Search results for "STRATIGRAPHY"
showing 10 items of 904 documents
Ammonites on the Brink of Extinction: Diversity, Abundance, and Ecology of the Order Ammonoidea at the Cretaceous/Paleogene (K/Pg) Boundary
2015
We examined the stratigraphic distribution of ammonites at a total of 29 sites around the world in the last 0.5 myr of the Maastrichtian. We demarcated this interval using biostratigraphy, magnetostratigraphy, cyclostratigraphy, and data on fossil occurrences in relation to the K/Pg boundary in sections without any facies change between the highest ammonites and the K/Pg boundary. The ammonites at this time represent all four Mesozoic suborders comprising six superfamilies, 31 (sub)genera, and 57 species. The distribution of ammonites is dependent on the environmental setting. Recent data suggest that ammonites persisted to the boundary and some species may have survived for several tens of…
Albian ammonites of the Benguela Basin (Angola): a biostratigraphic framework.
2007
20 pages; The study of the Albian ammonite fauna of the sedimentary series in the Benguela Basin (Angola) allows a major revision of the biostratigraphy of the south Atlantic area. The new biostratigraphic approach allows the recognition of 17 horizons distributed in 8 subzones correlated with the ammonite zonation of the Tethyan Province. The Lower Albian is characterized by the Douvilleiceras inaequinodum Subzone (including the D. mammillatum aequinodum Horizon). The Middle Albian is represented by the Oxytropidoceras (Mirapelia) buarquianum Subzone (subdivided into O. (M.) buarquianum and O. (M.) sergipense horizons). The Upper Albian is characterized by the Dipoloceras sp. Subzone (defi…
The earliest tupilakosaurid amphibian with diplospondylous vertebrae from the Late Permian of southern France
2007
5 pages; International audience; A well-preserved vertebral column from the Late Permian of Southern France (Lopingian, La Lieude Formation, Lodève Basin) is described. It is composed of diplospondylous vertebrae and is most comparable with the temnospondyl Tupilakosaurus previously known from the Early Triassic of Greenland and Russia. This new specimen therefore represents the earliest occurrence of a diplospondylous tupilakosaur, and extends the geographic range of the group to Western Europe. It is an aquatic temnospondyl that used the anguilliform undulatory mode of swimming.
Microcrinoids from the lower and middle Albian of the Anglo-Paris Basin (southern England, UK, Seine Maritime, Pas de Calais and Aube, France).
2021
16 pages; International audience; Microcrinoids of the family Roveacrinidae Peck, 1943 are described from lower and middle Albian clays of the Anglo-Paris Basin (Seine Maritime, Pas de Calais and Aube, France; Kent and Bedfordshire, UK). They are referred to two subfamilies - the Orthogonocrininae Gale, 2019 and the Plotocrininae Gale, 2020. Orthogonocrinines include the long-ranging (middle Albian-lower Cenomanian) species Orthogonocrinus apertus Peck, 1943, and Styracocrinus peracutus (Peck, 1955), known from Texas, USA, Morocco, the UK and France, and two stratigraphically successive species of the genus Hyalocrinus, H. magniezii Destombes, 1984 and H. bulliensis Destombes, 1984, known o…
A recipe for the use of rutile in sedimentary provenance analysis
2012
Abstract Rutile has received considerable attention in the last decade as a valuable petrogenetic indicator mineral. Based on both new and previously published data, we carve out advantages and pitfalls regarding TiO 2 -minerals in sedimentary provenance analysis. This results in a recipe for the use of rutile in provenance studies. The main points are: Rutile geochemistry from different grain size fractions does not differ systematically, and hence rutiles should be extracted from the fraction containing the most rutile grains (usually 63–200 μm). Similarly, different magnetic susceptibility of rutile does not systematically imply different trace element composition. Before interpretation …
Exploring the validity of the long term data record V4 database for land surface monitoring
2015
The last (and final) version of the Long Term Data Record (LTDR) — Version 4 — has been released recently by NASA. This database includes daily information for all AVHRR (Advanced Very High Resolution Radiometer) channels, as well as ancillary data, since July 1981 up to present. This database is the longest available record of remotely sensed data useful for land surface monitoring, since it allows the estimation of vegetation indices at daily resolution, as well as the daily estimation of land surface temperature (LST). Here, we analyze the fitness of this database for land surface monitoring. To that end, we first estimated NDVI (Normalized Difference Vegetation Index), LST, as well as e…
Segmentation and differential post-rift uplift at the Angola margin as recorded by the transform-rifted Benguela and oblique-to-orthogonal-rifted Kwa…
2010
29 pages; International audience; We analyse tectonic and sedimentary field and subsurface data for the Angola onshore margin together with free-air gravity anomaly data for the offshore margin. This enables us to characterize the mode of synrift tectonism inherited from the Precambrian and its impact on the segmentation of the Angola margin. We illustrate that segmentation by the progressive transition from the Benguela transform-rifted margin segment to the oblique-rifted South Kwanza and orthogonal-rifted North Kwanza margin segments. The spatial variation in the intensity of post-rift uplift is demonstrated by the study of a set of geomorphic markers detected in the post-rift succession…
Lanthanides Revealing Anthropogenic Impact within a Stratigraphic Sequence
2014
Difficulties to differentiate between anthropogenic and natural processes in the formation of archaeological deposits are crucial for a correct interpretation not only of the actions involved in the development of archaeological sites, but also of their occupation-abandonment dynamics and the understanding of their spatial behaviors and relationship with the environment. We have carried out lanthanides (rare earth elements “REE”) analysis to distinguish anthropogenic from natural stratigraphic units in sediments using the advantage of the high sensibility, precision, and accuracy of ICP-MS measurements. In the Neolithic site of Mas d’Is (Alacant, Spain), we have applied REE analysis in a hu…
Orbital chronology of the lower-middle Aptian: palaeoenvironmental implications (Serre Chaitieu section, Vocontian Basin).
2013
4 pages; International audience; A detailed cyclostratigraphic study conducted on several proxies including spectral gamma ray, magnetic susceptibility, clay minerals, and carbonate content suggests that the return to equilibrium in the carbon cycle after the major disturbance linked with Oceanic Anoxic Event 1a occurred in about 2 Myr. The minimum duration of the D. furcata zone is estimated at 0.46 Myr and that of the E. subnodosocostatum zone at 1.45 Myr. Strengthening of the obliquity record in the furcata zone confirms the cooling that characterizes this period.
Palaeoceanographic significance of the Tethyan ‘Livello Selli’ (Early Aptian) from the Hybla Formation, northwestern Sicily: biostratigraphy and high…
2002
High-resolution micropalaeontological and chemostratigraphic records for the Hauterivian–Aptian succession outcropping at Calabianca (NW Sicily) provide new insight into the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean. Calcareous nannofossil and planktonic foraminiferal biostratigraphy together with δ13C chemostratigraphy allowed the identification of a hiatus in the Barremian and a major one including most of the Upper Aptian, the entire Lower Albian and part of the Middle Albian. The Livello Selli equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy as well as by the δ13C curve. The multi-proxy record from …