stable isotope stratigraphy of brachiopods from pennsylvanian shales in texas stable isotope stratigraphies have been generated for brachiopods from five late pennsylvanian sections upper winchell cycle finis shale colony creek shale necessity cycle and wayland shale in north central texas to examine the relationship between isotopic composition paleoenvironment and sea level change nonluminscent calcite from more than 300 specimens of 4 species of brachiopod composita subtilita crurithyris planoconvexa eridmatus texana neospirifer cameratus was analyzed sedimentological and paleontological data are used as evidence for paleoenvironmental change higher 18 o values of brachiopod shells occur in intervals of greatest paleodepth as indicated by fossil content and lithology these higher 18 o values reflect a decrease in bottom temperature with increased water depth normalized for paleodepth the 18 o values of the brachiopods are similar in all of the units except the wayland shale for which they are 0 5 higher this suggests either cooler temperatures or greater continental ice volume during the time of wayland deposition brachiopod 13 c values do not correlate with paleodepth the 13 c values of composita are consistently higher than those of crurithyris and eridmatus composita 13 c values are similar in the upper winchell cycle necessity cycle and wayland shale averaging 4 8 to 4 9 in contrast crurithyris 13 c values range from 2 5 in the necessity cycle to 4 4 in the wayland shale eridmatus values are also lowest in the necessity cycle 3 4 and greatest in the wayland shale 3 9 these differences between species do not correlate with susceptibility to diagenesis and appear to reflect a pore water influence on semi infaunal crurithyris forms the 13 c values of composita shells suggest that the late pennsylvanian ocean off eastern laurussia was enriched in 13 c by about 1 relative to the ocean off western laurussia

green river laminites does the playa lake model really invalidate the stratified lake model proponents of the playa lake model have proposed deposition of most of the green river formation microlaminated carbonates including oil shales in lakes that were not perennially stratified meromictic however there is a variety of evidence favoring a meromictic depositional environment 1 close similarity of much of the lamination to varves in modern meromictic lakes 2 evidence that hydrologic events favoring development of meromixis chemical stratification occurred prior to deposition of major accumulations of oil shale 3 mutually exclusive distribution of fossil nekton especially fish and normal lacustrine benthos including mollusks and 4 analogy with a quaternary playa that became a meromictic lake following increased inflow the playa lake model is untenable for the typical fish bearing kerogen rich microlaminated sediments these laminites were probably deposited in a large ectogenic meromictic lake a chemically stratified lake that formed when increased fresh water inflow drowned a saline playa complex

milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr bp an atmospheric general circulation model has been used to simulate the climates of january and july at 3 000 yr intervals from 15 kyr bp onwards the model simulates a strengthened monsoon circulation and increased precipitation in the northern hemisphere tropics culminating at 9 6 kyr bp the computed hydrological budgets were used to estimate the area of closed lakes between 8 9 and 26 6 n giving with minor exceptions results in good agreement with geological evidence

late palaeozoic corals of tibet xizang and west yunnan southwest china successions and palaeobiogeography abstract a dynamic pattern of coral faunal provincialism in the carboniferous to permian sequence is preserved in tibet west yunnan during the early carboniferous an undifferentiated eurasian province was present containing the kueichouphyllum keyserlingophyllum siphonophyllia and cyathaxonia faunas that reflect major environmental differences relative to previous interpretations during the late carboniferous early permian the indoralian province and the cathaysian province can be distinguished the former is recognised by an absence of late carboniferous asselian corals and by the presence of the sakmarian artinskian cyathaxonia fauna the latter contains the late carboniferous and early permian compound corals nephelophyllum and kepingophyllum as many blocks drifted northward beginning in the late early permian the indoralian province had evolved into two discrete provinces the himalayan and cimmerian provinces the himalayan province as a relic of the indoralian province was in the northern margin of gondwanaland the cimmerian province between the himalayan and the cathaysian provinces consists of the present tectonic blocks lhasa qiangtang tengchong and baoshan in tibet and west yunnan it is characterised by roadian non dissepimental solitary corals and wordian capitanian compound waagenophyllidae as well as some endemic cimmerian taxa such as thomasiphyllum and wentzellophyllum persicum the cathaysian province is dominated by szechuanophyllum and ipciphyllum during the late permian the himalayan province and the cathaysian province can be recognised the former contains only small solitary corals referred to as the lytvolasma fauna and the latter is identified by liangshanophyllum a fasciculate waagenophyllid

