Intensity and duration of chemical weathering: An example from soil clays of the southeastern Koolau Mountains, Oahu, Hawaii

Johnsson, Mark J.; Ellen, Stephen D.; McKittrick, M.A.

doi:10.1130/spe284-p147

Cited by 20 publications

(12 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3B), much of which may be from eolian input. These background data indicate that clay minerals, potentially formed through weathering of volcanic bedrock in the Neogene, are typified by smectite, as expected in arid environments (Birkeland, 1984;Weaver, 1989;Johnsson et al, 1993). However, effective moisture in the Pliocene was great enough at times to possibly weather potassium-rich volcanic material to kaolinite, a process that typically occurs in temperate to tropical environments (Birkeland, 1984;Weaver, 1989).…”

Section: Results and Interpretationsmentioning

confidence: 79%

Ancient hillslope deposits: Missing links in the study of climate controls on sedimentation

Pederson

Pazzaglia

Smith

2000

Geol

View full text Add to dashboard Cite

Rare outcrops of Miocene-Pliocene buried hillslopes and colluvium present in proximal basin-fill exposures in the arid southwestern United States, in settings free of tectonic influences, reveal hillslope-sediment production and delivery to piedmonts that vary as a function of climate change. A petrologic weathering index for sand, clay-mineral data, and stratigraphic relations indicates that episodes of greater production and delivery of colluvium from hillslopes coincide with more intense chemical weathering and thus greater effective moisture. Strata recording limited colluviation, less intense weathering, and piedmonts dominated by eolian processes very likely correspond to drier conditions. The mode of climate-driven hillslope and piedmont landscape responses evident in these older stratigraphic records corroborates the conceptual model developed by Quaternary researchers for arid environments-even though climate change was operating at higher amplitudes and different frequencies in the Quaternary. This evidence of long-term continuity in the mode of landscape response to climate change provides a new level of support for using the geologic record to understand the effects of future climate change.

show abstract

Section: Results and Interpretationsmentioning

confidence: 79%

Ancient hillslope deposits: Missing links in the study of climate controls on sedimentation

Pederson

Pazzaglia

Smith

2000

Geol

View full text Add to dashboard Cite

show abstract

“…Commonly assumed conservative elements include Zr (Harden, 1987), Ti (Johnsson et al, 1993), Nb (Brimhall and Dietrich, 1987), or some rare earth elements. However, there is considerable disagreement in the literature as to the relative motilities of these elements under differing weathering conditions (Gardner, 1980;Hodson, 2002).…”

Section: Mass Transfermentioning

confidence: 99%

Natural Weathering Rates of Silicate Minerals

White

Buss²

2014

Treatise on Geochemistry

View full text Add to dashboard Cite

“…Locally, smectite may occur (Nelson et al, 2013;Dessert et al, 2003;Chadwick et al, 2003;Johnsson et al, 1993), and may be an intermediate phase of weathering before recrystallization to kaolinite or halloysite (Glassman and Simonson, 1985;Eggleton et al, 1987). Joussein (2016) and Vitousek et al (2007) suggested that soil mineralogy ripens through a series of steps from allophane or imogolite to halloysite and finally kaolinite on a time frame of ~1 m.y.…”

Section: Mineralogy Of Hawaiian Lateritesmentioning

confidence: 99%

A conceptual model for the rapid weathering of tropical ocean islands: A synthesis of geochemistry and geophysics, Kohala Peninsula, Hawaii, USA

et al. 2018

View full text Add to dashboard Cite

Much of the world's population lives in developing countries in regions with deeply weathered soils and thick, subjacent saprolites. These areas are widespread in the tropics and compose an important component of the critical zone (CZ). The Hawaiian Islands (USA) make an excellent natural laboratory for examining the tropical CZ, where the bedrock composition (basalt) is nearly uniform but of variable age and where climate (rainfall) varies greatly. The purpose of this study is to develop a model for rapid weathering to deep regolith profiles in tropical ocean islands.In the Kohala Peninsula, Hawaii, a variably weathered, thick soil and saprolite profile is exposed along sea cliffs in a mesic climate setting. Laterite development includes the entire vadose zone, with a mineralogy that chiefly includes halloysite ± gibbsite and Fe-oxides and mixed Fe-oxides and hydroxide species developed on a 303 ka substrate. Gibbsite-rich horizons occur in enhanced zones of weathering. At the base of the weathering front and on the rinds of core stones, transient smectite clays are developed, but rapidly break down to halloysite. Excess Al and Fe found in soil and saprolite likely originated from the decomposition of volcanic ash deposited on the ground surface from later effusive volcanism.Shear-wave velocity data derived from multichannel analysis of surface waves (MASW) and common depth point (CDP) seismic reflection profiles reveal important internal details of the weathering profiles that complement information derived from nearby rock outcrop along a sea cliff. In addition to identifying the depth of the weathering front, stiff horizons within the laterite correlate to high gibbsite abundances in the MASW profile. Parallel to the paleo-lava flow direction, relict igneous stratigraphy is expressed as seaward-dipping reflectors on CDP profiles, whereas perpendicular to flow, reflector geometry suggests lenticular bodies within laterite.A synthesis of geochemistry and geophysical studies leads to the development of a conceptual model to explain variable weathering within the CZ. First, although there is an overall trend for the downward migration of the weathering front with time, zones of high initial permeability (rubble above or below a'a flows; tephra or scoria deposits) are influenced by both downward and lateral fluxes of water, leading to enhanced weathering in what are now gibbsite-rich horizons. Second, the dense cores of a'a flows with widely spaced joints preserve large core stones that weather inward where halloysite-rich saprolite gives way to smectite-rich rims. Thus, differential weathering is a natural consequence of textural variations in primary igneous stratigraphy with superimposed additions of Al and Fe from the dissolution of basaltic glass. This study shows how weathering features and processes may be synthesized from outcrop, geochemical observations, and geophysical profiles into a multi-stage conceptual model of weathering.

show abstract

Intensity and duration of chemical weathering: An example from soil clays of the southeastern Koolau Mountains, Oahu, Hawaii

Cited by 20 publications

References 0 publications

Ancient hillslope deposits: Missing links in the study of climate controls on sedimentation

Ancient hillslope deposits: Missing links in the study of climate controls on sedimentation

Natural Weathering Rates of Silicate Minerals

A conceptual model for the rapid weathering of tropical ocean islands: A synthesis of geochemistry and geophysics, Kohala Peninsula, Hawaii, USA

Contact Info

Product

Resources

About