biogeographic relationships of the coniacian and santonian inoceramid bivalves of northern spain abstract coniacian and santonian ammonite and foraminifera faunas of northern spain show affinities with those of tethyan and north temperate realms the inoceramid faunas are also similar to those of central and northern europe they show a broad palaeongeographical distribution particularly in the coniacian examples are species of inoceramus cremnoceramus and subspecies of i magadiceramus subquadratus santonian inoceramid faunas of northern spain very similar to those of northern germany inoceramus platyceramus undulatoplicatus undulatoplicatus and i p cycloides wegneri both subspecies with divergent ribs are characteristic of the lower santonian while species of inoceramus cordiceramus are common in the middle and upper santonian the two subgenera volviceramus and sphenoceramus are absent from northern spain the later could be due to a tethyan paleobiogeographic influence

facies analysis of the lo valdes formation tithonian hauterivian of the high cordillera of central chile and the palaeogeographic evolution of the andean basin

thermal decay of carbonate dimension stones fabric physical and mechanical changes this paper deals with the effects of thermal stresses on selected carbonate rocks used as dimension stones they are mesozoic calcareous and dolomitic rocks cropping out in apulia southern italy that for their physico mechanical and aesthetic properties have always been finding a large application both as ornamental stones and as simple construction materials their use is attested not only in italy in works of archaeological historical and artistic interest too the cause effect relationships of thermal degradation were studied by means of an artificial accelerated ageing test in order to provide a perspective about the decay of carbonate stones due to diurnal and seasonal temperature fluctuations as well as thermal shocks during events of fire development the stone samples were subjected to thermal cycles in a muffle furnace ranging from 100 to 700 c after each cycle several non destructive and semi destructive tests were carried out mass and volume measurements mercury intrusion porosimetry sclerometer tests ultrasonic tests thin section observations and determination of chromatic alterations through image analysis and munsell charts method in this way the qualitative and quantitative modifications induced in fabric physical and mechanical properties were discussed the results highlight the fundamental role of depositional and diagenetic fabric that together with mineralogical composition represents the most significant discriminating factor in the response of the stone to thermal stresses

implications of pore space characteristics on diffusive transport in basalts and granites a detailed characterization of the pore space is crucial for understanding of transport and element transfer in rocks here the effect of differences in texture and content of secondary minerals on transport in pore systems was determined for two rocks of widespread occurrence mid ocean ridge basalts morb and granites pore space characteristics were analyzed by hg porosimetry intrusion of a molten alloy and synchrotron based x ray tomographic microscopy for evaluating the role of pore space characteristics for the prediction of diffusive transport data on porosity and the effective diffusion coefficient deff were compared extended connective pore systems due to cracks and mineral dissolution are present in samples of both rocks indicating high internal specific surface area uneven pore size distributions in altered morb samples can be assigned to secondary minerals pore spaces determined by x ray tomography used to determine main direction of pores in the 3 d orthogonal system suggest a slight anisotropy in log log plots both rocks show roughly a linear dependence of deff for h2o and compounds with comparable diffusivities d2o monovalent cations and anions on porosity but at same porosity deff is clearly higher in granitic than in basaltic samples this difference is increasing with decreasing porosity indicating that at low porosities the efficiency of element transport in basaltic samples is diminished mainly inherited by the presence of small pores slowing down diffusion the fact that diffusive transport in basaltic rocks is stronger dependent on porosity than in granitic rocks shows that also other rock characteristics such as pore size distribution and tortuosity of the pore network highly affected by the alteration degree can markedly affect transport and reactivity of pore solution

late mesozoic bipolar bivalve faunas bipolar bivalve genera probably existed through the greater part of late mesozoic i e late jurassic late cretaceous time of the various theories put forward to account for their presence those based on some form of global climatic zonation seem most appropriate although equatorial polar temperature gradients were substantially less in late mesozoic time than at the present day high latitude regions were subjected to temperate or even cool temperate climatic regimes macro benthonic marine faunas may have been more susceptible to differentiation in response to these climatic patterns than nektonic ones this is particularly so in the late mesozoic strata of the southern hemisphere

