The stratigraphy and structural geology of the Twillingate region

Stander, Edward (1984) The stratigraphy and structural geology of the Twillingate region. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Twillingate region is underlain by three lithologic units. The oldest of these is the Sleepy Cove Group, a one to two kilometer thick volcanic pile which exhibits ophiolitic affinities. To the west, and in thrust contact with this group is the Moretons Harbour Group, a massive, 8 to 9 kilometer thick volcanic pile which most likely developed in an island arc environment. The Twillingate Granite is intrusxve into both units and is thus the youngest unit in the region. -- The Twillingate Granite and its basaltic hosts were affected by four deformational episodes. The earliest of these events (D₁) produced two high temperature shear zones. Of these, the SHTI zone parallels the southern boundary of the study area and is characterized by recrystallized quartz grains enclosed in a recrystallized sodic plagioclase matrix. The BBB zone forms the contact between the Moretons Harbour Group and the Sleepy Cove Group, and is characterized by sheared and elongate pillow basalts and dykes. -- The D₂ deformation resulted in the development of open to tight upright folds in the basalt and a strong, localized L-S fabric in the granite body. Quartz microstructures and petrofabrics in the granite suggest that this deformation occurred at much lower temperatures than D₁. -- D₃ was also a low temperature deformation episode and was mainly responsible for developing broad, upright folds in the basalts of North and South Twillingate Island. This event does not appear to have affected the granite terrain to any great extent. -- The last event to affect the region (D₄), produced local kinks and faults in both the Twillingate Granite and the surrounding volcanic groups.

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