Organic geochemistry of a high-latitude Lower Cretaceous lacustrine sediment sample from the Koonwarra Fossil Beds, South Gippsland, Victoria, Australia

Abstract

The Koonwarra Fossil Beds are widely recognized for their high-fidelity preservation of freshwater/terrestrial vertebrate and invertebrate fossils. A preliminary investigation suggests that organic biomarkers are also exceptionally well preserved and could contribute significantly to understanding the ecology of this ancient lake system. Solvent-extractable organic matter was collected from a single feldspathic siltstone/mudstone sample and analyzed using gas chromatography-mass spectrometry (GC-MS). The distribution of n-alkanes suggests a significant input of terrestrial plant material into the lake. The very low ratio of eukaryotic steranes to bacterial hopanes may reflect the decomposition of abundant plant material in the lake. Polycyclic aromatic hydrocarbons may record wildfire activity in the surrounding watershed.