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Marie-Françoise André Samuel Etienne Denis Mercier Franck Vautier Olivier Voldoire 《Environmental Geology》2008,56(3-4):677-688
A first application of geomorphological methods to the assessment of sandstone deterioration at Angkor is presented. Damage diagnosis was carried out on the first eastern tier of the central pyramid of the 1,000 year-old Ta Keo temple. Methods combine field observations and measurements at 230 sampling points, high-resolution lasergrammetry and stereophotogrammetry on a 2-m2 test zone, and SEM observations. The first results indicate that decay operates through a synergistic combination of weathering phenomena dominated by scaling and solution, and exhibits a high spatial variability. Percentages of deteriorated surfaces vary from 17.6 to 93.8%, and average stone recession values from 0.00 to 2.71 cm (minimum) and 0.34 to 5.49 cm (maximum). On the test-zone, stereophotogrammetry and 3D-mapping of the present and reconstructed initial states using lasergrammetry indicate that erosion scars up to 6 cm deep have formed since 1963. On the whole, the amount of deteriorated surfaces more than tripled between 1963 and 2008. The degree of implication of salts in stone decay remains unclear for most efflorescences are composed of calcite (CaCO3), with secondary importance of barite (BaSO4) and gypsum (CaSO4·2H2O). Future prospects aim to evaluate the impact on stone decay of the clearing out of the temple from the forest in the 1920s. 相似文献
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Marie-Françoise Bonifay 《Quaternary Research》1980,14(2):251-262
This study is the first test of correlation between the results obtained on the large Plio-Pleistocene European faunas and the main climatic stages (cold as well as temperate) demonstrated in marine isotopic records. In particular, there are cold stages which often explain the disappearance of some species, as well as climatic events that promote the substitution of some species by other groups. A rather evident parallelism appears between the European succession of large faunal associations and paleoclimatic stages revealed in oceanic areas, but some discordance occurs in the later periods. Faced with the great diversification of the Quaternary faunas, probably due to the multiplicity of climatic environments, and with global information from oceanic records, only local biostratigraphic studies will allow precise reconstruction of the different biotopes. 相似文献
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Weathering of sandstone lotus petals at the Angkor site: a 1,000-year stone durability trial 总被引：1，自引：1，他引：0
Marie-Françoise André Bruno Phalip Olivier Voldoire Franck Vautier Yves Géraud Mhammed Benbakkar Christophe Constantin Fabienne Huber Gilles Morvan 《Environmental Earth Sciences》2011,63(7-8):1723-1739
This article is based on field investigations carried out at Ta Keo and Banteay Srei temples (Angkor, Cambodia), which have similar environmental histories and display the same recurrent decorative pattern (lotus petal) in three different sandstone lithotypes. Based on two original scales of mechanical and chemical weathering, the degree of deterioration of c.2000 sandstone petals was visually assessed, resulting in the proposal of a durability scale. An explanatory scheme was provided, based on laboratory analyses of stone materials (ICP-AES, XRD, SEM-EDS, polarizing microscopy and mercury injection). The key drivers of sandstone durability are both mineralogical and petrophysical. The remarkable preservation of the pink sandstone is due to the quartzose nature of its clasts, the non-swelling clay content of its abundant matrix (kaolinite) and its porosity structure (large connected pores and probable non-connected porosity). The overall good preservation of the green sandstone is due to its extremely low porosity and specific surface area, associated with its strong cementation. The severe deterioration of the grey sandstone is due to its laminated structure (oriented biotites), the susceptibility to hygric swelling and solution of its binding agents (chlorite/smectite and calcite) and its porosity structure, which evolves during a two-stage weathering sequence. The first stage is characterized by a bimodal porosity due to the partial clogging of macropores by swelling clays, and the second stage by a substantial increase in porosity and the penetration of salts (barite and anhydrite). Conversely, oxidation phenomena associated with weathering can lead to a drastic reduction of porosity. 相似文献
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Jean-François Oehler Marie-Françoise Lequentrec-Lalancette 《Comptes Rendus Geoscience》2019,351(1):1-9
Marine magnetic data extracted from the geophysical database of the SHOM (the French Hydrographic and Oceanographic Service) offer a first overview of the magnetic offshore environment in the Gulf of Saint-Malo (Brittany, France). Their cross-interpretation with available geological and geophysical knowledge provides a new land and sea model of the western part of the Late Proterozoic North Armorican Cadomian belt. In particular, marine data exhibit relatively intense and heterogeneous magnetic signatures, mainly interpreted as the offshore prolongation of plutonic, volcanic, and metamorphic geologic formations recognized onshore. Imprints of major faults well known on land can be inferred at sea from discontinuities and shifting of magnetic anomalies or followed by high-resolution bathymetry. An impressive and dense dolerite dyke swarm propagated on more than 50 km from the coast seaward. Dykes are characterized by both 1-km-deep and less than 50-m-deep superficial magnetic responses, suggesting the existence of deeply rooted super dykes to which individual small-scale structures are connected. 相似文献
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AbstractSubsidence analysis is used here to get a better understanding of the Eo-Cimmerian continental accretion to Eurasia of a block (the Iran Block) of Gondwanian origin. The drift of the block from Gondwana to Eurasia is classically considered as a late Triassic event but the lack of unquestionable age evidence leads to investigate the whole Permian to Jurassic history. Indeed, the subsequent Alpine deformation along the proposed suture that should mark the Eo-Cimmerian collision forbids to characterize the collisional event without ambiguity. Moreover, the Iran block is presently represented by different continental slivers that are disconnected from each other, being in places separated by Cretaceous ophiolites, and it makes unclear if one or several blocks should be taken into account. Subsidence analysis is introduced to solve the problem, in the hope that the sedimentary history in any part of the slivers has registered important crustal events such as breakup and collision and that the few well-preserved stratigraphic sections bear the corresponding subsidence signals. Subsidence analysis is thus applied to geologically disconnected objects in a manner that departs from its traditional use in basin analysis. However, as it introduces quantified data on the behaviour of the crust in response to tectonics, it was shown to be an efficient tool in sorting out the major events amongst various local evidences for crustal unstability. Major results are: – dating the breakup as Early Permian and collision as Middle Triassic; – showing that the accretion of the Iran Block to Eurasia was accompanied by a new breakup that formed a passive margin in Nayband to the Southeast, in contrast to the new active margin that was established along the Abadeh, south-western side; – emphasising the tectonic instability that controlled the continental Jurassic deposits upon the new continent before stabilisation was reached during Late Jurassic-Early Cretaceous times. 相似文献
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