geochemistry and skeletal structure of diploria strigosa implications for coral based climate reconstruction abstract geochemical tracers incorporated into the skeleton of reef building corals are ideal proxies for reconstructing environmental parameters of ambient seawater such as temperature and salinity at subseasonal resolution however validation concerns of these environmental proxies due to the complex skeleton of some tropical atlantic corals have hindered such coral based environmental reconstructions in this region compared to the tropical pacific in order to identify complications associated with the complex skeletal architecture of the massive brain coral diploria strigosa we performed microsampling experiments along and across individual skeletal elements we demonstrate that the mesoscale heterogeneity of sr ca 18o and 13c is a systematic feature of d strigosa and is linked to different vital effects between skeletal elements the thecal wall is significantly depleted in sr 18o and 13c compared to the adjacent septa and columella and differences between apparent temperature signatures of several degrees are greater for sr ca suggesting that this temperature proxy is more sensitive to skeletal mixing than 18o parallel subseasonal microsampling experiments performed along individual skeletal elements of a single corallite of a d strigosa coral which grew at a rate of 0 65 cm year allow for investigating potential biases associated with its complex skeletal mesoarchitecture highest correlation between sr ca and 18o from skeletal material retrieved from the centre of the thecal wall suggests that microdrilling the theca provides the best environmental signal compared to adjacent microsampling profiles moreover based on monthly mean climatology the temperature dependence of sr ca for this profile is comparable to previous calibrations published from faster growing d strigosa based on these results we conclude that accurate microsampling along the centre of the thecal wall of d strigosa is a prerequisite for generating robust climate reconstructions from its skeleton

fossil organic matrices of the callovian aragonitic ammonites from lukow poland location and composition the micro and nanostructures of modern and fossil aragonitic nacreous layers of cephalopod shells were studied with scanning electron microscope sem and atomic force microscope afm the nacreous tablets are organized in sectors composed of acicular units the acicular units are composed of small granules the fossil and modern shells show some differences in granule size but the granules are surrounded by a thin envelope in both samples electrophoretic and amino acid compositions show that organic matrices are present in the fossil shells thus the organic nature of the granule envelopes can be inferred from the two analytical approaches the afm microscopy allows us to study the nanostructures of the recent and fossil hard tissues and to observe the diagenetic changes of both the mineral and organic components

isotopic records of brachiopod shells from the russian platform evidence for the onset of mid carboniferous glaciation we performed isotopic analyses of carboniferous brachiopod shells from the russian platform to examine global and regional environmental change along the western and eastern margins of laurussia during the formation of pangea and specifically to examine the isotopic evidence for the onset of mid carboniferous glaciation shell preservation was evaluated from shell microstructure cathodoluminescence trace element content and isotopic comparison with matrix material most interior nonluminescent nl prismatic shell appears to be chemically well preserved as indicated by low to undetectable si al fe and mn contents with minor exception nl shell 13c and 18o values are higher than those of corresponding cements and matrix the 13c record for the russian platform clearly shows a 3 increase from 2 4 0 7 to 5 5 0 6 in the serpukhovian or early bashkirian this shift was first reported by popp et al popp b n anderson t f sandberg p a 1986 brachiopods as indicators of original isotopic compositions in some paleozoic limestones geol soc am bull 97 1262 1269 but had not been documented for a single region widespread occurrence of high 13c values in the late carboniferous support the interpretation of popp et al with regard to this shift as a record of increased burial of organic carbon north american sections show a mid carboniferous 13c shift of only 1 5 we hypothesize that the reduced 13c shift reflects enhanced upwelling on the epicontinental seas of north america after the closing of the seaway between laurussia and gondwana the 18o record for the russian platform shows a 1 8 increase in the mid carboniferous correlative with increased occurrence of glacial sediments and a drop in sea level as a first approximation ice volume calculations suggest that 0 7 of the mid carboniferous 18o shift is due to changes in seawater 18o and 1 1 is due to 5 c cooling concurrent positive 13c and 18o shifts provide evidence for a relationship between mid carboniferous glaciation and burial of organic carbon presumably through changes in atmospheric co2 levels

direct radiometric age determination of carbonate diagenesis using u pb in secondary calcite abstract carbonate rocks and corals from the middle devonian lucas formation ontario have 238 u 204 pb values ranging from 132 to 559 and give concordant apparent 206 pb 238 u and 207 pb 235 u ages in approximate agreement with the primary age of sedimentation a carbonate rock from one part of the section gives an anomalously young age and contains patches of secondary calcite spar this spar is predominantly pale purple under cathodoluminescence cl and contains 250 600 ppb u and 15 22 ppb pb the values range from 2 10 3 10 4 making the pb very radiogenic apparent 206 pb 238 u ages range from 208 to 249 ma and 232 th 238 u values are from 0 005 to 0 040 the younger ages are correlated with an increase in orange cl and higher apparent values the age scatter is attributed to mixing of a subordinate calcite spar which infiltrated the older spar the young calcite is bright orange under cl has 7200 ppb u of 6 2 10 4 a of 0 23 and is dated at 45 ma the age of the older spar has been determined by a sequential dissolution technique the resulting u pb data can be plotted as u pb age spectra and yield lplateau dates ranging from 231 5 1 4 to 244 9 1 6 ma and an integrated 206 pb 238 u age of 238 2 1 1 ma also the sequential dissolution increases the values progressively to a5 10 4 making these ages independent of the initial pb correction the occurrence of two young ages of diagenetic calcite in these strata is consistent with the idea of recurrent fluid activity along fracture zones in subsurface sediments in the michigan basin this study shows that it is now possible to date secondary carbonate diagenesis by u pb and by inference to determine precisely the timing of activity on ancient fracture zones in carbonate rocks

