Fission track evidence for tilting of the Peninsular Ranges batholith of southern California: An alternative to long-distance northward transport

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5999107

George, P G; Dokka, R K ^[1]

---

1. Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Geology and Geophysics

Paleomagnetic directions of Mesozoic plutonic rocks from the Peninsular Ranges batholith in southern California and Baja California are discordant with the expected Cretaceous magnetic field direction. The difference between expected and observed directions suggests ca 25[degree] of clockwise tectonic rotation and ca 11[degree] northward translation of peninsular California with respect to cratonic North America. Lithologic correlations between peninsular California and Sonora, however, support only 300 [+-] 10 km of north-northwest translation along the San Andreas transform system. Southwest tilting of the batholith about an axis subparallel to its trend has been proposed in order to explain the discordant paleomagnetic directions, thereby eliminating the need for long-distance transport. The distribution of zircon and apatite fission-track ages across the western half of the batholith between Palomar Mountain and Escondido, California support this proposal. In the northeastern part of the study area apatite and zircon fission-track ages of Early Cretaceous tonalities and granodiorites range from 73.9 to 81.9 Ma and 74.8 to 79.9 Ma, respectively. The show no systematic increase or decrease with changes in elevation or distance along the ca N37E line of sampling. Towards the southwest, however, apatite and zircon fission-track ages increase progressively from 82 to 96 Ma and 83 to 93 Ma, respectively. The author interprets these results as indicating rapid, episodic uplift of the study area during Late Cretaceous time followed by regional tilting of the batholith and its fission-track age surfaces to the southwest. The amount of tilt estimated from the distribution of the fission-track ages is compatible with those based on geobarometry data and the distribution of U-Pb and K-Ar ages.

• OSTI ID: 5999107
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC FORMATIONS
PALEOMAGNETISM
TECTONICS
AGE ESTIMATION
APATITES
FISSION TRACKS
LITHOLOGY
PLUTONIC ROCKS
ROTATION
ZIRCON
DEVELOPED COUNTRIES
GEOLOGY
IGNEOUS ROCKS
MAGNETISM
MINERALS
MOTION
NORTH AMERICA
PARTICLE TRACKS
PETROLOGY
PHOSPHATE MINERALS
ROCKS
SILICATE MINERALS
USA
580000* - Geosciences