scholarly journals Updated Cariaco Basin 14C Calibration Dataset from 0–60 cal kyr BP

Radiocarbon ◽  
2020 ◽  
Vol 62 (4) ◽  
pp. 1001-1043 ◽  
Author(s):  
Konrad A Hughen ◽  
Timothy J Heaton
Keyword(s):  
Primary Source ◽  
Cariaco Basin ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Calibration Dataset ◽  
The Past ◽  
Climate Shifts ◽  
Depth Scale ◽  
Age Model ◽  
Reservoir Age

ABSTRACTWe present new updates to the calendar and radiocarbon (14C) chronologies for the Cariaco Basin, Venezuela. Calendar ages were generated by tuning abrupt climate shifts in Cariaco Basin sediments to those in speleothems from Hulu Cave. After the original Cariaco-Hulu calendar age model was published, Hulu Cave δ18O records have been augmented with increased temporal resolution and a greater number of U/Th dates. These updated Hulu Cave records provide increased accuracy as well as precision in the final Cariaco calendar age model. The depth scale for the Ocean Drilling Program Site 1002D sediment core, the primary source of samples for 14C dating, has been corrected to account for missing sediment from a core break, eliminating age-depth anomalies that afflicted the earlier calendar age models. Individual 14C dates for the Cariaco Basin remain unchanged from previous papers, although detailed comparisons of the Cariaco calibration dataset to those from Hulu Cave and Lake Suigetsu suggest that the Cariaco marine reservoir age may have shifted systematically during the past. We describe these recent changes to the Cariaco datasets and provide the data in a comprehensive format that will facilitate use by the community.

scholarly journals Insensitivity of alkenone carbon isotopes to atmospheric CO<sub>2</sub> at low to moderate CO<sub>2</sub> levels

2019 ◽  
Vol 15 (2) ◽  
pp. 539-554 ◽  
Author(s):  
Marcus P. S. Badger ◽  
Thomas B. Chalk ◽  
Gavin L. Foster ◽  
Paul R. Bown ◽  
Samantha J. Gibbs ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Ice Core ◽  
Co2 Uptake ◽  
Geological Time ◽  
Ocean Drilling Program ◽  
Time Intervals ◽  
Ocean Drilling ◽  
The Past ◽  
Global Carbon ◽  
Carbon System

Abstract. 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 kyr, 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 Pliocene and across a Pleistocene glacial–interglacial cycle at Ocean Drilling Program (ODP) Site 999. 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.

Reunion hotspot magma chemistry over the past 65 m.y.: Results from Leg 115 of the Ocean Drilling Program

Geology ◽  
1989 ◽  
Vol 17 (10) ◽  
pp. 934 ◽  
Author(s):  
Martin R. Fisk ◽  
Robert A. Duncan ◽  
Alistair N. Baxter ◽  
John D. Greenough ◽  
Robert B. Hargraves ◽  
...  
Keyword(s):  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
The Past

scholarly journals An Approach to the Paleoceanographic Characteristics of the Sea-Surface at the Western Mediterranean (Balearic Area) during the Pliocene and Gelasian

Geosciences ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 302
Author(s):  
Francisco Serrano
Keyword(s):  
Estimation Error ◽  
Western Mediterranean ◽  
Sea Surface ◽  
Ocean Drilling Program ◽  
Average Value ◽  
Ocean Drilling ◽  
Calibration Dataset ◽  
Current Water ◽  
Water Surplus ◽  
Temperature Seasonality

From the study of the planktonic foraminifer assemblages of the sediments of the Ocean Drilling Program (ODP)-Site 975 (Baleares), sea-surface temperature, seasonality and salinity for the Pliocene and Gelasian of the Western Mediterranean were estimated. The estimates were carried out by the modern analog technique (MAT) using PaleoUma, a calibration dataset of 735 North-Atlantic and Mediterranean core-tops. In order to compare Pliocene–Gelasian and present-day analog assemblages, the necessary reduction of the taxonomic variables leads to statistically insignificant increases in estimation error, assessed on the calibration dataset itself. In addition, the correlation with δ18O results as an independent proxy, supports the use of MAT in order to establish the dominant paleoceanographic frameworks during the Pliocene and Gelasian. The SST curve shows an increase trend of the average value since the Early Zanclean (19.7 ± 1.8 °C) to the Late Piacenzian (20.9 ± 1.7 °C) and a decrease until the Late Gelasian (18.1 ± 1.4 °C). The seasonality offers permanently lower estimates than the current value (9.8 °C), reaching the closest values during the Late Gelasian (8.6 ± 0.8 °C). The salinity estimates are overall slightly lower during the Zanclean (36.7‰ ± 0.5‰) than today (37.3‰), whereas they reach up to more than 38.5‰, in the Early Piacenzian. The paleoceanographic frameworks deduced from the combination of the paleoceanographic parameters suggest that the current water-deficit regime in the Mediterranean was clearly predominant throughout the Pliocene and Gelasian. However, since the Piacenzian this regime alternates with stages of water surplus, which are especially frequent in the late Piacenzian. By the middle of the Early Gelasian the regime becomes more predominantly in deficit again.