chemical labelling of oyster shells used for time calibrated high resolution mg ca ratios a tool for estimation of past seasonal temperature variations abstract the geochemical compositions of biogenic carbonates are increasingly used for palaeoenvironmental reconstructions the skeletal 18o temperature relationship is dependent on water salinity so many recent studies have focused on the mg ca and sr ca ratios because those ratios in water do not change significantly on short time scales thus those elemental ratios are considered to be good palaeotemperature proxies in many biominerals although their use remains ambiguous in bivalve shells here we present the high resolution mg ca ratios of two modern species of juvenile and adult oyster shells crassostrea gigas and ostrea edulis these specimens were grown in controlled conditions for over one year in two different locations in situ monthly mn marking of the shells has been used for day calibration the daily mg ca ratios in the shell have been measured with an electron microprobe the high frequency mg ca variation of all specimens displays good synchronism with lunar cycles suggesting that tides strongly influence the incorporation of mg ca into the shells highly significant correlation coefficients 0 70

a cretaceous scleractinian coral with a calcitic skeleton it has been generally thought that scleractinian corals form purely aragonitic skeletons we show that a well preserved fossil coral coelosmilia sp from the upper cretaceous about 70 million years ago has preserved skeletal structural features identical to those observed in present day scleractinians however the skeleton of coelosmilia sp is entirely calcitic its fine scale structure and chemistry indicate that the calcite is primary and did not form from the diagenetic alteration of aragonite this result implies that corals like other groups of marine calcium carbonate producing organisms can form skeletons of different carbonate polymorphs

primary biogenic skeletal structures in multithecopora tabulata pennsylvanian abstract corals are significant components of fossil marine communities and important for paleoenvironmental reconstructions throughout the phanerozoic despite their abundance and diversity in paleozoic rocks the presence and criteria for the recognition of primary biogenic skeletal structures is highly controversial the aim of this study is a multilevel analysis of the diverse morphological elements that form well preserved specimens of the carboniferous multithecopora tabulate coral skeleton results indicate that samples are minimally altered by diagenesis but most importantly that skeletal structures are biogenic in nature and similar to those of modern and fossil carbonate producing organisms nano and microcrystals form a complex framework of different domains of crystal morphologies that comprise the bulk of the skeleton in multithecopora these domains are thought to be the possible phenotypic response of the genotype of these corals and had a structural importance during the life of the organism overall this study sheds light for a better understanding on the controversy that exists about the biogenic or abiogenic origin of the paleozoic coral microstructures

tabulate corals across the frasnian famennian boundary architectural turnover and its possible relation to ancient photosymbiosis abstract the frasnian famennian biodiversity crisis has traditionally been considered one of the big five mass extinctions among deep changes in the biosphere it almost completely erased shallow water marine ecosystems like coral stromatoporoid reefs which were widespread on the carbonate platforms in the devonian the high biodiversity of bioconstructors during the givetian frasnian acme of palaeozoic reef development contrasts sharply with very low biodiversity levels during the famennian one of major bioconstructing groups in the palaeozoic was tabulate corals a statistical analysis of colony architecture of givetian frasnian and famennian tabulates from the holy cross mountains poland reveals that givetian and frasnian tabulate faunas had smaller corallite diameters and higher colony integration compared to the famennian faunas a similar pattern occurs in the devonian of the ardennes in the holy cross mountains the biodiversity drastically decreases in the late frasnian we interpret givetian frasnian tabulate communities as generally photosymbiotic and their famennian counterparts as generally aposymbiotic in recent corals temperatures above 32 c are generally considered as a threshold for bleaching expulsion of photosymbionts a literature review indicates that in the late frasnian sea surface temperatures exceeded this threshold this leads to a discussion of the late frasnian rise of temperature as a contributing cause of extinction of photosymbiotic bioconstructors and possibility of a late devonian bleaching event

belemnite biomineralization development and geochemistry the complex rostrum of neohibolites minimus abstract belemnites a group of extinct coleoid cephalopods were important components of mesozoic marine ecosystems their calcitic rostra are extensively used in biostratigraphy and geochemistry the preservation state of the rostra is a crucial factor for the interpretation of their geochemical data however their preservation is difficult to assess since no modern cephalopod forms calcitic rostra the biomineralization process of the rostrum which functioned as an internal skeleton is poorly understood for most species this also applies for the epirostrum a late ontogenetic extension of the rostrum which is only present in some belemnite species the primary structure and function of this character are still being debated controversially we have investigated the microstructure stable isotope 13 c 18 o and elemental composition mg ca sr ca fe ca mn ca of both ortho and epirostra of the belemnite species neohibolites minimus early cretaceous albian for comparison we studied argonauts argonauta argo these recent octopuses build a calcitic shell ortho and epirostra of n minimus show microstructural and geochemical differences cathodoluminescence microscopy and the microstructures of belemnites and argonauts indicate that blue orange luminescent growth lines in the studied belemnites are largely a primary biomineralization phenomenon and not solely due to diagenesis based in part on analogy to argonaut shell we suggest that the inner part of the belemnite epirostrum is a continuation of an originally organic apical line the development and evolution of the epirostrum as a potential sexually selected character is discussed well preserved epirostrum calcite has higher element ca ratios than the calcite of the orthorostrum suggesting a vital effect affecting these values we further found evidence for vital effects on the stable isotope signatures due to metabolic and kinetic fractionation our findings suggest a complex mineralization process of the studied rostra different microstructures with distinctive geochemical signatures occur in a single belemnite species vital effects played an important role in the rostrum geochemistry complicating the application of the rostra as paleoclimatic archives

