Long-term landscape evolution and denudation rates in shield and platform areas: a morphostratigraphic approach

Abstract

International audienceIn shield and platform areas, various methods are expected to give indications on surface ages, e.g. dating of weathering mantles or reconstruction of the thermal history of upper crust rocks which presently crop out. Radiochronometry and thermochronology were widely used in the last decades to give estimated denudation depths and rates in active orogens as well as in shield and platform areas. Although usefully integrated in the modern geomorphology, these methods sometimes reveal discrepancies with the results of field-based geomorphology. The principles of morphostratigraphy are first presented, and then the paper presents a review of some French researches, which were recently carried out in Québec, north-eastern Brazil and southern Africa. We explain why possible discrepancies occur between the results of physical analyses and morphostratigraphic methods. Finally the paper highlights how significant is to relate the thermal history of each sample to the local geological and geomorphic history

Phanerozoic denudation across the Kola Peninsula, Northwest Russia: implications for long-term stability of Precambrian shield margins

“…Erosion rates over the last 360 Myr on the Kola Peninsula and in adjacent parts of Karelia and Finnish Lapland are similar to estimates for the Canadian Shield of <2.5 m/Myr since 1.7 Ga (Flowers et al, 2006) and 2-8 m/ Myr since the Palaeozoic (Peulvast et al, 2009). There is growing evidence that such low erosion rates are typical of many shield regions (Gunnell, 2003;Peulvast et al, 2008;Beauvais & Chardon, 2013).…”

Stepped Surfaces, Palaeolandforms and Morphostratigraphy: Reconstructing the Long-Term Landscape Evolution Since the Mesozoic

“…As shown by other recognized discrepancies between AFTA results and morphostratigraphic evidence (French Massif Central: Ricordel-Prognon et al 2010;NW England, SW Scotland: Łuszczak et al 2014) and discussed in various publications (Gunnell 2003;Peulvast et al 2008Peulvast et al , 2009Wildman et al 2014), these results remain in the uncertainty domain of the method. They may also reflect a change in the geothermal gradient in the Oligocene, which is the time of volcanism in surrounding regions (Oliveira and Medeiros 2012).…”

Landforms and Landscape Evolution of the Equatorial Margin of Northeast Brazil

“…As shown by other recognized discrepancies between AFTA results and morphostratigraphic evidence (French Massif Central: Ricordel-Prognon et al 2010;NW England, SW Scotland: Łuszczak et al 2014) and discussed in various publications (Gunnell 2003;Peulvast et al , 2009Wildman et al 2014), these results remain in the uncertainty domain of the method. They may also reflect a change in the geothermal gradient in the Oligocene, which is the time of volcanism in surrounding regions (Oliveira and Medeiros 2012).…”

“…Planation surfaces (peneplains, pediplains or etchplains) form valuable set of landmarks for reconstructing landscape evolution and analysing tectonic deformations, but the problem most often encountered concerns their age (Watchman and Twidale 2002;Peulvast et al 2009). This age may be found if a surface is preserved within a stratigraphy, by dating the rocks immediately above and below, but in most cases, exposed surfaces prevail and only a maximum age is yielded by the bedrock upon which they developed.…”