A deep-sea agglutinated foraminifer tube constructed with planktonic foraminifer shells of a single species

Agglutinated foraminifera are marine protists that show apparently complex behaviour in constructing their shells, involving selecting suitable sedimentary grains from their environment, manipulating them in three dimensions, and cementing them precisely into position. Here we illustrate a striking and previously undescribed example of complex organisation in fragments of a tube-like foraminifer (questionably assigned to Rhabdammina) from 1466 m water depth on the northwest Australian margin. The tube is constructed from well-cemented siliciclastic grains which form a matrix into which hundreds of planktonic foraminifer shells are regularly spaced in apparently helical bands. These shells are of a single species, Turborotalita clarkei, which has been selected to the exclusion of all other bioclasts. The majority of shells are set horizontally in the matrix with the umbilical side upward. This mode of construction, as is the case with other agglutinated tests, seems to require either an extraordinarily selective trial-and-error process at the site of cementation or an active sensory and decision-making system within the cell

Biostratigraphic and paleoecologic potential of calcareous nannofossils in nearshore environments : IODP Expedition 313 New Jersey shallow shelf

International audienc

Public diplomacy and Slovenian Embassy in Washington, D.C.

Re-examination of sediment cores from Deep Sea Drilling Project (DSDP) Site 277 on the western margin of the Campbell Plateau (paleolatitude of ∼65°S) has identified an intact Paleocene-Eocene (P-E) boundary overlain by a 34 cm thick record of the Paleocene-Eocene Thermal Maximum (PETM) within nannofossil chalk. The upper part of the PETM is truncated, either due to drilling disturbance or a sedimentary hiatus. An intact record of the onset of the PETM is indicated by a gradual decrease in δ13C values over 20 cm, followed by a 14 cm interval in which δ13C is 2‰ lighter than uppermost Paleocene values. After accounting for effects of diagenetic alteration, we use δ18O and Mg/Ca values from foraminiferal tests to determine that intermediate and surface waters warmed by ∼5-6° at the onset of the PETM prior to the full development of the negative δ13C excursion. After this initial warming, sea temperatures were relatively stable through the PETM but declined abruptly across the horizon that truncates the event at this site. Mg/Ca analysis of foraminiferal tests indicates peak intermediate and surface water temperatures of ∼19 and ∼32°C, respectively. These temperatures may be influenced by residual diagenetic factors and changes in ocean circulation, and surface water values may also be biased towards warm-season temperatures

Organic-rich sedimentation in the South Pacific Ocean associated with Late Paleocene climatic cooling

A distinctive organic-rich marine mudstone of Late Paleocene age occurs in most of New Zealand's sedimentary basins and has been identified as a potential source rock for oil and gas. Identified as the Waipawa Formation in the East Coast Basin and the Tartan Formation in the Great South and Canterbury Basins, the unit is a relatively uniform massive mudstone that varies greatly in thickness (2–70 m) and grades laterally into distinctive facies equivalents, notably greensand and a thin-bedded siliceous mudstone. All these facies are characterised by relatively high TOC (0.5–10 wt.%) and 13C enrichment (δ13CTOC N −24‰), and we refer to them collectively as “Waipawa organofacies”. Our detailed stratigraphic and geochemical studies refine the age (58.7 to 59.4 Ma), distribution and nature of the Waipawa organofacies. We have determined that deposition occurred in continental margin settings throughout much of the southwest Pacific under cool, dysoxic conditions associated with a significant influx of terrestrial organic matter, high marine productivity, a global fall in sea level, and a regional unconformity across shallow and deep marine settings. The combination of cool temperatures, lowered sea level and bathyal erosion suggests that deposition was linked to short-lived growth of an Antarctic ice sheet in the earliest Late Paleocene (~59 Ma)

Organic-rich sedimentation in the South Pacific Ocean associated with Late Paleocene climatic cooling

A distinctive organic-rich marine mudstone of Late Paleocene age occurs in most of New Zealand's sedimentary basins and has been identified as a potential source rock for oil and gas. Identified as the Waipawa Formation in the East Coast Basin and the Tartan Formation in the Great South and Canterbury Basins, the unit is a relatively uniform massive mudstone that varies greatly in thickness (2–70 m) and grades laterally into distinctive facies equivalents, notably greensand and a thin-bedded siliceous mudstone. All these facies are characterised by relatively high TOC (0.5–10 wt.%) and 13C enrichment (δ13CTOC N −24‰), and we refer to them collectively as “Waipawa organofacies”. Our detailed stratigraphic and geochemical studies refine the age (58.7 to 59.4 Ma), distribution and nature of the Waipawa organofacies. We have determined that deposition occurred in continental margin settings throughout much of the southwest Pacific under cool, dysoxic conditions associated with a significant influx of terrestrial organic matter, high marine productivity, a global fall in sea level, and a regional unconformity across shallow and deep marine settings. The combination of cool temperatures, lowered sea level and bathyal erosion suggests that deposition was linked to short-lived growth of an Antarctic ice sheet in the earliest Late Paleocene (~59 Ma)

