pt group metal anomalies in the lower mississippian of southern oklahoma four iridium pt group elements abundance anomalies have been found within a stratigraphic span of 3 m in the lower mississippian of oklahoma in ascending order the first anomalies occur at the top of the woodford shale ir 0 25 ppb pt 48 ppb os 7 5 ppb and au 18 ppb the anomalies occur just below a redox boundary and we suspect that the enriched elements were precipitated from sea water that contacted the organic and sulfide rick black shale two more anomalies occur in the welden limestone the lower one weak and the upper one strong ir 0 42 ppb pt 50 ppb os 0 075 ppb and au 0 14 ppb the excess ir and pt also co as and ni might have been enriched from sea water by bacteria at these two horizons a 70 cm thick interval of excess heavy siderophiles occurs in the overlying caney shale the interval contains the following peak concentrations ir 0 56 ppb pt 150 ppb os 0 51 ppb co 725 ppm and ni 1450 ppm these elements vary in proportion to the al clay content and we suspect that they were carried in with detrital material from erosion of ultramafic source rocks we found no evidence of microspherules or shocked mineral grains in any of these anomaly zones

reinterpretation of moraines at 4000 m in the mount kenya afroalpine area abstract moraines at 4000 m on mount kenya have been assigned different radiocarbon ages ranging from the late pleistocene to the mid holocene by various investigators some workers consider that these moraines result from advances of holocene ice out of local cirques and still others from stillstand following recession of late pleistocene glaciers new evidence presented here shows that moraines at 4000 m a s l are the result of stillstand following recession of liki wurm wisconsinan ice on mount kenya the minimum radiocarbon ages of bog and lacustrine sediments associated with several moraines in teleki hausberg and liki north valleys are approximately 12 000 yr b p placing them within the late glacial the implications for reconstruction of late pleistocene and holocene paleoclimate are that no early or mid holocene glacial advances occurred and equilibrium line altitudes ela s of most cirque glaciers fluctuated by no more than 100 m during the neollacial which began at 1000 yr b p

holocene glaciations and paleoclimate of mount kenya and other east african mountains abstract this paper summarizes available glacial geological data including sediments landforms paleosols and paleoclimate for major mountain areas in east africa from 1890 to the present a number of workers have tried with varying degrees of success to reconstruct holocene glacial and paleoclimatic records most of the mountains are surfaced with late pleistocene and late holocene glacial sediments which are poorly dated and in many cases stratigraphic units are only recognized by their topographic positions only on mount kenya is there an emerging glacial stratigraphy based on dating both holocene and pleistocene glacier fluctuations appear to have been broadly synchronous in the east african mountains terminal moraines on mount kenya extend to 3200 m in most drainage basins and yield minimum 14 c ages of 15 ka bp recessional moraines of liki iii age at 3700 4200 m appear to date from the late glacial later pleistocene see coetzee 1967 for a discussion while younger neoglacial see mahaney 1982 1984 for a discussion moraines are either little ice age in age or are older late holocene deposits the neoglacial sequence on mount kenya is younger than 1 ka bp while on other east african mountains it may have commenced about 2 ka bp most of holocene time appears to have been warmer and perhaps wetter than today when glaciers disappeared altogether or were distributed much as they are today

determining the dilation factor in 4d monitoring of compacting reservoirs by rock physics models hydrocarbon depletion and fluid injection cause compaction and stretching of the reservoir and overburden layers 4d prestack seismic data can be used to detect these changes because compaction stretching causes changes in traveltimes and seismic velocities we show that by using two different petro elastic models at varying effective pressures a good approximation is to assume that the fractional changes in layer

