The Monoman-Coonambidgal boundary: a transformation in the physical and cultural landscapes of the Murray River in South Australia

This paper reviews geomorphological and Aboriginal archaeological records from the upper Riverland region of South Australia (SA) in the context of a change in sedimentary environments within the Murray River tract during the deglacial period c. 15 ka. This has traditionally been recognised as a transition from a lower to upper valley fill; the Monoman and Coonambidgal Formations, respectively. A programme of archaeological dating and survey on the Calperum and Pike floodplains near Renmark provides evidence of a significant change in the ways Aboriginal peoples had interacted with this riverscape after c. 15 ka, expressed as an abrupt development of large-scale shell middens. This change was concomitant with a shift from broad, bedload-dominated channels in the river to a regime more akin to the modern river – a shift from a palaeo to the modern Murray river system. In this paper, we propose that the complementary archaeological and geomorphological evidence should be used to redefine the Monoman‒Coonambidgal boundary in the upper Riverland. The evidence also provides an opportunity to re-examine palaeoclimate narratives from the broader Murray-Darling Basin (MDB) against a record from the lower end of the system. Importantly, the research demonstrates a novel use of archaeological data in interpreting hydroclimate records.