Rocky Cape Research Articles

Late Quaternary fan gravels and slope deposits at Rocky Cape, northwestern Tasmania: their palaeoenvironmental significance

The paper describes a sequence of stratified quartzite slope deposits and alluvial fan gravels from a small catchment at Rocky Cape. A lower series of indurated slope deposits overlain by a podzol soil profile suggests that cold climatic conditions, which favoured frost fracturing of exposed 13 rock surfaces and gelifluction of detritus, occurred prior to the Last Glacial Stage. An upper series of unconsolidated slope deposits contains wedge structures. These deposits appear to have resulted from frost fracturing and to have been moved downslope by gelifluction processes. The wedge structures may have been produced by seasonal freezing of the ground surface during the period of maximum cold in the Last Glacial Stage (after 22,000 and before 10,000 BP). Radiocarbon dating of charcoal and wood from organic horizons and a buried soil in the lower part of a thick sequence of alluvial fan gravels shows that they began to accumulate mainly between about 33,000 and 22,000 BP, when strong but episodic erosion of the open Eucalyptus forested catchment occurred. The upper part of the alluvial fan gravels does not contain organic horizons but probably accumulated after 22,000 and before 10,000 BP. The gravels were largely derived from the upper series of slope deposits which were formed in a non-forested environment.

Geology of central western Tasmania

The Queenstown-Zeehan-Rosebery area is geologically complex. It lies on a belt of folded Ecocambrian and early Palaeozoic rocks which were deposited in the Dundas Trough, a rift structure which developed between the metamorphosed Precambrian rocks of the Cradle Mountain- Frenchmans Cap area ( Tyennan Nucleus ) to the east and the relatively unmetamorphosed Proterozoic rocks of t he Rocky Cape Geanticline to the west .

Foraminiferal Trends in Oregon Sublittoral: ABSTRACT

Benthic foraminiferal species from a part of the central Oregon shelf are grouped into four distinct bathymetric faunas. Elphidiella hannai and Buccella spp. are indicative of Fauna A (17-50 m). Fauna B (50-100 m) is characterized by Buliminella elegantissima and Elphidium magellanicum. In the rocky area off Cape Arago Cassidulina californica, C. limbata, Cibicides fletcheri, and C. lobatulus become dominant. Spiroplectammina biformis, Textularia earlandi, and Trifarina angulosa are important species of Fauna C (100-175 m). Abundant species of Fauna D (175-339 m) include Eggerella advena, Epistominella exigua, and Uvigerina juncea. Species diversity increases offshore to a maximum of about 35 benthic species near 100 m and then decreases slightly with depth. The standing crop is small nearshore, increases to a maximum of approximately 300 specimens per 20 cm3 between 125 and 150 m, and then declines. The total benthic population reaches a maximum of approximately 6,000 specimens per sample between depths of 150 and 175 m. Values then decrease to about 2,000 specimens at 339 m. A maximum of 15-20 percent live benthic specimens occurs near 50 m. Planktonic Foraminifera normally constitute less than 10 percent of the total population. Maximum percentages generally are in water shallower than 100 m, whereas maximum specimens per sample are at the deepest stations. Porcelaneous specimens do not exceed 6 pe cent of the benthic population. Agglutinated Foraminifera are more abundant than calcareous specimens at depths greater than 100 m. Miscellaneous biofacies trends indicate that: thecameobians are most abundant between 50 and 125 m; statoliths and otoliths are most abundant between 75 and 200 m; the largest number of ostracods are between 25 and 150 m; and radiolarians generally predominate over Foraminifera below 250 m. End_of_Article - Last_Page 466------------

A revised stratigraphy for the precambrian in North-West Tasmania

Within the Proterozoic rocks of the Rocky Cape Geanticline in north-west Tasmania, three contrasting sedimentary assemblages are recognised. The Rocky Cape Group, which has been previously used very broadly, is redefined to include only one of these assemblages. The revised definition includes the orthoquartzite, siltstone and shale which form a continuous sequence in the Rocky Cape area. Some new formations are defined. The Smithton Dolomite, and related rocks, unconformably overlie the Rocky Cape Group to the west at Black River. The Burnie Formation is a thick sequence flanking the Rocky Cape Group to the east. The Rocky Cape Group and the Burnie Formation are separated by the Keith Metamorphics, which is a belt of low grade regional metamorphic greenschist, amphibolite and pelitic schist.