formation and evolution of lateritic profiles in the middle amazon basin insights from radiation induced defects in kaolinite abstract the content of radiation induced defects rids in kaolinite samples originating from lateritic soils and continental detritic sediments of the middle amazon basin brazil is investigated using electron paramagnetic resonance the paleodose registered by kaolinites ranges from 80 to 900 kgy present day dose rates of radiation determined from the whole rock u and th content range between 4000 and 40 000 mgy ka in most samples u and th concentrations are correlated suggesting that u has not been remobilized by lateritization this observation is consistent with the fact that 80 of the total u content is incorporated in resistant minerals such as zircon and ti oxides the heterogeneous distribution of u observed by induced fission tracks mapping makes it possible to neglect the radiation contribution of the u decay chains in the dose rate calculation the interpretation of the measured content of rids in kaolinite is then performed using the calculated present day dose rate and assuming equilibrium in the radioactive decay chains for the sedimentary samples the amount of rids is broadly correlated to the dose rate and provides apparent absolute ages older than 20 ma the rid contents in kaolinites from the lateritic soils provide apparent ages ranging from 10 to 6 ma the high rid content of these lateritic kaolinites shows that their chemical isotopic and crystallographic properties are not representative of present day weathering conditions models assuming the dynamical equilibrium of kaolinites with local physical chemical conditions prevailing in lateritic soils are thus questionable alternatively our findings bring strong support for the use of the isotopic composition of kaolinites to decipher continental paleo climates

deep weathering through time in central and northwestern europe problems of dating and interpretation of geological record abstract upland and shield areas of central and northwestern europe are characterised by an abundance of relict weathering mantles saprolites these saprolites if accurately dated and interpreted may serve as an important complementary source of information about long term environmental history in this paper methods used to establish ages of weathering mantles are reviewed such as stratigraphic and morphostratigraphic dating clay mineral and stable isotope analysis k ar and cosmogenic isotope dating particularly with reference to european examples the record of deep weathering in the mesozoic and cainozoic is examined to explain the peculiarities of the evidence and controls on the changing style of weathering through time weathering has been a continuous process through time but general and local geological conditions have resulted in different ages of preserved mantles an apparent trend from an earlier kaolinitic ferrallitic style of weathering in the mesozoic and early tertiary towards a grussic style by the end of the cainozoic does not only reflect climate change but it is also broadly consistent with tectonic geomorphic history and related changes in land surface stability miocene and plio pleistocene saprolites in particular show that in different geomorphological and lithological circumstances different types of weathering mantles could have evolved

flanking structure development in anisotropic viscous rock flanking structures typically occur in foliated or banded rock and this marked planar structure implies a significant mechanical anisotropy which has not been considered in previous mechanical models of flanking structure development both analytical and numerical techniques are used to investigate the influence of anisotropic viscosity on flanking structure formation reorientation of the principal stress axes in anisotropic materials can cause the sense of shear along a fracture in certain orientations to be opposite to that expected in an isotropic material applying the principle of stress reorientation in anisotropic rocks to natural flanking structures allows a qualitative estimation of the degree of anisotropy during flanking structure formation it is shown that a strong foliation or banding does not necessarily imply a strong mechanical anisotropy which calls for caution in inferring mechanical anisotropy directly from the structure of rocks without additional rheological information

