Date of Award
Program or Major
Earth Sciences: Geology
Master of Science
William C Clyde
The Kittery Formation is an early Silurian metaturbidite sequence that formed just before the Acadian Orogeny in central coastal New England. Despite a long history of tectonism and deformation, the Kittery Formation preserves primary sedimentary features suggesting that paleomagnetic data may further elucidate current tectonic and metamorphic interpretations of the Merribuckfred basin. A paleomagnetic study of the Kittery Formation was carried out to determine its original geographic location, to confirm its current age assignment, and to analyze its remagnetization history.
Seven or more cores were drilled from each of 17 different sites within the Kittery Formation. All cores were demagnetized in thermal increments from 25 to 400°C and measured by a SQUID spinner magnetometer at the University of New Hampshire. IRM, XRD, and reflected light microscopy confirm greigite as the dominant carrier of the ChRM. AMS indicates the percent anisotropy of Cape Elizabeth and Ft. McClary is larger than 20%, while the rest were less than 16%. To a first order, K1 at all sites follows the F2 fold directions of the Kittery Formation in tectonic coordinates, suggesting a regional scale expression of the outcrop scale F2 folds with a wavelength of approximately 50 miles. At all localities the Kittery Formation fails the fold test because of tectonism and/or multiple generations of greigite growth. However, it does pass the baked contact test and therefore the magnetization age must be older than Jurassic, but younger than late Silurian/early Devonian. ChRM sample directions are well clustered within sites, but comparison of different sites do not cluster in either geographic or tilt adjusted coordinates. Some site VGPs cluster more closely with the middle Paleozoic of the North America APWP, and some are discordant. This suggests rotation of fault bounded blocks and/or magmatic shouldering during the Acadian and Alleghanian orogenies in central coastal New England. These results also indicate that greigite can remain stable over hundreds of millions of years, which is significantly longer than previously documented.
Boucher, Julianne Batchelder, "Paleomagnetism of the Kittery Formation: A record of tectonism and rotation" (2011). Master's Theses and Capstones. 625.