A Late Cretaceous terebratulid brachiopod from Jamaica, and its significance for Mesozoic brachiopod palaeobiogeography and evolution

The paleolatitudinal distribution of bivalve rudists has important significance for the Baja British Columbia (Baja BC) hypothesis that western Canadian superterranes from British Columbia have been displaced 3000 km since Cretaceous time. Rudists are not observed in Baja BC sedimentary rocks, yet they are common in Late Cretaceous strata in California and Baja California, which have the same paleomagnetically determined paleolatitudes (approximately 25°N) as Baja BC rocks of Late Cretaceous age. In order to resolve this contradiction and to delimit more exactly the southern paleolatitudes of Baja BC, paleomagnetic inclinations corrected for the effects of burial compaction were used to determine the paleolatitudinal distribution of rudists along the California margin. Compaction-corrected paleomagnetic data from the Peninsular Ranges and Salinia terranes indicate that rudists were restricted to paleolatitudes between 34° and 40°N. Evidence of coastal upwelling in the latest Cretaceous Marca Shale may explain the northern limit of the rudist distribution. These data suggest that Baja BC was no farther south than 40°N in the Late Cretaceous, thus limiting its post-Cretaceous displacement to less than 1500 km, and that burial compaction has also affected the paleomagnetism of Nanaimo Group sedimentary rocks from Vancouver Island. This result also helps resolve the conflict between paleomagnetic results, which show 1500 km of post–Late Cretaceous offset between the Insular–Coast Plutonic Complex superterrane and the Intermontane superterrane and geologic observations, which can allow only tens of kilometers of offset between these terranes in the Methow- Tyaughton basin.

The rudist-bearing carbonate platform succession of Marsia, in the northern Simbruini Mts. (Central Apennines), is here described for the first time through the analysis of two stratigraphic sections, and better characterized by the study of three single significant outcrops. Rudist determination and microbiofacies analysis allowed to assess the age of the studied succession and the definition of a biostratigraphic frame. The Marsia composite stratigraphic section encompasses the late Turonian-early/middle Campanian interval, and records the evolution from inner Platform-low hydrodynamic setting in the late Turonian, to an open platform setting characterized by high hydrodynamism in the late Santonian-early/middle Campanian. This succession has been compared with the already described Trevi, S.M. dei Bisognosi and Subiaco carbonate platform stratigraphic successions, and with regional bioevent schemes, in order to consider the evolution of carbonate facies in a wider sedimentological context. Since the late Turonian, a spreading of rudist facies occurred in the whole central-southern Apennines, representing the first late Cretaceous rudist bioevent. In the Simbruini area inner platform environments, characterized by soft fine-grained sediment are widespread. The successions of Marsia and Trevi, which are marked by upper Turonian inner platform facies with abundant oligospecific radiolitids association with infaunal or semi-infaunal lifestyle, record this bioevent. During the Santonian and the early Campanian a gradual increase in hydrodynamic conditions is testified by by rudist assemblages with hippuritids and robust radiolitids, associated with rare corals and echinoids which mark the second and third late Cretaceous rudist bievent, recorded at Marsia, Trevi and S. M. dei Bisognosi. The middle Campanian-Maastrichtian bioevents, are only represented at S. M. dei Bisognosi and Subiaco where high energy bioclastic facies, dominated by the peculiar radiolitid Sabinia sp. occur.

Lungfish are a poorly represented component of the Mesozoic fossil record in North America, as most lungfish fossils consist of rare, isolated dental plates that are of little diagnostic value due to their conservative nature. In eastern North America, the paucity of lungfish fossils in Late Cretaceous strata is further compounded by the occurrence of geologic units that are primarily marine in origin, unlike the Late Jurassic to mid-Cretaceous fluvial deposits of the American west that contain comparatively more specimens. Lungfish fossils from the eastern side of the Late Cretaceous Western Interior Seaway (Appalachia) have previously been reported from the Cenomanian Woodbine Formation of northeast Texas and the Campanian Mount Laurel Formation of New Jersey. Here we report two new occurrences of eastern North American lungfish tooth plates from the Santonian Eutaw Formation of Alabama and Mississippi. These two specimens are referred to Ceratodus frazieri Ostrom, 1970 and Ceratodus carteri Main et al., 2014, species that are better known from the mid-Cretaceous of the Western Interior of North America. This discovery is the first published record of lungfish of any age from the states of Alabama and Mississippi. It partially bridges the temporal gap in the fossil record between the Cenomanian lungfish of Texas and the Campanian lungfish of New Jersey and extends the biogeographic range of Late Cretaceous lungfish to the eastern Gulf Coastal Plain of the United States.

