@article {495,
	title = {Reconstructing Holocene conditions under the McMurdo Ice Shelf using Antarctic barnacle shells},
	journal = {Earth and Planetary Science Letters},
	volume = {298},
	year = {2010},
	note = {id: 1960; PT: J; UT: WOS:000283756600013},
	pages = {385-393},
	abstract = {This study evaluates the potential of barnacles for paleoceanographic reconstruction and, in particular, of the Antarctic species Bathylasma corolliforme to reconstruct past under ice shelves Like other barnacle species, this Antarctic barnacle secretes a robust low-Mg calcite shell with distinct growth increments on the external surface indicating growth over a number of years (30-50 in samples studied here). The Bathylasma samples used in this study grew in the Ross Sea and became entrained at the grounding line of a coastal ice shelf in McMurdo Sound, offering potential as an archive of changing conditions in this difficult to access environment under the McMurdo ice shelf. Nine barnacle shells were subsampled at high resolution (60 pun) for delta(18)O and delta(13)C analysis. These samples were dated with (14)C and U-Th techniques, although the later did not yield useful age information due to open-system behaviour of barnacle calcite. Measured delta(18)O values indicate that Bathylasma calcifies close to equilibrium with ambient seawater. One older sample (approximate to 200 ka) has similar delta(18)O and delta(13)C values as the eight Holocene samples, suggesting that barnacle calcite is not prone to significant diagenesis in this setting. Apparent isotope equilibrium and lack of diagenesis make barnacles a promising archive for reconstruction of past ocean conditions. Cycles of delta(18)O observed within each sample sometimes correlate with the external growth ridges, but not always, and have amplitudes of typically 0.6 parts per thousand. This magnitude of variation suggests shell growth during a significant portion of the year. although it remains unclear whether growth continues throughout the year. However, the prominent growth bands suggest at least a signficant seasonal slowing in growth rate. Variations in barnacle delta(18)O within each plate and between plates are too large to be caused by temperature. and instead reflect changes in delta(18)O of the seawater, allowing some assessment of seawater salinity under the ice shelf. Salinities are lowered by addition of meltwaters, but the barnacle delta(18)O data suggest values do not go below 33 parts per thousand.. These data indicate that Bathylasma has potential as an archive of paleoclimate information for shallow/intermediate water depths and, in particular, for difficult to reach environments such as below ice-shelves of Antarctica. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2010.08.015},
	author = {Burgess, S. N. and Henderson, G. M. and Hall, B. L.}
}
@article {828,
	title = {U-Th dating of carbonate platform and slope sediments},
	journal = {Geochimica Et Cosmochimica Acta},
	volume = {65},
	year = {2001},
	note = {462zlTimes Cited:49Cited References Count:44},
	month = {Aug},
	pages = {2757-2770},
	abstract = {Absolute chronology of marine sediment beyond the C-14 age range provides a test for models of climate change and has many other applications. U-Th techniques have been used for such chronology by dating corals, but extending these techniques to marine sediment is complicated by the presence of significant initial Th-230-both in detrital material and scavenged from seawater. In this study, we investigate four methods of solving the initial Th-230 problem for a particular type of marine sediment-the aragonite-rich sediments of carbonate platforms and slopes. Bulk sediment U-Th analyses can be corrected for initial Th to yield ages with approximate to2 to 3 kyr precision for highstand periods when sediment aragonite contents are particularly high. Uncertainty on the corrections causes inadequate precision for sediment from other periods, however. Removal of scavenged Th before analysis would enable a dramatic increase in this precision but has not proved successful despite a range of chemical leach approaches. Using heavy liquids to separate the various carbonate minerals found in Bahamas sediment enables an isochron approach to correct for initial Th, but the presence of initial Th from two sources requires correction or removal of one source of initial Th before the other is deconvolved by the isochron. Quantitative removal of detrital material before isochron analysis proves a successful approach. Such isochron data demonstrate that, although sediment remains closed to U-Th on a centimetre scale, nuclides are moved from grain to grain by alpha -recoil. Such intergrain exchange is expected to