scholarly journals Holocene climate variability of the Western Mediterranean: Surface water dynamics inferred from calcareous plankton assemblages

The Holocene ◽  
2020 ◽  
Vol 30 (5) ◽  
pp. 691-708 ◽  
Author(s):  
Pietro Bazzicalupo ◽  
Patrizia Maiorano ◽  
Angela Girone ◽  
Maria Marino ◽  
Nathalie Combourieu-Nebout ◽  
...  
Keyword(s):  
Surface Water ◽  
Western Mediterranean ◽  
Water Dynamics ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Climate Shifts ◽  
Oceanic Forcing ◽  
Calcareous Plankton ◽  
Florisphaera Profunda ◽  
Gyre Circulation

A high-resolution study (centennial scale) has been performed on the calcareous plankton assemblage of the Holocene portion of the Ocean Drilling Program Site 976 (Alboran Sea) with the aim to identify the main changes in the surface water dynamic. The dataset also provided a seasonal foraminiferal sea surface water temperatures (SSTs), estimated using the modern analog technique SIMMAX 28, and it was compared with available geochemical and pollen data at the site. Three main climate shifts were identified as (1) the increase in abundance of Syracosphaera spp. and Turborotalita quinqueloba marks the early Holocene humid phase, during maximum summer insolation and enhanced river runoff. It is concomitant with the expansion of Quercus, supporting high humidity on land. It ends at 8.2 ka, registering a sudden temperature and humidity reduction; (2) the rise in the abundances of Florisphaera profunda and Globorotalia inflata, at ca. 8 ka, indicates the development of the modern geostrophic front, gyre circulation, and of a deep nutricline following the sea-level rise; and (3) the increase of small Gephyrocapsa and Globigerina bulloides at 5.3 ka suggests enhanced nutrient availability in surface waters, related to more persistent wind-induced upwelling conditions. Relatively higher winter SST in the last 3.5 ka favored the increase of Trilobatus sacculifer, likely connected to more stable surface water conditions. Over the main trends, a short-term cyclicity is registered in coccolithophore productivity during the last 8 ka. Short periods of increased productivity are in phase with Atlantic waters inflow, and more arid intervals on land. This cyclicity has been related with periods of positive North Atlantic Oscillation (NAO) circulations. Spectral analysis on coccolithophore productivity confirms the occurrence of millennial-scale cyclicity, suggesting an external (i.e. solar) and an internal (i.e. atmospheric/oceanic) forcing.

scholarly journals Atmospheric CO<sub>2</sub> estimates for the Miocene to Pleistocene based on foraminiferal δ<sup>11</sup>B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific

2021 ◽  
Author(s):  
Maxence Guillermic ◽  
Sambuddha Misra ◽  
Robert Eagle ◽  
Aradhna Tripati
Keyword(s):  
Inductively Coupled Plasma ◽  
Ice Core ◽  
Warm Pool ◽  
Atmospheric Co2 ◽  
Ocean Drilling Program ◽  
Planktic Foraminifera ◽  
Ocean Drilling ◽  
The Past ◽  
Co2 Levels ◽  
Climate Transition

