sulfur in coals a review of geochemistry and origins geochemical studies of sulfur in coals comprise several major aspects relating to the nature and origin of sulfur in coals including the abundance and distribution of sulfur in coal seams abundance of sulfur in coal lithotypes and macerals characteristics and geochemical significance of sulfur containing organic compounds sulfur isotopic studies relating to the sources of sulfur in coals and sedimentary environments controlling the geochemistry of sulfur in coal a review of the evidence suggests that the variation of sulfur in coals is closely related to the depositional environments of coal seams for low sulfur coal 1 s sulfur is derived primarily from parent plant material for medium sulfur 1 to 3 s and high sulfur 3 s coals there are two major sources of sulfur 1 parent plant material and 2 sulfate in seawater that flooded peat swamps abundances of sulfur in coal are largely controlled by the degree of seawater influence during peat accumulation and by postdepositional changes diagenesis in high sulfur coals seawater sulfate diffuses into the peat which is subsequently reduced by bacteria into hydrogen sulfide polysulfides and elemental sulfur reaction of hydrogen sulfide with ferrous iron generates fine pyrite crystals and mackinawite fes0 9 mackinawite reacts with elemental sulfur to converts to greigite fe3s4 and then to framboidal pyrite the reduced sulfur species in the peat hydrogen sulfide elemental sulfur and polysulfides react with the organic matter to form organic sulfur compounds during coal diagenesis nodular pyrite forms permineralized peat was formed during diagenesis which contains appreciable fraction of pyrite after coal is solidified pyrite can deposit in the cleats from circulating groundwater epigenetic pyrite veins may be deposited from basinal fluids thus pyrite forms during various stages of coal formation from peat to coal as well as late epigenetic activity the relationships between sulfur abundance in coal seams and depositional environments of coals were reviewed for cases from the u s china u k germany hungary turkey indonesia and brazil in most cases low sulfur coals formed in a fluvial environment and high sulfur coals were deposited in seawater influenced environments there are exceptions for example turkish lignites formed in freshwater environments are high sulfur sulfur sources other than seawater are needed for these high sulfur coals the superhigh organic sulfur shos coals are highly enriched in organic sulfur but depleted in pyritic sulfur the shos coals were deposited in sulfur rich iron poor environments such as carbonate platforms or in an iron poor and clastic starved environment in which algae accumulate speciation of organic sulfur compounds in coal appears to be related to coal rank thiophenic compounds are more abundant in bituminous coal and anthracite than in low rank coals

research on the fracture structure and activity of the qinling mountains thrust nappe system in western hubei the western hubei section of the liangyun fault is an important structural belt of the southern qinling mountains thrust nappe system as the significant activity of the liangyun fault since the qu

teleseismic virtual source imaging of the basin structures in the three gorges region china abstract the teleseismic virtual source reflection tvr profiling method uses free surface reverberations of the teleseismic p wave ppdp phase data to produce an image of the subsurface upper crustal reflections can be retrieved by deconvolving the average source wavelet for all stations in an array from the teleseismic p wave coda recorded at each station of the array we present a case study for which we construct the upper crustal tvr images in the three gorges tg region china based on a dataset of four teleseismic events recorded by a linear regional array of geophones the features in the resultant tvr images such as the geometry of the zigui and sichuan basins correlate well with the surface geologic observations at the tg region we identified reflectors in the zigui and sichuan basins that indicated their maximum depths at 2 6 and 7 km respectively the basin structure is consistent with the compressional stress regime that is evident by two reverse faults in the region the gaoqiao fault corresponding to a basement ridge in the tvr image that separates the two basins and the xiannvshan fault online material figures and discussion on choosing source length

