Geology of islands

 Stephen K Donovan (The Netherlands) Islands are attractive places to visit, not just for geologists. Nonetheless, for us, they provide three advantages that favour collecting and research in the Earth Sciences. One of the attractions of an island is its small size in comparison with continents. The corollary of this small size is its relatively long coastline. Assuming that our island is not the mound of sand with a palm tree so loved by cartoonists, a long coastline indicates abundant exposures of rock, commonly well-exposed and accessible. Second, because of their relatively small size, islands offer a limited possible area of outcrop. The island may be volcanic in origin, so you may have one (or a few) volcanoes and its deposits to map, log and sample, producing a self-contained study. A particular sedimentary deposit may be (probably will be) limited to a single island. If you want to determine the palaeontology or palaeoenvironments of this deposit, the only place it can be studied is on one island. To give one example (among many), the Middle Miocene Grand Bay Formation, exposed on the east coast of Carriacou in the Grenadines, Lesser Antilles, includes the only crinoid-rich deposits in the Caribbean Islands. I had been studying the few Antillean fossil crinoids for ten years until I went to Carriacou and the sum total of specimens I had collected until then could have rested, comfortably, in the palm of one hand. From Carriacou, I collected bags of crinoid-rich bulk sediment samples (Donovan and … Read More

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