anoxic events in the late frasnian causes of the frasnian famennian faunal crisis carbon isotope data collected from five frasnian famennian boundary sections in central europe show two positive 13 c excursions in the late frasnian 367 ma both anomalies coincided with the deposition of the bituminous lower and upper kellwasser horizons the carbon isotope patterns indicate two phases of enhanced burial and subsequent recycling of organic carbon a maximum formation of warm saline waters on the subtropical to tropical epicontinental shelves during late frasnian transgressive episodes may have induced oceanic oxygen deficits variations in the c org burial rates may have resulted in changes in the co 2 concentrations in the oceans and in the atmosphere culminating in global climatic changes we propose that the repeated co occurrences of sea level fluctuations anoxic conditions and global climatic changes during the late frasnian would affect especially the subtropical to tropical shallow water communities and reef ecosystems which were severely affected during the frasnian famennian faunal crisis

depositional environment thermal maturity and irradiation effects on porphyrin distribution alum shale sweden abstract the swedish alum shale which was deposited from middle cambrian to lower ordovician time in the shallow marine waters of the lapetus ocean contains abundant uranium the sedimentary organic matter associated with these shales has undergone irradiation which has affected both the insoluble and soluble portions rock extracts from the alum shale contain exclusively vanadyl porphyrins indicating deposition under a marine anoxic environment the decrease in the concentration of porphyrins with increasing uranium content indicates that irradiation has destroyed porphyrins comparison of the detailed vanadyl porphyrins distribution does not show any preferential destruction of particular vanadyl porphyrin i e dpep or etio due to irradiation hence the porphyrin maturity parameter which is based on the changes in the relative concentration of etio and dpep porphyrins can be used for estimating the maturity of the alum shale regardless of its uranium concentration this also suggests that the effect of irradiation on porphyrins is different from that of heating

the geochemistry of uranium and thorium in some lower carboniferous sedimentary rocks great britain abstract mass spectrographic determinations have been made on 32 limestones dolostones and nine shales from the lower carboniferous succession of anglesey island uranium is found to be enriched in calcareous dark shales which are rich in organic carbon and were precipitated in small amounts in calcareous shales pure shales and limestones dolostones in the carbonate rocks u is associated principally with the soluble fraction which represents the carbonate plus u loosely adsorbed on clay minerals no correlation exists between u and organic carbon and between u and phosphate analyses of the detrital and non detrital fractions of twelve limestones showed that th is mostly associated with the non detrital fraction correlation tests between th and k for 32 limestones showed that a median correlation exists between th and k

neoglacial chronology and floristics in the middle teton area central teton range western wyoming the relative ages of neogfacial deposits above 2900m near cloudveil dome middle teton and teepe glaciers central teton range western wyoming were determined using topographic position weathering features lichenometry vegetation characteristics and soils a three fold deposit sequence is identified and correlated with the gannett peak audubon and indian basin neoglacial advances described elsewhere in the teton and nearby wind river ranges while soil profile morphology proved very useful in distinguishing deposits of different age other age indicators such as clay mineralogy and soil chemistry proved of only marginal value in age discrimination this chronosequence emplaced over the last 5000yr provides an excellent setting upon which to test changes in plant species composition and its use as a relative dating method vascular plant species composition cannot be used to discriminate deposits of the different advances possibly because of random colonisation and establishment combined with extensive mass wasting during the neoglacial however certain vegetation features such as total cover and species densities appear useful as relative dating methods

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

geochemical anomalies at the cenomanian turonian boundary northwest new mexico a high resolution section of 64 carbonates and calcareous shales from northwest new mexico spanning the cenomanian turonian c t boundary is examined for selected elemental concentrations as well as carbon isotopic and molecular distributions spatial and temporal sampling resolutions for the entire sample set are 1 spl 19 cm and 1 spl 33 ka respectively in proximity to the c t boundary respective spatial and temporal resolutions increase to 1 spl 10 cm and 1 spl 17 ka results show the occurrence of several geochemical anomalies all with coincident maxima at about 0 5 m below the c t boundary stable carbon isotope ratios of the kerogen and the aliphatic and aromatic hydrocarbon fractions increase by approximately 4 within 20 m of the boundary this entire c t boundary event isotope anomaly occured over approximately 2 5 ma a 5 fold increase in the concentrations of u and th occurs synchronous with the isotope excursion although this u th spike occurs over a period of only 0 2 0 3 ma elevated u and th concentrations at this spike co occur with a the highest 20s 20s 20r sterane epimer ratios b c27 c27 30 sterane homolog ratios and c the lowest n alkane yields in kerogen pyrolyzates these observations suggest an effect of radiogenic heat production on the organic matter in the section the origin of the carbon isotope excursion is attributed as in previous studies to atmospheric co2 drawdown in latest cenomanian time caused by rapid burial of organic matter due to a global marine transgression the u and th spike is probably secondary perhaps resulting from adsorption of these elements onto clays concentrated at the c t boundary although the occurrence of coeval maxima for these isotopic and elemental anomalies suggests a common cause extrapolation of the co2 drawdown model to explain the u th anomaly is unwarranted at this time ongoing mineralogical analysis of clays and carbonates close to the c t boundary in the red wash section may ultimately explain the occurrence of this u and th spike

