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Formation of waterfalls by intermittent burial of active faults

Luca C. Malatesta and Michael P. Lamb
Formation of waterfalls by intermittent burial of active faults
Geological Society of America Bulletin (October 2017) 130 (3-4): 522-536

Abstract

Waterfalls commonly exist near bounding faults of mountain ranges, where erosional bedrock catchments transition to depositional alluvial fans. We hypothesize that aggradation on alluvial fans can bury active faults, and that the faults accumulate slip in the subsurface to produce a bedrock scarp. Following entrenchment of the alluvial fan, the scarp can be exposed as a waterfall. To explore this hypothesis, we derived a geometric model for waterfall height that depends on alluvial fan length and the relative time scales of (1) tectonic uplift, (2) a forcing mechanism for cycles of fan aggradation and incision, and (3) a response of fan aggradation to changes in sediment flux. We find that the model is consistent with observations at Gower Gulch, Death Valley, California, where a man-made drainage capture event in 1941 caused rapid fan incision and exposed a waterfall at the canyon-fan transition. We also compared the model to 62 waterfalls in 18 catchments of the Death Valley area and found that at least 15 of the waterfalls are best explained by the fault-burial mechanism. Using field measurements of grain size and channel geometries, we show that the fault-burial mechanism can produce the observed waterfall heights, measuring 4-19 m, under a uniform climatic forcing scenario requiring variations of 20% in precipitation during the late Pleistocene. The fault-burial mechanism, through the creation of upstream propagating waterfalls, may allow catchment-fan systems to experience frequent cycles of enhanced erosion in catchments and deposition on fans that likely convolve tectonic and climatic signals.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 130
Serial Issue: 3-4
Title: Formation of waterfalls by intermittent burial of active faults
Affiliation: California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Pages: 522-536
Published: 20171010
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 95
Accession Number: 2018-022486
Categories: Geomorphology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017320
Illustration Description: illus. incl. 2 tables, sketch maps
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 201812
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