salt crystallization in pores quantification and estimation of damage the objective of this study is to understand and predict the alteration of porous rock by crystallization of salts samples of different rocks have been tested according to the en 12370 standard test two parameters are proposed to evaluate the alteration of a rock during these tests the alteration index ai represents the cycle in which the first damages occur the alteration velocity av represents the alteration rate at the end of the experiment when the decay has become regular these parameters can be estimated with the help of a microstructural study of the rocks the most relevant intrinsic parameters of the stones for this estimation are capillary coefficient evaporation coefficient tensile strength and p waves velocity an evaluation of the alteration pattern is also proposed depending on the eventual heterogeneities and anisotropies of the rocks the influence of the dimension and shape of the samples is also discussed

granitic dimensional stones in uruguay evaluation and assessment of potential resources in uruguay commercial granite varieties comprise mafic rocks granitoids and syenitoids there is a long tradition in uruguay as well as worldwide of using dimensional stones in architecture and art specially granitic ones some of the present applications of these dimensional stones are as facade cladding countertops and outdoor and indoor floor slabs the color spectrum of the uruguayan granitic dimensional stones varies from black to light gray covering a wide variety of red and pink and minor greenish gray the decor of these granitic dimensional stones is mainly determined by their fabric fundamentally the grain size and the color distribution between the different minerals that compose the rocks in the present research the most important commercial granites were sampled to analyze their petrography and petrophysical properties a detailed structural analysis has been performed in several deposits as well as the application of the software 3d block expert for modeling the possible raw block size distribution other factors controlling the mining viability of the deposits were also studied e g homogeneity heterogeneity of color and decor and the possible reserves were calculated

a lower cretaceous ichthyosaur graveyard in deep marine slope channel deposits at torres del paine national park southern chile remnants of ophthalmosaurid ichthyosaurs recently discovered in the vicinity of the tyndall glacier in the torres del paine national park of southern chile are extremely abundant and well preserved after three field campaigns to the area a total of 46 articulated and virtually complete ichthyosaur specimens both adults and juveniles were tentatively assigned to four different species of ophthalmosauridae preservation is excellent and occasionally includes soft tissue and embryos the skeletons are associated with ammonites belemnites inoceramid bivalves and fishes as well as numerous plant remains the enormous concentration of ichthyosaurs is unique for chile and south america and places the tyndall locality among the prime fossil lagerstatten for early cretaceous marine reptiles worldwide the deposit is early cretaceous valanginian hauterivian in age and forms part of a monotonous bathyal to abyssal sequence of the late jurassic to late early cretaceous rocas verdes back arc basin in this region the tyndall ichthyosaur population may have profited from cold upwelling currents that caused abundant life at the shelf edge including masses of belemnites and small fish the preferred diet of ichthyosaurs the abundance of almost completely articulated ichthyosaur skeletons in the tyndall area suggests that some animals fell victim to episodic mass mortality events caused by turbidity currents traveling downslope through a submarine canyon they lost orientation drowned and were dragged into the deep sea by these turbulent high energy gravity flows their bodies ended up in an oxygen deficient basin environment where they were immediately embedded by the fine turbidite suspension fallout the tyndall ichthyosaur locality thus combines characteristics of both concentration and conservation lagerstatten

studies on the early cretaceous longzhaogou and jixi groups of eastern heilongjiang northeast china and their bearing on the age of supposedly jurassic strata in eastern asia abstract the coal bearing longzhaogou and jixi groups in eastern heilongjiang northeast china consist of alternating marine and non marine deposits containing abundant marine animal and plant fossils the jixi group also yields members of the johel fauna that is widely distributed in northern and eastern china the two groups have been considered as jurassic or mainly jurassic in age for a long time however recent studies documented that the ammonites bivalves dinoflagellates angiosperms and sporopollens are all of early cretaceous rather than jurassic age it has been demonstrated that 1 the longzhaogou and jixi groups and their equivalents the johel group of china and the transbaikalian group of russia are of early cretaceous age 2 the barremian albian was also a very important period of coal accumulation in northeastern china and perhaps in all of eastern asia 3 there existed a large shallow embayment connecting with the palaeo pacific in eastern heilongjiang and it was the climate of the embayment that controlled the origin and development of the animal and plant communities of northeastern china during the early cretaceous correlation between formations in the jixi and longzhaogou groups has also been revised in this paper

