Site U1334

Integrated Ocean Drilling Program (IODP) Site U1334 (7°59.998?N, 131°58.408?W; 4799 meters below sea level [mbsl]) (Fig. F1; Table T1) is located ~380 km southeast of previously drilled Ocean Drilling Program (ODP) Site 1218 (~42 Ma crust) in the central area drilled during the Pacific Equatorial Age Transect (PEAT) program (IODP Expedition 320/321). Site U1334 (~38 Ma crust) is situated ~100 km north of the Clipperton Fracture Zone on abyssal hill topography draped with ~280 m sediment (Fig. F2). The fabric of the abyssal hills within the sites is oriented either due north or slightly east of due north.Water depth in the vicinity of Site U1334 ranges between 5.0 and 5.1 km for the depressions between the abyssal hills. The abyssal hills range between 4.70 and 4.85 km water depth and generally show a thicker and more consistent sediment cover than the basins. In fact, a significant amount of the bathymetric difference between hills and basins is controlled by the amount of sediment cover. The comparison of sediment thickness and clarity of seismic sections led us to select a location on the middle elevation of one of the abyssal plateaus.Site U1334 sediments were estimated to have been deposited on top of late middle Eocene crust with an age of ~38 Ma and target the events bracketing the Eocene–Oligocene transition with the specific aim of recovering carbonate-bearing sediments of latest Eocene age prior to a large deepening of the calcium carbonate compensation depth (CCD) that occurred during this greenhouse to icehouse transition (Kennett and Shackleton, 1976; Miller et al., 1991; Zachos et al., 1996; Coxall et al., 2005). The Eocene–Oligocene transition experienced the most dramatic deepening of the Pacific CCD during the Paleogene (van Andel, 1975), which has now been shown by Coxall et al. (2005) to coincide with a rapid stepwise increase in benthic oxygen stable isotope ratios, interpreted to reflect a combination of growth of the Antarctic ice sheet and decrease in deepwater temperatures (DeConto et al., 2008; Liu et al., 2009).<br/

Astronomically paced changes in overturning circulation in the Western North Atlantic during the middle Eocene

North Atlantic Deep Water (NADW) currently redistributes heat and salt between Earth’s ocean basins, and plays a vital role in the ocean-atmosphere CO2 exchange. Despite its crucial role in today’s climate system, vigorous debate remains as to when deep-water formation in the North Atlantic started. Here, we present datasets from carbonate-rich middle Eocene sediments from the Newfoundland Ridge, revealing a unique archive of paleoceanographic change from the progressively cooling climate of the middle Eocene. Well-defined lithologic alternations between calcareous ooze and clay-rich intervals occur at the ∼41-kyr beat of axial obliquity. Hence, we identify obliquity as the driver of middle Eocene (43.5–46 Ma) Northern Component Water (NCW, the predecessor of modern NADW) variability. High-resolution benthic foraminiferal δ18O and δ13C suggest that obliquity minima correspond to cold, nutrient-depleted, western North Atlantic deep waters. We thus link stronger NCW formation with obliquity minima. In contrast, during obliquity maxima, Deep Western Boundary Currents were weaker and warmer, while abyssal nutrients were more abundant. These aspects reflect a more sluggish NCW formation. This obliquity-paced paleoceanographic regime is in excellent agreement with results from an Earth system model, in which obliquity minima configurations enhance NCW formation

Pacific Equatorial Age Transect : expeditions 320 and 321 of the riserless drilling platform from and to Honolulu, Hawaii (USA), Sites U1331–U1336, 5 March–4 May 2009 and Honolulu, Hawaii (USA), to San Diego, California (USA), Sites U1337–U1338, 4 May–22 June 2009