the last ice sheet in north west scotland reconstruction and implications recent models of the last scottish ice sheet suggest that nunataks remained above the ice surface in areas peripheral to the main centres of accumulation this proposition has been investigated on 140 mountains over an area of 10 000 km2 in nw scotland outside the limits of the later loch lomond readvance in this area there is evidence for a single high level weathering limit that separates glacially eroded terrain from higher areas of in situ frost debris this limit occurs at altitudes ranging from 425 to 450 m in the outer hebrides to 950 m on the mainland and is best developed on lithologies that resisted breakdown after ice sheet downwastage interpretation of this weathering limit as a periglacial trimline cut by the last ice sheet at its maximum thickness is supported by 1 joint depth and schmidt hammer measurements that indicate significantly more advanced rock breakdown above the weathering limit 2 a much greater representation of gibbsite a pre late devensian weathering product in the clay fraction of soils above the limit 3 cosmogenic isotope dating of the exposure ages of rock outcrops above and below the limit 4 the sharpness of the limit at some sites and its regular decline along former ice flowlines and 5 shear stress calculations based on the inferred altitude and gradient of the former ice surface reconstruction of the ice surface based on trimline evidence indicates that the mainland ice shed lay near or slightly east of the present watershed and descended northwards from 900 m to ca 550 m at the north coast independent dispersion centres fed broad ice streams that occupied major troughs on skye an ice dome 800 m deflected the northwestwards movement of mainland ice but the mountains of rum were over ridden by mainland ice up to an altitude of ca 700 m the outer hebrides supported an independent ice cap that was confluent with mainland ice in the minches extrapolation of the trimline evidence indicates that most reconstructions of ice extent are too conservative and suggests that low gradient ice streams extended across the hebridean shelf offshore wider implications of this research are 1 that blockfields and other periglacial weathering covers are not all of the same age or significance depending on the resistance of different lithologies to frost weathering 2 that the contrasting degree of glacial modification in the western and eastern highlands of scotland may reflect a former cover of predominantly warm based ice in the former and predominantly cold based ice in the latter and 3 that the approach and techniques developed in this study have potential application for constraining ice sheet models not only in areas peripheral to the main centres of ice accumulation in britain and ireland but also in other mountain areas where nunataks protruded through warm based late pleistocene ice masses

felsenmeer persistence under non erosive ice in the torngat and kaumajet mountains quebec and labrador as determined by soil weathering and cosmogenic nuclide exposure dating soil analyses and terrestrial cosmogenic nuclide exposure dating are combined and a conceptual model proposed to explain altitudinal weathering contrasts in high latitude highlands we show that summits in the torngat and kaumajet mountains were covered by ice during the last glacial maximum and that their felsenmeer cover probably survived multiple glaciation events for similar lithologies soils on felsenmeer covered summits are signigicantly more weathered than those below the felsenmeer limit displaying higher concentrations of crystalline iron amorphous aluminium and silicium extracted with oxalate secondary minerals such as gibbsite and kaolinite occur in felsenmeer soils whereas those formed in till lacked these secondary minerals 10be and 26al exposure ages for nine of ten samples from high elevation tors and autochthonous felsenmeer blocks range from 73 6 to 157 15 ka by contrast ages of 11 4 1 0 and 11 7 1 0 ka are measured for bedrock in the much lower saglek zone indicating extensive 3 m glacial erosion of this zone during late wisconsinan glaciation 26al 10be ratios demonstrate that exposure of the high elevation surfaces was interrupted during at least one cosmic ray shielding event by either ice or till cover in either case late wisconsinan glaciers could not have extensively eroded these surfaces five erratics dated above the saglek zone including one in the felsenmeer zone have exposure ages ranging from 11 6 1 0 to 13 6 0 7 ka this indicates that valley and high elevation ice persisted through the younger dryas chron and provides further evidence that the highlands were not nunataks during the late wisconsinan period

calibration of the speleothem delta function an absolute temperature record for the holocene in northern norway the speleothem delta function sdf provides a new transfer function between the d18o signal of speleothem calcite and surface ground temperature the function is based on physical principles relating d18o of the calcite to thermodynamic fractionation and to the dripwater function which in turn relates d18o of dripwaters to that of the local precipitation and thus to the modification of source water in relationship to the geographical position of the site the sdf must be calibrated against at least two reliable and well dated palaeotemperature points the end product is a reconstruction of absolute cave and surface temperatures the technique is tested using a holocene speleothem from north norway sg93 dated by 12 tims u th dates the reconstructed temperature curve is presented and compared with the gisp2 ice core record and with the historic record in both cases the correlation with sg93 is impressive indicating the validity of the technique

properties and genesis of a soil and the underlying gibbsite bearing saprolite cape breton island canada brownish yellow saprolite derived from granite gneiss is exposed beneath 1 2 m of reddish brown till along a roadcut in the cape breton highlands the strongly acid soil is similar to other podzolic soils of the region except for the presence of gibbsite in the silt and clay fractions in the saprolite feldspar and biotite have weathered to poorly crystalline kaolinite gibbsite and a minor component of iron oxide the poorly crystalline kaolinite does not occur in the overlying till the evidence presented is consistent with the view that the area was covered either by cold based or by stagnant warm based glaciers that eroded the pre quaternary surface only slightly and deposited a thin discontinuous veneer of till derived mainly from local bedrock and saprolite weathering products from the saprolite are probably incorporated commonly in tills of the area during the formation of soils in these tills the poorly crystalline kaolinite and most of the gibbsite are either transformed to other minerals

