Silcrete plant fossils from Lightning Ridge, New South Wales: new evidence for climate change and monsoon elements in the Australian Cenozoic

Abstract

Diverse Cenozoic (possibly latest Oligocene to mid–late Miocene) macrofossils from the Lightning Ridge opal fields are illustrated and discussed. Specimens identified to, or closely comparable with, extant taxa include ferns (Lygodium, Gleichenia and others), conifers now extinct in Australia (Dacrydium, Retrophyllum and Papuacedrus), Lauraceae (Cryptocarya/Cinnamomum), sclerophyllous Proteaceae (Banksia, Lomatia and Grevillea), Cunoniaceae/Elaeocarpaceae and Eucalyptus (and/or other Myrtaceae). Overall, at least four fern, three conifer and 30 angiosperm taxa are recognised. The climate supported many species with close relatives in wet Australasian habitats, including rainforests. However, a drier or more seasonal (?monsoonal) aspect is especially indicated by the presence of lobed leaves that resemble extant species of Brachychiton (Malvaceae), Erythrina (Fabaceae) and tribe Cercideae (Fabaceae). A degree of water stress is also suggested by the prevalence of narrow, toothed and/or deeply lobed angiosperm leaves.