Integrated Ocean Drilling Program Expedition 320/321, "Pacific Equatorial Age Transect" (Sites U1331–U1338), was designed to recover a continuous Cenozoic record of the equatorial Pacific by coring above the paleoposition of the Equator at successive crustal ages on the Pacific plate. These sediments record the evolution of the equatorial climate system throughout the Cenozoic. As we gained more information about the past movement of plates and when in Earth's history "critical" climate events took place, it became possible to drill an age transect ("flow-line") along the position of the paleoequator in the Pacific, targeting important time slices where the sedimentary archive allows us to reconstruct past climatic and tectonic conditions. The Pacific Equatorial Age Transect (PEAT) program cored eight sites from the sediment surface to basement, with basalt aged between 53 and 18 Ma, covering the time period following maximum Cenozoic warmth, through initial major glaciations, to today. The PEAT program allows the reconstruction of extreme changes of the calcium carbonate compensation depth (CCD) across major geological boundaries during the last 53 m.y. A very shallow CCD during most of the Paleogene makes it difficult to obtain well-preserved carbonate sediments during these stratigraphic intervals, but Expedition 320 recovered a unique sedimentary biogenic sediment archive for time periods just after the Paleocene/Eocene boundary event, the Eocene cooling, the Eocene–Oligocene transition, the "one cold pole" Oligocene, the Oligocene–Miocene transition, and the middle Miocene cooling. Expedition 321, the second part of the PEAT program, recovered sediments from the time period roughly from 25 Ma forward, including sediments crossing the Oligocene/Miocene boundary and two major Neogene equatorial Pacific sediment sections. Together with older Deep Sea Drilling Project and Ocean Drilling Program drilling in the equatorial Pacific, we can delineate the position of the paleoequator and variations in sediment thickness from ~150°W to 110°W longitude

Insensitivity of alkenone carbon isotopes to atmospheric CO₂ at low to moderate CO₂ levels

Atmospheric pCO2 is a critical component of the global carbon system and is considered to be the major control of Earth’s past, present and future climate. Accurate and precise reconstructions of its concentration through geological time are, therefore, crucial to our understanding of the Earth system. Ice core records document pCO2 for the past 800 kyrs, but at no point during this interval were CO2 levels higher than today. Interpretation of older pCO2 has been hampered by discrepancies during some time intervals between two of the main ocean-based proxy methods used to reconstruct pCO2: the carbon isotope fractionation that occurs during photosynthesis as recorded by haptophyte biomarkers (alkenones) and the boron isotope composition (δ11B) of foraminifer shells. Here we present alkenone and δ11B-based pCO2 reconstructions generated from the same samples from the Plio-Pleistocene at ODP Site 999 across a glacial-interglacial cycle. We find a muted response to pCO2 in the alkenone record compared to contemporaneous ice core and δ11B records, suggesting caution in the interpretation of alkenone-based records at low pCO2 levels. This is possibly caused by the physiology of CO2 uptake in the haptophytes. Our new understanding resolves some of the inconsistencies between the proxies and highlights that caution may be required when interpreting alkenone-based reconstructions of pCO2

Synchronizing the timing of anoxia, volcanism and the pacing of the Earth’s orbit in the Early Cretaceous

Recurrent acceleration of the hydrolysing cycle, so-called Episodes of Environmental Changes, occur in the Early Cretaceous. As the geologic time scale show large uncertainties, the pacing and the chronological relationship of these events remain obscure. We present here new radio-astrochronologic data from the Neuquén Basin (Argentina) anchored to the Tethyan realm. The new time sale of the Valanginian-Hauterivian provides ages of ammonite zones with an uncertainty of ± 0.2 myr and provides much precise age of the start of the Weissert Event. The age of the start of the Weissert Event is at 134.5 ± 0.2 myr, which is exactly synchronous with the main phase of the Paraná-Etendeka large igneous province activity. Most recent duration and age estimates from the Berriasian to the Barremian are reviewed and differ from the Geologic Time Scale 2016 by several million of years. Thanks to this new time scale, belemnite δ13C are reviewed and show a strong pacing with a period of 2.4 myr, which correspond to the long-eccentricity cycle. Higher amplitudes of the 2.4-myr cycle are observed at time of large igneous province emplacement, which may be due to accelerated hydrolysis cycle following CO2 input to the atmosphere from the volcanic activity.Fil: Martinez, Mathieu. Universite de Rennes I; FranciaFil: Aguirre Urreta, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Lescano, Marina Aurora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Omarini, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Tunik, Maisa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Frederichs, Thomas. Universitat Bremen; AlemaniaFil: Nickl, Anna-Leah. Universitat Bremen; AlemaniaFil: Pälike, Heiko. Universitat Bremen; AlemaniaEGU General Assembly 2019VienaAustriaEuropean Geosciences Unio

