Tectonics of crystalline forearcs: insights from the southern Andes and Indentor experiments

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6612299

Forsythe, R D

South of Peru over 90% of the Andean forearc is dominated by metamorphic or plutonic rocks, the bulk of which are exposed above sea level within the coastal ranges of the western Chile. These coastal ranges are divisible into 9 elongate, semi-independent blocks, that are separated from each other by zones of oblique faulting and from the main South American lithosphere by longitudinal fault zones that parallel the magmatic arc. Most of the fault zone have had late Tertiary and Quaternary movements. Constrained by the underlying subduction zone, north and south bounding oblique faults, and eastern longitudinal faults, 6 of the 9 blocks have geometries of a doubly-tapered wedge. Transverse, principally normal, faults develop as splays to the main longitudinal faults, producing a distinctive batwing fault pattern. Strike-slip motion on longitudinal faults leads to four kinematic and two dynamic classes of block terminations. These terminations correlate with the limits of rupture zones to great earthquakes and anomalous regions of both coastal uplift and shelf subsidence. Since Nazca-South American relative motion has been almost normal to the margin for the last 25 Ma, components of oblique convergence cannot easily account for late Cenozoic block movements. Variations in the gravitational potential energy associated with the subduction of bathymetric highs along the Peru-Chile Trench should produce variations in the resolved horizontal stress acting normal to the plate boundary. This offers a dynamic alternative to kinematic models that have principally relied on oblique convergence to explain strike-slip movements on faults that parallel the arc or trench. Modified rigid indentor/plasticine experiments have been run to model collision of a bathymetric high.

• Research Organization: Rutgers Univ., New Brunswick, NJ (USA)
• OSTI ID: 6612299
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
ANDES
CENOZOIC ERA
CHILE
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GEOMETRY
IGNEOUS ROCKS
LATIN AMERICA
MATHEMATICS
METAMORPHIC ROCKS
MOUNTAINS
OROGENESIS
PERU
PLATE TECTONICS
PLUTONIC ROCKS
ROCKS
SOUTH AMERICA
SUBDUCTION ZONES
TECTONICS