Interpretation of sediment cores from the Ross Ice Shelf Site J-9, Antarctica

Abstract

Stratigraphical interpretations of sediments beneath the Ross Ice Shelf, Antarctica, are derived from 58 short gravity cores (up to 1.22 m in length) taken by Webb and Brady through an ice access hole at the Ross Ice Shelf (RISP) Site J-9 (82°22′ S), 168°38′W) during the austral summers of 1977 and 1978. Some scientific reports on microfossil groups of diatoms^1,2, foraminifera³, and silicoflagellates⁴ have interpreted the sedimentary succession as in situ and of Miocene age. Webb⁵ has also reported reworked clasts of Cretaceous foraminifera. Brady and Martin² suggested that the pollen assemblage within the cores, similar to a reported Oligocene flora⁶, may have reflected a remnant of this flora living in the Miocene, but Wrenn⁷ has shown that these pollen have probably been reworked. However, Kellogg and Kellogg's⁸ diatom-based Pleistocene age determinations for sediment exposed on the sea floor at Site J9 relies on misquoted data from published literature and on misinterpreted taxonomy. Evidence is presented here that supports an earlier proposal that Miocene sediments crop out on the present sea floor.