The two-stage concept of landform and landscape development involving etching: origin, development and implications of an idea

Twidale, C. R.

doi:10.1016/s0012-8252(01)00059-9

Cited by 112 publications

(75 citation statements)

References 74 publications

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“…Deep weathering along fracture zones, an irregular weathering front and the formation of core stones controlled by a broadly orthogonal joint system are well known features of long-term, deep weathering of granite and gneiss terrains in temperate and tropical weathering zones (e.g. Anand and Pain, 2002;Kroonenberg and Melitz, 1983;Nesbitt and Markovics, 1997;Ollier, 1984;Shaw, 1997;Thomas, 1966;Twidale, 2002). In glaciated areas, thick saprolite mantles have been preserved below for instance Cretaceous cover rocks, as documented in Minnesota, USA (Setterholm and Morey, 1996) and in southern Sweden (Lidmar-Bergström 1989;LidmarBergström et al 1997;Olvmo et al 2005).…”

Section: Deep Weathering As a Starting Pointmentioning

confidence: 99%

“…In contrast, the etch surface that has appeared from beneath Cretaceous cover sediments has a relative relief of up to 50 m, with locally thick saprolite remnants (Johansson, 1999;Lidmar-Bergström, 1989;. The depth of a weathering mantle and the roughness of the weathering front prior to Pleistocene glaciation depends on a range of factors including lithology, fracture zone density, climate, vegetation, atmospheric chemistry, time of exposure and whether or not a weathering mantle was removed previously and/or covered by other rocks (Kroonenberg and Melitz, 1983;Lidmar-Bergström, 1995;Ollier, 1984;Twidale, 2002). Little is known or understood about weathering processes during the Precambrian but it appears that the mechanisms of producing and retaining Precambrian weathering mantles was very different from Phanerozoic weathering due to lack of terrestrial vegetation and other factors (e.g.…”

Section: Implications For Sub-glacial Bed Roughness Under Modern Ice mentioning

confidence: 99%

“…These studies have shown that the weathering front is typically highly irregular (e.g. Anand and Paine, 2002;Lidmar-Bergström et al, 1997;Lindström, 1988;Shaw, 1997;Thomas, 1966;Twidale, 2002). To examine the glacial vs. non-glacial impact on exposed gneiss terrains as a whole, one would ideally examine an etch surface in a non-glaciated gneiss terrain that is exposed over a large area.…”

Section: Introduction To Non-glaciated Gneiss Terrainsmentioning

confidence: 99%

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Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Krabbendam

Bradwell

2014

Quaternary Science Reviews

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Vast areas previously covered by Pleistocene ice sheets consist of rugged bedrock-dominated terrain of innumerable knolls and lake-filled rock basins -the 'cnoc-and-lochan' landscape or 'landscape of areal scour'. These landscapes typically form on gneissose or granitic lithologies and are interpreted (1) either to be the result of strong and widespread glacial erosion over numerous glacial cycles; or (2) formed by stripping of a saprolitic weathering mantle from an older, deeply weathered landscape.We analyse bedrock structure, erosional landforms and weathering remnants and within the 'cnoc-andlochan' gneiss terrain of a rough peneplain in NW Scotland and compare this with a geomorphologically similar gneiss terrain in a non-glacial, arid setting (Namaqualand, South Africa). We find that the topography of the gneiss landscapes in NW Scotland and Namaqualand closely follows the old bedrock-saprolite contact (weathering front). The roughness of the weathering front is caused by deep fracture zones providing a highly irregular surface area for weathering to proceed. The weathering front represents a significant change in bedrock physical properties. Glacial erosion (and aeolian erosion in Namaqualand) is an efficient way of stripping saprolite, but is far less effective in eroding hard, unweathered bedrock. Significant glacial erosion of hard gneiss probably only occurs beneath palaeo-ice streams.We conclude that the rough topography of glaciated 'cnoc-and-lochan' gneiss terrains is formed by a multistage process: 1) Long-term, pre-glacial chemical weathering, forming deep saprolite with an irregular weathering front;2) Stripping of weak saprolite by glacial erosion during the first glaciation(s), resulting in a rough land surface, broadly conforming to the pre-existing weathering front ('etch surface');3) Further modification of exposed hard bedrock by glacial erosion. In most areas, glacial erosion is limited, but can be significant beneath palaeo-ice stream. The roughness of glaciated gneiss terrains is crucial for modelling of the glacial dynamics of present-day ice sheets. This roughness is shown here to depend on the intensity of pre-glacial weathering as well as glacial erosion during successive glaciations.