be observed in all sediments containing mineral grains with different U concentrations. Measured U-234/U-238 allows the recoil movement to be corrected and results in isochron ages with precision sometimes as low as 3 kyr. The accuracy of this approach has been proved by dating samples within the 14C age range. Sediments spanning the penultimate deglaciation have also been dated. After a small correction for bioturbation, the age for this event is found to be 135.2 +/- 3.5 ka. TWs date is approximate to8 kyr before the peak in northern hemisphere insolation and suggests that deglaciation is initiated by a mechanism in the southern hemisphere or tropics. This isochron approach shows considerable promise for dating of sediments older than this event, which will provide further information about the timing and mechanisms of global climate change. Copyright (C) 2001 Elsevier Science Ltd.},
	issn = {0016-7037},
	doi = {10.1016/S0016-7037(01)00621-4},
	author = {Henderson, G. M. and Slowey, N. C. and Fleisher, M. Q.}
}
@article {633,
	title = {Evidence from U-Th dating against Northern Hemisphere forcing of the penultimate deglaciation},
	journal = {Nature},
	volume = {404},
	year = {2000},
	note = {HendersonSloweyengEngland2000/03/15 09:00Nature. 2000 Mar 2;404(6773):61-6.},
	month = {Mar 02},
	pages = {61-6},
	abstract = {Milankovitch proposed that summer insolation at mid-latitudes in the Northern Hemisphere directly causes the ice-age climate cycles. This would imply that times of ice-sheet collapse should correspond to peaks in Northern Hemisphere June insolation. But the penultimate deglaciation has proved controversial because June insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier. There is a clear signature of the penultimate deglaciation in marine oxygen-isotope records. But dating this event, which is significantly before the 14C age range, has not been possible. Here we date the penultimate deglaciation in a record from the Bahamas using a new U-Th isochron technique. After the necessary corrections for alpha-recoil mobility of 234U and 230Th and a small age correction for sediment mixing, the midpoint age for the penultimate deglaciation is determined to be 135 +/- 2.5 kyr ago. This age is consistent with some coral-based sea-level estimates, but it is difficult to reconcile with June Northern Hemisphere insolation as the trigger for the ice-age cycles. Potential alternative driving mechanisms for the ice-age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean-atmosphere system or changes in atmospheric CO2 concentration controlled by a process in the Southern Hemisphere.},
	issn = {0028-0836 (Linking)},
	doi = {10.1038/35003541},
	author = {Henderson, G. M. and Slowey, N. C.}
}
@article {751,
	title = {Direct U-Th dating of marine sediments from the two most recent interglacial periods},
	journal = {Nature},
	volume = {383},
	year = {1996},
	note = {Vh315Times Cited:39Cited References Count:40},
	month = {Sep 19},
	pages = {242-244},
	abstract = {A KNOWLEDGE of the age of marine sediments is necessary to determine the timing of events and rates of processes in the marine realm, and the relationships among marine and other climatically sensitive records. The establishment of an accurate chronology for Pleistocene marine sediments beyond the range of radiocarbon dating (approximately the past 45 kyr) has therefore been a goal of palaeoceanographers for decades. Early attempts(1,2) based on measurements of the radionuclides Th-230 and Pa-231 mere beset with problems, and subsequent studies focused on tying fluctuations in marine sediment oxygen-isotope records to events such as the formation of col al reef terraces and changes in the Earth{\textquoteright}s magnetic polarity(3,4), and tuning the resultant chronologies to the Earth{\textquoteright}s orbitally driven insolation variations(5-8). But these chronologies (especially the age and duration of the last interglacial period) have been challenged by several studies(9-12), raising questions about the fundamental cause of Pleistocene climate fluctuations. Here we report the direct U-Th dating of aragonite-rich marine sediments from the Bahamas, and present an accurately dated marine oxygen-isotope record for the last two interglacials. We obtain dates of 120-127 kyr BP for the last interglacial and 189-190 kyr np for the late stage 7 interglacial. These dates are in accord with the general theory of orbitally forced climate fluctuations and demonstrate the potential of our direct-dating approach for developing an absolute chronology for the Pleistocene marine oxygen-isotope record.},
	issn = {0028-0836},
	doi = {10.1038/383242a0},
	author = {Slowey, N. C. and Henderson, G. M. and Curry, W. B.}
}