geochemical and palaeontological studies of the δ13c anomaly in boreal and north tethyan cenomanian turonian sediments in germany and adjacent areas in two sections of the upper cenomanian and lower turonian of northwest germany boreal realm north sea basin and southeast germany north tethys regensburg area stable isotopes 13c 18o acid soluble manganese carbonate contents and foraminifera were investigated in addition other sections across norttwest and middle europe are reviewed with respect to the detailed stratigraphy of a positive 13c anomaly which was found earlier to be of global importance in the archaeocretacea foraminiferal zone cenomanian turonian transition the 13c excursion was found to be isochronous with the lower limit marked by the extinction of the foraminiferal genus rotalipora the upper limit is found immediately above the entry of the foraminiferal praeglobotruncana helvetica bolli in the macrofossil zonation the base is marked by the occurrence of the belemnite actinocamax plenus blainville in the upper part the metoicoceras geslinianum ammonite zone the upper limit falls in the watinoceras coloradoense ammonite zone just above the entry of the inoceramid genus mytiloides in some cases the 13c excursion refers to a maximum of a more or less well expressed oscillation of the 13c values with minima in the lowermost cenomanian and the upper turonian in other cases 13c is constant with a marked spike at the position of the anomaly the locally different structures of the 13c trends point to incomplete mixing of water masses between basins in northwest europe a manganese anomaly associated with the 13c excursion in the anglo paris basin was found at a higher position in northwest germany and is apparently absent from the german north tethys in both cases high mn contents appear to be associated with a markedly increased terrigenous input expressed by an increase in grainsize of the acid insoluble residue the stratigraphical value of the mn anomaly is therefore limited the palaeoecological conditions are discussed in terms of foraminiferal diversity and the occurrences of macrofossils a shift to higher 18o values coincident with the 13c excursion is possibly a response to cooling of ocean water for which evidence is provided by a low diversity globular planktonic assemblage the correlation of 18o and foraminiferal diversity is suggested to provide a tool for bathymetric interpretations of sections but needs further investigations

late quaternary vegetation history of the south tanganyika basin climatic implications in south central africa abstract pollen evidence from two cores recovered from the mpulungu basin south lake tanganyika reveals a significant pattern of changes in vegetation in relation to climatic fluctuations between 25 000 and 9000 yr b p prior to 15 000 yr b p open and poorly diversified zambezian woodlands at low and mid altitudes with local included patches of montane components such as podocarpus and numerous ericaceae are registered this indicates cooler and drier climatic conditions than now with a probably incidence of light frost during the night at low altitude the coldest episode could be placed between 22 000 and 15 000 yr b p the period between 15 000 and 12 000 yr b p appears to be transitional a significant retreat of ericaceous shrublands suggests an increase in temperature the permanence of local floristically poor woodlands and the presence of drought tolerant montane elements on the plateaus suggest that climate was still drier than today the development of wetter zambezian woodlands with a composition similar to the modern vegetation and the occurrence of some arboreal taxa which have more affinities with the west and central african flora than with the zambezian one imply a great increase in rainfall after 12 000 yr b p