a sequence stratigraphic investigation of a miocene formation supported by coal seam quality parameters central paratethys n hungary abstract a stratigraphic investigation of the coal bearing miocene siliciclastic succession in structurally dissected basins of northern hungary was performed based on log correlations and is supported by coal petrology and sulphur data the succession represents the karpatian lower order global eustatic cycle of the paratethys and was dissected into six higher order sedimentary sequences sq 1 sq 6 the coal bearing strata in the nograd basin sq 1 sq3 represent a lowstand systems tract lst prior to the karpatian relative sea level rise the transgressive systems tract tst starts with the oncophora beds sq 4 accumulated above a regional unconformity and containing coal beds in the borsod basin the tst is superimposed by tectonically forced higher order lowstand systems tracts sq 5 sq 6 containing coal beds only in the relatively elevated east borsod basin to support the sequence stratigraphic model the average maceral and sulphur content of coal seams was also interpreted the low sulphur 0 47 content in sq 1 reflects the lowstand environment determined by continental derived freshwater input transitional sulphur contents 0 66 1 02 in the late lowstand sq 2 and sq 3 indicate occasional saline invasions related to relative sea level rises high 2 3 2 6 sulphur contents in the tst sq 4 were caused by regular seawater inundations into the lagoon while decreasing sulphur contents in sq 5 and sq 6 2 28 2 09 reflect the increasing rate of freshwater income in association with the stepwise basinward shifts of the shoreline and the lagoonal facies within the lower to middle miocene salgotarjan lignite formation the analysis of coal seams contributed to the interpretation of relative sea level changes and the sequence stratigraphic context facilitated both the interpretation of sulphur content in coals and the reliable correlation of coal seams

paleoclimate controls on late paleozoic sedimentation and peat formation in the central appalachian basin u s a abstract in the central appalachian basin at least two major climate changes affected sedimentation during the late paleozoic stratigraphically these two changes are indicated by the distribution of coal beds the variation in coal quality and the variation in rock lithologies in latest mississippian or earliest pennsylvanian time the climate changed from dry seasonal tropical to ever wet equable tropical the equable climate prevailed into the middle pennsylvanian influencing the morphology and geochemistry in peat forming environments many of the peat deposits which formed under the equable climate were probably domed raised bogs low concentrations of dissolved solids in peat formation water resulted in low buffering capacity organic acids caused acidic ph another climate change occurred in late middle pennsylvanian time when evapopation periodically exceeded rainfall resulting in an increase of both dissolved solids and ph 4 to 7 in surface and near surface water throughout the remainder of the pennsylvanian the surfaces of peat deposits were probably planar not domed water in peat forming and other depositional environments became more nearly neutral the coal beds derived from these peats are highly variable in both ash and sulfur contents drier or more seasonal climates are also indicated by sequences of 1 calcareous sandstone and shale 2 nonmarine limestone that shows shallow water and subaerial exposure features and 3 calcareous paleosols that have caliche characteristics our data and observations indicate that physical depositional environment models for the origin of coal do not adequately explain variations in mineral matter content and composition in commercial quality coal beds in the central appalachian basin stratigraphic variation in mineral matter in coal beds and in syngenetic and early diagenetic minerals in rocks associated with the coal beds appears to be better explained by changes in geochemical conditions of nonmarine sedimentation paleoclimate was a principle control on these geochemical conditions

an overview of the earth crust under china abstract we assess the results of a number of deep seismic soundings performed in china over the last few decades and study the variations in crustal structure in 18 tectonic units comprised of three platforms and 15 fold systems thickness data on 344 mesozoic cenozoic sedimentary basins as well as data on moho depth are collected in order to discuss the relationship between the thickness of the basins and the average thickness of the consolidated crust in each tectonic unit the degree of mirror image symmetry between mesozoic cenozoic sedimentary basins and the uplifting topmost parts of the mantle is herein analyzed using deep geophysical data on sedimentary basins by applying standard methods of least squares analysis to both datasets we have obtained both the average thickness of the consolidated crust and the mirror image symmetry factor for every platform and tectonic fold system thereby allowing us to explore the correlation between the depths of the bottom of the sedimentary basins and the top of the uplifting mantle the thickness of the consolidated crust in china is found to be between 20 and 63 km following a pattern of gradual thickening from east to west expressed in terms of spatial seismicity and the concentration of seismic energy and according to the sharing out of earthquake hypocenters in the top 80 km of the earth the rheology of the area does not appear to suit the widely accepted jelly sandwich model for the continents which does not seem to be entirely valid in china the findings on the mirror image symmetry factor show that this parameter varies mainly in the range 0 5 to 1 8 compared with each other tectonic unit most of the tectonic systems in china appear to be isostatically compensated tibet is an exception in that the symmetry factor is positive for the gangdise nyainqentanglha 1 0 and himalayan 0 1 fold systems implying that these tectonic zones are far from being in the isostatic equilibrium of the other regions we have also analyzed the zoning characteristics through the logarithmic relationship ln r ln h a using the average thickness of the consolidated crust and the absolute value of the symmetry factor the key finding is that regardless of geographical location all the values of r h a for those sedimentary basins in which oil gas reservoirs have to date been found fall into the narrow range of values between 19 38 and 37 40 there is some appeal in a possible relationship involving the ratio of crustal thickness to symmetry factor more so when the results obtained appear to suggest a prognostic tool for exploratory practice in relation to oil gas reservoirs