Site U1435

20 page(s

Site U1432

21 page(s

Expedition 349 summary

43 page(s

Expedition 374 summary

The marine-based West Antarctic Ice Sheet (WAIS) is currently locally retreating because of shifting wind-driven oceanic currents that transport warm waters toward the ice margin, resulting in ice shelf thinning and accelerated mass loss. Previous results from geologic drilling on Antarctica’s continental margins show significant variability in ice sheet extent during the late Neogene and Quaternary. Climate and ice sheet models indicate a fundamental role for oceanic heat in controlling ice sheet variability over at least the past 20 My. Although evidence for past ice sheet variability is available from ice-proximal marine settings, sedimentary sequences from the continental shelf and rise are required to evaluate the extent of past ice sheet variability and the associated forcings and feedbacks. International Ocean Discovery Program Expedition 374 drilled a latitudinal and depth transect of five sites from the outer continental shelf to rise in the central Ross Sea to resolve Neogene and Quaternary relationships between climatic and oceanic change and WAIS evolution. The Ross Sea was targeted because numerical ice sheet models indicate that this sector of Antarctica responds sensitively to changes in ocean heat flux. Expedition 374 was designed for optimal data-model integration to enable an improved understanding of Antarctic Ice Sheet (AIS) mass balance during warmer-than-present climates (e.g., the Pleistocene “super interglacials,” the mid-Pliocene, and the Miocene Climatic Optimum). The principal goals of Expedition 374 were to Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates; Reconstruct ice-proximal oceanic and atmospheric temperatures to quantify past polar amplification; Assess the role of oceanic forcing (e.g., temperature and sea level) on AIS variability; Identify the sensitivity of the AIS to Earth’s orbital configuration under a variety of climate boundary conditions; and Reconstruct Ross Sea paleobathymetry to examine relationships between seafloor geometry, ice sheet variability, and global climate. To achieve these objectives, postcruise studies will Use data and models to reconcile intervals of maximum Neogene and Quaternary ice advance and retreat with far-field records of eustatic sea level; Reconstruct past changes in oceanic and atmospheric temperatures using a multiproxy approach; Reconstruct Neogene and Quaternary sea ice margin fluctuations and correlate these records to existing inner continental shelf records; Examine relationships among WAIS variability, Earth’s orbital configuration, oceanic temperature and circulation, and atmospheric pCO2; and Constrain the timing of Ross Sea continental shelf overdeepening and assess its impact on Neogene and Quaternary ice dynamics. Expedition 374 departed from Lyttelton, New Zealand, in January 2018 and returned in March 2018. We recovered 1292.70 m of high-quality core from five sites spanning the early Miocene to late Quaternary. Three sites were cored on the continental shelf (Sites U1521, U1522, and U1523). At Site U1521, we cored a 650 m thick sequence of interbedded diamictite and diatom-rich mudstone penetrating seismic Ross Sea Unconformity 4 (RSU4). The depositional reconstructions of past glacial and open-marine conditions at this site will provide unprecedented insight into environmental change on the Antarctic continental shelf during the late early and middle Miocene. At Site U1522, we cored a discontinuous late Miocene to Pleistocene sequence of glacial and glaciomarine strata from the outer shelf with the primary objective of penetrating and dating RSU3, which is interpreted to reflect the first continental shelf–wide expansion of East and West Antarctic ice streams. Site U1523, located on the outer continental shelf, targeted a sediment drift beneath the westward-flowing Antarctic Slope Current (ASC) to test the hypothesis that changes in ASC vigor regulate ocean heat flux onto the continental shelf and thus ice sheet mass balance. We also cored two sites on the continental rise and slope. At Site U1524, we recovered a Plio–Pleistocene sedimentary sequence from the levee of the Hillary Canyon, one of the largest conduits of Antarctic Bottom Water from the continental shelf to the abyssal ocean. Site U1524 was designed to penetrate into middle Miocene and older strata, but coring was initially interrupted by drifting sea ice that forced us to abandon coring in Hole U1524A at 399.5 m drilling depth below seafloor (DSF). We moved to a nearby alternate site on the continental slope (Site U1525) to core a single hole designed to complement the record at Site U1524. We returned to Site U1524 after the sea ice cleared and cored Hole U1524C with the rotary core barrel system with the intention of reaching the target depth of 1000 m DSF. However, we were forced to terminate Hole U1524C at 441.9 m DSF because of a mechanical failure with the vessel that resulted in termination of all drilling operations and forced us to return to Lyttelton 16 days earlier than scheduled. The loss of 39% of our operational days significantly impacted our ability to achieve all Expedition 374 objectives. In particular, we were not able to recover continuous middle Miocene sequences from the continental rise designed to complement the discontinuous record from continental shelf Site U1521. The mechanical failure also meant we could not recover cores from proposed Site RSCR-19A, which was targeted to obtain a high-fidelity, continuous record of upper Neogene and Quaternary pelagic/hemipelagic sedimentation. Despite our failure to recover a continental shelf-to-rise Miocene transect, records from Sites U1522, U1524, and U1525 and legacy cores from the Antarctic Geological Drilling Project (ANDRILL) can be integrated to develop a shelf-to-rise Plio–Pleistocene transect