the cenomanian turonian oceanic anoxic event ii palaeoceanographic controls on organic matter production and preservation correlation of the 13c spike with the well dated occurrences of strata rich in organic carbon detailed in schlanger et al this volume indicates that a global episode of intense organic carbon orgc burial took place during the latest cenomanian earliest turonian oceanic anoxic event oae a plenus through i labiatus macrofossil zones and upper r cushmani trz through w archecretacea prz foraminiferal zones over a period of no more than 1 million years m y the shape of the 13c curve indicates that rates of orgc burial gradually increased in the early part of the late cenomanian increased more rapidly in the later cenomanian and levelled off at peak values in latest cenomanian early turonian time during the maximum rate of orgc burial the 13c values decreased nearly to pre late cenomanian levels in the early to middle turonian the decrease in 13c reflects decreasing rates of orgc burial following the cenomanian turonian oceanic anoxic event as well as the probable oxidation and return of significant amounts of orgc to the oceans following regression and re oxygenation of much of the deeper water masses in contact with the seafloor

the stratigraphic and palaeogeographic setting of the late cenomanian anoxic event the late cenomanian carbon isotope excursion can be shown to be synchronous over most areas of the globe where micropalaeontological data are adequate the sedimentological variations seen in these different areas are thought to be due to palaeobathymetry the relationship between this anoxic event and the major faunal change in the late cenomanian is described

irradiation of organic matter by uranium decay in the alum shale sweden the alum shale of sweden contains black shales with anomalously high uranium concentrations in excess of 100 ppm syngenetic or early diagenetic origin of this uranium indicates that organic matter within these shales has been irradiated by decaying uranium for approximately 500 ma radiation induced polymerization of alkanes through a free radical cross linking mechanism appears to be responsible for major alterations within the irradiated organic matter specific radiation induced alterations include generation of condensate like oils at reduced yields from hydrous pyrolysis experiments decrease in atomic h c ratios of kerogens decrease in bitumen organic carbon ratios and a relative increase in low molecular weight triaromatic steroid hydrocarbons conversely stable carbon isotopes of kerogens reflectance of vitrinite like macerais oil generation kinetics and isomerization of 20r to 20s c29 steranes were not affected by radiation the radiation dosage needed to cause the alterations observed in the alum shale has been estimated to be in excess of 105 mrads with respect to organic carbon this value is used to estimate the potential for radiation damage to thermally immature organic matter in black shales through the geological rock record high potential for radiation damage is not likely in cenozoic and mesozoic black shales but becomes more likely in lower paleozoic and precambrian black shales

trace element anomalies at the mississippian pennsylvanian boundary in oklahoma and texas trace element abundance anomalies have been found at the mississippian pennsylvania boundary at sites in oklahoma and texas where the boundary has been precisely located on the basis of an abrupt change in conodont diversity and species composition enriched elements include osmium indium platinum chromium most chalcophiles rare earths and uranium the anomalies are more intense e g os 4 ppb ir 0 38 ppb pt 6 ppb cr 12000 ppm u 380 ppm and peisist through a thicker interval at the south central texas locality than in oklahoma and in bolh locations the anomalies are associated with an increase in phosphate content of the rocks there is no tangible evidence of an asteroid or comet impact source for the excess pt group elements and fauna crisis the cause of the elemental enrichments and the biological disturbance may possibly be related to a change in the ocean chemistry of the paleozoic seaway such as increased upwelling stagnation or nearby submarine volcanism