present day crustal deformation in china constrained by global positioning system measurements global positioning system gps measurements in china indicate that crustal shortening accommodates most of india s penetration into eurasia deformation within the tibetan plateau and its margins the himalaya the altyn tagh and the qilian shan absorbs more than 90 of the relative motion between the indian and eurasian plates internal shortening of the tibetan plateau itself accounts for more than one third of the total convergence however the tibetan plateau south of the kunlun and ganzi mani faults is moving eastward relative to both india and eurasia this movement is accommodated through rotation of material around the eastern syntaxis the north china and south china blocks east of the tibetan plateau move coherently east southeastward at rates of 2 to 8 millimeters per year and 6 to 11 millimeters per year respectively with respect to the stable eurasia

organic geochemistry in pennsylvanian tidally influenced sediments from sw indiana abstract tidal rhythmites are vertically stacked small scale sedimentary structures that record daily variations in tidal current energy and are known to overlie some low sulfur coals in the illinois basin tidal rhythmites from the pennsylvanian brazil formation in indiana have been analyzed sedimentologically petrographically and geochemically in order to understand the character and distribution of organic matter om preserved in an environment of daily interactions between marine and fresh waters the concentration of organic matter toc ranges from traces to 6 9 and sulfur rarely exceeds 0 1 in individual laminae angular vitrinite is the major organic matter type accounting for 50 90 of total om the c s ratio decreases as the vertical distance from the underlying coal increases a decreasing c s ratio coupled with decreases in pr ph pr n c17 ph n c18 ratios and a shift of carbon isotopic composition towards less negative values suggest an increase in salinity from freshwater in the mudflat tidal rhythmite facies close to the coal to brackish marine in the sandflat tidal rhythmite facies further above from the coal within an interval spanning one year of deposition toc and s values show monthly variability on a daily scale toc and s oscillations are still detectable but they are of lower magnitude than on a monthly scale these small scale variations are believed to reflect oscillations in water salinity related to tidal cycles

coals of the brazil formation pennsylvanian in indiana observations of correlation inconsistencies and their implications the coals of the upper part of the mansfield brazil and the lower part of the staunton formations atokan and desmoinesian pennsylvanian in indiana illinois basin are characteristically thin and discontinuous as a result problems with correlation and identification of the seams have persisted for both researchers and industry these discrepancies affect coal exploration mine planning and subsequently coal fired utilities this study presents exploration and operational examples demonstrating some of the correlation problems associated with the coals of the brazil formation and the upper block and lower block in particular and the surrounding upper part of the mansfield formation and lower part of the staunton formations based on exploration boreholes mine scale observations and coal quality and petrographic data this study suggests that 1 the coal mapped as the upper block coal member of clay county may in fact be the same seam as the lower block coal member of daviess county and 2 the lower block coal of clay county is not present south of the switz city area of central greene county in

block coals from indiana inferences on changing depositional environment significant differences in coal petrography palynology and coal quality were found between the lower block and upper block coal members brazil formation pennsylvanian in daviess county indiana the lower block coal member ranges in thickness from 51 to 74 cm and the upper block coal member ranges from 20 to 65 cm average sulfur content and ash yield of the lower block coal 0 98 7 65 are lower than in the upper block coal megascopically the coals show distinct differences the lower block is a banded coal with numerous thin fusain horizons and a thin clay parting in the lower third of the seam the upper block coal has a dulling upward trend with a bright clarain found at the base that grades into a clarain and then into a durain in the upper portion of the seam vitrinite content of the lower block coal ranges from 63 to 78 with the highest vitrinite content found in the middle portion of the seam in the upper block coal vitrinite content ranges from 40 to 83 with the highest values found in the lower part of the seam ash yield is higher in the upper part of the upper block coal reaching up to 40 the lower block coal is dominated by lycopod trees and tree ferns the upper block coal shows marked differences in spore assemblages between lower and upper parts of the seam the lower half is dominated by large lycopod trees and tree ferns similar to the lower block coal the upper half is dominated by small lycopods mainly densosporites and radiizonates these differences between the lower block and upper block coal members are significant correlation tools applicable to mining exploration and chronostratigraphy

