FLORISTIC AND CLIMATIC CHANGES RECORDED IN SEDIMENTS OF AN ACID SALINE LAKE SYSTEM IN SOUTHERN WESTERN AUSTRALIA

A 60-meter core from Lake Aerodrome near Norseman in southern Western Australia drilled as part of a multidisciplinary project to study the evolution and origin of acid saline lakes yielded a complex suite of lithologic units. The core drilled through clay, clayey siltstone, gypsum sand, quartz sand, bedded bottom-growth gypsum, and soft coal toward the bottom. Palynomorph and palynofacies analyses indicate that pollen recovery is very good in the first one meter of section and the bottom coal unit, but the 30-meter interval between them is organic matter-poor and barren of palynomorphs. Asteraceae, Myrtaceae, and Chenopodiaceae dominate the pollen assemblage in the top unit, and they are indicative of a sclerophyll flora typical of the modern dry climatic conditions in Western Australia. The coal contains pollen of Nothofagus, Proteaceae, Casuarina and some extinct groups, which indicate warm and humid climate. The presence of Nothofadigidites falcatus, Dryadopollis retequetrus and Propylipollis annularis suggests a Late Eocene age for the coal unit. Thus, these pollen assemblages record a major floristic and climatic turnover in the region.