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

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.

Rock varnish revisited

“…In contrast, evidence of Fe enhancement shown in this section by budding bacteria can also be seen the following papers (along with Mn-enhancement): Figures 7–9 in (Dorn and Krinsley, 2019); Figures 4(A)–11 in (Krinsley et al, 2017); Figures 7 and 9 in (Krinsley et al, 2013); Figures 9 and 21 in (Dorn et al, 2013); Figure 5 in (Dorn and Krinsley, 2011); Figure 5 in (Krinsley et al, 2009); Figure 1 in (Dorn et al, 1992); plate 3 in (Dorn and Dragovich, 1990); Figure 3 in (Dorn and Oberlander, 1982); and Figure 1 in (Dorn and Oberlander, 1981a).…”

“…The third test links the proposed process of varnish formation to the dominance of clay minerals. The silica binding model depends on the interpretation that clay minerals are not a dominant part of rock varnish (Perry et al, 2006)—an interpretation that is contradicted by prior scholarship (Potter, 1979; Potter and Rossman, 1977, 1979) establishing clay minerals as the dominant component: (Chaddha et al, 2021, 2022; Diaz et al, 2002; Dietzel et al, 2008; Dorn et al, 2012b; Dorn and Krinsley, 2019; Dorn and Oberlander, 1982; Drake et al, 1993; Duerden et al, 1986; Fang et al, 2023; Haberland, 1975; Israel et al, 1997; Johnson et al, 2002; Krinsley, 1998; Krinsley et al, 1995, 2012; Liu and Broecker, 2007; Martínez-Pabello et al, 2022; Probst et al, 2002; Sarmast et al, 2017; Spilde et al, 2007).…”

Birnessite-clay mineral couple in the rock varnish: a nature's electrocatalyst

“…1 These black-brown veneers are often made up of Fe and Mn oxides mixed with clay minerals, 2 and they form on the rock surfaces over time as a result of various environmental and chemical processes. 3 These enigmatic coatings have always been employed to create petroglyphs and have piqued the interest of archaeologists. Geologists, on the other hand, are always interested in learning more about how these varnish layers originate, examining their characteristics, and even assessing their paleoclimatic significance.…”