We will drill on Magellan, Manihiki, and Hikurangi Plateaus in the central Pacific Ocean to recover complete sedimentary and basement Cretaceous sections. Previous drilling (DSDP Sites 167 and 317) indicates that the Cretaceous is represented here by pelagic carbonates with cherts and black shales as minor lithologies, in addition to volcanic basement recording igneous events. The sedimentary and basement sections offer the opportunity to investigate an 80 m.y.-long interval characterized by the most extreme climates (mid-Cretaceous greenhouse) of the past 200 Ma, global anoxia (OAEs), perturbations of geochemical cycles (large C and Sr isotopic excursions) and major changes in marine biota, all possibly triggered by emplacement of LIPs associated with the Ontong Java and Galapagos hotspots. Correlation of basement rocks may provide evidence of the largest igneous event in Earth history. At Magellan Plateau we can also study an initial greenhouse climate episode from the Late Valanginian and consider similarities and differences to the Aptian-Turonian “super-greenhouse”. The overall goal is a quantitative characterization and understanding of geochemical cycles and marine ecosystem reactions to environmental and climate changes at the onset, during and after major greenhouse episodes. These plateaus are located in the largest oceanic basin, in a “pure” carbonate system and in an open marine setting. Paleowater depth of the summits of these plateaus is <2000m and shallow burial depths minimize dissolution and diagenetic overprints. Along their flanks, they preserve a paleobathymetric record to trace the history of OMZ, CCD and vertical temperature structure in the Cretaceous Pacific. The proximity of Magellan and Manihiki to the Ontong Java and the Galapagos hotspots also offers the opportunity to investigate chemical, physical and biotic changes in an area close to emplacement of LIPs, and similarities-differences related to proximal versus distal locations. Early to mid-Cretaceous paleolatitudes (20° - 50°S) minimize the occurrence of biogenic cherts and make these plateaus ideal for characterization of marine ecosystems in a low productivity area. Basement samples will provide radiometric ages for Magellan, Manihiki, and Hikurangi Plateaus to reconstruct their volcanic history. Integration of radiometric and bio-magneto-chemo-stratigraphic data will provide a robust chronology for dating and correlation of igneous and geological events. Geochemistry of lava flows will allow for characterization of the melting and crystallization history, and constructional environment of Manihiki and Hikurangi Plateaus, and understanding of their tectonic relationship with Ontong Java Plateau.
|Titolo:||Cretaceous igneous and paleoceanographic events recorded at Manihiki, Hikurangi and Magellan Plateaus, centralPacific Basin|
ERBA, ELISABETTA (Primo)
|Data di pubblicazione:||2005|
|Settore Scientifico Disciplinare:||Settore GEO/01 - Paleontologia e Paleoecologia|
|Citazione:||Cretaceous igneous and paleoceanographic events recorded at Manihiki, Hikurangi and Magellan Plateaus, centralPacific Basin / E. Erba, R. L. Larson, R. A. Duncan. - Japan-US : null, 2005.|
|Appare nelle tipologie:||08 - Relazione interna o rapporto di ricerca|