significance of shallow seismic reflection ssr and ground penetrating radar gpr profiling on the modern coast line history of the bedre area egirdir lake isparta turkey abstract lake level changes and settlement places constitute the main problems in controlling the coastal environment along the egirdir lake sw turkey the quaternary geology in the bedre coast was studied based on shallow seismic reflection ssr survey ground penetrating radar gpr profiles and the data derived from boreholes and investigations in the field thus six seismic and five radar facies were determined respectively the geological units from the basement rock to the holocene deposits were imaged by the ssr technique gpr technique is used for the shallower part ranging from the ancient to the modern lacustrin sediments the quaternary lake level changes borehole seismic and radar data indicate that a pond with a connected to the lake around the bedre area existed in the last century sand barriers climate topographical elevation and erosions of the basement rocks control the sedimentation of the back barrier of the coastal line marsh muddies and ancient beach sands are the main sediments of the pond area from the profiles ancient buried sand barriers were also seen in the lake side in our view as the previous lake level dropped from the highstand the ancient sand barrier was formed which divided the lake and the pond and isolated a small inland lake which lies 4 m below the level of the coastal barrier for agricultural purposes artificial man made constructions were done on the barrier and channels thus dry agricultural land appeared in the last 50 years on the pond side

a test for the analogy of tropical domed peat deposits to dulling up sequences in coal beds preliminary results abstract megascopic and microscopic characteristics of a domed peat deposit in sarawak malaysia were examined to test their analogy to dulling up sequences in low ash coal beds preliminary petrographic results show high concentrations 95 of vitrinite precursor material for all peat types but that fibrous peats in the upper central portion of the deposit contain more preserved plant material than peats toward the base and margins which although more decomposed contain large fragments 5 150 cm of wood these results present contradictory evidence in support of a dulling up model and suggests that modern tropical peat domes are perhaps poor petrographic analogues for dulling up sequences this deposit would produce an all bright coal seam with bright vitrain bands of variable thickness and amount set in bright high vitrinite matrix

3 d tomographic static correction a 3 d tomographic inversion approach based on a surface consistent model for static corrections is presented in this paper direct reflected and refracted waves are used simultaneously to update the near surface model we analyze the characteristics of the first break traveltime in complicated low velocity layers to improve the accuracy for the velocity model the various first break times from direct reflected and refracted waves are considered for model inversion a fractal algorithm which overcomes the error caused by wavelet shape differences is applied to pick first breaks it also overcomes the leg jump of refractions the method can pick a large number of first breaks automatically the raypaths and traveltimes are calculated with a 3 d ray tracer that does not increase computation time for complicated geological models our method can determine the raypath associated with minimum traveltimes regardless of wave mode direct refracted or reflected we use a least squares approach in conjunction with a matrix decomposition to reconstruct a 3 d velocity model from the actual first break times obtained from 3 d data finally long and short wavelength static corrections are calculated concurrently based on the reconstructed velocity profile the method can be applied to wide line profiles crooked lines and 2 d and 3 d seismic survey geometries the results applied to a real 3 d data example indicate that the 3 d tomographic static corrections are effective for field data

sulfur variability and petrology of the lower block coal member pennsylvanian in southwest indiana abstract the lower block coal member pennsylvanian atokan westphalian c is an economic low to medium sulfur low ash coal resource in the illinois basin sulfur content is generally low averaging 1 0 in the study area but varies over short distances higher sulfur areas occur as isolated pods and epigenetic pyrite increases significantly in the upper third of the selected columns in higher sulfur areas sulfur variations cannot be predicted by typical geologic characteristics such as roof lithology seam thickness or seam elevation petrographic analysis shows that pyrite is generally associated with brighter microlithotypes except in higher sulfur areas where infilling pyrite forms are associated with inertite higher sulfur areas reflect the water chemistry of the paleomire during and shortly after peat accumulation locally abundant pyrofusinite provided additional pore space for pyrite precipitation