influence of fracture system on the exploitation of building stones the case of the mondim de basto granite north portugal the most negative aspects in the exploitation of weathered granites as ornamental stones tend to be heterogenic coloration and fracturing therefore an accurate study is needed for a comprehensive evaluation of the granite resources during an exploration campaign this paper presents the results of the fracturing evaluation of a region located in north of portugal where the mondim de basto granite a stone with a high weathering degree is exploited the regional fracturing was evaluated from lineaments in aerial photos and then compared with local jointing in quarries the jointing in each quarry is characterized according to the strike and dip joint spacing and volumetric joint count two indices were proposed to facilitate the jointing comparison among quarries the joint space length ljs and joint set spacing sjs ljs is based on the sum of all the spacing values obtained perpendicularly to the strike direction sjs is computed based on the overall mean median spacing and on the number of joint sets observed in each quarry the most important joint sets in the subdivision of the rock mass were found not to be in accordance with the regional fracturing patterns highlighting the necessity of studying the fracturing at all scales

andean tectonics as a consequence of sea floor spreading abstract the evolution of sea floor spreading directions and rates in the southeast pacific shows a close relationship with the andean structural directions and the plutonic episodicity as well as the succession of short compressive orogenic phases alternating with relatively longer periods of extension the orogenic periods coincided with the beginning of periods of relatively higher rates of plate convergence immediately after periods of relative quiescence with the following periodicity 110 85 76 70 63 60 49 45 35 33 16 13 7 m y the presence of oceanic structures as aseismic ridges or fracture zones produces weak benioff zones shallow and poorly defined without a corresponding active volcanism on the other hand ancient continental structures such as the precambrian paleozoic orogenic belts have active volcanism and neat deep and well developed benioff zones

the determination of uniaxial compressive strength from point load strength for pyroclastic rocks abstract the point load test has often been reported as an indirect measure of compressive strength it has been used widely in practice due to easy testing the simplicity of specimen preparation and possible field applications many researchers have investigated the relation between uniaxial compressive strength ucs and point load index is for different rock types however there are limited studies in the literature for soft rocks such as pyroclastic rocks in this study the relation between ucs and is was investigated for pyroclastic rocks having ucs values are less than 50 mpa very strong exponential relations were found for dry rocks saturated rocks and both dry and saturated rocks the results were also compared to the studies in the literature

determination of strength parameters and quality assessment of denizli travertines sw turkey abstract travertine carbonate rich sedimentary rocks which are deposited by hot and cold waters as with all natural stones strength properties of travertines have great importance depending on the using conditions and places naturally porous structure of travertines is the most important parameter affecting the overall strength denizli basin is one of the world s major travertine regions in this study strength properties and relations between obtained parameters of denizli travertines were studied uniaxial compressive strength ucs values of travertines are widely ranging between 9 58 and 132 32 mpa noche type travertines are identified to have 59 100 higher strength than other type of travertines flexural strength under concentrated load 3 point flexural strength fls 3 and flexural strength under constant moment 4 point flexural strength fls 4 tests which are required for ce certification were also carried out on travertine samples between these tests linear relationship expressed as fls 4 0 98 fls 3 0 094 was found variations of strength parameters depending on the stone cutting type have been presented for the first time in this study it is found that the strength values under parallel loading to lamination are 1 44 times higher than the perpendicular loading

