Multianalytical provenance analysis of Eastern Ross Sea LGM till sediments (Antarctica): Petrography, geochronology, and thermochronology detrital data

Abstract

In order to reveal provenance of detrital sediments supplied by West Antarctic Ice Sheet (WAIS), 19 glaciomarine cores of Last Glacial Maximum age were analyzed from Eastern Ross Sea and Sulzberger Bay. Analytical techniques included petrographic analysis of gravel‐sized clasts, geochronology (zircon U‐Pb: Zrn‐UPb) and thermochronology (apatite fission track: AFT) of sand‐sized fractions. Petrographic analysis revealed a similarity with the lithologies presently exposed in western Marie Byrd Land (MBL), with major roles played by low‐grade metamorphic rocks and granitoids. Furthermore Zrn‐UPb and AFT data allowed to identify the ages of formation and cooling of sedimentary source area, consisting of Cambrian‐Precambrian basement (i.e., Swanson Formation in western MBL) which underwent at least two episodes of magma intrusion, migmatization and cooling during Devonian‐Carboniferous and Cretaceous‐Paleocene times. Scarcity of volcanic clasts in the region of Ross Sea along the front of West Antarctica Ice Streams in association with the occurrence of AFT Oligocene‐Pliocene dates suggests a localized tectonic exhumation of portions of MBL, as already documented for the opposite side of West Antarctic Rift System in the Transantarctic Mountains. Furthermore, a Zrn‐UPb and AFT population of Late Triassic‐Jurassic age indicates the presence of unexposed rocks that formed or metamorphosed at that time in the sedimentary source area, which could be identified in McAyeal Ice Stream and Bindschadler Ice Stream catchment areas.

Ross Sea West Antarctic Ice Sheet History

“…Climate snapshots near magnetic reversals will be targeted (e.g., the M2 glacial in Figure F4) because these events can be traced to more continuous records from the continental rise (Site U1524) and global sea level records. Sediment provenance studies (clast/sand petrology, mineral thermochronology, and radiogenic isotope analysis) at Sites U1521 and U1522 will enable understanding of the changes in the origin of sediments (e.g., local ice caps versus ice sheet expansion and provenance from East versus West Antarctic sources) ( Figure F7) (Licht et al, 2005(Licht et al, , 2014Talarico et al, 2012;Cook et al, 2013;Perotti et al, 2017;Simões Pereira et al, 2018). As with all objectives, data integration with modeling studies will be undertaken ( Figure F4) (Golledge et al, 2012;Wilson et al, 2013;DeConto and Pollard, 2016;Gasson et al, 2016;Colleoni et al, 2018b).…”

Apatite Fission Track Signatures of the Ross Sea Ice Flows During the Last Glacial Maximum

“…Such young grains are also present in data sets detected on offshore drill holes such as CIROS‐2 and ANDRILL and were interpreted as related to the widespread Cenozoic volcanic event in the WRS (Zattin et al, 2012). On the contrary, these ages are not present in the fission track detrital distributions in the ERS (Perotti et al, 2017) and in the U‐Pb detrital zircon signature of West Antarctic sites (Licht et al, 2014). Actually, some volcanic centers exist in West Antarctica, but their contribution to the detritus that is flowing into the eastern Ross Sea is very minor (Anderson et al, 1992; Licht et al, 2005; Perotti et al, 2017).…”

“…Marie Byrd Land is one of the major crustal blocks forming the West Antarctica. Its western portion is situated today adjacent to the Ross Sea ( Figure 2) (Spiegel et al, 2016), and it is largely covered by the WAIS and mostly grounded below sea level (Licht et al, 2005) although there the best exposed rock outcrops in West Antarctica can be found (Perotti et al, 2017).…”

“…A review of the existing literature (Anderson et al, 1992; Balshaw, 1980; Farmer et al, 2006; Hughes, 1977; Licht et al, 2005; Perotti et al, 2017) indicates that the eastern Ross Sea (ERS in Figure 2) tills are provided uniquely by the WAIS. This is proved, for example, by clay mineralogy of tills, which shows the highest concentration of smectite in the ERS troughs, whereas the content in the western Ross Sea (WRS) and the central Ross Sea (CRS) (Figure 2) troughs is lower (Balshaw, 1980).…”

“…U‐Pb zircon age populations (100–110, 450–475, and 330–370 Ma) found in tills located in Bindschadler and Kamb ice streams are consistent with ERS tills (Licht et al, 2014). Multianalytical provenance analysis (petrographic analysis of gravel‐sized clasts, geochronology, and thermochronology) of samples in the ERS and Sulzberger Bay by Perotti et al (2017) also implied a WAIS source. As a general pattern, the common view is that the ERS is dominated by ice derived from West Antarctica, with minor if not null sources from East Antarctica.…”