Analysis of Pinnate Joints in the Mount Desert Island Granite: Implications for Postintrusion Kinematics in the Coastal Volcanic Belt, Maine
Engelder T. 1989. Analysis of Pinnate Joints in the Mount Desert Island Granite: Implications for Postintrusion Kinematics in the Coastal Volcanic Belt, Maine. Geology. 17(6):564-567
This analysis is of the characteristics of 'surface morphology on fractures'. 'The Mount Desert Island granite is cut by fractures displaying one of four types of surface morphology: (1) smooth to undulatory; (2) stepped in the form of en ecelon cracks; (3) striated with linear fibers; and (4) irregular with cataclastic grains. These surfaces belong to joints, host fractures with pinnate joints, reactivated joints or fractures, and deformation bands (shear fractures), respectively. Pinnate joints, like striations on slickensides, are structures indicative of the orientation of the slip vector and sense of shear on host fractures. Although fractures in the Mount Desert Island granite cluster into two major sets (N20oW and N45oE), host fractures with pinnate joints and shear fractures favor the N45oE orientation. A kinematic analysis of the pinnate joints indicates a predominantly dextral strike-slip sense of movement on northeast-trending fractures. This result agrees with previous work suggesting that a prominent postintrusion tectonic event in southeast Maine consisted of dextral strike-slip motion on northeast-trending faults.' /STUDY LOCATIONS:/ /MOUNT DESERT ISLAND/
- Type
- Journal Article
- Authors
- Engelder, Terry
- Units
- ACAD
- Keywords
- Faults (Geologic), Fractures (Geologic), Geology, Mount Desert Island, surface morphology