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Thursday 3 May 2012

Earth Science: Dropstone

A stone embeded in a stratigraphy of rocks. Normally associated with ice rafting during Pleistocene. Ice were abundent at that time and sea level were low. Rocks/debris trapped within the ice escaped when the ice melt and it sanks into the suface (sea floor or rivers). Over times, it is lithified by overburden caused by new layers of sediments.

snowball earth.org
On some occasion, rock debris that are freed from melting may fall directly on sediment layers matrix like silt and clay) forming paraconglomerate rudites.

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