Climate and sea-level changes across a shallow marine Cretaceous-Palaeogene boundary succession in Patagonia, Argentina

Upper Maastrichtian to lower Paleocene, coarse-grained deposits of the Lefipán Formation in Chubut Province, (Patagonia, Argentina) provide an opportunity to study environmental changes across the K-Pg boundary in a shallow marine depositional environment. Therefore, marine palynological and organic geochemical analyses were performed on the K-Pg boundary interval of the Lefipán Formation at the San Ramón section. The palynological and organic geochemical records from the San Ramón K-Pg boundary section are characteristic of a highly dynamic, nearshore setting. High abundances of terrestrial palynomorphs, high BIT-index values and the occasional presence of plant fossils are indicative of a large input of terrestrial organic material. The organic-walled dinoflagellate cysts (dinocyst) assemblage is generally dominated by Senegalinium and other peridinioid dinocyst taxa, indicative of high-nutrient conditions and decreased salinities, likely associated with a large fluvial input. The reconstructed sea surface temperatures range between 25 and 27 °C, in accordance with the tropical climate inferred by palynological and megafloral studies. Similar to the Bajada del Jagüel section, ~500 km north-northeast of San Ramón, peaks of Senegalinium spp. were recorded below and above the K-Pg boundary, possibly related to enhanced runoff resulting from more humid climatic conditions. The lithological, palynological and organic geochemical records suggest a sea-level regression to have occurred across the K-Pg boundary, resulting in a hiatus directly at the K-Pg boundary in both sections, followed by a transgression in the Danian.status: publishe

Data from: Climate and sea-level changes across a shallow marine Cretaceous–Palaeogene boundary succession in Patagonia, Argentina

Upper Maastrichtian to lower Paleocene, coarse-grained deposits of the Lefipán Formation in Chubut Province, (Patagonia, Argentina) provide an opportunity to study environmental changes across the Cretaceous–Palaeogene (K–Pg) boundary in a shallow marine depositional environment. Marine palynological and organic geochemical analyses were performed on the K–Pg boundary interval of the Lefipán Formation at the San Ramón section. The palynological and organic geochemical records from the San Ramón K–Pg boundary section are characteristic of a highly dynamic, nearshore setting. High abundances of terrestrial palynomorphs, high BIT-index values and the occasional presence of plant fossils are indicative of a large input of terrestrial organic material. The organic-walled dinoflagellate cyst (dinocyst) assemblage is generally dominated by Senegalinium and other peridinioid dinocyst taxa, indicative of high-nutrient conditions and decreased salinities, probably associated with a large fluvial input. The reconstructed sea surface temperatures range from 25°C to 27°C, in accordance with the tropical climate inferred by palynological and megafloral studies. As in the Bajada del Jagüel section, ~500 km north-north-east of San Ramón, peaks of Senegalinium spp. were recorded below and above the K–Pg boundary, possibly related to enhanced runoff resulting from more humid climatic conditions. The lithological, palynological and organic geochemical records suggest the occurrence of a sea-level regression across the K–Pg boundary, resulting in a hiatus directly at the boundary in both sections, followed by a transgression in the Danian

Climate and sea-level changes across a shallow marine Cretaceous–Palaeogene boundary succession in Patagonia, Argentina

Upper Maastrichtian to lower Paleocene, coarse-grained deposits of the Lefipán Formation in Chubut Province, (Patagonia, Argentina) provide an opportunity to study environmental changes across the Cretaceous–Palaeogene (K–Pg) boundary in a shallow marine depositional environment. Marine palynological and organic geochemical analyses were performed on the K–Pg boundary interval of the Lefipán Formation at the San Ramón section. The palynological and organic geochemical records from the San Ramón K–Pg boundary section are characteristic of a highly dynamic, nearshore setting. High abundances of terrestrial palynomorphs, high BIT-index values and the occasional presence of plant fossils are indicative of a large input of terrestrial organic material. The organic-walled dinoflagellate cyst (dinocyst) assemblage is generally dominated by Senegalinium and other peridinioid dinocyst taxa, indicative of high-nutrient conditions and decreased salinities, probably associated with a large fluvial input. The reconstructed sea surface temperatures range from 25°C to 27°C, in accordance with the tropical climate inferred by palynological and megafloral studies. As in the Bajada del Jagüel section, ~500 km north-north-east of San Ramón, peaks of Senegalinium spp. were recorded below and above the K–Pg boundary, possibly related to enhanced runoff resulting from more humid climatic conditions. The lithological, palynological and organic geochemical records suggest the occurrence of a sea-level regression across the K–Pg boundary, resulting in a hiatus directly at the boundary in both sections, followed by a transgression in the Danian

Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): Paleogeographical implication

International audienceA palynological assemblage including the extinct araucarian dispersed pollen, Cyclusphaera scabrata, was analysed from the Achiri locality, Bolivian Altiplano. The fossil-yielding locality of Achiri is located in the Pacajes Province, La Paz Department, in the northwestern Altiplano, Bolivia. The Achiri locality is very well known by the fossil vertebrate faunas recovered from the Mauri Formation (M6). The palynological samples come from fine-grained and plant-rich lacustrine levels lower in the same unit. An age between late middle to early late Miocene? was inferred for the palynological association studied, based on local stratigraphy and radioisotopic ages obtained higher in the series. The retrieved association is mainly represented by angiosperms; although gymnosperms, bryophytes, ferns, and freshwater algae are also documented. Compositae are the most abundant group within angiosperms, and Polylepis also occurred but in low percentages. The presence of C. scabrata in the Bolivian Altiplano expands the taxon distribution outside northern South America and provides additional evidence to infer timing and distribution routes of conifers, restricted toward the tropics during the latest Neogene. Its occurrence supports a paleoelevation of no more than 2000 m for the northern area of the Altiplano in agreement with previous results. Compositae of Fenestrites type and Polylepis occur earlier in Bolivia and C. scabrata later, comparing their occurrence in miocene microfloras from low to mid-latitudes of South America

Fossil record of Ephedra in the Lower Cretaceous (Aptian), Argentina

Fossil plants from the Lower Cretaceous (upper Aptian) of the La Cantera Formation, Argentina, are described. The fossils studied represent a leafy shooting system with several orders of articulated and striated axes and attached leaves with unequivocal ephedroid affinity. We also found associated remains of ovulate cones with four whorls of sterile bracts, which contain two female reproductive units (FRU). Ovulate cone characters fit well within the genus Ephedra. Special characters in the ovulate cones including an outer seed envelope with two types of trichomes, allowed us to consider our remains as a new Ephedra species. Abundant dispersed ephedroid pollen obtained from the macrofossil-bearing strata also confirms the abundance of Ephedraceae in the basin. The co-occurrence of abundant fossil of Ephedra (adapted to dry habitats) associated with thermophilic cheirolepideacean conifer pollen (Classopollis) in the unit would suggest marked seasonality at the locality during the Early Cretaceous. Furthermore, the floristic association is linked to dry sensitive rocks in the entire section. The macro- and microflora from San Luis Basin are similar in composition to several Early Cretaceous floras from the Northern Gondwana floristic province, but it may represent one of the southernmost records of an arid biome in South America.Fil: Puebla, Gabriela Griselda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Gomez, Maria Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; ArgentinaFil: Pramparo, Mercedes Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin