Where fast weathering creates thin regolith and slow weathering creates thick regolith

Earth Surface Processes and Landforms
By: , and 



Weathering disaggregates rock into regolith – the fractured or granular earth material that sustains life on the continental land surface. Here, we investigate what controls the depth of regolith formed on ridges of two rock compositions with similar initial porosities in Virginia (USA). A priori, we predicted that the regolith on diabase would be thicker than on granite because the dominant mineral (feldspar) in the diabase weathers faster than its granitic counterpart. However, weathering advanced 20 deeper into the granite than the diabase. The 20  -thicker regolith is attributed mainly to connected micron-sized pores, microfractures formed around oxidizing biotite at 20 m depth, and the lower iron (Fe) content in the felsic rock. Such porosity allows pervasive advection and deep oxidation in the granite. These observations may explain why regolith worldwide is thicker on felsic compared to mafic rock under similar conditions. To understand regolith formation will require better understanding of such deep oxidation reactions and how they impact fluid flow during weathering.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Where fast weathering creates thin regolith and slow weathering creates thick regolith
Series title Earth Surface Processes and Landforms
DOI 10.1002/esp.3369
Year Published 2013
Language English
Publisher Wiley Online
Contributing office(s) Eastern Geology and Paleoclimate Science Center
Description 12 p.
First page 847
Last page 858
Country United States
State Virginia
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