crustal structure across the three gorges area of the yangtze platform central china from seismic refraction wide angle reflection data abstract we present active source seismic data recorded along a 300 km long profile across the three gorges area of the western yangtze platform central china from west to east the profile crosses the zigui basin huangling dome and jianghan basin the derived crustal p wave velocity structure changes significantly across the tongchenghe fault that lies at the transition from the huangling dome to the jianghan basin west of the tongchenghe fault beneath the zigui basin and the huangling dome we observe a 42 km thick crust of relatively low average velocity 6 3 6 4 km s in contrast east of the tongchenghe fault beneath the jianghan basin the crust is only 30 km thick and has a high average velocity 6 6 6 7 km s a west east variation in crustal composition along the tongchenghe fault is also inferred west of the fault p wave velocities suggest a felsic composition with an intermediate layer at the base of the crust whilst east of the fault felsic intermediate and mafic crustal layers are apparent our results suggest that the crust beneath the jianghan basin has been thinned by rifting accompanied by intrusion of the lower crust by mafic dikes and sills the west to east division of the crust in the three gorges area coincides with first order geophysical contrasts in gravity topography crustal and lithospheric thickness

lower silurian hot shales in north africa and arabia regional distribution and depositional model abstract lowermost silurian organic rich hot shales are the origin of 80 90 of palaeozoic sourced hydrocarbons in north africa and also played a major role in petroleum generation on the arabian peninsula in most cases the shales were deposited directly above upper ordovician peri glacial sandstones during the initial early silurian transgression that was a result of the melting of the late ordovician icecap deposition of the main organic rich shale unit in the north african arabian region was restricted to the earliest silurian rhuddanian stage acuminatus atavus and probably early cyphus graptolite biozones during this short period 1 2 m y a favourable combination of factors existed which led to the development of exceptionally strong oxygen deficiency in the area in most countries of the study area the post rhuddanian silurian shales are organically lean and have not contributed to petroleum generation the distribution and thickness of the basal silurian hot shales have been mapped in detail for the whole north african region using logs from some 300 exploration wells in libya tunisia algeria and morocco in addition all relevant accessible published and unpublished surface and subsurface data of the lower silurian shales in north africa and arabia have been reviewed including sedimentological biostratigraphic and organic geochemical data the lowermost silurian hot shales of northern gondwana are laterally discontinuous and their distribution and thickness were controlled by the early silurian palaeorelief which was shaped mainly by glacial processes of the late ordovician ice age and by pan african and infracambrian compressional and extensional tectonism the thickest and areally most extensive basal silurian organic rich shales in north africa occur in algeria tunisia and western libya while on the arabian peninsula they are most prolific in saudi arabia oman jordan and iraq the hot shales were not deposited in egypt which was a large palaeohigh at that time the depositional model presented may help in better understanding the source potential of the basal silurian shales in less explored regions of north africa and arabia including morocco northern niger and the kufra basin in southeast libya

application of palynology and petrography in the correlation of the pennsylvanian brazil and staunton formation coals in the eastern part of the illinois basin abstract the coals of the brazil and the lower part of the staunton formations atokan and early desmoinesian pennsylvanian in indiana illinois basin are typically thin and discontinuous as a result both researchers and the industry have experienced problems with coal bed identification and correlation the discrepancies in coal nomenclature and frequent miscorrelations affect coal exploration mine planning and communication between mines and customers our previous study based on exploration boreholes mine scale observations and coal quality and petrographic data from daviess greene and clay counties indiana suggested that the coal mapped as the upper block coal member of clay county might be the same seam as the lower block coal member of daviess county this study is an extension of the previous research conducted farther south to pike warrick and spencer counties indiana in the southern part of indiana correlation of these late atokan and early desmoinesian coal beds is even more difficult because of the absence of well defined marker horizons and limited mining and subsurface well data although palynological and coal petrography data generally correspond these data alone cannot resolve the correlation of the coal beds in this southern region with the coals of clay or greene counties and they must be supplemented with the analysis of associated limestones the ability to accurately identify the perth limestone member which occurs close to the buffaloville coal member of the brazil formation and the holland limestone member which occurs higher up in the staunton formation will help to distinguish between brazil and staunton formation coals

basin centered gas systems basin centered gas systems bcgss are potentially one of the more economically important unconventional gas systems in the world in the united states they contribute as much as 15 of the total annual gas production these regionally pervasive gas accumula tions are different from conventionally trapped accumulations in several respects the basin centered gas accumulations bcgas associated with bcgss are typically characterized by regionally pervasive accumulations that are gas saturated abnormally pres sured commonly lack a downdip water contact and have low permeability reservoirs the accumulations range from single isolated reservoirs a few feet thick to multiple stacked reservoirs several thousand feet thick two types of bcgss are recognized a direct type characterized by having gas prone source rocks and an indirect type characterized by having liquid prone source rocks during the burial and thermal histories of these systems the source rock differences between the two types of bcgss result in strikingly different characteristics that impact exploration strategies the majority of known bcgas are the direct type exploration activity for bcgas is in the early stages and thus far has been focused in north america in other parts of the world concepts of basin centered gas systems are poorly known and exploration activity focused on basin centered gas accumulations is minimal

