The spatial and temporal occurrence and significance of dinoflagellates and other marine fossils within onshore coal measures, Gippsland Basin, Australia
The fossils of the Coal Measures of South Wales have probably not been studied so systematically or for so many years as those of certain coalfields of he north of England, and it is only within recent years that any marked progress has been made in their investigation; this is especially true of the marine fossils.
The Gippsland Basin of south-eastern Victoria is considered as the depositional area of Tertiary sediments lying beneath the Gippsland Plains and extending southwards beneath the Tasman Sea. This area is bounded by Mesozoic and Palaeozoic rocks.The initial marine transgression across the landward extent of the basin appears to have commenced in uppermost Eocene to lowermost Oligocene times. The nature of the initial marine Tertiary sedimentation is controlled by:four regional lower Tertiary structures—the Woodside-Seaspray Deep, the Baragwanath Anticline, the Lake Wellington Trough, and the Lakes Entrance Platform; andthe nature of the rocks upon which these sediments were deposited.Because of the progressive onlap in some areas, particularly on the Baragwanath Anticline, the initial marine transgression is diachronous.The initial marine Tertiary sediments—constituting the Lakes Entrance Formation (as redefined in this paper)—can be divided into two broad lithological units, a lower sandy one and an upper marly one. Oil traces have been recorded in the basal sands throughout the basin, particularly in the Lakes Entrance area where minor production was undertaken during the 1930s.The offshore areas of the basin appear to have the greatest oil potential. The prospective reservoir beds would be the offshore extensions of the hasal marine Tertiary sands, or else offshore marine equivalents of the Latrobe Valley Coal Measures (which underlie the marine sediments in all but the Lakes Entrance Platform area)—provided that these beds have not been flushed by artesian waters.
In the Gippsland Basin, the seaward extent of paralic coal occurrences can be mapped in successive time slices through the Paleocene and Eocene to provide a series of straight to gently arcuate surrogate palaeoshorelines within the petroliferous Latrobe Group. Palaeogeographic reconstructions that incorporate this information provide a unique perspective on the changes affecting a siliciclastic depositional system on a passive continental margin where basin development has been primarily controlled by thermal sag. In contrast, the absence of calcareous marine fossils and lack of extensive, widespread and thick fine-grained sediments on the marine shelf and continental slope, beyond the seaward limits of coal accumulation, have contributed to the false impression that the Latrobe Group accumulated in a largely non-marine basin. Based on the proposed model for palaeoshoreline delineation, seismic data, sequence analysis, petrography and palynology can be integrated to subdivide the main depositional environments into distinct facies associations that can be used to predict the distribution of petroleum systems elements in the basin. The application of such palaeogeographic models to the older section of the Latrobe Group can improve the identification of these petroleum systems elements in as yet unexplored parts of the Gippsland Basin. Given the recent attention paid to the basin as a CO2 storage province, palaeogeographic interpretations may be able to assist with the selection of appropriate injection sites.
The paucity of animal remains in the Coal-measures of Somerset has been recognized for many years. More recently Dr. H. Bolton has described fossils from various horizons in the coalfield, but his records relate chiefly to insects and marine fossils, while non-marine Lamellibranchs appear to be unusually rare at most horizons. A number of species of non-marine Lamellibranchs have been recorded by various authors, but in view of the wide interpretation formerly given to the various species, many of these records cannot be used for zonal purposes.
Previous to 1858, the Northumberland and Durham Coalfield was considered to be destitute of any fauna other than the usual non-marine type. In 1858, J. W. Kirkby gave the first indication of marine fossils in this coalfield. He obtained specimens of Lingula credneri (Geinitz) from shales some 17 feet above the Five-Quarter seam during the sinking of a shaft at Ryhope, 3 miles south of Sunderland (9). Some of these specimens are figured by T. Davidson (2).
Up to the present marine fossils have been recorded in Middle Coal-measures in the South Lancashire Coal-field at two horizons only. They are (1) in the banks of the Tame, near Ashtonunder-Lyne, found by Professor A. H. Green, and at Ashton Moss Colliery, about 750 feet above the Great Mine, discovered by the late George Wild. (2) Mr. H. Bolton, F.R.S.E., informs me that the Californian or Thin Bed of Fulledge Colliery, Burnley, which is 410 feet above the Arley Mine, is a marine horizon.
In many coalfields in the zone of Anthracomya pulchra and Carbonicola similis there is a marine band, viz. Mansfield, Yorkshire; Dukinfield, S.E. Lancashire; The Gin Mine, North Staffordshire; Rimbert, North of France; but, apart from a doubtful Lingula from the roof of the Brassy coal at Bersham Colliery, no marine fossils have previously been recorded from undisputed Coal Measures of the Denbighshire Coalfield.
On the Occurrence of Marine Fossils in the Coal-measures of Fife
