Early formation of gnammas (weathering pits) in a recently glaciated area of Torres del Paine, southern Patagonia (Chile)

Domínguez‐Villar, David

doi:10.1016/j.geomorph.2005.10.006

Cited by 25 publications

(27 citation statements)

References 31 publications

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“…Additionally, our results show that the volume of gnammas from measurement stations with several sub-populations varies by 2 or 3 orders of magnitude (b1 to >1000 litres). These data have been reported in all of our morphometry analyses (Domínguez-Villar, 2006, 2007Domínguez-Villar and Jennings, 2008;Domínguez-Villar et al, 2009). Therefore, based in our experience, we consider more realistic for gnammas to develop continuously or episodically (depending on the environmental conditions affecting weathering) from the time of rock exposure.…”

supporting

confidence: 54%

“…Thus, according with scenario 1 the spillway is eroded more rapidly than the base of the cavity. This scenario is thought to follow the descriptions of gnamma evolution by Domínguez-Villar (2006), Domínguez-Villar and Jennings (2008) and Domínguez-Villar et al (2009). However, this scenario is contrary to what is observed and reported in these publications; the constraints of scenario 1 are based on a misunderstanding and do not represent the data described.…”

mentioning

confidence: 56%

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Weathering phases recorded by gnammas: Response to comments by Norwick, Pages 400–401

Domínguez‐Villar

Gilsanz²,

Carrasco

2012

Quat. res.

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supporting

confidence: 54%

mentioning

confidence: 56%

Weathering phases recorded by gnammas: Response to comments by Norwick, Pages 400–401

Domínguez‐Villar

Gilsanz²,

Carrasco

2012

Quat. res.

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“…Measuring weathering pits (Dahl 1966;Ives 1978;Nesje and Dahl 1990;Landvik 1994;Dominguez-Villar 2006) or relative heights of protruding rock fragments (André 2002;Nicholson 2009) can provide information about the relative age of the rock surface, however these methods were used for coarse-grained rocks and relatively long time-scales spanning the entire Holocene. Measuring rock surface roughness, rather than single elements of weathering micro-relief, was performed by McCarroll (1992) and McCarroll and Nesje (1996) working on gneiss in the Storbreen marginal zone and Oldedalen in Norway.…”

Section: Introductionmentioning

confidence: 99%

Application of the Handysurf E-35B electronic profilometer for the study of weathering micro-relief in glacier forelands in SE Iceland

Dąbski

2015

Acta Geologica Polonica

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ABSTRACT:Dąbski, M. 2015. Application of the Handysurf E-35B electronic profilometer for the study of weathering micro-relief in glacier forelands in SE Iceland. Acta Geologica Polonica, 65 (3), 389-401. Warszawa.This article presents the results of weathering micro-roughness measurements performed with the use of a Handysurf E-35B electronic profilometer, a new tool in geomorphological studies. Measurements were performed on glacially abraded basaltic surfaces within the Little Ice Age (LIA) glacial forelands of Hoffelsjökull, Fláajökull, Skálafellsjökull and Virkisjökull in Iceland. Results show a statistical increase in micro-roughness in a direction from the glacial termini to LIA moraines. However, a major change in the micro-roughness of basaltic surfaces only occurs during the first 80 to 100 years since the onset of subaerial weathering. Increase in rock surface micro-roughness is accompanied by an increase in weathering rind thickness and a decrease in Schmidt hammer R-values. Micro-roughness measurements with the use of the Handysurf E-35B can provide insights into initial rates of rock surface micro-relief development. The use of this instrument as a relative dating technique is limited to fine-grained rocks and decadal time-scales of weathering because of the limited range of measureable micro-relief amplitude.

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“…Several estimates of shallow weathering pits on granite indicate deepening of pits on the order of a few centimetres per 1000 years to a few centimetres per 10 000 years (Matthes, 1930;Twidale, 1982;Birkeland et al, 1987;Dominguez-Villar, 2006;Hall and Phillips, 2006). Initial estimates of the maximum age of giant weathering pits in Glen Canyon, based on initial exposure of the bedrock by downcutting rates of the Colorado River, indicated ages of 700-800 ka for the highest, oldest pits (Netoff et al, 1995).…”

Section: Discussionmentioning

confidence: 99%

Aeolian activity at a giant sandstone weathering pit in arid south‐central Utah

Netoff

Chan

2008

Earth Surf Processes Landf

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Aeolian abrasional, depositional and deflational features indicate exceptionally strong southwesterly winds in a giant sandstone weathering pit in Grand Staircase Escalante Monument, about 22 km southeast of Escalante, Utah. The 60 m wide, 5-20 m deep pit has developed near the summit of a broad, barren 160-m-high dome on the Lower Jurassic Navajo Sandstone. Unlike other giant weathering pits (10-30 m diameter) in the region, the bedrock floor of this pit is undulatory, and there is a cylindrical, 10-m-high rock pedestal in the centre of the pit. An active dune surrounds the central pedestal and at times has as much as 8 m of local relief. The dune shifts considerably over brief (<1 year) periods of time. Fine-grained (<250 μm) dunal sand on the pit floor is periodically removed by deflation, leaving coarser sand (>250 μm) trapped in the pit. Dunal sand is typically derived from external sources (other than the pit walls and floor). Centimetre to metre-scale abrasional features such as grooves, flutes and dedos occur on the bedrock walls and floor of the pit. These dedos and other streamlined aeolian sculpted host-rock features occur in clusters and typically form in the lee of iron concretions. The dedos are similar to the controversial stalked blueberries on Mars. Above the western rim of the pit there is a 29-m-long, 5-m-wide aeolian groove with a fluted bedrock floor. A 1·2-km-long bedrock valley descends to the southwest from the pit and groove, amplifying southwesterly winds. Data from hand-held anemometers suggest that southwesterly winds can be accelerated 200-300 per cent or more by local topography.

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Early formation of gnammas (weathering pits) in a recently glaciated area of Torres del Paine, southern Patagonia (Chile)

Cited by 25 publications

References 31 publications

Weathering phases recorded by gnammas: Response to comments by Norwick, Pages 400–401

Weathering phases recorded by gnammas: Response to comments by Norwick, Pages 400–401

Application of the Handysurf E-35B electronic profilometer for the study of weathering micro-relief in glacier forelands in SE Iceland

Aeolian activity at a giant sandstone weathering pit in arid south‐central Utah

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