The South Shetland Islands, Antarctica: Lithostratigraphy and geological map

Abstract

Over the last few decades, numerous geological studies have been carried out in the South Shetland Islands, which have greatly contributed to a better understanding of its geological evolution. However, few attempts have been conducted to correlate the geological units throughout this archipelago. We present herein a review of the literature available in the South Shetland Islands, which we use to propose a lithostratigraphical correlation that constitutes a coherent stratigraphy for the main Mesozoic and Cenozoic rocks of the South Shetland Islands along with a new geological map. The lithostratigraphical correlation shows that the geological and environmental evolution comprises three main stages: 1) deep marine sedimentation from ∼164 to 140 Ma, 2) subaerial volcanism and sedimentation with a proliferation of plants and fauna from ∼140 to 35 Ma and 3) glacial and interglacial deposits from ∼35 Ma. The lithostratigraphical correlation also shows a broad geographical trend of decreasing age of volcanism from southwest to northeast, which has been previously suggested. However, this spatial age trend is disrupted by the presence of Eocene magmatism in Livingston Island, located in the centre of the archipelago. We suggest that the migration of volcanism occurred from the Late Cretaceous until the early Eocene. Subsequently, enhanced magmatic activity took place from the mid-Eocene until the Miocene, which we associate with processes related with the waning of subduction. Constraining the protolith age of the metamorphic complex of Smith Island remains challenging, yet holds key implications for the tectonic and accretionary evolution of the Antarctic Peninsula. The rocks recording the glaciation of this sector of Antarctica are well exposed in the northern South Shetland Islands and hold critical information for understanding the timings and processes that lead to the greenhouse to icehouse transition at the end of the Eocene. Finally, contemporaneous rocks to the breakup of Antarctic Peninsula from Patagonia that led to the opening of the Drake Passage and the development of the Scotia Sea are exposed in the centre and north of the South Shetland archipelago. Better constraints on the age and tectonic settings on these units may lead to further understanding the paleobiogeographical evolution of the region, which may have played an important role for speciation as a land bridge between South America and Antarctica. The dataset containing the geological map and associated information is shared as a shapefile or KML file.

A continent-wide detailed geological map dataset of Antarctica

“…Some of their map units have been grouped and/or simplified for subsequent digital data 32 and GeoMAP v.2022-08. Numerous small-scale geological maps at ≤1:50,000 scale have also been published locally within the South Shetland Islands [49][50][51][52][53][54] . However, these maps are discontinuous and recent works appear to contain some marked interpretational differences.…”

Plate Rotation of the Northern Antarctic Peninsula Since the Late Cretaceous: Implications for the Tectonic Evolution of the Scotia Sea Region

“…Paleomagnetic reconstructions attached the South Shetland Islands to the Pacific margin of the southern Patagonia‐Fuegian Andes before ∼140 Ma, with a southward translation at ∼120–100 Ma following rapid CCW rotation during ∼100–90 Ma (Gao et al., 2021). The Jurassic marine sediments are covered by Early Cretaceous to Late Pleistocene arc magmatism and sediments in the South Shetland Islands (Bastías et al., 2023; Hervé, Faúndez, et al., 2006; Smellie, Hunt, et al., 2021). From Livingston Island to King George Island, the age of the magmatism indicates a tendency toward decreasing age (Figure 1b; Gao et al., 2018; Haase et al., 2012; Leat & Riley, 2021; Smellie, Hunt, et al., 2021; Willan & Kelley, 1999).…”