Abstract. Constraints on the evolution of atmospheric CO2 levels throughout Earth's history are foundational to our understanding of past variations in climate. Despite considerable effort, estimates of past CO2 levels do not always converge and therefore new records and proxies are valuable. Here we reconstruct atmospheric CO2 values across major climate transitions over the past 17 million years using the boron isotopic composition (δ11B) of planktic foraminifera from 89 samples obtained from two sites in the West Pacific Warm Pool, Ocean Drilling Program (ODP) Sites 806 and 807. These sites are in a region that today is in equilibrium with the atmosphere and are thought to have been in equilibrium with the atmosphere for the interval studied. We use high-precision multi-collector inductively-coupled plasma mass spectrometry and show that data from these sites can reproduce the ice core record. Estimates of early Miocene pCO2 are generally higher than published reconstructions from other sites, while values for the Pliocene and Pleistocene are more similar to other datasets. We find evidence for reductions in pCO2 of ~280 µatm during the Middle Miocene Climate Transition, ~270 µatm during Pliocene Glacial Intensification, and ~50 µatm during the Mid-Pleistocene Climate Transition. There is possible evidence for a larger reduction in glacial pCO2 during the Mid-Pleistocene Transition compared to interglacial pCO2, and a minimum in pCO2 during glacial MIS 30. Our results are consistent with a coupling between pCO2, temperature and ice sheet expansion throughout the past 17 million years.

scholarly journals A revised and improved age model for the middle Miocene part of IODP Site U1318 (Porcupine Basin, offshore southwestern Ireland)

2017 ◽  
Vol 155 (5) ◽  
pp. 1105-1116
Author(s):  
WILLEMIJN QUAIJTAAL ◽  
STEVEN TESSEUR ◽  
TIMME H. DONDERS ◽  
PHILIPPE CLAEYS ◽  
STEPHEN LOUWYE
Keyword(s):  
North Atlantic ◽  
Middle Miocene ◽  
Ocean Drilling Program ◽  
Carbon And Oxygen Isotopes ◽  
Ocean Drilling ◽  
The North ◽  
Integrated Ocean Drilling Program ◽  
Isotope Record ◽  
Porcupine Basin ◽  
Age Model

AbstractIntegrated Ocean Drilling Program Leg 307 Site U1318 is one of the few relatively complete middle Miocene drillcores from the North Atlantic (Porcupine Basin, offshore southwestern Ireland). Using benthic foraminiferal stable carbon and oxygen isotopes, the existing age model for Site U1318 was improved. The stable isotope record displays globally recognized isotope events, used to revise the existing magnetostratigraphy-based age model. Two intervals contained misidentified magnetochrons which were corrected. The sampled interval now has a refined age of 12.75–16.60 Ma with a temporal resolution of c. 29 ka.

The application of Neodymium isotope as a chronostratigraphic tool in North Pacific sediments

2019 ◽  
Vol 157 (5) ◽  
pp. 768-776 ◽  
Author(s):  
Wenfang Zhang ◽  
Gaojun Li ◽  
Jun Chen
Keyword(s):  
North Pacific ◽  
North Pacific Ocean ◽  
Ice Sheets ◽  
Asian Dust ◽  
Ocean Drilling Program ◽  
Nd Isotope ◽  
Aeolian Dust ◽  
Ocean Drilling ◽  
The Past ◽  
Dust Generation

AbstractIt has been suggested that dust generation was closely linked to the development of global ice sheets and/or cooling. This feature has allowed Asian dust to be a potential chronostratigraphic tool in North Pacific Ocean (NPO) sediments. The orbital-scale age control in NPO sediments is usually established by adjusting the benthic-foraminiferal δ18O to the global δ18O stack (LR04). However, it would become difficult if the sediments did not contain enough foraminifera. This study investigates Sr and Nd isotopes, trace elements, mineralogy and grain size of the ‘operationally defined aeolian dust’ (ODED) extracted from the sediments recovered at Ocean Drilling Program (ODP) site 1209B on the Shatsky Rise in the NPO covering the past five glacial–interglacial cycles. The geochemical results show that the ODED at site 1209B is actually a mixture of Asian dust and volcanic ash. The variation of Nd isotope mimics the cycles of glacial–interglacial ice sheets as revealed by the global benthic foraminifera’s oxygen isotope stack (LR04) over the past 500 ka. The low (high) ϵNd values corresponded with the cool (warm) periods. We propose that ϵNd variation reflects the evolving aeolian dust in site 1209 sediments. The excellent agreement between ϵNd values at site 1209B and LR04 stack over the past 500 ka allows establishing the orbital-timescale age control by tuning ϵNd to the LR04 curve. We thus propose that Nd isotope provides a chronostratigraphic technique in NPO sediments, especially for sediments with a limited amount of foraminifera.

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