ALBERT

Description: A consistent chronostratigraphic framework is required to understand the effect of major paleoclimate perturbations on both marine and terrestrial ecosystems. Transient global warming events in the early Eocene, 56-54 Ma ago, show the impact of large scale carbon input into the ocean-atmosphere system. Here we provide the first time-scale synchronization of continental and marine deposits spanning the Paleocene-Eocene Thermal Maximum (PETM) and the interval just prior to the Eocene Thermal Maximum 2 (ETM-2). Cyclic variations in geochemical data come from continental drill cores of the Bighorn Basin Coring Project (BBCP, Wyoming, USA) and from marine deep-sea drilling deposits retrieved by the Ocean Drilling Program (ODP). Both are dominated by eccentricity modulated precession cycles used to construct a common cyclostratigraphic framework. Integration of age models results in a revised astrochronology for the PETM in deep-sea records that is now generally consistent with independent 3He age models. The duration of the PETM is estimated at ~200 kyr for the CIE and ~120 kyr for the associated pelagic clay layer. A common terrestrial and marine age model shows a concurrent major change in marine and terrestrial biotas ~200 kyr before ETM-2. In the Bighorn Basin, the change is referred to as Biohorizon B, and represents a period of significant mammalian turnover and immigration, separating the upper Haplomylus-Ectocion Range Zone from the Bunophorus Interval Zone and approximating the Wa-4-Wa-5 land mammal zone boundary. In sediments from ODP Site 1262 (Walvis Ridge), major changes in the biota at this time are documented by the radiation of a "2nd generation" of apical spine-bearing sphenoliths species (e.g., S. radians and S. editus), the emergence of T. orthostylus, and the marked decline of D. multiradiatus.

Description: These files contain individual core images generated from core box photos using the Code for Ocean Drilling Data (CODD) software set. There are PNG images with mcd depth scales attached for use in graphics programs as well as scaled Igor binary images for use with CODD. MCD depths are from the offsets.

Description: Ocean Drilling Programme (ODP) Site 982 represents a key location for understanding the evolution of climate in the North Atlantic over the past 12 Ma. However, concerns exist about the validity and robustness of the underlying stratigraphy and astrochronology, which currently limits the adequacy of this site for high-resolution climate studies. To resolve this uncertainty, we verify and extend the early Pliocene to late Miocene shipboard composite splice at Site 982 using high-resolution XRF core scanning data and establish a robust high-resolution stable isotope stratigraphy and astrochronology between 4.5 and 8.0 Ma. Splice revisions and verifications resulted in ~11 m of gaps in the original Site 982 isotope stratigraphy. Our new stratigraphy reveals previously unseen benthic d18O excursions, particularly prior to 6.65 Ma. The benthic d18O record displays distinct, asymmetric cycles between 7.7 and 6.65 Ma, confirming that high-latitude climate is a prevalent forcing during this interval. An intensification of the 41-kyr beat in both the benthic d13C and d18O is also observed ~6.4 Ma, marking a strengthening in the cryosphere-carbon cycle coupling. A large ~0.7 per mil double excursion is revealed ~6.4-6.3 Ma, which also marks the onset an interval of average higher d18O and large precession and obliquity-dominated d18O excursions between 6.4-5.4 Ma, coincident with the culmination of the late Miocene cooling. The two largest benthic d18O excursions ~6.4-6.3 Ma and TG20/22 coincide with the coolest alkenone-derived SST estimates from Site 982, suggesting a strong connection between the late Miocene global cooling and deep-sea cooling and dynamic ice sheet expansion. The splice revisions and revised astrochronology resolve key stratigraphic issues that have hampered correlation between Site 982, the equatorial Atlantic and the Mediterranean. Comparisons of the revised Site 982 stratigraphy to high-resolution astronomically tuned benthic d18O stratigraphies from ODP Site 926 (equatorial Atlantic) and Ain el Beida (north western Morocco) show that prior inconsistencies in short-term excursions are now resolved. The identification of key new cycles at Site 982 further highlights the requirement for the current scheme for late Miocene marine isotope stages to be redefined. Our new integrated deep-sea benthic stable isotope stratigraphy and astrochronology from Site 982 will facilitate future high-resolution late Miocene to early Pliocene climate research.

