Tectonic Controls on Non-Marine Sedimentation in a Cretaceous Fore-Arc Basin, Baja California, Mexico

  1. L. E. Frostick2 and
  2. R. J. Steel3
  1. M. M. Fulford and
  2. C. J. Busby

Published Online: 16 APR 2009

DOI: 10.1002/9781444304053.ch17

Tectonic Controls and Signatures in Sedimentary Successions

Tectonic Controls and Signatures in Sedimentary Successions

How to Cite

Fulford, M. M. and Busby, C. J. (1994) Tectonic Controls on Non-Marine Sedimentation in a Cretaceous Fore-Arc Basin, Baja California, Mexico, in Tectonic Controls and Signatures in Sedimentary Successions (eds L. E. Frostick and R. J. Steel), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304053.ch17

Editor Information

  1. 2

    Reading, UK

  2. 3

    Bergen, Norway

Author Information

  1. Department of Geological Sciences, University of California, Santa Barbara, CA 93106, USA

Publication History

  1. Published Online: 16 APR 2009
  2. Published Print: 28 FEB 1994

ISBN Information

Print ISBN: 9780632037452

Online ISBN: 9781444304053

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Keywords:

  • tectonic controls on non-marine sedimentation in Cretaceous fore-arc basin, Baja California, Mexico;
  • Late Cretaceous peninsula ranges;
  • El Gallo Formation;
  • sedimentology and stratigraphy;
  • lithology and sedimentary structures

Summary

The El Gallo Formation is a 1300-m-thick sequence of Upper Campanian fluvial sedimentary rocks which are exposed along the west coast of Baja California, Mexico. The formation was deposited along the eastern margin of the Rosario embayment of the Late Cretaceous Peninsular Ranges fore-arc basin. Palaeocurrent directions measured from imbrication and trough cross-bedding, combined with evidence of compositional and textural immaturity and lack of alteration of sandstones throughout the formation, indicate that deposition occurred in a transverse fluvial system. Sedimentation along the basin margin was controlled by the interplay between high and gradually increasing basin subsidence rates and variable sediment influx and to a lesser degree a rising eustatic sea-level.

Single-crystal laser probe40 Ar/39 Ar dates on individual sanidine grains from four rhyolitic tuff horizons within the El Gallo Formation permit the calculation of depositional rates that indicate that the depocentre was undergoing rapid subsidence (approximately 600 m/My). The effect of high and increasing subsidence rates on deposition can be recognized in the overall thickness and ‘retrogradational’ character of the deposit, as depositional environments changed from a proximal alluvial plain to braidplain through to floodplain and finally to a tidally-influenced coastal plain.

Rapid vertical movements of both the basin floor and the volcanoplutonic arc source terrane largely controlled sedimentation in the El Gallo Formation. Coarse-grained non-marine deposits at the base of the formation overlie Lower Campanian bathyal marine deposits (Punta Baja Fm) along a 15° angular unconformity. The magnitude of this relative sea-level change (000–2000 m) requires tectonic uplift of the basin, although erosion along the unconformity may have been enhanced during two possible eustatic low stands proposed for this time frame. This unconformity thus records tectonic uplift of the basin. Subsequent accumulation of non-marine deposits of the El Gallo Formation resulted from a combination of rapid tectonic subsidence of the basin and a contemporaneous 3rd-order sea-level rise. An abrupt lithological change from gravelly to sandy deposits between the La Escarpa and El Disecado members of the El Gallo Formation is inferred to be the result of downfaulting and sediment trapping along the fore-arc basin margin. Higher in the section, sandstone compositions record an increase in plutonic relative to volcanic and sedimentary fragments coincident with an apparent increase in sediment supply to the basin. This reflects an uplift event in the volcanoplutonic arc source terrane.