Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico

Paul J Umhoefer, Sara J. Maloney, Beverly Buchanan, J. Ramón Arrowsmith, Genaro Martinez-Gutiérrez, Graham Kent, Neal Driscoll, Alistair Harding, Darrell S Kaufman, Tammy Rittenour

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The southwest margin of the Gulf of California has an array of active normal faults despite this being an oblique-divergent plate boundary with spreading centers that localized deformation along the plate boundary 2-3 million years ago. The Carrizal and Centenario faults form the western border fault of the Gulf of California marginal fault system within and south of La Paz Bay, and ̃20-30 km west of the capital city of La Paz, Baja California Sur, Mexico. Geologic and geomorphic mapping, optically stimulated luminescence (OSL) geochronology, and paleoseismic investigations onshore, compressed high-intensity radar pulse (CHIRP) profi ling offshore, and analysis of uplifted marine terraces in the footwall of the offshore Carrizal fault provide some of the fi rst numerical and geometrical constraints on late Pleistocene-Holocene faulting along the Carrizal fault. The onshore Carrizal fault has ruptured with up to ̃1-2 m of vertical displacement per event, likely producing ̃M 6.3-6.9 earthquakes, and at least two to three surface rupturing earthquakes have occurred since 22 ka. Onshore paleoseismic excavations and uplifted marine terraces on the western side of La Paz Bay both suggest offset rates of 0.1-0.2 mm/yr, with a footwall uplift rate of 0.13 mm/yr since 128 ka, and an approximately constant rate since marine oxygen- isotope stage (MIS) 11 terraces (420 ka). A CHIRP survey identifi ed underwater fault scarps with heights ranging from 21 to 86 m on the Carrizal fault in La Paz Bay and from 3 to 5 m along the Centenario fault. The offshore Carrizal fault lies 8-10 km east of the western edge of La Paz Bay, forming a right step from the onshore Carrizal fault. The offshore Carrizal fault is the oldest fault of the fault system, and the fault likely grew in the latest Miocene to Pliocene in a complex way to the south toward the onshore Centenario and Carrizal faults. When the Alarcon spreading center started its modern rates at 2.4 Ma, the Carrizal fault likely slowed to the 0.1-0.2 mm/yr rates of the late Quaternary determined in this study.

Original languageEnglish (US)
Pages (from-to)476-504
Number of pages29
JournalGeosphere
Volume10
Issue number3
DOIs
StatePublished - 2014

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faulting
history
terrace
spreading center
footwall
plate boundary
radar
earthquake
capital city
luminescence
active fault
geochronology
normal fault
oxygen isotope
Pliocene
excavation
uplift
Miocene
rate
Holocene

ASJC Scopus subject areas

  • Geology
  • Stratigraphy

Cite this

Umhoefer, P. J., Maloney, S. J., Buchanan, B., Arrowsmith, J. R., Martinez-Gutiérrez, G., Kent, G., ... Rittenour, T. (2014). Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico. Geosphere, 10(3), 476-504. https://doi.org/10.1130/GES00924.1

Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico. / Umhoefer, Paul J; Maloney, Sara J.; Buchanan, Beverly; Arrowsmith, J. Ramón; Martinez-Gutiérrez, Genaro; Kent, Graham; Driscoll, Neal; Harding, Alistair; Kaufman, Darrell S; Rittenour, Tammy.

In: Geosphere, Vol. 10, No. 3, 2014, p. 476-504.

Research output: Contribution to journalArticle

Umhoefer, PJ, Maloney, SJ, Buchanan, B, Arrowsmith, JR, Martinez-Gutiérrez, G, Kent, G, Driscoll, N, Harding, A, Kaufman, DS & Rittenour, T 2014, 'Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico', Geosphere, vol. 10, no. 3, pp. 476-504. https://doi.org/10.1130/GES00924.1
Umhoefer, Paul J ; Maloney, Sara J. ; Buchanan, Beverly ; Arrowsmith, J. Ramón ; Martinez-Gutiérrez, Genaro ; Kent, Graham ; Driscoll, Neal ; Harding, Alistair ; Kaufman, Darrell S ; Rittenour, Tammy. / Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico. In: Geosphere. 2014 ; Vol. 10, No. 3. pp. 476-504.
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