elemental abundance anomalies in the late cenomanian extinction interval a search for the source s elemental abundances have been measured by neutron activation methods across the cenomanian turonian late cretaceous extinction interval in samples collected from sixteen sites in the western interior basin of north america and from twelve widely separated locations around the globe including six odp dsdp sites in most western interior basin sites in colombia and in western europe weaker two closely spaced elemental abundance peaks occur in the upper cenomanian 92 m y spanning the ammonite zones ofsciponoceras gracile throughneocardioceras juddii elements with anomalously high concentrations include sc ti v cr mn co ni ir pt and au the lower peak coincides with the disappearance extinction of the foraminiferrotalipora cushmani in north american sectionsr greenhornensis also disappears at or just below this horizon but in europe it disappears considerably earlier thanr cushmani a series of molluscan extinction and speciation or migration events also begins near the stratigraphic level of the lower elemental abundance peak the well documented positive 13c excursion begins just before the extinctions and the elemental anomalies and continues into the lower turonian well above the upper anomaly this carbon isotope excursion has been observed in east european sections where we find little or no evidence of the elemental anomalies suggesting that the two phenomena may not be tightly coupled elemental abundance ratios in the anomalies closely resemble those of mid atlantic ridge basalt or hawaiian lava tholeiitic but not those of c1 chondrite black shale average crustal rocks or lamproite and kimberlite of roughly similar age in southeastern kansas the excess ir and other siderophiles hint at possible large body impact s for the source however we have not located microspherules other than biogenic calcispheres or shocked mineral grains in any of our samples furthermore sc ti v and mn are not enriched in differentiated solar system bodies although the weak geochemical signal from comet impact s could be masked by the strong terrestrial like overprint these anomalies more likely resulted either from intense seafloor spreading activity or merely from increased circulation of deep metal rich water associated with the large late cenomanian through early turonian eustatic rise and deep water opening of the south atlantic the flooding of continental seaways and margins also could have contributed to the anomalies by preventing much continental detritus from diluting the normal background marine geochemical component

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

use of organic carbon content as a chronostratigraphic tool abstract in the mulhouse potash basin france the lithology and the organic carbon content reveal an extended succession of recurrent sequences variation in lithology shales anhydrite halite reflects variations in depositional environment organic matter exclusively present in the shaly horizons shows variations in content and origin these changes highlight small variations of their depositional environment which are not detected in the lithology of the shales on the other hand when these variations increase and are large enough they are recorded by the lithology in homogeneous facies i e shaly facies analysis of the distribution of the organic content in sediments thus appears to be an interesting method for determining small variations of the depositional environment the organic carbon signal showsvariations of sedimentation rates over time and can be interesting for small scale geochronology quite a similar duration for each cycle lasting an average of 13 000 3400 yr has been calculated this time span based on biostratigraphy is in agreement with results obtained by lamination counts this duration can be criticized due to the lack of precision of the dating methods but is significantly different from the well known periodicities of milankovitch

organically bound metals and biomarkers in the monterey formation of the santa maria basin california abstract systematic variations in metal concentration ratios and biomarker ratios are observed with depth in cores of the monterey formation of the union leroy 51 18 well in the santa maria basin california specific metal ratios v v ni and mo mo cr correlate between kerogen and extractable organic matter further the organic matter in the two predominant lithofacies siliceous shales vs phosphatic shales can be distinguished based upon metal concentration ratios e g v v ni and certain biomarker characteristics e g sterane terpane mono triaromatic steroid hydrocarbon ratios maximum 28 30 bisnorhopane hopane ratios occur over a narrow range of v v ni ratios in kerogen concentrates and extractable organic matter this suggests that metal ratios in kerogen concentrates and eom may be useful for oil source rock correlation studies in the monterey further while kerogen parameters metals are discontinuous at the lithofacies boundary extract parameters biomarkers are gradational at this boundary suggesting about 30 ft 9 m of vertical hydrocarbon migration across the lithofacies contact

chemostratigraphy versus biostratigraphy data from around the cenomanian turonian boundary a detailed isotopic profile is presented for a stratigraphically expanded cenomanian turonian boundary section in chalk facies exposed at eastbourne sussex and compared with data from pueblo colorado in both sections macro and micropalaeontological markers first appearances and disappearances are well constrained and their relative positions and relationship to the structure of the carbon isotope curve are identical this consistent relationship between two independent phenomena one geochemical the other biostratigraphical is taken as evidence for the likely synchroneity of both the biostratigraphical markers and the carbon isotope excursion in these two areas this interpretation contrasts with suggestions made recently by other authors whose data have been taken to imply a lack of correlation between the carbon isotope excursion in europe and north america