a mass balance approach to basin sedimentation constraints on the recent history of the turkana basin abstract the turkana basin provides some excellent examples of mass balance constraints on recent basin history high sedimentation rates in the basin imply that major river captures occurred in the recent geologic past the chemistry of the lake is that to be expected for a relatively deep closed basin alkaline lake after several thousand years mass balance in the water budget shows that major changes in lake levels over a short time interval can only result from catastrophic events

strontium content of ostracods indicates lacustrine palaeosalinity individual non marine ostracod valves contain sr in proportion to the sr content of their host lake water two commonly coexisting large planktonic species mytilocypris praenuncia and australocypris robusta have a sr distribution coefficient kd sr ca of 0 082 which is independent of temperature in the range 10 18 c if the relationship between salinity and the sr content of a hydrologically simple lake is known palaeosalinities can be calculated from fossil ostracods we present here palaeosalinities for the past 10 000 yr for lake keilambete victoria calculated from ostracod sr ca of fossil material which are in striking agreement with independent interpretations of palaeosalinity the range of salinity spans 14 95 we also show that a reliable quantitative continuous indicator of lacustrine palaeosalinity is important for the elucidation of continental palaeoenvironments for palaeoclimatology and archaeology and ocean continent climatic correlations and interactions

zigzag microstructure in rugose corals a possible indicator of relative seawater mg ca ratios low mg calcite lmc and high mg calcite hmc have been identified confidently as original biominerals in different rugose corals devonian tabulophyllum had a lmc skeleton whereas pennsylvanian lophophyllidium had a hmc skeleton zigzag microstructure a diagenetic microstructure in rugose corals may be related to early migration of mg2 ions during transformation of hmc into lmc therefore zigzag microstructure may indicate that the original mineral was hmc even in specimens that subsequently converted to lmc stratigraphically corals with zigzag microstructure are confined to the late paleozoic which is coincident with the aragonite sea of p a sandberg hence fluctuating mg ca ratios may have directly controlled oscillations in marine carbonate chemistry and the mineral composition of rugose corals so that hmc skeletons as indicated by zigzag microstructure formed during intervals with aragonite seas and lmc skeletons e g tabulophyllum formed during intervals with calcite seas

freshwater on the route of hominids out of africa revealed by u th in red sea corals a fundamental issue in the evolution of human culture concerns the route and conditions of anatomically modern hominids during the migration out of africa a particular question is how could anatomically modern hominids cross the hyperarid arabian deserts here we outline the evidence for significant presence of freshwater along the red sea shores during the last interglacial period freshwater caused an extensive recrystallization of coral reefs from aragonite to calcite indicating uplift of the reefs through well developed phreatic freshwater coastal aquifers applying novel open system u th dating methodology to the calcitic corals we dated the freshwater recrystallization to ca 140 ka consistent with other geological lines of evidence placing the migration of anatomically modern hominids out of africa at the onset of the last interglacial

evidence for a composite organic inorganic fabric of belemnite rostra implications for palaeoceanography and palaeoecology carbonate skeletons of fossil marine organisms are widely used to reconstruct palaeoceanographic parameters specifically the geochemistry of jurassic and cretaceous belemnite rostra is traditionally interpreted to represent near sea surface seawater properties more recently an increasing number of workers have reported significant scatter in geochemical data e g 18o 13c element ca ratio when comparing rostra from the same stratigraphic level or within a single belemnite rostrum this scatter is not explained by differential diagenetic overprint alone here we report petrographic evidence on the primary ultrastructure of rostra of megateuthis middle jurassic and belemnitella and gonioteuthis late cretaceous the biogenic ultrastructure consists of a filigree framework of triaxial branches and tetrahedrons of variable size forming a honeycomb like network data presented here suggest that these rostra yielded as much as 50 to 90 primary pore space on the level of a working hypothesis and in analogy with modern cephalopods we propose that the pore space was formerly filled with body fluid and or organic compounds during the life time of these organisms intra rostral porosity was post mortem occluded by earliest diagenetic isopachous calcite cements of a non biogenic origin these may have been precipitated due to increased alkalinity related to the decay of organic matter if this holds true then the resulting fabric represents a composite biogenic abiogenic structure in order to optically separate the two calcite phases forming a single calcite fibre we employed a wide range of state of the art analytical tools to thin sections and ultra thin sections of well preserved specimens pending a verification of these well supported ultrastructural data by means of high resolution geochemical analyses from biogenic and abiogenic phases we suggest that these findings have significance for those using belemnite rostra as archives of their palaeoenvironment

mass balance in the glacier bay area of alaska usa and british columbia canada 1995 2011 using airborne laser altimetry the glacier bay region of southeast alaska usa and british columbia canada has undergone major glacier retreat since the little ice age lia we used airborne laser altimetry elevation data acquired between 1995 and 2011 to estimate the mass loss of the glacier bay region over four time periods 1995 2000 2000 05 2005 09 2009 11 for each glacier we extrapolated from center line profiles to the entire glacier to estimate glacier wide mass balance and then averaged these results over the entire region using three difference methods normalized elevation area weighted method and simple average we found that there was large interannual variability of the mass loss since 1995 compared with the long term post lia average for the full period 1995 2011 the average mass loss was 3 93 0 89 gt a 1 0 6 0 1 m w e a 1 compared with 17 8 gt a 1 for the post lia 1770 1948 rate our mass loss rate is consistent with grace gravity signal changes for the 2003 10 period our results also show that there is a lower bias due to center line profiling than was previously found by a digital elevation model difference method

