Wednesday, June 10, 2009

Cool samples from fieldwork #04

This samples that I took during fieldwork is an ideal example of the Humphriesi-Oolite from the Middle Jurassic. The Bajocian Humphriesi-Oolite is an iron-ooid rich sandy limestone with ooids of up to 2 mm in diameter. According to the available literature it has been mined as an iron ore in the Dark Ages but lost its significance since then. Sadly there is not a single outcrop of this in my entire mapping area. This sample is one of the few good pieces (mostly it looks more like a boring marl with few ooids) of float that can be encountered occasionally. It can be confused with the Aalenian Murchisonae-Oolite which, however, has much smaller oolites and is sparry, marly and can often be found as small plates, unlike the Humphriesi-Oolite.

Iron-oolite with red-brown ooids of up to 2 mm

This sample is cool because the ooids are so wonderfully preserved and can be easily observed even without a magnifying glas!

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