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These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

Legacy product - no abstract available

Legacy product - no abstract available

During 1950-51 pendulum gravity observations were made at 59 stations throughout Australia using invar pendulums on loan from the Department of Geodesy at Cambridge University. A national gravity base station was established at Melbourne. Subsequent comparisons with gravity meter ties suggest that the pendulum value is about 2 mgal. low. The standard errors of the gravity differences from Melbourne to the other stations have been estimated from internal consistency of the pendulum observations and from comparison with gravity meter measurements; the mean standard error is about 0.6 mgal. A small systematic difference from gravity meter values is assumed to be caused by the effect of the earth's magnetic field on the pendulums; after correction for this, the results agree fairly well with the American calibration system. Free air, Bouguer and isostatic anomalies have been calculated for all stations. The isostatic anomalies are for both Airy-Heiskanen and Pratt-Hayford hypotheses, and for four different assumed crustal thicknesses in each case. The isostatic and Bouguer anomalies are predominantly negative. A degree of isostatic compensation is present, but some large anomalous areas are uncompensated. The pendulum survey forms a basic network to which past and future gravity surveys can be referred.

The original aim of this study was to investigate some of the early Palaeozoic Bryozoa of Australia so as to study the development of skeletal structures in the zoaria and the significance of distribution of species in the different stratigraphic successions. It was found that areas with abundant bryozoan faunas were not readily located; in many areas such as the Yass-Taemas and Tamworth districts, New South Wales, where Silurian and Devonian marine faunas are abundant, Bryozoa were poorly represented. Thus the work became an investigation of areas where Bryozoa were located. The Middle and Upper Ordovician exposures in parts of central-western New South Wales and the Middle and Upper Devonian sequence of the Fitzroy Basin (collected by the field parties of the Bureau of Mineral Resources) contained abundant bryozoan faunas at certain horizons; but they were not distributed continuously through any considerable thickness of succession. Many samples from which Bryozoa are described in the text are isolated occurrences from which two, sometimes three, species have been collected.