petrology of a suite of sedimentary rocks associated with some cole bearing basins in northwestern thailand abstract a number of basins in northwestern thailand contain thick sequences of cenozoic sedimentary rocks oil shales and coals are prominent lithologies within these sequences and occur together in some basins most of the sequences are however dominated by either oil shales or coals the major oil shale deposit is in the mae sot basin but oil shales also occur in the ban huay dua mae moh ban pa ka li mae teep ban na hong and jae hom basins drilling and detailed mapping in the mae sot basin indicate thick sequences of oil shales and organic petrological studies show that they contain abundant lamalginite trace amounts of telalginite liptodetrinite bitumen resinite and huminite inertinite are also present in some of the rocks the parts of the sequences rich in authigenic minerals are in general petrographically similar to green river formation lamosites where clay silt sized epiclastics are more abundant similarities exist to australian tertiary lamosites vitrinite reflectance date from the oil shales and associated coals indicate a low level of maturity oil shales from the other basins are petrographically similar to the mae sot lamosites however some differences do exist the mae sot and other lamosites were deposited in lacustrine environments that probably had highly variable water depths

petroleum geochemistry and depositional setting of lacustrine source rocks abstract lacustrine sequences are increasingly being recognised as hosts for commercial reserves of petroleum petroleum source rocks in lacustrine sequences have organic carbon contents ranging from 20 and kerogen types range from type i to type iii the organic matter can be of land plant algal or bacterial origin most undegraded lacustrine oils are extremely paraffinic and waxy but a few are asphaltic and rich in sulphur the crude oils and source rocks contain a wide diversity of biological marker compounds reflecting different source inputs the diversity of chemistries displayed by lacustrine source rocks and crude oils reflect the wide variety of organic source materials and depositional conditions operative in lakes lacustrine sequences preserved in the geological record represent sediments deposited in fluvial lakes on humid flood plains and tectonic lakes in humid semi arid and arid environments preservation of organic matter in lakes is dependent on the formation of anoxic or micro oxic bottom waters this is favoured by stratification of lake waters brought about by temperature and salinity contrasts organic material preserved in oligotrophic lakes is largely of land plant origin which has been extensively modified by bacteria under mildly oxidizing conditions and supplemented by the bacterial remains source rocks of this type are found in 1 fluvial lacustrine settings e g jurassic of eromanga basin australia and 2 the oligotrophic phase of larger tectonic lakes e g early stages of green river formation uinta basin usa as these freshwater lakes become productive algal remains are contributed to the sediment and anoxic bottom waters can become more firmly established the green algae pediastrum and botryococcus appear to be particularly important although land plant detritus is still significant e g cretaceous source rocks songliao basin china saline lakes conditions tend to restrict the diversity of the source biota although preservation may be enhanced through anoxia brought about by salinity stratification and inhibition of bacterial decay e g later stages green river formation uinta basin usa sulphate rich and hypersaline lacustrine systems result in the formation of sulphur rich sources and oils e g jianghan basin china because of the diversity of organic matter types maturation criteria for hydrocarbon generation in lacustrine sequences also vary however in most cases higher maturation levels are required for significant hydrocarbon generation at present it is uncertain the extent to which algal and bacterial organic matter contribute to the source for the waxy hydrocarbons which are characteristic of lacustrine oils organic rich rocks formed in large freshwater and saline lakes are the most productive type of lacustrine source rock although sources formed in lakes of flood plains and deltas are also widespread

the hydrological setting occurrence and significance of gypsum in late quaternary salt lakes in south australia well exposed often laminated gypsum sequences occur in many quarternary salt lakes in southern south australia the gypsum in the salt lakes is classified by increasing grain size into gypsite gypsarenite and selenite the salt lakes are classified by age and hydrological setting into coastal salinas which are holocene sea water fed groundwater lakes and continental playas which are late pleistocene endorheic basins a study of the relationships between coastal salina hydrology and the associated gypsum deposition has shown the different types of gypsum form under distinct hydrological regimes as the hydrology above a coastal salina depositional surface changes through time so does the type of gypsum deposited application of a gypsum depositional model derived from a study of the coastal salina gypsum to those portions of a continental playa gypsum unit where deposition is no longer occurring confirms the applicability of the model to non salina gypsum deposits

understanding biomineralization in the fossil record abstract biomineralization the formation of minerals by organisms is a key aspect in the understanding of the fossil record knowing how biominerals form and their properties is important in the correct use of fossils in geochemistry the understanding of evolution and in the interpretation of how geological events have influenced the fossil record throughout the phanerozoic the focus of this contribution rather than a conventional review on the status of this research field is on the importance of highlighting the traditional link between paleontology and biomineralization

