The spatial and temporal occurrence and significance of dinoflagellates and other marine fossils within onshore coal measures, Gippsland Basin, Australia

Abstract Relationships between terrestrial formations in the central Latrobe Valley of southeastern Australia and coeval terrestrial and marine formations further to the east have been elucidated over the past several decades. In the Gippsland Basin’s Latrobe Valley and Seaspray depressions, Eocene to Miocene fossils including rare foraminifera and more common dinoflagellates have been recovered from all five interseam sediments in the Morwell Formation, six interseam splits within the Traralgon Formation that includes age diagnostic Gippslandia extensa, and three interseams in the Alberton coal measures. The dinoflagellate assemblages generally are species-poor but do provide some age control and indicate episodic marine conditions within the Latrobe Valley Coal Measures. Some dinoflagellates may tolerate lower salinity near-shore waters, but above the Eocene acme of Gippslandia extensa are interpreted to indicate offshore conditions. The occurrence of dinoflagellates between seams of the Latrobe Valley and Alberton coal measures within the Gippsland Basin provides useful paleogeographic information, constraining paleo-shorelines. KEY POINTS Fossils, including rare foraminifera and more common dinoflagellates, have been recovered from all five interseam sediments in Gippsland Basins Morwell Formation, six interseam splits within the Traralgon Formation and three interseams in the Alberton coal measures. Six interseam splits within the Traralgon Formation include the age diagnostic Gippslandia extensa, which indicates a late Eocene (latest Bartonian to Priabonian) age. Species of Spiniferites, Operculodinium and Hystrichokolpoma dominate in the coal interseams in the Morwell and Alberton formations (Oligocene and Miocene ages) and reflect typical species found in the Operculodinium Superzone of Partridge. The occurrence of dinoflagellates between seams of the Latrobe Valley and Alberton coal measures within the Gippsland Basin provides useful paleogeographic information, constraining paleo-shorelines.

[1]  G. Holdgate.  The influence of sea-level changes on coal seam deposition and equivalent facies onshore Gippsland Basin , 2021 .

[2]  G. Holdgate,et al.  The T0 coal seam in the Latrobe Valley: a revised age and implications to Traralgon Formation stratigraphy , 2021 .

[3]  F. Hilgen,et al.  On the Geologic Time Scale , 2012, Newsletters on Stratigraphy.

[4]  Vera A. Korasidis,et al.  Depositional setting for Eocene seat earths and related facies of the Gippsland Basin, Australia , 2019, Sedimentary Geology.

[5]  Siddhartha K. Rastogi,et al.  New age controls on Oligocene and Miocene sediments in southeastern Australia , 2018, Review of Palaeobotany and Palynology.

[6]  P. King,et al.  Sequence stratigraphy and controls on reservoir sandstone distribution in an Eocene marginal marine-coastal plain fairway, Taranaki Basin, New Zealand , 2012 .

[7]  B. Mcgowran.  The Australo-Antarctic Gulf and the Auversian facies shift , 2009 .

[8]  C. Clowes.  Dinoflagellate Taxonomy and Biostratigraphy of the Mid- to Late Eocene and Early Oligocene of New Zealand , 2009 .

[9]  W. Berger.  Cenozoic cooling, Antarctic nutrient pump, and the evolution of whales , 2007 .

[10]  S. Gallagher,et al.  Cenozoic stratigraphic succession in southeastern Australia , 2004 .

[11]  S. Gallagher,et al.  A review of the Traralgon Formation in the Gippsland Basin — a world class brown coal resource , 2000 .

[12]  S. Gallagher,et al.  Microfossil paleoenvironments and sequence stratigraphy of Tertiary cool-water carbonates, onshore G , 1997 .

[13]  G. Wefer,et al.  Expeditions into the Past: Paleoceanographic Studies in the South Atlantic , 1996 .

[14]  A. Partridge.  THE GEOLOGICAL EXPRESSION OF EUSTACY IN THE EARLY TERTIARY OF THE GIPPSLAND BASIN , 1976 .

[15]  P. Reynolds,et al.  Radiometric Age Determinations , 1974 .

[16]  P. Wellman.  Potassium‐argon ages on the Cainozoic Volcanic rocks of Eastern Victoria, Australia , 1974 .

[17]  P. R. Evans,et al.  Upper Cretaceous-Eocenespore-pollen zonation, offshore Gippsland Basin, Australia. , 1973 .

[18]  A. Partridge,et al.  Tertiary and Late Cretaceous spores and pollen from the Gippsland Basin, Southeastern Australia. , 1973 .

[19]  C. M. Barton.  The Morwell interseam “sands” , 1971 .

[20]  P. R. Evans,et al.  THE STRATIGRAPHY OF THE OFFSHORE GIPPSLAND BASIN , 1971 .

[21]  W. H. Blow.  Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy , 1969 .