IODP New Ventures in Exploring Scientific Targets (INVEST): Defining the New Goals of an International Drilling Program

No abstract available. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.9.12.2010" target="_blank">10.2204/iodp.sd.9.12.2010</a

Geochemical analysis of bulk marine sediment by Inductively Coupled Plasma–Atomic Emission Spectroscopy on board the JOIDES Resolution

Geochemical analyses on board the JOIDES Resolution have been enhanced with the addition of a Jobin-Yvon Ultrace inductively coupled plasma-atomic emission spectrometer (ICP-AES) as an upgrade from the previous X-ray fluorescence facility. During Leg 199, we sought to both challenge and utilize the capabilities of the ICP-AES in order to provide an extensive bulk-sediment geochemical database during the cruise. These near real-time analyses were then used to help characterize the recovered sedimentary sequences, calculate mass accumulation rates of the different sedimentary components, and assist with cruise and postcruise sampling requests. The general procedures, sample preparation techniques, and basic protocol for ICP-AES analyses on board ship are outlined by Murray et al. (2000) in Ocean Drilling Program Tech Note, 29. We expand on those concepts and offer suggestions for ICP-AES methodology, calibration by standard reference materials, data reduction procedures, and challenges that are specific to the analysis of bulk-sediment samples. During Leg 199, we employed an extensive bulk-sediment analytical program of ~600 samples of varying lithologies, thereby providing several opportunities for refinement of techniques. We also discuss some difficulties and challenges that were faced and suggest how to alleviate such occurrences for sedimentary chemical analyses during future legs

A lower to middle Eocene astrochronology for the Mentelle Basin (Australia) and its implications for the geologic time scale

The geologic time scale for the Cenozoic Era has been notably improved over the last decades by virtue of integrated stratigraphy, combining high-resolution astrochronologies, biostratigraphy and magnetostratigraphy with high-precision radioisotopic dates. However, the middle Eocene remains a weak link. The so-called “Eocene time scale gap” reflects the scarcity of suitable study sections with clear astronomically-forced variations in carbonate content, primarily because large parts of the oceans were starved of carbonate during the Eocene greenhouse. International Ocean Discovery Program (IODP) Expedition 369 cored a carbonate-rich sedimentary sequence of Eocene age in the Mentelle Basin (Site U1514, offshore southwest Australia). The sequence consists of nannofossil chalk and exhibits rhythmic clay content variability. Here, we show that IODP Site U1514 allows for the extraction of an astronomical signal and the construction of an Eocene astrochronology, using 3-cm resolution X-Ray fluorescence (XRF) core scans. The XRF-derived ratio between calcium and iron content (Ca/Fe) tracks the lithologic variability and serves as the basis for our U1514 astrochronology. We present a 16 million-year-long (40-56 Ma) nearly continuous history of Eocene sedimentation with variations paced by eccentricity and obliquity. We supplement the high-resolution XRF data with low-resolution bulk carbon and oxygen isotopes, recording the long-term cooling trend from the Paleocene-Eocene Thermal Maximum (PETM – ca. 56 Ma) into the middle Eocene (ca. 40 Ma). Our early Eocene astrochronology corroborates existing chronologies based on deep-sea sites and Italian land sections. For the middle Eocene, the sedimentological record at U1514 provides a single-site geochemical backbone and thus offers a further step towards a fully integrated Cenozoic geologic time scale at orbital resolution