A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20ka, 15ka, 10ka and 5ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorit. © 2014 The Authors

Mineralogy of fossils and matrices of various Talbragar specimens.

<p>Mineralogy of fossils and matrices of various Talbragar specimens.</p

<i>Cavenderichthys talbragarensis</i> (“Fish3”).

<p>The fish presents as a typical “split fossil” with (<b>a</b>) “part” (“Fish3-P”; AM F.142434) and (<b>b</b>) “counterpart” (“Fish3-CP”; AM F.142435). In this case, the “part” contains the main body with the majority of the bones exposed, while the “counterpart” contains less bone material but shows more scales. The original fish bones are largely replaced by white minerals. The specimen has not been prepared and is shown as found. The specimens are identical with those named “Fish3-P”and “Fish-CP” in Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.t002" target="_blank">2</a>, and Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.g001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.g008" target="_blank">8</a>.</p

Photoluminescence/Fluorescence of a plant fossil (“Plant1”).

<p>(<b>a</b>) Rock with two leaves of the gymnosperm <i>Pentoxylon australicum</i> (AM F.142427) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.ref011" target="_blank">11</a>]. (<b>b</b>, <b>c</b>) Higher magnification of the right leaf, showing lateral and central veins photographed under normal (white) light. (<b>d</b>–<b>g</b>) Same areas photographed with a microscope equipped to detect photoluminescence/fluorescence: (<b>d</b>) fluorescence of violet/blue light after excitation with long-wave UV light; (<b>e</b>, <b>f</b>) emission of green light after excitation with blue light; and (<b>g</b>) emission of red light after excitation with green light. (<b>e</b>) Area identical to the part of the leaf shown in (<b>b</b>); (<b>d</b>, <b>f</b>, <b>g</b>) area identical to the part of the leaf shown in (<b>c</b>). The specimen (i.e. the larger leaf on the right) is identical to “Plant1” in Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.t002" target="_blank">2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.g004" target="_blank">Fig 4</a>.</p

Elemental and mineralogical maps of a <i>Rintoulia</i> leaf (“Plant3”).

<p>(<b>a</b>) Video image of the measured area. (<b>b</b>, <b>c</b>, <b>d</b>) Elemental maps of manganese (Mn), barium (Ba) and potassium (K), respectively. The data show that there is little Mn, Ba or K, except in the dark, manganese-rich area at the leaf base. (<b>e</b>, <b>f</b>) Mineralogical maps showing the entire leaf and details of the manganese-rich area at the base of the leaf, respectively. The key shows the main mineral of the leaf to be quartz, with intergrown Fe and Mn minerals at the base. The role of Ba and K in these minerals remains unclear.</p

Elemental composition of fossil and matrices of various Talbragar specimens.

<p>Elemental composition of fossil and matrices of various Talbragar specimens.</p

Fluorescence of fish fossils from Talbragar.

<p>Teleost fish <i>Cavenderichthys talbragarensis</i> (“Fish3”, AM F.142434) photographed under normal (white) light (<b>a</b>, <b>b</b>, <b>d</b>–<b>f</b>) or UV light (<b>c</b>, <b>g</b>–<b>i</b>). Photographs were taken with a digital single-lens reflex camera mounted on a motorised stand (<b>a</b>, <b>d</b>–<b>f</b>), a digital camera of a gel-imaging system normally used for analysing ethidium-bromide-stained DNA bands in agarose gels (<b>b</b>, <b>c</b>) or with a digital camera of a microscope equipped to detect fluorescence/photoluminescence (<b>g</b>–<b>i</b>). Detail images show pectoral fin bones (<b>d</b>, <b>g</b>), vertebrae (<b>e</b>, <b>h</b>) and dorsal fin bones (<b>f</b>, <b>i</b>). For more images of the same fish, see Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.g007" target="_blank">7</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179029#pone.0179029.g008" target="_blank">8</a>. Scale bars for panels <b>a</b>–<b>c</b> and <b>d</b>–<b>i</b> are given in <b>a</b> and <b>g</b>, respectively.</p