periglacial features on the margins of a receding plateau ice cap lyngen north norway some features around the perimeter of the balgesvarri plateau ice cap are described sorted stone circles were found beneath a slowly retreating ice margin the basal ice in this area appears to be below the pressure melting point no absolute dating of features was possible but a relative chronology is suggested resume le retrait glaciaire et les manifestations piriglaciaires sur les marges d un glacier de calotte a lyngen norvege du nord on decrit quelques traits caracteristiques du pourtour du glacier de calotte de balgesvarri des sols polygonaux ont ete decouverts a l aval d un front glaciaire en leger retrait la glace de fond dans cette zone semble ttre en dessous du point de fusion correspondant a la pression il n a pas ete possible d etablir une datation absolue de ces manifestations periglaciaires mais on propose une chronologie relative zusammenfassung gletscherriickgang und periglaziale erscheinungen an den riindern einer plateau eiskappe lyngen nordnorwegen einige erscheinungen an der peripherie der balgesvarri plateaukappe werden beschrieben unter einem langsam zuruckgehenden eisrand wurden steinkreise gefunden das eis am untergrund dieser region durfte si ch unter dem druckschmelzpunkt befinden eine absolute datierung der erscheinungen war nicht moglich doch llisst sich eine relative zeitliche abfolge ermitteln

the biogenic methane potential of european gas shale analogues results from incubation experiments and thermodynamic modelling abstract core samples from the lower jurassic posidonia shale lower toarcian wealden black shales both from the lower saxony basin northern germany and from the cambrian ordovician alum shale southern sweden have been investigated for their biogenic gas potential in incubation experiments the sample set represents all stages of thermal maturity from immature to overmature methane and to a higher degree carbon dioxide are generated from all samples by added microorganisms in general overmature samples rr 1 5 show lowest gas generation rates the highest generation rates for produced methane up to 89 mol g 1 day 1 and carbon dioxide 139 mol g 1 day 1 were detected in immature alum shale samples when different hydrocarbon degrading inocula where added whereas the lowest methane production rates were detected in wealden sediments the lightest 13c values for produced methane and carbon dioxide have been detected in posidonia shale samples of oil window maturity such samples are some of the most sensitive for gas generation and exhibit the strongest decreases of hydrogen indices after incubation hydrogeochemical modelling of methane generation fate and behaviour showed that methane formed during the early diagenesis got lost from posidonia shale the mainly investigated shale in this study as the mature posidonia shale is according to the incubation experiments still sensitive for gas generation a production scenario of generically generated methane due to oil degradation is simulated the basic conditions resemble the conditions in the antrim shale in the michigan basin gas production due to dewatering and pressure decrease results in an increase of the gas volumes coupled to a progressive enrichment of carbon dioxide in the produced gas moreover calcite scaling may be the consequence during progressive production similar to the antrim shale in the michigan basin such calcite precipitation has been demonstrated to predominantly occur in natural samples at oil window maturity

stable carbon isotopic ratios of ch4 co2 bearing fluid inclusions in fracture fill mineralization from the lower saxony basin germany a tool for tracing gas sources and maturity abstract the stable carbon isotopic ratios 13 c of methane ch 4 and carbon dioxide co 2 of gas rich fluid inclusions hosted in fracture fill mineralization from the southern part of the lower saxony basin germany have been measured online using a crushing device interfaced to an isotopic ratio mass spectrometer irms the data reveal that ch 4 trapped in inclusions seems to be derived from different source rocks with different organic matter types the 13 c values of ch 4 in inclusions in quartz hosted by carboniferous rocks range between 25 and 19 suggesting high maturity coals as the source of methane methane in fluid inclusions in minerals hosted by mesozoic strata has more negative carbon isotope ratios 45 to 31 and appears to represent primary cracking products from type ii kerogens i e marine shales there is a positive correlation between increasing homogenization temperatures of aqueous fluid inclusions and less negative 13 c ch 4 values of in co genetic gas inclusions probably indicating different mtaturity of the potential source rocks at the time the fluids were released the co 2 isotopic composition of ch 4 co 2 bearing inclusions shows slight negative or even positive 13 c values indicating an inorganic source e g water rock interaction and dissolution of detrital marine calcite for co 2 in inclusions we conclude that the 13 c isotopic ratios of ch 4 co 2 bearing fluid inclusions can be used to trace migration pathways sources of gases and alteration processes furthermore the 13 c values of methane can be used to estimate the maturity of the rocks from which it was sourced results presented here are further supported by organic geochemical analysis of surface bitumens which coexist with the gas inclusion rich fracture fill mineralization and confirm the isotopic interpretations with respect to fluid source type and maturity