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

brachiopods as indicators of original isotopic compositions in some paleozoic limestones the original stable isotopic composition of paleozoic marine carbonate rocks is important to establish a baseline for evaluating diagenetic alteration and providing a reliable data base for modeling exogenic geochemical cycles of the elements we have compared the 18 o and 13 c values in the nonluminescent portions of brachiopods with similar published data of whole brachiopods other whole fossils and estimates of original isotopic composition of marine cements the oxygen and carbon isotopic records for each of these paleozoic components show generally good internal consistency significant discrepancies however were noted between results on the different components isotopic and trace element data presented in this study suggest that permo carboniferous whole brachiopods are little altered chemically nonetheless a more reliable but not fool proof approach for obtaining pristine isotopic values is microsampling of least altered regions based on cathodoluminescence in conjunction with staining techniques and elemental analyses the carbon and oxygen isotopic compositions of all components decrease in 18 o and 13 c in geologically older material neither temporal trend is monotonic however oxygen isotopic results suggest an important positive shift in 18 o of about 2 during the early carboniferous whereas the carbon isotope trend shows a major positive shift 2 3 during the mid carboniferous

chemical variation in pennsylvanian brachiopod shells diagenetic taxonomic microstructural and seasonal effects abstract to improve our ability to use minor and trace element mte variation in biotic carbonates as diagenetic and paleoenvironmental indicators we performed electron probe microanalysis on more than 100 late pennsylvanian brachiopod shells from texas kansas missouri and new mexico texturally preserved specimens of the genera crurithyris composita and neospirifer from all three regions were analyzed as were eridmatus specimens from texas twenty measurements were made in two transects across each shell shell microstructure and cathodoluminescence were described for each spot analyzed three modern shells were analyzed for comparison diagenesis as indicated by cathodoluminescence and or absence of microstructure tends to enrich shells in fe and mn x ca 0 7 mmol mol and deplete shells in na and s mg content shows no consistent trend with diagenesis in fabric retentive nonluminescent shell areas mg na and s contents vary twofold to sevenfold depending on taxonomy microstructure and season overall taxonomy is the dominant factor controlling mte composition na and s concentrations are consistently highest in crurithyris and eridmatus intermediate in neospirifer and lowest in composita in taxa with mixed microstructure composita neospirifer secondary fibrous layer calcite contains 1 5 to 2 times more na than does interlayer prismatic calcite thus whole shell na contents of these taxa depend on the proportion of fibrous and prismatic shell seasonal cycles are revealed in mte transects across growth lines mg na and s contents commonly vary by more than a factor of two between maxima presumably summer and minima winter within the same shell retention of taxonomic microstructural and seasonal effects in shell chemistry argues for preservation of original chemistry in fabric retentive nonluminescent paleozoic brachiopod shells

morphological and compositional changes in the skeletons of new coral recruits reared in acidified seawater insights into the biomineralization response to ocean acidification 1 we reared primary polyps new recruits of the common atlantic golf ball coral favia fragum for 8 days at 25 c in seawater with aragonite saturation states ranging from ambient 3 71 to strongly undersaturated 0 22 aragonite was accreted by all corals even those reared in strongly undersaturated seawater however significant delays in both the initiation of calcification and subsequent growth of the primary corallite occurred in corals reared in treatment tanks relative to those grown at ambient conditions in addition we observed progressive changes in the size shape orientation and composition of the aragonite crystals used to build the skeleton with increasing acidification densely packed bundles of fine aragonite needles gave way to a disordered aggregate of highly faceted rhombs the sr ca ratios of the crystals measured by sims ion microprobe increased by 13 and mg ca ratios decreased by 45 by comparing these variations in elemental ratios with results from rayleigh fractionation calculations we show that the observed changes in crystal morphology and composition are consistent with a 80 decrease in the amount of aragonite precipitated by the corals from each batch of calcifying fluid this suggests that the saturation state of fluid within the isolated calcifying compartment while maintained by the coral at levels well above that of the external seawater decreased systematically and significantly as the saturation state of the external seawater decreased the inability of the corals in acidified treatments to achieve the levels of calcifying fluid supersaturation that drive rapid crystal growth could reflect a limit in the amount of energy available for the proton pumping required for calcification if so then the future impact of ocean acidification on tropical coral ecosystems may depend on the ability of individuals or species to overcome this limitation and achieve the levels of calcifying fluid supersaturation required to ensure rapid growth

stable carbon isotopes of amorphous kerogens from phanerozoic sedimentary rocks amorphous kerogens from phanerozoic sedimentary rocks may be divided into two groups on the basis of their 13c values h amorphous kerogens have isotopic values in the range of 24 to 20 per mil and l amorphous kerogens have isotopic values in the range of 35 to 26 per mil the occurrence of amorphous kerogens in the intermediate isotopic range from one rock unit in the data set suggests a weak continuum may exist between these two groups phytoplankton and to a lesser extent zooplankton and bacteria are considered to be the precursors for both kerogen types a plausible explanation for this dichotomy may be found in the source of co2 utilized by phytoplankton which is considered to be controlled by environmental factors h amorphous kerogens are expected to occur in silled basins that are overlain by expansive well circulated deep 500 m water where the prevailing source of carbon in the photic zone is atmospheric derived co2 conversely l amorphous kerogens are expected to occur in restricted basins that are overlain by stratified shallow 200 m water where the prevailing source of carbon in the photic zone may be organic derived co2

