A multi-proxy study of anthropogenic sedimentation and human occupation of Gledswood Shelter 1: exploring an interior sandstone rockshelter in Northern Australia

Abstract

Rockshelters contain some of the most important archives of human activity in Australia but most research has focused on artifacts and cultural context. This study explores geomorphological and geoarchaeological approaches for understanding a sandstone rockshelter in interior northern Australia: Gledswood Shelter 1. At this site, magnetic susceptibility and micromorphology techniques were integrated with bulk sedimentology, soil chemistry and geochronology to better understand the record of human impact and site formation processes. The micromorphology studies indicate that primary depositional fabrics, such as graded bedding or laminations, are absent, and sediment structural development is low throughout the entire sequence, with most samples exhibiting a high degree of post-depositional mixing. The sediment magnetic susceptibility analysis reveals magnetic changes coinciding with human occupation, a result of anthropogenic burning. Specifically we highlight that combustion features are prevalent in this sandstone shelter and provide critical insights into the human usage of the shelter.

How do we distinguish termite stone lines from artefact horizons? A challenge for geoarchaeology in tropical Australia

“…In contrast, artefact horizons may show enhanced magnetic susceptibility (particularly frequency dependence) because of the effects of fires associated with occupation, and the introduction of Fe-rich materials (e.g., hematite and ochres). This is shown in other studies in northern Australia, where magnetic susceptibility has been successfully used as a proxy for rock shelter occupation (Lowe, Mentzer et al, 2018;Lowe et al, 2016).…”

“…Studies beneath and around mounds show that termite activity creates elevated levels of N, Ca, K, Mg, and Na, (Asawalam & Johnson, ; Petts, Hill, & Worrall, ; Watson, ), sometimes down to 2–7 m. Other effects include changes in pH (from pH 4 to 6), an increase in organic C, as well as changes in the formation of carbonates, phosphates, and Fe oxyhydroxides. Although these chemical changes promote the formation of biogenetic ferrimagnetic material (Maher, ), it has been difficult to identify this material in soil profiles (Lowe, Cole et al, ). Termite modification of wood can be detected by measuring cellulose percentage (e.g., by using Fourier‐transform infrared spectroscopy analysis or by scanning electron microscope imaging; Li, Lu, & Mo, ).…”

Making the Invisible Stratigraphy Visible: A Grid-Based, Multi-Proxy Geoarchaeological Study of Umhlatuzana Rockshelter, South Africa

“…The high content of SiO 2 in the bedrock and sediments of sandstone rockshelters like Umhlatuzana is known to correlate with acidic conditions and affects the baseline pH of the deposits (Lowe et al, 2018;Miller et al, 2016;Stewart et al, 2012). In the case of Umhlatuzana, the pH of the Pleistocene deposits might further be influenced by a decrease in Fe 2 O 3 above z 529.5, resulting in less acidic conditions than present in the bottom of the sequence (Figures 5 and 6K,L).…”

Extinction of eastern Sahul megafauna coincides with sustained environmental deterioration

“…The earliest evidence for human occupation, that is closest to the FRB, comes from two sites over 660 km to the north and northwest of SWC. The two locations, Gledswood Shelter 67 and Ngarrabullgan 61 , record human occupation at or younger than 40 ka and occur within the north and westerly-draining Flinders and Mitchell River Basins of Gulf of Carpentaria. Neither basin shares topographic or hydrological connection with the FRB to the southeast.…”