weathering characteristics of arctic islands in northern norway the arctic islands of the lofoten vesteralen archipelago in northern norway have a wide distribution of weathered land surfaces commonly located above 250 m with several apparent similarities in order to investigate the characteristics of deep weathering in this region northern langoya and hadseloya were chosen for in depth analyses eight weathering profiles were excavated from various surfaces and the stratigraphies were logged in detail material was collected throughout the weathering horizons and all samples were subsequently analysed for clay mineralogy 40 000 years of subaerial conditions considering the steady surface erosion this figure should be viewed as an absolute minimum age estimate mapping of the superficial sediments and geomorphological features of the study areas has revealed several common morphological features which indicate dominance of glacial and periglacial processes in the areas lying below the lower boundary of blockfields c 250 m the weathering mantles are not a periglacial end product but rather a relict tertiary landform that were modulated by permafrost processes as well as biological processes at later stages the regolith cover constrain the vertical extension of warmbased quaternary ice sheets challenging the notion of a parabolic ice mass consuming every mountain top of lofoten and vesteralen

degree of rock surface weathering as an indicator of ice sheet thickness along an east west transect across southern norway rock surface weathering as reflected by rock surface hardness and roughness was measured at six mountains along an east west transect across southern norway at most sites the results show significant differences in rock surface weathering across the autochthonous blockfield boundary suggesting that the areas above the boundary have been exposed to subaerial weathering for a considerably longer time span that the areas below the results are interpreted as reflecting the surface profile of an asymmetric west centred low gradient ice sheet

autochthonous block fields in southern norway implications for the geometry thickness and isostatic loading of the late weichselian scandinavian ice sheet the consistent geographical and altitudinal distribution of autochthonous block fields mantle of bedrock weathered in situ and trimlines in southern norway suggests a multi domed and asymmetric late weichselian ice sheet low gradient ice sheet profiles in the southern baltic region in the north sea and along the outer fjord areas of southern norway are best explained by movement of ice on a bed of deforming sediment although water lubricated sliding or a combination of the two may not be excluded the ice thickness distribution of the late weichselian scandinavian ice sheet is not in correspondence with the modern uplift pattern of fennoscandia early holocene crustal rebound was apparently determined by an exponential glacio isostatic rise later however crustal movements appear to have been dominated by large scale tectonic uplift of the fennoscandian shield centred on the gulf of bothnia the region of maximum lithosphere thickness

δd δ18o relationships and the thermal history of basal ice near the margins of two glaciers in lyngen north norway les resultats des mesures combinees d et 18 o pour 2 glaciers en norvege du nord sont rapportes ainsi que leurs implications pour l histoire thermique de la glace et les variations observees dans l entrainement des debris

preglacial surface remnants and quaternary glacial regimes in northwestern sweden abstract we present a detailed map of the distribution of preglacial surface remnants in the kebnekaise region of northwestern sweden in this mountain area we discern four important large scale geomorphological units each representing a specific set of erosional agents and formative conditions these are i intact preglacial surface remnants characterized by gentle slopes round summits wide shallow valleys and an absence of rock basins ii preglacial surface remnants showing signs of minor glacial erosion and deposition iii glacially scoured surfaces including glacial troughs iv deep fluvial valleys cut into the preglacial surface the pattern of glacial erosion is explained as the result of three specific modes of glaciation known to have existed during the last 120 000 years and inferred to have repeatedly prevailed during the last 2 75 million years cirque glaciation mountain ice sheets and fennoscandian ice sheets a deep ocean oxygen isotope record of foraminifera from the north atlantic dsdp 607 was used to infer the temporal extent of these modes of glaciation during the last 2 75 million years we interpret the preglacial landscape preservation and the pattern of glacial erosion in terms of the configuration the basal thermal regime and the duration of such glaciation events the average subglacial thermal regime of both ice sheet types was frozen on the uplands and melting in the main valleys where outlet glaciers and ice streams formed the pre glacial landscape is best preserved at intermediate elevations low enough not to have been covered by cirque glaciers and apparently high enough not to have experienced melted bed conditions and subglacial erosion during ice sheet overriding events in a narrow high relief zone along the elevation axis interglacial fluvial erosion was morphologically important the absence of glacial erosion on uplands in this zone allowed fluvial erosion to commence on the same locations during each ice free interval in contrast no persistent fluvial valley pattern could develop in zones subjected to repeated glacial scouring and hence derangement of fluvial patterns

