretaceous–Tertiary boundary. We advocate that the base of anomaly 29 be tentatively accepted as the best worldwide physical approximation of the Cretaceous–Tertiary boundary. Eleven K–Ar dates on bentonite sanidines near this boundary yield a mean age of 63.1 ± 0.5(2σ) Myr.

Angiosperm pollen zonation of the continental cretaceous of the Atlantic coastal plain and its application to deep wells in the Salisbury embayment

Abstract This paper presents and illustrates an informal palynological zonation of the pre‐Magothy continental Cretaceous sediments of the Atlantic Coastal Plain (Potomac Group, Raritan Formation), based primarily on new and previously published studies of angiosperm pollen from two wells near Delaware City, Delaware, and from outcrop samples from Virginia through New Jersey, following lines established by Brenner (1963). Monosulcate angiosperm pollen (with columellar exine structure) is present from the base of Brenner's Zone I (Patuxent Formation and Arundel Clay equivalents, Barremian‐lower Albian?). Reticulate tricolpates enter in upper Zone I and diversify in Brenner's Subzones II‐A and II‐B (Patapsco Formation equivalents, middle‐upper Albian?); tricolporoidates appear in Subzone II‐B. Very small, psilate tricolporoidates and Rugubivesiculites rugosus enter in our Subzone II‐C (uppermost Albian?), larger triangular tricolporates and new tricolpates in Zone III (lower Cenomanian?); these two units are represented in “Maryland Raritan”; or Elk Neck beds. The first triporate Normapolles (Complexiopollis, Atlantopollis) appear in Zone IV (lower part of the true Raritan Formation of New Jersey, middle Cenomanian‐lower Turonian?), additional Normapolles in Sirkin's Zone V (upper part of the Raritan, middle Turonian‐lower Santonian?). Application of this zonation shows that all but the top of the very thick continental‐nearshore marine section in three deep wells in the Salisbury Embayment (Hammond, Bethards, Taylor) is of Early Cretaceous age (though in part older than the outcrop Potomac Group), including “red beds”; previously considered Triassic or Jurassic. Maximum marine incursions occurred in the late Albian and early Cenomanian. Equivalents of the Raritan Formation of New Jersey (Zone IV), lacking at the Maryland‐Delaware outcrop, are identified for the first time in the Taylor and Bethards wells. Potomac and lower Raritan equivalents are separated from overlying Magothy Formation equivalents (upper Santonian‐Campanian?) by a regional unconformity.

Ensaio sobre a Tectonica moderna do Brasil

Ensaio sobre a Tectonica moderna do Brasil