evaporites marine or non marine division of evaporites into those types that retain information about primary mineralogy textures and structures primary evaporites and those types so extensively altered that few or no primary features remain secondary evaporites only primary evaporites can give unequivocal data bout their marine or non marine origin to help evaluate such primary deposits they have been further divided using the following attributes 1 whether the depositional setting was marine or non marine 2 whether the source water was a seawater b meteoric c hydrothermal d diagenetic e volcanogenic or f mixed specific criteria for making distinctions are 1 kinds of fossils 2 sedimentology of the associated non saline facies 3 kinds of primary saline minerals 4 association of such saline minerals both in qualitative and quantitative terms 5 trace element isotope and fluid inclusion geochemistry of such saline minerals modified journal abstract

stable isotopes in late pennsylvanian brachiopods from the united states implications for carboniferous paleoceanography stable isotopic analyses have been performed on nearly 500 nonluminescent brachiopod shells from kansas new mexico and texas to evaluate temporal and geographic variability in the carbon and oxygen isotopic record for late pennsylvanian time brachiopod specimens were collected from missourian and virgilian shales and examined in thin section for preservation of microstructure and absence of cathodoluminescence as a primary test for shell preservation regional variations are observed in the 18o and 13c values of nonluminescent brachiopod shells of the same genera average 18o values for the three genera analyzed crurithyris composita and neospirifer are highest in kansas 1 9 intermediate in texas 2 3 and lowest in new mexico 3 6 vital effect on the 18o of these genera appears minimal 18o data and other evidence suggest warmer temperatures for the shallow new mexico localities and slightly higher salinity for the kansas sea relative to the texas sea the 13c values of composita average about 1 higher than those of co occurring crurithyris and neospirifer suggesting microhabitat differences or vital effects preservation of this species effect argues for preservation of original 13c values average 13c values are highest in texas intermediate in kansas and lowest in new mexico although these values range from 2 6 to 4 9 for individual genera the regional variation in 13c averages less than 1 data for nonluminescent brachiopods and marine cements reveal a mid carboniferous 13c increase of 2 in paleotethyan sea water this increase is not seen in samples from the north american epicontinental seas which opened to the panthalassa ocean this regional difference in 13c appears to be due to changes in ocean circulation associated with the closing of the equatorial seaway and formation of pangea

holocene sedimentology of hypersaline lake urmia northwestern iran abstract a limnogeological expedition examined the sedimentary record of lake urmia one of the world s largest saline lakes located in a tectonically active arid intermontane plateau in northwestern iran near the cradle of western civilization lake urmia resembles the great salt lake u s a in many respects of morphology water chemistry and sediments the present lake area is about 5000 km 2 shallow 8 12 m and a perennial sodium chloride sulfate system 22 salts high resolution 3 5 khz seismic profiles show morphological relicts from a desiccation playa phase buried below only a few meters of sediments from lacustral phases in places around the deeper areas the lake floor is not smooth but covered with mounds aligned in prevailing current directions these are erosional relicts rather than bioherms sediments comprise aragonite chemical precipitates fecal pellet sands detrital clayey muds thin aragonite crusts oolites various gypsum types and occurrences of dolomite in peripheral areas organic matter characteristic of the present shorelines is not preserved at depth in basinal areas piston cores up to 6 m long penetrated a holocene sequence of hypersaline facies with laminated aragonite fecal pellet muds and bottomed in a playa mudflat facies with central gypsiferous muds and marginal terrigenous to dolomitic muds preliminary radiocarbon and pollen analyses suggest a playa stage prior to 9000 yr b p with saline lake deposition in a cool arid climate from 9000 to 7500 yr b p higher energy facies prevailed in a shallow saline lake and since then present day saline environments have persisted with evidence of numerous second order water level fluctuations the preliminary results suggest a lake system out of phase with north african and some other middle eastern lakes

low productivity and slow deep water circulation in mid cretaceous oceans paleofertility estimates are derived from organic carbon accumulation rates determined in nonbioturbated mid cretaceous deep sea deposits using organic carbon preservation factors observed in laminated sediments from anoxic holocene environments the estimated mid cretaceous primary production rates are as much as an order of magnitude lower than those measured in today s oceans an evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep water renewal rates in mid cretaceous oceans 28 references 2 tables 4 figures

