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The AAPG/Datapages Combined Publications Database
Journal of Sedimentary Research (SEPM)
Abstract
Biological Forcing of Hemipelagic Sedimentary Laminae: Evidence from ODP Site 893, Santa Barbara Basin, California
Kurt A. Grimm (1), Carina B. Lange (2), Amarpal S. Gill (1)
ABSTRACT
Laminae at Site 893 have two prominent components: biosilica and terrigenous detritus. Compositional contrasts between adjacent laminae in X-radiographs reflect short-term (seasonal and subseasonal) heterogeneities in sediment flux. Core intervals with large contrasts in density and/or composition between adjacent laminae are termed as having high bimodality (HB); HB couplets produce distinctly laminated sediments that intergrade vertically with indistinctly laminated and nonlaminated sediments. Adjacent laminae in indistinctly laminated sediments possess minimal contrasts in bulk density and composition; nonlaminated sediments are compositionally and texturally homogeneous.
Many biosiliceous laminae responsible for distinctly laminated, HB couplets
record mass flocculation and sedimentation of ungrazed diatom frustules
formed during discrete bloom events. Ecological interpretation of diatomite
laminae suggests that many were effectively self-sedimenting (i.e., the
production of gelatinous exudates by phytoplankton facilitated their aggregation
and rapid sedimentation). The results indicate that lamination style preserves
meaningful ocean climate data concerning episodicity, heterogeneity, and
export efficiency of biologically mediated sedimentary flux in upwelling-dominated
coastal ecosystems.
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