Description: This is the full dataset for the manuscript Astronomical calibration of the Ypresian timescale: implications for seafloor spreading rates and the chaotic behavior of the solar system? by Westerhold, T., Röhl, U., Frederichs, T., Agnini, C., Raffi, I., Zachos, J. C., and Wilkens, R. H. published in Climate of the Past, 13, 1129-1152, https://doi.org/10.5194/cp-13-1129-2017, 2017. It contains 48 tables with XRF core scanning data, bulk and benthic stable isotope data compiled, raw inclination-declination-intensity data, Paleomagnetic interpretation, magnetostratigraphy, calcareous nanofossil events, mapping pairs for correlation of different hole in a drill site, tie points to correlated between drill sites for ODP Sites 1258, 1262, 1263, 1265, 1267 (Tables S1-44). Tables S45 to 48 contain a combined magnetostratigraphy, a 405-kyr tuning age model, tie points for a detailed astronomical age model, and comparison of magnetochron durations.

Description: The boron isotope composition (d11B) of planktic foraminiferal calcite, which reflects seawater pH, is a well-established proxy for reconstructing palaeo-atmospheric CO2 and seawater carbonate chemistry. However, to translate d11B measurements determined in calcareous fossils into pH we need to know the boron isotope composition of the parent seawater (d11Bsw). While a number of d11Bsw reconstructions exist, the discrepancies between them reveals uncertainties and deficiencies that need to be addressed. Here we present a new d11Bsw record based on the d11B difference between planktic and benthic foraminifera and an estimate of the pH gradient between surface and deep water. We then calculate d11Bsw two different ways. One variant of our method assumes that the pH gradient between surface and deep has remained the same as today over the past 23 Ma; the other uses the d13C gradient between surface and deep to represent change in the pH gradient through time. The results of these two methods of calculating d11Bsw are broadly consistency with each other, however, based on extensive carbon cycle modelling using CYCLOPS and GENIE we favour the d13C gradient method. In our favoured d11Bsw reconstruction, d11Bsw is around 2 per mil lower than today at ~37.5 per mil during the early and middle Miocene and increases to the modern value (39.61 per mil) by ~5 Ma. A similar pattern of change is evident in the seawater composition of three other stable isotope systems, Mg, Li and Ca. Concurrent shifts in the seawater isotopic composition of all four of these elements during the late Miocene, suggest a common forcing mechanism. We hypothesise the most likely cause of these shifts is a change in the isotopic composition of the riverine input, potentially driven by an increase in secondary mineral formation since ~15 Ma.

Description: This study reports neodymium isotopic (e-Nd) variability at a time resolution of 0.5 to 3 Ma since the Late Cretaceous as recorded in a marine sedimentary core from the Western Pacific (ODP 807; 3°36'N, 156°3?E; Ontong Java Plateau). Our core is mainly fine-grained and composed of continuous sequences of nannofossil oozes. The e-Nd measured in the carbonate fraction was used as a proxy of e-Nd of seawater of the Western Pacific. On a long term, our results indicate a general increase in e-Nd of seawater by 4.5 e-Nd units from the Late Cretaceous (e-Nd = - 6) to modern times (e-Nd = - 1.7). This pattern was related to the emergence of the West Pacific margin and the progressive isolation of the Pacific Ocean from the other oceanic basins, resulting in its progressive shift to more radiogenic values through the Cenozoic. This long-term pattern is in accordance with previously published Fe-Mn crusts data from the same study area. Nonetheless, by being at higher time resolution, our data records additional sharp and pseudo-cyclic variations (~ 7?11 Ma periods) superimposed on this long-term pattern from ~ 40 Ma to modern times. These oscillations might reflect the alternating dominance of the two main deep water masses (NPDW and UCDW) bathing our study area. In the same core, we also measured the e-Nd in the detrital fraction in order to trace back the local terrigenous inputs. The terrigenous record shows a significant variability up to + 12 e-Nd units. This was linked to the emergence of the west Pacific subduction zone ~ 50 Ma ago causing a higher input of radiogenic isotopes. In conclusion, the large variability observed in both seawater and detrital e-Nd records most probably result from a major tectonic and oceanic circulation reorganization of the Pacific Ocean.

Description: Determining the timing and amplitude of tropical sea surface temperature (SST) change is an important part of solving the puzzle of the Plio-Pleistocene ice ages. Alkenone-based tropical SST records from the major ocean basins show coherent glacial-interglacial temperature changes of 1° to 3°C that align with (but slightly lead) global changes in ice volume and deep ocean temperature over the past 3.5 million years. Tropical temperatures became tightly coupled with benthic d18O and orbital forcing after 2.7 million years. We interpret the similarity of tropical SST changes, in dynamically dissimilar regions, to reflect "top-down" forcing through the atmosphere. The inception of a strong carbon dioxide-greenhouse gas feedback and amplification of orbital forcing at ~2.7 million years ago connected the fate of Northern Hemisphere ice sheets with global ocean temperatures since that time.

