The Fossils of Al Jabal Al Akhdar(Green Mountain)
Amazingly, the high peaks of Jabal Akhdhar in the Western Hajjar Mountains of Northern Oman were once at the bottom of a huge tropical sea. These rocks are limestones, rich in calcium carbonate, formed during the Permian and Triassic Periods between 290 and 240 million years ago. Over time, billions of dead creatures, from tiny microscopic plankton to larger shells and corals, fell to the sea floor and were gradually buried and became fossils. This fine-grained limestone can be up to 3,000 metres thick. About 90 million years ago, though, it was pushed up 2,500 metres above sea level, where masses of fossils can now be clearly seen.
The organic remains of these extinct marine life forms were left sealed in rock. The soft parts became liquid petroleum, but those with harder parts were preserved. There are two main families of what we generally call ‘shells’, or molluscs. One has a coiled spiral shell like a snail. The biggest here are the giant lamp shells. The other consists of shells in two hinged parts, called bivalves. Oysters and clams belong to this group, and there are thousands of them visible in these rocks, including rudists. Spiral compartmented shells like nautilus and the elegant bullet-shaped internal shells of squid-like animals called belemnites, and sea urchin spines, are other highlights.The two most common extinct corals spectacularly fossilised here, but rare elsewhere, look like fine vermicelli and macaroni. There are also bigger chunks of rounded corals.
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