Site U1523

Abstract

A diverse assemblage of marine inicroplankton was recovered from lower Mioccne and Quaternary strata from the Cape Roberts Project drillhole. CRP-1. McMurdo Sound. This is the first diverse assemblage of marine palynomorphs of Miocene age rccovcred from the Antarctic continent. As well as foraminiferal linings and arthropod1 annelid parts. the in situ marine palynomorph assemblage can be subdivided into three groups: prasinophyte algae, acritarchs anddinoflagellate cysts (dinocysts). The prasinophyte algae are the most diverse and abundant: nine species are recognised. leiosphaerids and cyma[iosphaerids dominate. Seven species of acritarchs have been identified and arc dominated by Sigmopollis sp. and an unknown form referred to here as Acritarch 1. In situ dinocysts make up a sparse but moderately diverse group of nine species. Their greatest abundance and diversity occurs below 39.06 mbsf in the lower Miocene part of the section. It is suspected that most dinocysts recovered from above this level are a result of reworking. Almost all the in situ species are new. The prasinophytes and acritarchs are listed in open nomenclature pending more detailed investigations. whereas most new species of dinoeysts are described forn~ally. Several species of reworked dinocysts were recorded dominantly from lower Miocene strata.

Tephrochronology and Provenance of an Early Pleistocene (Calabrian) Tephra From IODP Expedition 374 Site U1524, Ross Sea (Antarctica)

“…but the XRF core logger data signature is similar to that of the U1524 tephra, which shows Si and Zr enrichment and Ba and Ti depletion. The age of this interval is also broadly compatible (early Pleistocene) with that of U1524 tephra (McKay et al., 2019c). We thus argue that the volcanoclastic layer at Site U1523 could be the reworked counterpart of U1524 tephra.…”

“…Of these sites, Sites U1524 and U1525 obtained near‐continuous high‐resolution Plio‐Pleistocene sedimentary records preserved on a continental rise levee system near the flank of the Hillary Canyon. However, the upper ∼50 m at Site U1525 consists of mass transport deposits emplaced over the past ∼0.8 Ma as part of a large trough‐mouth fan deposited to the west of the site (McKay et al., 2019c). The lower 100 m at Site U1525 and the entire 400 m of sediment at Site U1524 recovered near‐continuous records of the downslope flow of Ross Sea Bottom Water and turbidity currents, alongside records of enhanced iceberg discharge over the site.…”

“…The scientific target for the deep-drilling site was the recovery of sediments of channel-overspill and drift deposits. It recovered a high-resolution Plio-Pleistocene turbidite record related to the cascading of Ross Sea Bottom Water (RSBW) down the Hillary Canyon, feeding the AABW, thus providing a reconstruction of this critical component of the global oceanic overturning circulation over much of the past ∼3.3 Ma (McKay et al, 2019a(McKay et al, , 2019b(McKay et al, , 2019c(McKay et al, , 2019d. The ANtarctic DRILLing Project (ANDRILL) Site AND-1B previously recovered an exceptional Plio-Pleistocene record of ice sheet fluctuation over the continental shelf, alongside volcanic activity in the McMurdo Sound region (Naish et al, 2009).…”

Southern Ocean biogenic blooms freezing-in Oligocene colder climates

“…Onshore erosional and transport processes such as large delta systems or glacial trough mouth fans typically drive rapid deposition of large sedimentary packages. For example, comparable sedimentation rates in the Southern Ocean are only reported within sediment drift systems, on continental shelves and shelf breaks, e.g., upper Pliocene glacially sourced sediment in the Ross Sea (IODP U1523, 23 cm/kyr) 26 and other glacial outlets 19 .…”