building stone evaluation a case study of the sub himalayas muzaffarabad region azad kashmir pakistan abstract building stone is one of the oldest material used in construction the present study evaluated the physical and mechanical characteristics of dolomite limestone and sandstone as building stones these rocks were selected from the foothills of himalaya as a case study compressive strength tensile strength specific gravity durability under wetting drying water absorption pulse velocity and petrography of the selected rocks were evaluated relationships were established among these properties of the rocks total reserves of these rocks in the selected area were approximated and the influence of geological structures on the rock properties were also considered kashmir boundary thrust and kawai fault present in the study area have adversely affected the physico mechanical characteristics of the rocks dolomite shows a higher water absorption and lower strength values than expected kamsar dolomite shows high degree of fracturing and weathering which lowers its polishing character and degrades its quality as building and ornamental stone however yadgar dolomite reflects fair degree of polishing and could be used as ornamental stone and as non load bearing masonry units limestone also shows lower strength values but its good degree of polishing and other characteristics are suggestive of its use in internal flooring cladding stone veneer wall stone tabletops risers and treads the most suitable rock proven as building stone is pattika sandstone due to its sound petrographic characters higher tensile and compressive strengths very high durability and lower water absorption values deolian sandstone should be avoid in load bearing masonry units because of its lower strength values pattika sandstone can be used as curbs copings sills facing stone external pavements and as ashlar and rubble stone strength properties were found to be largely dependent on each other ultrasonic pulse velocity in these rocks shows close relation to the density than the strength characteristics durability under wetting drying was found to be more relevant to the water absorption and less relevant to the strength of rocks sandstone has fairly large reserves in the study area followed by dolomite and limestone

palaeoenvironmental implications and diagenesis of inoceramid shells bivalvia in the mid maastrichtian beds of the sopelana zumaya and bidart sections coast of the bay of biscay basque country inoceramid bivalve shells from the mid maastrichtian beds of the sopelana zumaya and bidart sections in the basque country were tested for their post depositional diagenetic alteration petrography cathodoluminescence cl and scanning electron microscope sem observations together with geochemical analyses indicate that the coarsely prismatic calcite of the shells from the sopelana and zumaya sections have undergone diagenetic alteration without there being substantial textural changes in the original prismatic microstructure a generalized bright yellowish to red colour is seen in all the samples observed by cl the 18o values obtained from the shell prisms range from 2 94 to 5 18 with a mean value of 3 6 0 5 in the sopelana section whereas in the zumaya section they range from 1 88 to 4 71 with a mean value of 3 2 0 3 these values are clearly lower than those from the bidart section from 0 32 to 1 48 mean value 0 7 0 3 other evidence of diagenetic alteration is inferred from both whole shell geochemistry and microprobe analysis a complementary zonation in the distribution of diagenetic tracers can be detected from the inner shell layer isl to the outer shell layer osl of inoceramid shells together with a rare earth element ree enrichment in the shells which have lighter 18o values in contrast the inoceramid bivalve shells and their host rock from the bidart section were less altered the calculated mean palaeotemperature 15 c and the value of 13 c estimated from the non luminescent middle shell layer seem to be consistent with palaeolatitudes about 30 n for deep marine waters of mid maastrichtian time as the last step of the long term climatic cooling of the late cretaceous greenhouse

a correlation between schmidt hammer rebound numbers with impact strength index slake durability index and p wave velocity the main objective of this study was to establish statistical relationship between schmidt hammer rebound numbers with impact strength index isi slake durability index sdi and p wave velocity these are important properties to characterize a rock mass and are being widely used in geological and geotechnical engineering due to its importance schmidt hammer rebound number is considered as one of the most important property for the determination of other properties like isi sdi and p wave velocity determination of these properties in the laboratory is time consuming and tedious as well as requiring expertise whereas schmidt hammer rebound number can be easily obtained on site which in addition is non destructive so in this study an attempt has been made to determine these index properties in the laboratory and each index property was correlated with schmidt hammer rebound values empirical equations have been developed to predict isi sdi and p wave velocity using rebound values it was found that schmidt hammer rebound number shows linear relation with isi and sdi whereas exponential relation with p wave velocity to check the sensitivity of empirical relations student s t test was done to verify the correlation between rebound values and other rock index properties

