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Earthquake clustering inferred from Pliocene Gilbert-type fan deltas in the Loreto Basin, Baja California Sur, Mexico

Rebecca J. Dorsey, Paul J. Umhoefer and Peter D. Falk
Earthquake clustering inferred from Pliocene Gilbert-type fan deltas in the Loreto Basin, Baja California Sur, Mexico
Geology (Boulder) (August 1997) 25 (8): 679-682

Abstract

A stacked sequence of Pliocene Gilbert-type fan deltas in the Loreto basin was shed from the footwall of the dextral-normal Loreto fault and deposited at the margin of a marine basin during rapid fault-controlled subsidence. Fan-delta parasequences coarsen upward from marine siltstone and sandstone at the base, through sandy bottomsets and gravelly foresets, to gravelly nonmarine topsets. Each topset unit is capped by a thin shell bed that records marine flooding of the delta plain. Several mechanisms may have produced repetitive vertical stacking of Gilbert deltas: (1) autocyclic delta-lobe switching; (2) eustatic sea-level fluctuations; (3) climatically controlled fluctuations in sediment input; and (4) episodic subsidence produced by temporal clustering of earthquakes. We favor hypothesis 4 for several reasons, but hypotheses 2 and 3 cannot be rejected at this time. Earthquake clustering can readily produce episodic subsidence at spatial and temporal scales consistent with stratigraphic trends observed in the Loreto basin. This model is supported by comparison with paleoseismological studies that document clustering on active faults over a wide range of time scales. Earthquake clustering is a new concept in basin analysis that may be helpful for understanding repetitive stratigraphy in tectonically active basins.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 25
Serial Issue: 8
Title: Earthquake clustering inferred from Pliocene Gilbert-type fan deltas in the Loreto Basin, Baja California Sur, Mexico
Affiliation: Northern Arizona University, Department of Geology, Flagstaff, AZ, United States
Pages: 679-682
Published: 199708
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 25
Accession Number: 1997-067713
Categories: StratigraphySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. block diags., sect., 1 table, geol. sketch map
N26°04'60" - N26°07'60", W111°27'00" - W111°22'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199722
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