Paleostress regime evolution in South China induced by dynamic changes in Izanagi-Pacific subduction since the Cretaceous

توالی کربناته بیستون با ضخامت حدود 2500 متر به عنوان بخشی از توالی رسوبی زاگرس مرتفع به سن تریاس پسین ـ کرتاسه پسین (سنومانین) در شرق شهر کرمانشاه رخنمون دارد. در این مطالعه برای اولین بار رخساره‌های رسوبی، محیط رسوبی و فرآیندهای دیاژنزی مؤثر بر سنگ آهک‌های بیستون (بخش کرتاسه زیرین) مطالعه شده است. مطالعات پتروگرافی صورت گرفته بر روی این توالی کربناته به شناسایی 8 رخساره کربناتی منجر شد که در بخش میانی و داخلی یک رمپ هموکلینال کربناته و در زیر محیط‌های دریای باز، پشته، لاگون و پهنه جزرومدی تشکیل شده است. از مهم‌ترین فرآیندهای دیاژنزی مؤثر بر توالی مورد مطالعه می‌توان به میکریتی شدن، آشفتگی زیستی، جانشینی (دولومیتی شدن، سیلیسی شدن، پیریتی شدن و ددولومیتی شدن)، فشردگی فیزیکی و شیمیایی (استیلولیتی شدن)، شکستگی و پرشدگی، نئومورفیسم، سیمانی شدن (بلوکی، رورشدی هم ‌محور، پوئی‌کیلوتاپیک، هم ضخامت، دروزی و هم بعد)، انحلال و هماتیتی شدن اشاره نمود که این فرآیند‌ها در سه محیط دیاژنز دریایی، تدفین (دفنی کم عمق و عمیق) و بالا آمدگی (بالا آمدگی و متئوریک) طی کرده‌اند.

Rudist bivalve assemblages and biofacies spanning from the Cenomanian to the Maastrichtian age interval have been detected in ten selected fossiliferous localities of Cilento and western Basilicata (southern Apennines, southern Italy). Their distribution shows a lateral transition from inner platform with mono-oligospecific radiolitid assemblages of the late Turonian - Coniacian, to more open depositional settings with well diversified fauna of the Santonian-Maastrichtian passing from south-western to eastern Cilento. In western Basilicata, prevailing grain-supported sediments and well diversified caprinid assemblages are indicative of open shelf and margin depositional settings of early - middle Cenomanian age. Furthermore, stratigraphic data point out (1) the lack of the Santonian - Maastrichtian deposits toward south is referred to incipient emersion of this sector of the Apennine Carbonate Platform (ACP), (2) the overall biofacies distribution also has to be related to the setting of the ACP as regards the paleooceanic circulation during the Late Cretaceous and (3) the occurrence of “out of context” radiolitid beds at Raparo Mt., up to now referred as a klippe, could be regarded as a still open point to discussion concerning its paleogeographic attribution.

Biogeography and diversity of South Atlantic Cretaceous echinoids: implications for circulation patterns