lateral development of coalification in the czech part of the upper silesian coal basin and its connection with gas deposits abstract the degree of coalification is an essential parameter influencing the quality of coal reserves modelling of the development of this parameter in the czech part of the upper silesian coal basin carboniferous mississippian to pennsylvanian lower namurian to westphalian a revealed the distribution of coalification within the basin in all its stratal units the grade of coalification was found in principle to be similar but its intensity in general decreases upwards into the hanging wall because of different areal extents of individual stratal units the degree of coalification is demonstrated on the oldest and areally most extensive unit the pet kovice member the studies and their results presented in this paper are based on more than 29 000 analyses of the dry and ash free volatile matter v daf in coal samples from surface and underground boreholes drilled in the years 1946 2000 three zones of enhanced coalification were distinguished the ostrava p ibor zone the ro nov frenstat zone and the p ibor t sin zone these zones were found to correlate fairly well with the occurrence of gas deposits confined to the weathered carboniferous rock massif or its mantle consequently the degree of coalification does not only determine the quality of coal reserves but may also be used as an auxiliary tool in the search for gas deposits in coal basins

development of n w europe s southern permian gas basin summary the southern permian basin contains over 4 1 10 12 m 3 of recoverable non associated gas most of which is found in early permian rotliegend sandstones the most important source of this gas is carboniferous coal deposited in a proto tethys foredeep basin where the coals were overlain by rotliegend desert sands and by late permian zechstein halite the scene was set for creating important reservoirs for gas deformation of the reservoir and seal to create a trap and the generation and migration of carboniferous gas resulted from the structural history of the area which was shaped in part by underlying crustal blocks and zones of crustal weakness much of this history was related to events most clearly expressed beyond the limits of n w europe in the north atlantic and tethys 1 e w tension which gave rise to the oblique slip induced subsidence of many sub basins within the southern permian basin caused the consecutive creation of the viking central graben system and rockall trough and ended with the crustal spreading of the atlantic ocean and 2 the early mesozoic opening of tethys its cretaceous closure and ensuing alpine orogeny which induced inversion in many areas of the southern permian basin that are now gas bearing

preservation of landforms under ice sheets and ice caps abstract this article addresses the question of whether or not distinct glacial and non glacial landforms can survive beneath ice sheets and ice caps with little or no morphological alteration a review of recent work documents the existence of pre last stadial landforms and landscapes in areas covered by the fennoscandian and laurentide ice sheets a substantial number of independent works indicate that landforms such as eskers drainage channels and boulder fields have escaped destruction despite complete ice overriding during several tens of millenia full preservation of former ground surfaces or delicate landforms probably is linked to areas where the ice sheet base was continuously frozen to its bed larger robust landforms such as large drumlins appear to have been preserved even under wet based conditions in glaciated areas patches preserved under dry cold based conditions provide important windows towards the past showing landscapes that were destroyed in surrounding areas affected by wet based and eroding ice some consequences for the research fields of non glacial geomorphology archaeology and botany include the possibility of subglacial museums and refugia a time space model describes geomorphological access to information from older events in glaciated areas

blockfields old or new evidence and implications from some plateaus in northern norway evidence is presented from investigations on plateau top blockfields in still glaciated regions of north norway pits dug into these blockfields typically show profile depths 0 5 m and sometimes in excess of 1 m analysis of fines shows enrichment in the silt and clay sized fraction suggestive of prolonged chemical weathering chemical alteration of parent material is supported by xrd analysis which identifies a number of clay minerals present in blockfield samples a chemical weathering origin suggests that these plateau top blockfields are features which have considerable longevity in the landscape and have been forming since perhaps tertiary times the original weathering profiles have been destroyed by frost heaving mechanisms protection of the blockfield by cold based ice occurred during periods of glacial coverage

