Middle to Late Paleozoic paleomagnetic results from the Appalachian-Caledonian and north Greenland fold belts.
New paleomagnetic constraints for Devonian paleogeographic reconstructions were undertaken. The locations of previously available Devonian paleopoles are constrained in latitude (from 20-35$\sp\circ$), but vary approximately 45$\sp\circ$ in longitude. Since many of the rock units studied are from th...
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| Format: | Thesis |
| Language: | English |
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1988
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| Online Access: | https://hdl.handle.net/2027.42/128188 http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:8812999 |
| Summary: | New paleomagnetic constraints for Devonian paleogeographic reconstructions were undertaken. The locations of previously available Devonian paleopoles are constrained in latitude (from 20-35$\sp\circ$), but vary approximately 45$\sp\circ$ in longitude. Since many of the rock units studied are from the Appalachian foldbelt, it is not known whether this longitudinal distribution is due to the rotation of the entire North American plate or to localized rotations of the individual sampling localities. No primary magnetizations were observed in either the Lower Devonian Llandstadwell Formation of southwest Wales or the Upper Devonian Perry Formation of Maine and New Brunswick. The characteristic directions seen in the Llandstadwell Formation pass a fold test. I interpret the results to represent a secondary direction acquired before Hercynian folding. No evidence for a 40$\sp\circ$ clockwise rotation of the Pembroke peninsula is seen in these data. A negative fold test indicates that the magnetization of the Perry Formation was acquired after folding and can no longer be considered representative of the Devonian geomagnetic field. Two superimposed sets of magnetic directions (D/I = 33/$-$2 and D/I = 7/$-$23), both appearing to be pre-Permian in age, were observed in samples from four lava flows in the Upper Devonian McAras Brook Formation of northern Nova Scotia. The corresponding paleopoles (35$\sp\circ$N, 76$\sp\circ$E, 32$\sp\circ$N, 109$\sp\circ$E) interpret the ages of the magnetizations to be Late Devonian. The longitudinal distribution of the two paleopoles for the McAras Brook Formation indicates some of the spread is due to the rotation of the North American plate as a whole, rather than to localized thrust sheet rotations. Results were obtained from an unnamed Cambro-Ordovician formation from northern Greenland. A negative breccia test and positive local and regional fold tests bracket the age of the northerly and shallow magnetic directions as post-depositional but pre-Ellesmerian (pre-Carboniferous). The ... |
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