Nanoscale Observations Support the Importance of Chemical Processes in Rock Decay and Rock Coating Development in Cold Climates

Ronald Dorn,David Krinsley

doi:10.3390/geosciences9030121

Abstract

Conventional scholarship long held that rock fracturing from physical processes dominates over chemical rock decay processes in cold climates. The paradigm of the supremacy of cold-climate shattering was questioned by Rapp’s discovery (1960) that the flux of dissolved solids leaving a Kärkevagge, Swedish Lapland, watershed exceeded physical denudation processes. Many others since have gone on to document the importance of chemical rock decay in all cold climate landscapes, using a wide variety of analytical approaches. This burgeoning scholarship, however, has only generated a few nanoscale studies. Thus, this paper’s purpose rests in an exploration of the potential for nanoscale research to better understand chemical processes operating on rock surfaces in cold climates. Samples from several Antarctica locations, Greenland, the Tibetan Plateau, and high altitude tropical and mid-latitude mountains all illustrate ubiquitous evidence of chemical decay at the nanoscale, even though the surficial appearance of each landscape is dominated by “bare fresh rock.” With the growing abundance of focused ion beam (FIB) instruments facilitating sample preparation, the hope is that that future rock decay researchers studying cold climates will add nanoscale microscopy to their bag of tools.

Highlights

Joint fractures rest at the core of geomorphic weakness [1,2,3,4]
Antarctic, and alpine cold-climate settings contextualized by micron-scale studies reveal the ubiquitous presence of chemical processes operating at rock surfaces
We found fossilized evidence of budding bacteria within cold climate rock varnishes

Summary

Introduction

Joint fractures rest at the core of geomorphic weakness [1,2,3,4]. Molnar et al ([1], p. 12) speculated that the “role of tectonics as a crusher of rock is that in those places where rock has dodged the rock crusher, it may be stronger and less removed by erosive agents.” While tectonic deformation and other rock-forming processes generate joints [1,5,6,7,8,9,10,11], these initial fractures open the way for physical and chemical rock decay processes. The visual appearance of bare rock in alpine, arctic and Antarctic landscapes certainly encouraged the paradigm of the dominance of “physical weathering” in cold climates championed in physical geology and physical geography textbooks [20,21,22]. It was surprising when actual measurements in the mid-twentieth century documented the importance of chemical processes, with Rapp [23] showing that the flux of dissolved solids leaving a Kärkevagge watershed in Sweden exceeded physical denudation processes

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