Strucural geology of the southwestern shore of Conception Bay, eastern Avalon zone, Newfoundland Appalachians

• Main Author: Riveros, Claudia Paz
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1998
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/6553/; https://research.library.mun.ca/6553/1/ClaudiaPazRiveros.pdf; https://research.library.mun.ca/6553/3/ClaudiaPazRiveros.pdf

The Newfoundland Avalon Zone of the eastern Appalachians has, for many years, been affected by two major tectonic events: the late Proterozoic Avalonian Orogeny. which occurred prior to the final collision of the Gondwanan and Laurentian continents, and the mid-Paleozoic Acadian Orogeny. associated with the final accretion of the Gondwanan to Laurentian continents. Recent geochronological data show, however, that the Avalon Zone was affected by multiple late Proterozoic thermal events (ca.760 Ma. ca. 680 Ma. ca. 630-600 Ma and ca. 575-550 Ma) and by the Paleozoic Salinic and Alleghenian-Hercynian orogenies. Systematic constraints on the structural characteristics of these tectonic events are lacking in the Avalon Zone. The present study addresses this problem via a detailed investigation of the structural and stratigraphic relationships observed along the southwestern shore of the Conception Bay, eastern Avalon Zone. The cross-cutting relationships between a pervasive regional (S₂) cleavage and structures truncated by the sub-Cambrian unconformity are used to distinguish between D₁ Proterozoic and D₂ post-Cambrian structures. Distinctive structural characteristics observed through the study site are used, further, to identify four distinctive styles and relative ages of deformation: D₁ₐ, D₁, D₂ₐ and D₂. D,. and D,b reflect two phases of deformation associated with the Avalonian Orogeny. Both appear to have occurred in a late period of this prolonged and diachronous orogenic event. D,. is a block faulting extensional event that produced north-trending block faults. These have produced the north-trending Brigus and Holyrood horsts. This . brittle" deformational event produced few identifiable mesoscale features and no cleavage. D,b was a north-south shortc:ning event. D,b structures include northwest-trending dextral kink band sets and northeast-trending sinistral kink band sets, northwest- and northeast-trending open to isoclinal F, folds, and regional dome and basin and periclinal structures. Some of the faults ...