african oil past present and future eighty three sedimentary basins cover 50 of africa s 11 7 million square miles hydrocarbons are produced from 20 of these basins and a further 13 have non produced hydrocarbons yet of all the basins only 18 have been explored through a semi mature stage this paper presents a simplified classification of basins in africa africa s recoverable hydrocarbon reserves of 100 billion barrels of oil equivalent account for 7 of the world s total proven reserves this paper documents that reserve base s development through time together with the significant discoveries oil and gas occurrences and the play potential of each basin type are systematically described with examples demonstrating exploration problems regarding particular basins africa contains an abundance of unexplored sedimentary basins that should demonstrate relatively high success ratios but which must be evaluated with some caution because of political fiscal and logistical concerns end page 339

coal facies studies in the eastern united states coals in the eastern united states east of the mississippi river have been the subject of a number of coal facies studies going back to the 19th century such studies would not necessarily fall within a strict modern classification of coal facies studies but if a study encompassed some aspects of paleobotany palynology petrology geochemistry or sedimentology we assumed that some data and interpretations may be of use in evaluations of the facies references are presented as a guide for further research with annotation in the tables

avoiding pitfalls in shallow seismic reflection surveys acquiring shallow reflection data requires the use of high frequencies preferably accompanied by broad bandwidths problems that sometimes arise with this type of seismic information include spatial aliasing of ground roll erroneous interpretation of processed airwaves and air coupled waves as reflected seismic waves misinterpretation of refractions as reflections on stacked common midpoint cmp sections and emergence of processing artifacts processing and interpreting near surface reflection data correctly often requires more than a simple scaling down of the methods used in oil and gas exploration or crustal studies for example even under favorable conditions separating shallow reflections from shallow refractions during processing may prove difficult if not impossible artifacts emanating from inadequate velocity analysis and inaccurate static corrections during processing are at least as troublesome when they emerge on shallow reflection sections as they are on sections typical of petroleum

drowning of a nearshore peat forming environment atane formation cretaceous at asuk west greenland sedimentology organic petrography and geochemistry abstract the cretaceous atane formation nuussuaq basin west greenland is dominated by non marine sandstones shales coals and delta front deposits marine incursions are frequent however and near asuk disko a coal seam is encased in shallow marine deposits notable changes in both petrography and geochemistry occur through the seam at the base and top of the seam the proportions of inertinite and liptinite increase at the expense of the huminite maceral group and within all maceral groups proportions of detrital macerals increase geochemical changes include systematic variations in toc ts n alkane acyclic isoprenoid aromatic hydrocarbon and di and triterpenoid biomarkers which include a number of rearranged hopanes and hopenes and six isomers of 28 30 bisnorhopane the variations reflect diagenetic changes related to the availability of clay as well as changes in depositional environment going from shallow marine conditions through fresh water mire back to open water conditions and to the eventual return of shallow marine conditions shown by the occurrence of delta front deposits containing ophiomorpha nodosa trace fossils c 50 cm above the top of the coal seam

determination of contributors to coal seam structure in sullivan county indiana abstract the structure of coal seams in sullivan county indiana is subject to local variability controlled by differential compaction underlying silurian reefs contribute to the maximum vertical variation and the underlying mississippian unconformity surface controls the distribution of the most extensive and mappable structural features the vertical magnitude orientation and lateral extent of the features should be considered during mine layout potential underlying silurian reefs can be distinguished from other contributors to coal seam structure for the purposes of petroleum exploration

paleoclimate controls on stratigraphic repetition of chemical and siliciclastic rocks climate is a primary control on sediment flux from continental sources into sedimentary systems in warm climates siliciclastic input is greatest under highly seasonal rainfall nonseasonal conditions favor formation of end member chemical rocks perennially wet climates are conducive to coal formation whereas dry climates produce carbonates and or evaporites stratigraphic repetition of siliciclastic and chemical rocks therefore appears to be related to paleoclimate cycles as well as to transgressive regressive events and tectonics