quaternary glaciations in africa abstract glaciers were active on the african mountains during several periods of the quaternary evidence exists of three old glaciations before 100 ka bp on kilimanjaro and two on mount kenya and ruwenzori the last glaciation which was synchronous with the last major glacial phase in temperate latitudes affected kilimanjaro mount kenya ruwenzori nyandarua range mount elgon the ethiopian highlands and several of the high mountains within and around the sahara desert the ice disappeared from most of these areas during the early holocene except from kilimanjaro mount kenya and ruwenzori where glaciers exist at the present day

high resolution organic record of bridge creek deposition northwest new mexico abstract organic and inorganic geochemical data are presented and interpreted for a high resolution sample set from the uppermost portion of a transgressive systems tract condensed interval spanning the cenomanian turonian boundary at red wash northwest new mexico source potential toc rock eval yields thermal maturity vr elemental ca th and u in whole rock and molecular n alkanes steranes terpanes data are presented for a 64 sample 12 4 m composite section of limestones marlstones and shales of the bridge creek member of the greenhorn formation vertical sampling resolutions of 1 spl 19 cm spatial and 1 spl 33 ka temporal are used to monitor the progress of the transgression from the uppermost cenomanian up to the beginning of the highstand systems tract the section is thermally immature and maturity fluctuations are absent indicating that organic parameters are a function of organic matter production and preservation including diagenesis the rhythmic lithologic fluctuation within the bridge creek is not reflected in the source potential elemental or molecular data which show either no obvious pattern e g carbonate content toc or a unidirectional trend toward development of anoxia upsection e g hydrogen index sterane distributions homohopane index the distribution of the triaromatic steroid hydrocarbons c 20 21 26 28 according to side chain length also varies significantly despite the absence of maturity differences all of the unidirectional trends in the data are interpreted as related to either productivity differences e g sterane hopane ratios and changes in the relative concentration of r c 28 and r c 30 desmethylsteranes or the development of anoxia in the lower water column e g decreases in the diasterane regular sterane ratio increases in the homohopane index westward movement of the paleoshoreline during bridge creek time is also monitored by upsection decreasing th u ratios at red wash

isotopic and petrographic studies of uraniferous hydrocarbons from around the irish sea basin stable carbon isotopic ratios of a suite of uraniferous hydrocarbons lower jurassic from the northeast wales ore field and related deposits have been determined the isotopic compositions 11 41 to 29 36 pdb become increasingly heavy with increasing uranium content 0 001 35 78wt fractionation is thought to occur by repeated preferred bond breaking between 12 c 12 c atoms with subsequent volatile production and loss removing 12 c atoms the extent of fractionation may also be controlled by the amount of stable aromatic material in the organic matter petrographic features of these uraniferous hydrocarbons and others from occurrences in south africa and scandinavia suggest reaction of radiation with organic matter alpha particles may be responsible for the development of high reflectance haloes around uraninite grains in uraniferous hydrocarbons from the witwatersrand region bitumen reflectance falls in a non linear trend from 3 75 to 1 75 in oil in a 20 m radius round the grains during irradiation bitumen anisotropy measured as bireflectance is developed in response to increasing aromaticity and the development of a short range ordered structure bireflectance measurements vary from 0 047 0 173 in samples from around the irish sea basin and 0 001 0 294 in a suite of samples from scandinavia the degree of anisotropy is dependent on the bitumen composition and varies between sample suites of differing geological histories

effects of radiation exposure on indicators of thermal maturity abstract study of fossil wood samples with varying contents of uranium suggests that radiation exposure over geologic time results in alteration of vitrinite the alteration is shown by increased reflectance of vitrinite increased values of thermal alteration index decreased atomic h c ratios and by loss of fluorescence each of these parameters is used to estimate the thermal maturity of kerogen unless recognized during interpretation of analytical results radiation damage of vitrinite results in over estimation of thermal maturity