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Section: Deep Weathering As a Starting Pointmentioning

confidence: 99%

Section: Implications For Sub-glacial Bed Roughness Under Modern Ice mentioning

confidence: 99%

Section: Introduction To Non-glaciated Gneiss Terrainsmentioning

confidence: 99%

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Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Krabbendam

Bradwell

2014

Quaternary Science Reviews

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“…O intemperismo químico em condições tropicais é fundamental no desenvolvimento dos regolitos (NAHON, 1991;TARDY, 1997) e das formas de relevo (TWIDALE, 2002). Estas condições permitem o desenvolvimento de duas superfícies que limitam os regolitos tropicais, a "Doppelten Einebnungsflächen", uma superior que está em contato com a atmosfera e sujeita a processos erosivos, e outra inferior que limita a ação da água e dos processos de intemperismo químico (BÜDEL, 1957).…”

Section: Introdução Relações Dos Solos Tropicais E Evolução Geomorfolunclassified

Mapeamento Da Superfície Basal Do Manto De Intemperismo Pelo Comportamento Da Resistidade Elétrica Do Distrito Federal

Martins¹,

Júnior²,

Mello³

et al. 2008

Rev. Bras. Geomorfol.

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ResumoEste trabalho apresenta o mapeamento do manto de intemperismo pelo comportamento da resitividade elétrica do Distrito Federal. O levantamento foi realizado entre 2004 e 2005, constituído de 260 sondagens elétricas verticais, que alcançam até 48 m de profundidade aparente, e de 10 estações de monitoramento mensal da resistividade elétrica para avaliação das variações sazonais. Os resultados mostraram que o comportamento da resistividade elétrica depende das características físicas do solo, das alterações de umidade relacionadas com as variações de pluviosidade e da posição na paisagem. Solos rasos apresentam um comportamento de aumento da resistividade elétrica com a profundidade, enquanto solos profundos mostram diversos padrões que se relacionam com o lençol freático, onde a resistividade elétrica é mais baixa. O comportamento da profundidade da camada mais condutiva pode ser relacionado com a superfície basal de etchplanos da região estudada.

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“…In the Maldonado Granite and especially in the Artigas Syenite the opposite occurs. A possible explanation for this abnormal behavior can be found in the two-stage landform development model proposed by Büdel (1957) and described by Twidale (2002). In the first stage, surface rock is affected by the weathering of the materials around the joints, and boulders start to form.…”

Section: Block Sizesmentioning

confidence: 99%

Granitic dimensional stones in Uruguay: evaluation and assessment of potential resources

Demarco

Oyhantçabal

Stein³

et al. 2012

Environ Earth Sci

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In Uruguay commercial granite varieties comprise mafic rocks, granitoids, and syenitoids. There is a long tradition in Uruguay, as well as worldwide, of using dimensional stones in architecture and art, specially granitic ones. Some of the present applications of these dimensional stones are as façade cladding, countertops, and outdoor and indoor floor slabs. The color spectrum of the Uruguayan granitic dimensional stones varies from black to light gray, covering a wide variety of red and pink and minor greenish-gray. The décor of these granitic dimensional stones is mainly determined by their fabric, fundamentally the grain size and the color distribution between the different minerals that compose the rocks. In the present research the most important commercial granites were sampled to analyze their petrography and petrophysical properties. A detailed structural analysis has been performed in several deposits, as well as the application of the software 3D Block Expert for modeling the possible raw block size distribution. Other factors controlling the mining viability of the deposits were also studied (e.g., homogeneity/heterogeneity of color and décor) and the possible reserves were calculated.

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The two-stage concept of landform and landscape development involving etching: origin, development and implications of an idea

Cited by 112 publications

References 74 publications

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Mapeamento Da Superfície Basal Do Manto De Intemperismo Pelo Comportamento Da Resistidade Elétrica Do Distrito Federal

Granitic dimensional stones in Uruguay: evaluation and assessment of potential resources

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