upper triassic to lower cretaceous continental and coastal saline lake evaporites inthe atacama region of northern chile evaporites within upper triassic to lower cretaceous sequences in the atacama region of northern chile are interpreted as the deposits of continental and coastal saline lakes halite casts and finely laminated calcareous evaporites intercalated with alluvial and fluvial sediments are probably playa lake deposits these continental evaporites have been recognized in upper triassic alluvial sediments cifuncho formation in upper triassic lower jurassic braided river deposits basal unit of the pan de azucar formation and within a sequence of lower cretaceous aeolian alluvial and playa lake mudflat sediments quebrada monardes formation lower cretaceous evaporites between marine limestones lautaro formation and continental redbeds quebrada monardes formation were probably deposited in coastal saline lagoons produced during a regionally extensive marine regression these sequences and other similar successions in northern chile provide a record of almost continuous evaporite deposition and hence of arid to semi arid conditions since upper triassic times these conditions were primarily the result of a constant latitudinal position within the subtropical zone a contributary factor was the geographical position of the area initially on the west coast of gondwanaland and subsequently on the coast of south america with cold northward flowing ocean currents and offshore winds

late mesozoic stratigraphy in western liaoning china a review abstract based on progress in stratigraphic and paleontological studies we discuss the subdivision of late mesozoic strata in western liaoning focusing on the controversies surrounding the relationship of the jiufotang and shahai formations and whether or not the zhanglaogongtun and banlashan formations exist as distinct lithologic units we describe the late mesozoic strata at representative sections associated with the new discoveries we also discuss the correlation of late mesozoic strata between western liaoning and eastern heilongjiang and their implications for the ages of the strata in liaoning

black dimensional stones geology technical properties and deposit characterization of the dolerites from uruguay dimensional stones with a black color occupy a prominent place on the international market uruguayan dolerite dikes of andesitic and andesitic basaltic compo sition are mined for commercial blocks of black dimen sional stones a total of 16 dikes of both compositions were studied and samples collected for geochemical and petro graphical analysis color measurements were performed on different black dimensional stones in order to compare them with the uruguayan dolerites samples of the two commercial varieties absolute black and moderate black were obtained for petrophysical analysis e g density porosity uniaxial compressive strength tensile strength etc detailed structural analyses were performed in sev eral quarries geochemistry and petrography determines the intensity of the black color the uruguayan dolerite absolute black is the darkest black dimensional stone analyzed in this study the petrophysical properties of uruguayan dolerites make them one of the highest quality black dimensional stones structural analyses show that five joint sets have been recognized two sub vertical joints one horizontal and two diagonal these joint sets are one of the most important factors that control the deposits since they control the block size distribution and the amount of waste material

macrofossil magnetobiostratigraphy for the upper santonian lower campanian interval in the western interior of north america comparisons with european stage boundaries and planktonic foraminiferal zonal boundaries magnetostratigraphic samples were collected from the milk river and pakowki formations of southeastern alberta to determine the polarity chron 34 33r boundary this boundary was located in the upper half of the deadhorse coulee member and is below the first local occurrence of the western interior ammonite baculites obtusus comparison with the laterally equivalent eagle sandstone of montana and niobrara formation of colorado indicates that the 34 33r contact is within either the baculites sp smooth or baculites sp weak flank ribs ammonite zone in the western interior of north america direct correlation of the desmoscaphites erdmanni through baculites asperifomis western interior ammonite zones with magnetobiostratigraphic sections of the upper santonian lower campanian stages in europe suggests that i the santonian campanian boundary as defined in europe is within the lower baculites obtusus zone and ii the western interior appearance of some ammonites and crinoids scaphites hippocrepis trachyscaphites spiniger marsupites uintacrinus is profoundly time transgressive relative to the appearance of these same species in europe the date of 84 ma for the santonian campanian boundary is too old and a date of around 80 ma may be more accurate the santonian campanian boundary defined by ammonites crinoids and belemnites in europe is within the lower part of chron 33r and is younger than the santonian campanian boundary as determined by planktonic foraminifera at gubbio italy

