Neogene Billa Kalina Basin and Stuart Creek silicified floras, northern South Australia: a reassessment of their stratigraphy, age and environments

Abstract

Silicified fossil macrofloras of the Willalinchina Sandstone, at Stuart Creek in the Billa Kalina Basin of northern South Australia, are most likely early Miocene–early Pliocene with preference for the younger age, based on reinterpretation of published evidence including basin stratigraphy, paleogeography, isotopic and other dating. The macrofloras include Eucalyptus and occur in fluvial channel sandstones. The Willalinchina Sandstone is equated with the Danae Conglomerate Member of the Mirikata Formation, interpreted as older than the Watchie Sandstone, Millers Creek Dolomite Member and Billa Kalina Clay Member, and here regarded as of upper Neogene age. The Billa Kalina Basin lies between Lake Eyre, Torrens and Eucla basins, and has affinities with all three. The Kingoonya Paleochannel, peripheral to the Eucla Basin, joins the southern margin of the Billa Kalina Basin across the Stuart Range Divide, and contains the Garford Formation of mid-Miocene to Pliocene age (palynological dating), here partly equated with the Mirikata Formation. Interpretations of paleolake Billa Kalina and associated paleochannel environments are made, based on a new assessment of stratigraphic and paleogeographic relationships.

KEY POINTS

1. The Billa Kalina Basin sediments in northern South Australia are equated with the later Neogene ‘upper’ Garford Formation of the Kingoonya Paleochannel, which flowed into the Eucla Basin, and depositional processes are clarified.

2. A variety of consistent age data from adjacent basins and the Kingoonya Paleochannel indicate the Stuart Creek ‘silcrete floras’, associated with the Willalinchina Sandstone channel deposits, are Neogene, probably early Pliocene, but the possibility remains that they may be incised into the Watchie Sandstone and therefore late Pliocene.

3. The Billa Kalina Basin was linked to the Kingoonya Paleochannel through much of its history, with flow disrupted by the Stuart Range Divide, local tectonics, and regional tilting.

Keywords:

• fossil macrofloras
• Billa Kalina Basin
• Lake Eyre Basin
• Kingoonya Paleochannel
• Neogene
• paleogeography
• Cenozoic
• Stuart Creek
• lacustrine environments

Acknowledgements

Robert Hill (Institute of Environmental Studies, Adelaide University) instigated this review, read the initial manuscript and assisted in sourcing some material. Yelarney Kim Beer of the same institute is especially thanked for the extensive drafting project, courtesy of Prof. Hill’s research fund, as is Rachel Froud of Dept. for Energy and Mining, SA (EMSA) who provided additional work and advice. Wayne Cowley of the Geological Survey of South Australia (EMSA) read the manuscript, and with Peter Waring assisted with data sourcing (SARIG database and SA State Archives). Wolfgang Preiss generously organised completion of the figures through EMSA and also critiqued the manuscript. Richard Flint (Geosurveys Mineral Exploration PL) is thanked for his detailed review and useful suggestions, along with an anonymous reviewer. Geological mapping was accomplished by the author during employment at the Geological Survey of South Australia from 1985–1992 and included a levelling survey by John Harrison (formerly Survey Drafting Branch, Dept. Mines and Energy, SA). Richard Wright (Hobart, Tasmania), then of Shell/Newmont Corp. Ltd, originally brought the Stuart Creek fossils to the attention of the author. The author did not receive external funding for this project. Permission to publish was given by the Department of Mining South Australia.

Disclosure statement

No potential conflict of interest was reported by the author.