landscape preservation under fennoscandian ice sheets determined from in situ produced 10be and 26al some areas within ice sheet boundaries retain pre existing landforms and thus either remained as ice free islands nunataks during glaciation or were preserved under ice differentiating between these alternatives has significant implications for paleoenvironment ice sheet surface elevation and ice volume reconstructions in the northern swedish mountains in situ cosmogenic 10be and 26al concentrations from glacial erratics on relict surfaces as well as glacially eroded bedrock adjacent to these surfaces provide consistent last deglaciation exposure ages 8 13 kyr confirming ice sheet overriding as opposed to ice free conditions however these ages contrast with exposure ages of 34 61 kyr on bedrock surfaces in these same relict areas demonstrating that relict areas were preserved with little erosion through multiple glacial cycles based on the difference in radioactive decay between 26al and 10be the measured nuclide concentration in one of these bedrock surfaces suggests that it remained largely unmodified for a minimum period of 845 418 461 kyr these results indicate that relict areas need to be accounted for as frozen bed patches in basal boundary conditions for ice sheet models and in landscape development models subglacial preservation also implies that source areas for glacial sediments in ocean cores are considerably smaller than the total area covered by ice sheets these relict areas also have significance as potential long term subglacial biologic refugia

the thermal setting of carboniferous basins in relation to the variscan orogeny in central and western europe abstract the coal basins at the variscan front in western europe provided the first examples of prefolding coalification that was linked to an early high geothermal history the coalification occurred almost contemporaneous with sedimentation and prior to folding the examination of a number of basins from southwestern britain to poland suggests a generalization of this coalification scheme and an extension of it to the inner variscan parts of the rhenish and harz massifs the latter form with the coal basins a repetition of similar troughs from the first flysch deposits up to the last molasse deposits intermontane coal basins of various types in this belt also reveal coalification linked to high geothermies concomitant to variscan sedimentation although sometimes ending during folding conversely the great platforms surrounding the orogen only display normal burial coalification with the exception of isolated structures that were active during and mostly after the variscan period the variscan range was recently interpreted as having been formed under a double influence crustal extensions in the framework of insular arcs and continental collisions that were responsible for folding high paleogeothermal flows are characteristic of the former so they accompanied the formation of subsidence basins

recent advances in coalification studies and their application to geology abstract recent advances in coalification studies since 1970 are reported concerning microscopic methods causes of coalification the coalification process as such and application to geology the degree of coalification rank is mostly determined on the basis of vitrinite reflectance measured on finely dispersed material in rocks for rocks bare of vitrinite other microscopic methods are used such as fluorescence properties of liptinites and graptolite reflectance under incident light or coloration of microfossils like palynomorphs and conodonts in transmitted light the validity of the various methods is discussed maximum rock temperature and its duration are the main causes of chemical coalification reactions heating rates during subsidence influence the attainment of rank equilibrium contact metamorphic coals and natural cokes formed from bituminous coals are characterized by a relatively high reflectance and anisotropy strong frictional heat may cause local increase of rank adjacent to thrust planes graphitization is thermodynamically not possible in nature without pressure and shearing confining pressure retards the chemical coalification reactions tectonic stress especially shearing promotes the increase of maximum reflectance and of anisotropy it commonly leads to bi axial optical properties instead of the more typical uni axial negative geometry of vitrinite in undisturbed coal seams bi axial optical properties are common for vitrinite inclusions in clastic rocks on the basis of combined fluorescence microscopical and geochemical studies bituminization has been recognized as the characteristic part of coalification in the range between sub bituminous and bituminous coal it is characterized by the generation of petroleum like substances which enable the coal to soften and to agglomerate during carbonization hydrogenation properties are favoured by the bituminization process the different liptinite macerals behave differently during coalification and pass coalification jumps at different rank stages a considerable part of total inertinites is formed during early coalification brown coal to sub bituminous coal stage as rank inertinite this new knowledge appears to become important in relation to hydrocarbon exploration diagenetic methane some examples for the application of coalification studies to geology refer to vitrinite reflectance as an indicator of rock diagenesis and metamorphism palaeogeographical and structural history palaeogeothermics and hydrocarbon exploration large scale areal coalification studies in foredeeps and backdeeps of ancient and recent orogens suggest estimations of crustal thicknesses and relations to plate tectonics