GEOL 5900 Seminar Presentation - Leslie Boateng-Dwomoh - 4PM HSH 336
Huggins Science Hall 334 @ 4pm
THE RELATIONSHIP BETWEEN AVALONIA AND MEGUMA: CONTIGUOUS OR DISTANT TERRANES?
LESLIE BOATENG-DWOMOH
MSc GEOLOGY STUDENT, ACADIA UNIVERSITY
ABSTRACT
The evolutionary and accretionary relationships between peri-Gondwanan terranes that accreted to the composite Laurentian margin in the Canadian Appalachian orogen has been a controversial topic in geoscience. A specific challenge has been understanding these dynamics between Avalonia and Meguma terranes. Some research suggests that Meguma and Avalonia were part of the same microcontinental block that separated from Gondwana and accreted to the Laurentian margin during the Acadian orogeny. In contrast, other research suggests that an ocean existed between the two terranes before accretion and that these two terranes were not part of the same microcontinental block. Detrital zircon ages and Sm-Nd signatures of the Silurian-Devonian Rockville Notch (RNG) in the Meguma terrane have been compared with the Arisaig Group in Avalonia, with some research indicating that the similarities between the two groups are the consequence of an overstep sequence in the Silurian. They further propose that Meguma rocks were directly deposited on Avalonian basement in the Silurian. Supporting research suggests that metasedimentary granulite xenoliths, inferred to be from the structural basement of Meguma, show similarity to Avalonian rocks than Meguma, leading to the interpretation of Meguma being deposited on Avalonian basement or thrust over Avalonia. In contrast, a comparison of Meguma terrane to the Harlech Dome in Wales and Cadomian rocks in Germany appears to indicate that the Meguma terrane shows more similarity with those terranes than the Avalonian rocks. The occurrence of a 30-37 Ma hiatus before deposition of RNG in Meguma and its relative absence in Avalonia, coupled with lithological differences, defeats the assumption of an overstep sequence and contiguous relationship between Meguma and Avalonia
