Aligned ikaite porphyroblasts have been replaced by calcite with a maximum volume decrease of ~88% in Neoproterozoic Dalradian metalimestone exposed near Ballygrant on Islay, Scotland. Microscopic and structural analyses reveal that the ikaite minerals formed before deformation, at a time when Scotland was located at the lower latitudes, thus indicating a cold climate at the time of formation. The Ballygrant metalimestone underlies a ~900 meter thick glacial deposit that has previously been linked to the ‘Snowball Earth’ hypothesis. The discovery of these ikaite pseudomorphs below the glacial deposit points toward a relatively slow cooling of the climate near the equator reflecting a transition toward a ‘normal’ glacial period and thus refutes a suggested ‘Snowball Earth’ event, which is reported to reflect a more abrupt switch over from warm to cold climate in the sediment record.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:su-145322 |
| Date | January 2017 |
| Creators | Ohrazda, Christina |
| Publisher | Stockholms universitet, Institutionen för geologiska vetenskaper |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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