Lithofacies of deep marine basalts emplaced on a Jurassic backarc apron, Baja California (Mexico)
Basalts of the mid-Jurassic Gran Canon Formation, Cedros Island, Mexico, were emplaced on a volcaniclastic apron in a deep marine backarc basin. Elongate pillows and lava tubes, as well as paleocurrent data from the volcaniclastic apron, indicate a southward regional paleoslope away from the island arc source. Basalts emplaced on relatively proximal parts of the apron are nearly entirely pillowed and have thick flow units with mega-pillows. Basalts on distal parts of the apron (about 15 to 20 km down paleo-current) are dominated by pillow fragment breccias (flow foot rubble), and individual lava flows are generally thin, with small pillows, suggesting that the distal ends of lava flows, erupted upslope, are represented. These distal flow fronts, however, are interstratified with features that typically form close to a vent, including thick massive to mega-pillowed lavas and lava tubes up to 8 m in diameter. It is inferred that a fissure (or system of fissures) extended from the arc into the backarc basin, erupting basalt lavas onto both proximal and distal parts of the volcaniclastic apron. Such intraplate volcanism may be common on the hot frontal arc side of backarc basins. 26 references.
- Research Organization:
- Univ. of California, Santa Barbara
- OSTI ID:
- 5515980
- Journal Information:
- J. Geol.; (United States), Journal Name: J. Geol.; (United States) Vol. 95:5; ISSN JGEOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580202* -- Geophysics-- Volcanology-- (1980-1989)
BASALT
DEVELOPING COUNTRIES
FLUID FLOW
GEOLOGIC AGES
GEOLOGIC FISSURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
JURASSIC PERIOD
LATIN AMERICA
LAVA
LEVELS
MESOZOIC ERA
MEXICO
MORPHOLOGY
NORTH AMERICA
OFFSHORE SITES
ROCKS
UNDERWATER
VOLCANIC REGIONS
VOLCANIC ROCKS
VOLCANISM