ORCID Profile
0000-0002-3285-4022
Current Organisation
Texas A&M University
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Publisher: Copernicus GmbH
Date: 05-11-2013
DOI: 10.5194/SD-16-1-2013
Abstract: Abstract. IODP Expedition 339 drilled five sites in the Gulf of Cadiz and two off the west Iberian margin (November 2011 to January 2012), and recovered 5.5 km of sediment cores with an average recovery of 86.4%. The Gulf of Cadiz was targeted for drilling as a key location for the investigation of Mediterranean outflow water (MOW) through the Gibraltar Gateway and its influence on global circulation and climate. It is also a prime area for understanding the effects of tectonic activity on evolution of the Gibraltar Gateway and on margin sedimentation. We penetrated into the Miocene at two different sites and established a strong signal of MOW in the sedimentary record of the Gulf of Cadiz, following the opening of the Gibraltar Gateway. Preliminary results show the initiation of contourite deposition at 4.2–4.5 Ma, although subsequent research will establish whether this dates the onset of MOW. The Pliocene succession, penetrated at four sites, shows low bottom current activity linked with a weak MOW. Significant widespread unconformities, present in all sites but with hiatuses of variable duration, are interpreted as a signal of intensified MOW, coupled with flow confinement. The Quaternary succession shows a much more pronounced phase of contourite drift development, with two periods of MOW intensification separated by a widespread unconformity. Following this, the final phase of drift evolution established the contourite depositional system (CDS) architecture we see today. There is a significant climate control on this evolution of MOW and bottom-current activity. However, from the closure of the Atlantic–Mediterranean gateways in Spain and Morocco just over 6 Ma and the opening of the Gibraltar Gateway at 5.3 Ma, there has been an even stronger tectonic control on margin development, downslope sediment transport and contourite drift evolution. The Gulf of Cadiz is the world's premier contourite laboratory and thus presents an ideal testing ground for the contourite paradigm. Further study of these contourites will allow us to resolve outstanding issues related to depositional processes, drift budgets, and recognition of fossil contourites in the ancient record on shore. The expedition also verified an enormous quantity and extensive distribution of contourite sands that are clean and well sorted. These represent a relatively untapped and important exploration target for potential oil and gas reservoirs.
Publisher: Geological Society of London
Date: 2002
Publisher: International Ocean Discovery Program
Date: 15-12-2020
Publisher: Elsevier BV
Date: 09-2009
Publisher: Copernicus GmbH
Date: 24-10-2023
Abstract: Abstract. Nick Shackleton's research on piston cores from the Iberian margin highlighted the importance of this region for providing high-fidelity records of millennial-scale climate variability, and for correlating climate events from the marine environment to polar ice cores and European terrestrial sequences. During the Integrated Ocean Drilling Program (IODP) Expedition 339, we sought to extend the Iberian margin sediment record by drilling with the D/V JOIDES Resolution. Five holes were cored at Site U1385 using the advanced piston corer (APC) system to a maximum depth of ~155.9 m below sea floor (m b.s.f.). Immediately after the expedition, cores from all holes were analyzed by core scanning X-ray fluorescence (XRF) at 1 cm spatial resolution. Ca/Ti data were used to accurately correlate from hole-to-hole and construct a composite spliced section, containing no gaps or disturbed intervals to 166.5 m composite depth (mcd). A low-resolution (20 cm s le spacing) oxygen isotope record confirms that Site U1385 contains a continuous record of hemipelagic sedimentation from the Holocene to 1.43 Ma (Marine Isotope Stage 46). The sediment profile at Site U1385 extends across the middle Pleistocene transition (MPT) with sedimentation rates averaging ~10 cm kyr−1. Strong precession cycles in colour and elemental XRF signals provide a powerful tool for developing an orbitally tuned reference timescale. Site U1385 is likely to become an important type section for marine–ice–terrestrial core correlations and the study of orbital- and millennial-scale climate variability.
