Stretching lineations, shear zone kinematics and dextral transpression along the Flying Point/Norumbega fault zone, Casco Bay, Maine

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5688221

Swanson, M T ^[1]

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1. Univ. of Southern Maine, Gorham, ME (United States). Dept. of Geosciences

Stretching lineations (L2) throughout the high-grade metamorphic rocks of the Casco Bay area are defined by the alignment of grain aggregates and elongate minerals generally parallel to subhorizontal upright F2 fold hinges. L2 lineations were developed due to regional layer-parallel shear related to dextral transpression along the Flying Point segment of the Norumbega Fault Zone during the later Paleozoic. The reorientation of boudin partings, quartz veins and pegmatite intrusions, the asymmetry of boudin pods, late vein folds and crenulations as well as a range of microscopic kinematic indicators within these rocks clearly indicate an overall dextral shear sense and a variable dip-slip component with local transport directions parallel to L2 during deformation. The distribution of L2 lineations about the trace of the NE- trending Flying Point Fault Zone shows: (a) E-plunging L2 in a broad zone on the NW side within SE-dipping, locally, pegmatite-injected, porphyroclastic schists and gneisses and; (c) sub-horizontal L2 within subordinate fault slices of folded Casco Bay Group lithologies to the SE. The Flying Point Fault zone itself consists of the straight planar gneisses and related rocks as a 2 km wide corridor of high shear strain reflected in the development of quartz-vein sheath folds parallel to L2. Variably-deformed mafic and felsic intrusions preserved as asymmetric pods and lenses within the flanking lithologies have been obliterated within this zone of high shear strain. This kinematic pattern and distribution of lineations is interpreted as an asymmetric transpressional uplift dominated by a broad NW front suffering oblique escape toward the west under dextral reverse motions and a major near-vertical zone of decoupling that developed at a restraining bend at the southwest end of the Norumbega Fault Zone.

• OSTI ID: 5688221
• Report Number(s): CONF-9303211--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:2
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
DEFORMATION
DEVELOPED COUNTRIES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
GEOMETRY
MAINE
MATHEMATICS
METAMORPHIC ROCKS
NORTH AMERICA
ORIENTATION
PETROLOGY
ROCKS
SHEAR
TECTONICS
USA