Journal and Proceedings of
The Royal Society of New South Wales
Volume 123 Parts 3 and 4 [Issued December, 1991]
CONTENTS
| AUTHORS & TITLES | PAGES |
| Fowler, T.J., Limestone Olistoliths in the Kildrummie Formation near Cow Flat, New South Wales | 49-57 |
| Osborne, R.A.L., Palaeokarst Deposits at Jenolan Caves, New South Wales | 59-73 |
| Coenraads, Robert R., Palaeogeography of the Braemar Deep-Lead Sapphire Deposit, New South Wales | 75-84 |
| Theses Abstracts [Available in a separate page] | |
| Fenton, Ronald R., Stereochemical Studies on Metal Chelates of Novel Asymmetric Ligands | 85-86 |
| Minty, Jnr., E.J., Late Pleistocene Geocryology of the Bogong High Plains. | 87 |
v123 pts 3-4, pp.49-57
Limestone Olistoliths in the Kildrummie Formation Near Cow Flat, New South Wales
T. J. Fowler
Abstract. The Cow Flat limestone quarries, south of Bathurst expose massive tabular megaliths (up to 750m long) of coarsely granular limestone designated as Kildrummie Formation (formerly Group). These blocks are enclosed within a silicia volcaniclastic unit of the Campbells Formation.
Facies characteristics of the silicic volcaniclastics suggest that they are deep-water massflow deposits. Structural relations of limestones to host volcaniclastics indicates that the former are allochthonous blocks (olistoliths) . The silicic volcaniclastics and limestones are correlated with the shallow-marine Late Silurian Mullions Range Volcanics on the western side of the Hill End Trough, northwest of Cow Flat. It is suggested that at this time the Hill End Trough had a southward sloping basin floor. This and other occurrences of limestone olistoliths in the deep-marine areas flanking the Molong Rise may have resulted from vertical movements associated with the Late Silurian Bowning Orogeny, or from collapse of unstable fault scarps bordering the rifting Hill End Trough.
v123 pts 3-4, pp.59-73
Palaeokarst Deposits at Jenolan Caves, New South Wales
R.A.L. Osborne
Abstract. Limestone breccias and internal sediments with unconformable stratigraphic relations to bedrock are exposed in cave walls at Jenolan Caves. These deposits show no sign of deformation and geopetal structures in the deposits indicate that they were deposited after the last major deformation to affect the limestone. They are highly lithified and clearly pre-date the development of the present cave system. The breccias and internal sediments are interpreted here as palaeokarst deposits filling caves, or possibly an extensive cave system, that developed in the limestone during Permo-Carboniferous times.
v123 pts 3-4, pp.75-84
Palaeogeography of the Braemar Deep-Lead Sapphire Deposit, New South Wales
Robert R. Coenraads
Abstract. Exploration areas for deep lead sapphire deposits, such as those found at Braemar in the New England gemfields, northeastern New South Wales, may be defined via mapping of palaeochannels in which the deposits are situated. Palaeotopographic reconstruction was carried out using the elevation of the contact between the Tertiary volcanic rocks and the Palaeozoic basement, as well as drill hole data where available. The potential sapphire-bearing palaeochannels have been delineated within the zone in which the 19-23 million year old volcanics forming the western portion of the Central Volcanic Province (the West Central Province) overlap onto 32-38 million year old sapphire bearing volcanics forming the eastern portion of the province (the East Central Province). In this zone, the 19-23 million year old basaltic lavas flooded a number of major palaeodrainage systems already containing 32-38 million year old basalt flows and alluvial deposits reworked from them.
Potential sapphire deposits have been delineated in the Braemar palaeochannel and its tributaries up-palaeostream from the Braemar sapphire mine, in which sapphires are recovered along with other heavy minerals, with the highest concentration occurring at the base of the channel. "Braemar-type" deep lead deposits considered in this paper had approximately 10 million years in which to form, and required the presence of a younger basalt capping (19-23 niillion year old) for their preservation.
Potential sapphire-bearing alluvials are also delineated along the topographically inverted palaeo-Swan Brook. The extent of these "deep lead" deposits to the east of Braemar, in palaeochannels that drained the sapphire-bearing East Central Province, is related to the easternmost incursions of the lavas of the West Central Province.