Date of Award
Spring 5-1-1998
Document Type
Thesis
Degree Name
Master of Arts (MA)
Department
Geography, Geology, and Anthropology
First Advisor
Dutta
Second Advisor
Meert
Third Advisor
S. de Silva
Abstract
Chert is normally considered to be marine biogenic in origin. However, chert lenses and nodules in the volcanic ash horizon of the Reid's Mistake Formation at Swansea Head, Newcastle Coal Measures of the Sydney Basin appear to have formed differently. Their mode of occurrence and their close association with paper-thin clay layers within the same volcanic unit suggest that they formed as a result of chemical weathering of volcanic ash. This hypothesis is supported by the data gathered from thin section petrography and x-ray diffraction analyses. Petrographic studies indicate the precipitation of microcrystalline to cryptocrystalline quartz and the dissolution/replacement/alteration of volcanic quartz, feldspar, mica and glass shards. X-ray diffraction analyses show the presence of clay minerals, which are products of chemical weathering. iii Chemical analyses were used to compare the chemistry of the pyroclastic samples with that of the reference rock, and also to calculate the mass balance between the reference rock and the pyroclastic samples. However, the results were inconclusive with respect to silica enrichment and depletion of mobile elements, such as calcium, sodium and potassium, in the pyroclastic samples. Though chemical study proved to be inconclusive, the evidences gathered from petrological study indicate chemical weathering to be responsible for the formation of chert in the volcanic ash horizon of the Reid's Mistake Formation.
Recommended Citation
Wadia, Adil M., "Chemical Weathering of Volcanic Ash as a Probable Origin of Chert in the Reid's Mistake Formation of the Newcastle Coal Measures, Sydney Basin, Australia" (1998). All-Inclusive List of Electronic Theses and Dissertations. 3755.
https://scholars.indianastate.edu/etds/3755