The Chuacús Metamorphic Complex is located in Central Guatemala, between the Polochic and Motagua fault zones. It is made up of complexly intercalated, mafic and felsic high-grade gneisses, amphibolites, pelitic and quartzofeldsphatic metasediments and subordinate marbles. Mafic dikes and lenses metamorphosed to amphibolite and eclogite facies are tholeiitic and similar to mid-ocean ridge basalts. In contrast, metamorphosed intrusives (gabbro, diorite and granite) are calc-alkaline and have the geochemical signature of arc magmas. Laser Ablation Inductively Coupled Plasma Mass Spectrometry U-Pb zircon geochronology allows the recognition of three episodes of metamorphism. The first eclogite facies metamorphism (M1) is bracketed between Ordovician magmatism in the northern Chuacús Metamorphic Complex and the neighboring Rabinal granitic suite; the second corresponds to an Upper Triassic period of arc magmatism and migmatization (M2); the third high-grade metamorphic event (M3) occurred during the Late Cretaceous. The tectonic evolution of the Chuacús Metamorphic Complex began during the Early Paleozoic as a basin in the Rheic Ocean that received detrital material from the Maya Block, Acatlán and southeastern México. The Chuacús Metamorphic Complex evolved to an active margin that subducted to HP conditions during the Mid- Late Paleozoic, and then was exhumed and involved in two tectonothermal events during the Upper Triassic and Late Cretaceous. The Chuacús Metamorphic Complex was accreted to the southern Maya Block during the Late Cretaceous, as a result of the convergent tectonics between the latter and either the Greater Antillean arc or the Chortís Block

Description of Pseudosabinia klinghardti and some species of Pseudopolyconites (rudist bivalves) from the Late Cretaceous shallow-marine deposits from the Roşia Basin, Apuseni Mountains, Romania: Systematic palaeontology, biostratigraphy, and palaeobiogeography

The Xixia amber is the largest known Mesozoic amber deposit in China to date. Here we analyse amber collected over the years from 12 localities in the Upper Cretaceous Gaogou Formation in Xixia, Henan, including physical property tests and Fourier transform infrared spectroscopy (FT-IR) analysis. The main preservation forms of the Xixia amber include nest-like, vein-like, and layered irregular shapes, as well as gravel-like forms resulting from secondary transportation. Recent discoveries include numerous small-grained amber specimens preserved in grey-black silty shale rich in plant debris, suggesting a near-in-situ depositional environment. The Xixia Basin’s Late Cretaceous strata are renowned for their abundance in dinosaur eggs. In-depth research on the Xixia amber will help to understand the geological history and ecosystem evolution of the Xixia Basin during the Late Cretaceous, as well as the global distribution characteristics of Cretaceous amber.

Soft-sediment deformation structures in the Cretaceous Zhucheng depression, Shandong Province, East China; their character, deformation timing and tectonic implications

In the Late Cretaceous and Tertiary strata of the Eureka Sound and Beaufort Formations on Axel Heiberg and west central Ellesmere Islands, kaolinite and illite are the dominant clay minerals, with minor to major amounts of smectite and random mixed-layers, and trace amounts of vermiculite and chlorite. Smectite and associated mixed-layers in the basal Eureka Sound Formation formed by in situ alteration of volcaniclastic material, whereas mixed-layers in the deltaic-alluvial deposits probably result from in situ paleosol formation. These strata are a likely source rock for the younger Tertiary and Quaternary Arctic Ocean sediments.

Stratigraphic, palaeogeographic and evolutionary significance of late cretaceous and early tertiary normapolles pollen

Well-developed Cretaceous-Paleogene strata are exposed in the Guangzhou-Foshan area. Owing to limited volcanic activity, isotopically datable material is scarce, and the chronology of these strata relies primarily on biostratigraphic correlations. The Baihedong Formation has been generally regarded as a sedimentary sequence deposited during the late Early Cretaceous, although robust chronological constraints are lacking. In the Shuzhugang Hill area, located south of Guangzhou, a suite of volcanic rocks is exposed and is generally assigned to the upper part of the Baihedong Formation, though some scholars attribute it to the Paleogene. Zircon U-Pb dating conducted in this study yielded an absolute age of 83.5 ± 0.7 Ma for these volcanic rocks, thereby constraining the deposition of the Baihedong Formation to the Late Cretaceous. This study provides a crucial chronological reference for defining the Cretaceous-Paleogene stratigraphic chronology framework across the Sanshui and Zhujiangkou basins.

Enamel dentition microstructure of Mariliasuchus amarali (Crocodyliformes, Notosuchia), from the Upper Cretaceous (Turonian–Santonian) of the Bauru Basin, Brazil