The Global Boundary Stratotype Section and Point for the base of the Selandian Stage is defined in the Zumaia section (Spain) at an abrupt change in lithology (base of Itzurun Formation), which coincides with the onset of a negative carbonate carbon isotope shift. However, this lithological change is not always very well expressed in other sections. In order to document the stratigraphic position of the Danian/Selandian boundary (DSB) on a more global scale, we have investigated three sections across the DSB, the Zumaia reference section (GSSP), the Loubieng section (auxiliary DSB reference section, France) and the Sidi Nasseur section (Tunisia). The Danian/Selandian boundary interval is subdivided and correlated throughout low latitudes, from the Altlantic Bay of Biscay to the Southern Tethys, on the basis of seven calcareous nannofossil and planktonic foraminiferal events (E-events). The base of the Selandian is proved to coincide with the end of the Braarudosphaera acme, which correlates with the lowest consistent occurrence (LCsO) of Lithoptychius aff. bitectus (=Fasciculithus janii sensu Steurbaut and Sztrákos, 2008) (event E4), but which is slightly posterior to the second radiation of the fasciculiths, up to now considered to represent the primary correlation tool of the DSB. A short-term δ13Corg negative excursion, associated with an increase in pCO2 is recorded at the very base of the Selandian. It is interpreted as a short period of global warming (hyperthermal), the duration of which is estimated at ~30 kyr. It is followed in all the three studied sections by a long-term decoupled carbon isotope event, marked by increasing δ13Corg and decreasing δ13Ccarb values. It may reflect a period of climatic cooling of a few 100 kyr, interpreted as a possible precursor of the global cooling event, marking the late Paleocene in the North Atlantic realm. The integration of the biostratigraphic and the isotope data indicates major differences in sedimentation rates during the early Selandian in the studied sections, but there is no evidence of substantial breaks in sedimentation in any of the sections during this interval. The lithological shift at the base of the Selandian points to an abrupt palaeoenvironmental reorganisation, although our integrated bio-chemostratigraphical investigation does not allow for estimating its duration nor the presence of a hiatus at that time.
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Understanding of evolution and systematics of Calcarea (Porifera) have not yet met a corresponding increase in the knowledge of diversity and distribution of these sponges in several parts of the world. Peru is an emblematic example of this lack of taxonomic knowledge, as only three shallow-water species of sponges have hitherto been reported from its 3000 km coast. With the aim of studying sponges of Peru, an integrative taxonomy approach (morphology, molecules, and biogeography) was used in order to achieve sound species identifications. The first findings of Peruvian calcareous sponges are presented here. Eight species are described in the subclass Calcinea, of which five are new to science. The retrieved biogeographical patterns are either locally endemic, widespread, or discontinuous over large areas. Clathrina antofagastensis was previously known from Chile, while C. aurea and Ernstia tetractina had been reported from the Atlantic (Brazil), and thus represent the first genetically confirmed tropical amphi- American distributions of species not yet found on both sides of the Isthmus of Panama. Our results reveal a richer Tropical East Pacific sponge fauna than the Warm Temperate South-Eastern Pacific one.
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