THE third special presentation meeting of the Hamilton Field Naturalists Club for 2024 will be held at Hamilton Institute of Rural Learning on (edited) Thursday, July 18 at 7.30 pm featuring Dr Roland Maas and Andrew Prior presenting their research on the ages and geochemistry of the Grampians/Gariwerd Ranges.

This presentation will describe the geology of the Grampians Ranges, starting with the deposition of thick river and delta sandstone-mudstone formations some 430 million years ago, the subsequent period of faulting, folding, early erosion and magmatism, and finally the long history of gradual uplift and erosion which coincided with episodes of glaciation and basaltic volcanism.

Dr Maas and Mr Prior then look at the geochemistry of the sand and mudstones, to learn about their age and possible sources.

For example, tiny grains of the mineral xenotime provide the first isotopic age estimates of sandstone deposition, while age dating of hundreds of zircon crystals – small, hardy mineral grains eroded from older rocks and deposited in the sandy sediments – has revealed a previously unknown, possibly local sediment source component.

Combined with other chemical and isotopic provenance indicators, their work has added to earlier geological studies and established the Grampians Ranges as a geological link between the vast Gondwana continent to the west and the Palaeozoic marine rocks to the east.

Members and visitors are all welcome to attend with supper being provided at the end of the presentation.

A gold coin donation would be appreciated to help cover the cost of room hire.