Detrital zircons from upper Permian and lower Triassic Victoria Group sandstones, Shackleton Glacier region, Antarctica: Evidence for multiple sources along the Gondwana plate margin

Abstract

In the central Transantarctic Mountains region, siliciclastic strata of the Permian-Triassic Victoria Group (Beacon Supergroup), the Gondwana sequence in Antarctica, have both cratonic and magmatic arc provenance. Volcaniclastic strata occur in the upper part of the Permian Buckley Formation, whereas the Triassic Fremouw and Falla formations are more quartzose. Two sandstones in the upper Buckley and one near the base of the Fremouw, and immediately above the Permo-Triassic boundary, in the Shackleton Glacier region have yielded detrital zircon U/Pb SHRIMP age populations with clear evidence for a contemporaneous source. The stratigraphically lowest sample, about 70 m below the top of the Buckley Formation, is dominated by zoned igneous zircons of late Permian age. The sample from near the top of the Buckley Formation, about 40 m below the Permo-Triassic boundary, predominantly has zoned igneous zircons with the principal age peak again late Permian but with subordinate Devonian and Cambrian age peaks. The third sandstone from just above the Permo-Triassic boundary yielded zircons mainly of Neoproterozoic to Cambrian age. These results indicate a Permian-Triassic magmatic source existed during upper Buckley time, which is consistent with paleocurrent indicators of flow from the West Antarctic flank of the Permian-Triassic foreland basin, the inferred plate margin (Panthalassan) flank. The Devonian source is attributed to the Ford granodiorite suite in Marie Byrd Land, West Antarctica. Because Beacon strata cover the Cambrian Ross orogen and extend onto older basement, the Cambrian and Upper Proterozoic zircons are interpreted to be reworked from sandstones (Ordovician, Devonian, Early Permian in age) exposed in the Permian-Triassic Gondwanide orogen as a result of uplift of a fold and thrust belt by late Permian time.

Antarctica and supercontinent evolution: historical perspectives, recent advances and unresolved issues

“…More challenging are major populations of Pan-African (700-500 Ma) and Grenville-age (1200-800 Ma) zircons, which occur in most samples. Similar populations have been identified in other studies of the Beacon Supergroup (Elliot & Fanning 2008;, and they might represent second-cycle reworking of INTRODUCTIONoutboard sedimentary sequences or direct erosion of the inboard craton, although the absence of a Palaeoproterozoic (Mawson Continent) component is problematic. Interestingly, there is evidence for 700-500 Ma reworking of 1200-800 Ma zircon grains, suggesting a spatial association of these two events in the source region.…”

“…6b) (Vaughan & Storey 2000). Further evidence for the Late Palaeozoic -Mesozoic active margin in West Antarctica is preserved on the craton by the Devonian-Lower Jurassic sandstone-dominated Beacon Supergroup of the Transantarctic Mountains, which was in part derived from detritus shed by the evolving magmatic arc (Elliot & Fanning 2008;. As with the Palaeozoic subduction complex, the Mesozoic rocks record periods of episodic deformation, including the c. 200 Ma Peninsula Orogeny and the c. 110 Ma Palmer Land Event of the Antarctic Peninsula .…”

The Gondwana Plate margin in the Weddell Sea sector: Zircon geochronology of Upper Paleozoic (mainly Permian) strata from the Ellsworth Mountains and eastern Ellsworth Land, Antarctica

“…The persistence of such zircons is also seen in the volcaniclastic Permian and Triassic sandstones from the Shackleton Glacier area (Fig. 1) (Elliot and Fanning, 2008) and from Mt Bowers at the head of the Beardmore Glacier ( Fig. 1) (Elliot et al, 2014), both in the Transantarctic Mountains.…”

“…Deposition of the volcaniclastic upper Buckley Formation is no earlier than ca. 267 Ma (Elliot and Fanning, 2008 Fig. 10.…”

A peri-Gondwanan arc in NW IberiaI: Isotopic and geochemical constraints on the origin of the arc—A sedimentary approach

“…Using only analyses with < 10% discordance (shown in Fig. 4 for the youngest group of detrital zircons), the maximum depositional age can be estimated at c. 530 Ma, based on the average age of the largest group of young est zircons (Elliot and Fanning, 2008). However, it is possible that the age of the youngest zircon in this group is significant, in which case the maximum age of deposition could be as young as 510-520 Ma.…”