Description: Geochemical and Sr-Nd-Pb isotopic compositions of the detrital sediments from ODP Hole 1202B and Taiwan rivers were measured in this study, aiming to reveal changes in sediment provenance in the southern Okinawa Trough (SOT) since 28 ka, and to examine the weathering and sediment transport processes in response to monsoon climate variability. Large variations in Sr-Nd-Pb isotopic ratios at 11?9 ka suggest changes in detrital sediment provenance in the SOT from a dominance of the paleo-Changjiang (Yangtze River) and/or continental shelf sediment during the late deglaciation and to west Taiwan rivers since 9.5 ka. Volcanic rocks and eastern Taiwan sediments have not significantly contributed to the SOT. The large shift in sediment provenance during the early Holocene marks a major change in oceanic circulation, mainly caused by the intrusion of the Kuroshio Current into the trough. Clay mineral and geochemical proxies suggest that the Taiwan-derived sediments accumulated during the early-mid ?Holocene climate optimum? (ca. 9.5-4 ka) might be tightly related to the reworking of older altered sediments from terraces and floodplains, rather than having experienced more intense silicate weathering than in the late Holocene (~ 4-0 ka). Overall, silicate weathering in Taiwan was greatly inhibited by accelerating sediment production and transfer from land to ocean caused by monsoon intensification in Holocene. Our study illustrates that the radiogenic isotopic and geochemical compositions of fine-grained detrital sediments are sensitive tools for fingerprinting sediment sources and for reconstructing changes in oceanic currents and monsoon climate in river-dominated East Asian continental margin.

Description: Sea ice is a critical component in the Arctic and global climate system, yet little is known about its extent and variability during past warm intervals, such as the Pliocene (5.33-2.58 Ma). Here, we present the first multi-proxy (IP25, sterols, alkenones, palynology) sea ice reconstructions for the Late Pliocene Iceland Sea (ODP Site 907). Our interpretation of a seasonal sea ice cover with occasional ice-free intervals between 3.50-3.00 Ma is supported by reconstructed alkenone-based summer sea surface temperatures. As evidenced from brassicasterol and dinosterol, primary productivity was low between 3.50 and 3.00 Ma and the site experienced generally oligotrophic conditions. The East Greenland Current (and East Icelandic Current) may have transported sea ice into the Iceland Sea and/or brought cooler and fresher waters favoring local sea ice formation. Between 3.00 and 2.40 Ma, the Iceland Sea is mainly sea ice-free, but seasonal sea ice occurred between 2.81 and 2.74 Ma. Sea ice extending into the Iceland Sea at this time may have acted as a positive feedback for the build-up of the Greenland Ice Sheet (GIS), which underwent a major expansion ~2.75 Ma. Thereafter, most likely a stable sea ice edge developed close to Greenland, possibly changing together with the expansion and retreat of the GIS and affecting the productivity in the Iceland Sea.

Description: new data on the main components of organic matter, inorganic geochemistry, and stable isotopes along a north-south transect from the Cretaceous Western Interior Seaway (Portland-1 Colorado; Iona-1; Innes-1; Well X; Bouldin Creek outcrop - Eagle Ford Group, SW Texas, USA) and to the equatorial western Atlantic (ODP Sites 1260 and 1261) and Southern Ocean (ODP Site 1138)

Description: Authigenic neodymium isotopes, benthic foraminiferal stable isotopes and radiocarbon dates from ODP 929 in the deep equatorial western Atlantic Ocean.

Description: Recognizing and deciphering transient global warming events triggered by massive release of carbon into Earth's ocean-atmosphere climate system in the past are important for understanding climate under elevated pCO2 conditions. Here we present new high-resolution geochemical records including benthic foraminiferal stable isotope data with clear evidence of a short-lived (30 kyr) warming event at 41.52 Ma. The event occurs in the late Lutetian within magnetochron C19r and is characterized by a ~2°C warming of the deep ocean in the southern South Atlantic. The magnitudes of the carbon and oxygen isotope excursions of the Late Lutetian Thermal Maximum are comparable to the H2 event (53.6 Ma) suggesting a similar response of the climate system to carbon cycle perturbations even in an already relatively cooler climate several million years after the Early Eocene Climate Optimum. Coincidence of the event with exceptionally high insolation values in the Northern Hemisphere at 41.52 Ma might indicate that Earth's climate system has a thermal threshold. When this tipping point is crossed, rapid positive feedback mechanisms potentially trigger transient global warming. The orbital configuration in this case could have caused prolonged warm and dry season leading to a massive release of terrestrial carbon into the ocean-atmosphere system initiating environmental change.