Sedimentology and evolution of a modern barrier spit, Lake Machattie, central Australia

Shoreline deposits bordering ephemeral lakes can record large flood events, historical lake level variations, and temporal variations of climate patterns. Yet, the hydrological history of the Lake Eyre Basin, one of the world's largest endorheic basins, is mostly limited to records from its southern and eastern areas, such as Kati-Thanda Lake Eyre (KT-LE), Lake Frome and Cooper Creek. Here, we present the first modern-hydroclimatic history of Lake Machattie in KT-LE's most northern catchment, the Georgina, based on sedimentological data and spatial analysis of shoreline features. Barrier spit deposits on the northern margin of the lake are dominated by a series of landward-prograding overwash deposits generated during extreme lake fillings. Historical and modern flood events were identified from these sedimentary units, with those between 1974 and 2001 coinciding with the largest lake fillings observed from Landsat spectral data. All modern floods that interacted with the barrier spit reached the Diamantina River, confirming waters from the Georgina River can contribute to modern- and palaeo-KT-LE fillings. Our analysis also shows that modern Lake Machattie high stands are generally tied to La Niña events combined with negative phases of the Interdecadal Pacific Oscillation (IPO), suggesting precipitation over the northern Lake Eyre Basin could be strengthened by IPO-La Niña modulations.