Last millennium sedimentation in the Gulf of Cariaco (NE Venezuela): Evidence for morphological changes of gulf entrance and possible relations with large earthquakes
Résumé
The Cariaco Basin and the Gulf of Cariaco in Venezuela are two major basins along theseismogenic El Pilar right lateral fault, among which the Cariaco Basin is a pull-apart. Bothbasins are sites of anoxia and organic-rich deposits. To examine whether the sediments inthe Gulf of Cariaco have recorded traces of historical or prehistorical earthquakes, weextracted and analyzed twelve 1 m-long gravity cores, sampling the last millenniumsedimentation. We focused on analyzing the sediment sources with different techniques(particle size analysis, XRF, loss on ignition tests, magnetic properties, Rock-Eval pyrolysis,14C dating). The results confirm that major upwelling occurs at the western gulf entranceand makes deep water flowing from the Cariaco Basin into the Gulf of Cariaco. These flowscarry an organic-rich suspended load. Furthermore, we found evidence of a particular,widespread fine-grained siliciclastic deposit (named SiCL3) within the gulf, whose agesuggests that it likely formed during the large 1853 AD earthquake that stroke the Cumana´city. We suggest that the earthquake-induced large submarine landslides that modifiedthe topography of the gulf’s entrance, which in turn promoted upwelling and open marinewater flows from the Cariaco Basin. The layer SiCL3 would be the sediment loadremobilized during this chain of events.
Origine : Publication financée par une institution
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