oxygen isotope and mg ca composition of late visean mississippian brachiopod shells from sw iberia palaeoclimatic and palaeogeographic implications in northern gondwana abstract latest visean brachiopod shells gigantoproductus sp from the pedroches basin of sw spain were sampled in order to obtain chemical and isotopic evidence that may help first to assess if primary geochemical and isotopical signals are preserved in these shells and second to reconstruct temporal variations in palaeoceanographic and palaeoclimatic conditions in northern gondwana during this time span microtexture cathodoluminescence cl and ultrastructure under sem of the brachiopods were examined to avoid sampling of shell portions altered after deposition shell portions classified as non luminescent nl and non luminescent to slightly luminescent nl sl present geochemical signatures within the ranges considered normal for recent brachiopods that have not undergone significant diagenetic modification these include low to undetectable fe and mn contents high sr values and 18o values similar to those of carbonates in equilibrium with seawater on the other hand valve areas that are luminescent l or moderately luminescent with luminescent portions ml l present higher fe and mn contents lower sr concentrations and lower 18o values than those corresponding to nl and nl sl shells this suggests a greater diagenetic alteration of these portions and that they acted as microzones of reaction with the diagenetic fluids temporal trends through the studied interval show a spread in 13c values much lower than that observed for contemporaneous samples up to 1 6 thus obscuring the 13c global signal at the time scale resolution of this study in contrast the 18o record of brachiopod calcite 18oc shows an overall increase of 1 relative to v pdb from the oldest to the youngest samples this is accompanied by a 30 decrease in mg ca ratios of the brachiopod calcites confirming that at least part of this shift in 18oc was related to cooling combination of mg ca and 18oc proxies established in this paper although not full proof for brachiopods yet allowed for the calculation of a temperature drop of 3 3 c and a change in seawater 18ow that becomes 0 4 more positive during this interval the data are consistent with regional seawater cooling that accompanied an increase in continental ice volume over a relatively short time period of

high precision u series ages of transported coral blocks on heron reef southern great barrier reef and storm activity during the past century transported coral blocks scattered on reef flats have previously been identified as useful proxies for past storm occurrences high precision tims u series dating and detailed field observations of 110 coral samples collected from 102 individual transported coral colonies coral blocks and 4 transported sections of reef matrix reef blocks from the northern side of heron reef southern great barrier reef indicate that 1 the youngest age of corals attached to reef blocks may represent the age of possible past storm occurrence providing a proxy for historical storm reconstruction 2 most ages of dated storm transported coral and reef blocks match well relatively with known cyclone and storm events further supporting that they are good indicators of past storm events and 3 age distribution and relative probability frequency analysis of the dated coral and reef blocks suggest that there have been eight broad periods of storm occurrence since 1900 ad 1904 1909 1914 1916 1935 1941 1945 1960 1965 1967 1976 1977 1983 1988 and 2001 2007 roughly showing decadal variations the coral based storm reconstruction therefore extended the database of past storm occurrences around heron reef area these findings suggest that coral reefs in the southern great barrier reef are frequently influenced by periods of high storm activity and show strong resilience to natural disturbances over the past century additionally our results show for the first time that the blue skeletal coral heliopora coerulea order helioporacae has u concentrations of only 0 12 to 0 30 ppm similar to 5 10 that of common reef building corals with white skeletons order scleractinia which may be a unique chemical signature of the only living species of the helioporidae family c 2012 elsevier b v all rights reserved

primary and diagenetic carbonates in the anoxic sediments of lake bosumtwi ghana cores of organic rich muds from the tropical meteorite crater lake bosumtwi ghana contain laminae of authigenic calcite polyhedra and aragonite needles as well as scattered diagenetic calcite mg calcite spherulites and aggregates of dolomite crystals their respective origins are traced by analyses of oxygen and carbon stable isotopes anoxic dolomite and mg calcite formed in pore waters reflecting highest degrees of evaporative concentration and high rates of methanogenesis carbon dioxide reduction must have been the dominant methanogenic pathway producing diagenetic carbonates with delta sup 13 c values up to 27 pdb this example shows the inherent problems of interpreting bulk samples with progressive mineralogical sequences of calcite to mg calcite to aragonite to dolomite merely in terms of mg sup 2 ca sup 2 in lake waters it provides a model for the interpretation of ancient lacustrine carbonates from organic rich environments

paleotemperature variations of early jurassic seawater recorded in geochemical trends of belemnites from the basque cantabrian basin northern spain abstract here we present new o isotope mg ca and sr ca data of early jurassic belemnites from the basque cantabrian basin of northern spain a succession deposited in a periodically anoxic restricted hemipelagic basin nearly 200 pliensbachian lower toarcian belemnites were collected and examined using optical cathodoluminescence and chemical techniques to constrain the effects of potential diagenetic alteration after a precise diagenetic screening of samples 176 belemnites were selected to provide records of changes in seawater geochemistry and temperature the records show a fairly good correlation of 18o with mg ca ratios r 0 65 and a weak correlation of 18o with sr ca ratios r 0 34 the oxygen isotope data if interpreted in terms of paleotemperature have revealed a period of relatively uniform and warm seawater temperatures during the early pliensbachian followed by a sharp temperature drop during the late pliensbachian earliest toarcian the onset of this cooler period occurred within the protogrammoceras celebratum subzone and the coolest seawater temperatures were reached at the end pliensbachian pleuroceras spinatum zone this was followed by a rapid seawater warming during the harpoceras serpentinus zone of the early toarcian in addition the data set provides new information regarding paleoceanographic conditions for anoxic events in a critical region of connection between the boreal and tethys realms it is the background to relatively high 18o values that prevailed during the anoxic episodes concerning the impact of the early toarcian anoxic event in northern spain the detected 18o and mg ca excursions reached their minimum and maximum respectively during the lower h serpentinus zone while the anoxic black shale interval developed earlier during the upper dactylioceras tenuicostatum lowermost h serpentinus zones