Publisher: Copernicus GmbH
Date: 16-05-2014
Abstract: Abstract. Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, a robust astronomically calibrated age model was constructed for the middle Eocene to early Oligocene interval (31–43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the middle Eocene climate optimum and the Eocene–Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new timescale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and 320-U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently orbital tuning of the records to the La2011 orbital solution was conducted. The resulting new timescale revises and refines the existing orbitally tuned age model and the geomagnetic polarity timescale from 31 to 43 Ma. The newly defined absolute age for the Eocene–Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano, Italy, global stratotype section and point. The compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during 2.4 myr eccentricity cycle minima around 35.5, 38.3, and 40.1 Ma.
Publisher: Elsevier BV
Date: 04-2021
Publisher: American Geophysical Union (AGU)
Date: 12-05-2012
DOI: 10.1029/2012GC004080
Publisher: Geological Society of America
Date: 2009
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 07-2013
Publisher: American Geophysical Union (AGU)
Date: 09-2020
DOI: 10.1029/2020PA003947
Publisher: American Geophysical Union (AGU)
Date: 03-2019
DOI: 10.1029/2018JB016865
Publisher: American Geophysical Union (AGU)
Date: 06-1991
DOI: 10.1029/90TC01792
Publisher: American Geophysical Union (AGU)
Date: 10-11-2007
DOI: 10.1029/2007JB004963
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-06-2014
Abstract: The trickle of water that began to flow from the Mediterranean Sea into the Atlantic Ocean after the opening of the Strait of Gibraltar turned into a veritable flood by the end of the Pliocene 2 to 3 million years ago. It then began to influence large-scale ocean circulation in earnest. Hernández-Molina et al. describe marine sediment cores collected by an ocean drilling expedition (see the Perspective by Filippelli). The results reveal a detailed history of the timing of Mediterranean outflow water activity and show how the addition of that warm saline water to the cooler less-salty waters of the Atlantic was related to climate changes, deep ocean circulation, and plate tectonics. Science , this issue p. 1244 see also p. 1228
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 11-2003
Publisher: Elsevier BV
Date: 08-2000
Publisher: American Geophysical Union (AGU)
Date: 08-2014
DOI: 10.1002/2014GC005343
Publisher: American Geophysical Union (AGU)
Date: 2013
DOI: 10.1002/GGGE.20064
Publisher: Elsevier BV
Date: 15-10-2007
Publisher: Elsevier BV
Date: 04-1999
Publisher: Oxford University Press (OUP)
Date: 28-10-2013
DOI: 10.1093/GJI/GGT412
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 03-2006
Publisher: American Geophysical Union (AGU)
Date: 02-09-2010
DOI: 10.1029/2010GC003132
Publisher: Elsevier BV
Date: 09-2000
Publisher: Elsevier BV
Date: 07-2006
Publisher: Elsevier BV
Date: 08-2001
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 12-1996
Publisher: American Geophysical Union (AGU)
Date: 02-03-2007
DOI: 10.1029/2006JB004655
Publisher: Proceedings of the National Academy of Sciences
Date: 22-02-2016
Abstract: New information from the ANDRILL-2A drill core and a complementary ice sheet modeling study show that polar climate and Antarctic ice sheet (AIS) margins were highly dynamic during the early to mid-Miocene. Changes in extent of the AIS inferred by these studies suggest that high southern latitudes were sensitive to relatively small changes in atmospheric CO 2 (between 280 and 500 ppm). Importantly, reconstructions through intervals of peak warmth indicate that the AIS retreated beyond its terrestrial margin under atmospheric CO 2 conditions that were similar to those projected for the coming centuries.
Publisher: Elsevier BV
Date: 12-2001
Publisher: IEEE
Date: 2003
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 07-2006
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-05-2006
Abstract: S ling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.
Publisher: Elsevier BV
Date: 2002
Publisher: Elsevier BV
Date: 07-2006
Publisher: Geological Society of London
Date: 17-08-2012
DOI: 10.1144/SP373.7
Publisher: Wiley
Date: 19-12-2019
Publisher: Elsevier BV
Date: 05-2003
Publisher: Springer Science and Business Media LLC
Date: 08-2012
DOI: 10.1038/NATURE11360
Abstract: Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
Publisher: Elsevier BV
Date: 03-2008
Location: United States of America
Location: United States of America
No related grants have been discovered for Gary Acton.