Laminations from the Palmer Deep: A diatom-based interpretation

Abstract

Highly laminated, Holocene age, diatomaceous sediments are characteristic of the Palmer Deep, western Antarctic Peninsula (Ocean Drilling Program (ODP) Leg 178, Site 1098). From ∼10,000 years B.P. to the present, laminations are comprised of several groups of diatoms. Chaetoceros resting spores, the dominant laminae former, result from intense spring blooms. Rhizosolenia, Proboscia, Thalassiothrix, and Corethron are common also, the consequence of summer production marked by a well-stratified water column. Each lamination represents a single productivity event, but laminations are not necessarily annual. High concentrations of a subpolar from of Eucampia antarctica, in laminations between ∼9000 and 6700 years B.P., suggest early Holocene warmth, a consequence of southward intrusion of more subpolar waters. The glacial-interglacial transition is distinguished by pairs of laminae most likely deposited annually. Laminations with an overwhelming dominance of Chaetoceros resting spores alternate with more "terrigenous" laminae, representing alternation of intense spring blooms, with more mixed deposition during the summer. Proximity to retreating glacial ice results in the supply of silt and sand that provides a marker bed between successive blooms.