late mesozoic transgressions of eastern heilongjiang and their significance in tectonics and coal and oil accumulation in northeast china abstract the spatial and temporal distribution of late mesozoic marine and brackish water sediments in eastern heilongjiang records three main transgressive interludes the late middle callovian valanginian barremian aptian and albian marine invasion phases the callovian valanginian transgressions were limited to the northeastern corner of eastern heilongjiang but the others intermittently extended northwest southwest and westwards along the yunshan shallow embayment which opened into and deepened towards the northwestern palaeo pacific they not only flooded almost all of the subsiding basins surrounding the embayment but during peak transgressions also widely flooded areas outside eastern heilongjiang such as the yanji beipiao fuxin and songliao basins along the tan lu fault system of northeast china all the transgressions came from the northwestern palaeo pacific ocean and probably the arctic sea as well in addition to the eustatic sea level changes the late early cretaceous transgressions of northeast china were closely related to the tectonic movements within the tan lu fault system and the circum paleo pacific which were very pronounced and went hand in hand with a strong volcanic activity and ongoing subsidence during the late early cretaceous the long term existence of a marine embayment in eastern heilongjiang successive marine transgressions and flooding along the tan lu fault system in northeast china ensured a humid climate across all of northeast china these transgression and climatic conditions produced a number of extensive and long lasting swamps and marsh lands in both paralic and limnic environments luxuriant plant and thriving animal growth led to the accumulation of abundant organic matter in the deposits as a result a number of late early cretaceous coal basins and oil fields formed in eastern heilongjiang the yanji basin of eastern jilin beipiao fuxin basin of western liaoning and the songliao basin northeast china

characterization and quality assessment of granitic building stone deposits a case study of two different portuguese granites abstract several factors determine building stone exploration in order to maximize the extraction processing and application of these natural materials some factors are intrinsic to stones such as their physical mechanical properties while others are related to their exploitability such as quarry reserves or fracturing density during an exploration campaign these factors are not always considered or properly weighed in terms of the negative consequences on quarry activities or rock behaviour under particular conditions in this study two well known portuguese granites are assessed to highlight the main factors these granites have different characteristics weathered and sound and are exploited in quarries with different joint densities the most relevant physical mechanical properties were evaluated and related to the specific petrophysical features of each granite the fracture patterns were identified in the quarries and then modelled in order to compute the quarry yield the weathered granite shows an important microcrack network and a general alteration of the rock forming minerals which has an important impact on its physical mechanical properties and on the resistance to environmental factors moreover the extreme differences in the degree of weathering require careful choices for the possible applications in both quarries the joint sets are similar to the regional faulting but some random joints can be found and consequently diminish the quarry yield the development of horizontal sheet joints during the exploitation process could have a great influence on the quarry productivity if they are not used do delimitate the extracted blocks the modelling of the natural fracture pattern allows us to determine the potential volume of blocks that could be exploited however the quality of the information gathered could lead to an over estimation of the quarry production this example shows the importance of the exhaustive researches during a building stone assessment campaign

the pliensbachian and tithonian extinction events the claim by raup and sepkoski1 that an approximately 26 myr mass extinction periodicity can be recognized on a global scale at family level over the past 250 myr has excited much attention and provoked speculation about an ultimate extraterrestrial cause2 10 while the purported periodicity can be challenged on grounds of both the inaccuracy of the geological timescale11 and the method of extinction analysis12 there can be no doubting the reality of at least some of the 12 proposed extinction events such as those at or near the end of the permian triassic and cretaceous others are less widely acknowledged further analysis by raup and sepkoski13 confirms the importance of two of these events within the jurassic at the end of the pliensbachian and tithonian stages i demonstrate here that marine invertebrate mass extinctions at approximately these times occurred on a regional not a global scale they can be related to severe reductions in habitat area provoked either by regression of epicontinental sea or by widespread anoxia

salt and ice crystallisation in porous sandstones salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones the damaging effect of these processes can be traced back to physically induced stress inside of the rock while crystallizing the increasing scientific research done during the past century has shown that there are numerous parameters that have an influence on the weathering resulting from these processes however the working mechanisms of the stress development within the rock and its material dependency are still subject to discussion this article gives an overview of salt and ice weathering additionally laboratory results of various sandstones examined are presented salt crystallisation tests and freeze thaw tests were done to obtain information about how crystallisation weathering depends on material characteristics such as pore space water transportation and mechanical features simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed detailed information on the development of crystal in the pore spaces as well as the development of stress these findings can help to understand the damaging mechanisms

physical weathering of building stones induced by freeze thaw action a laboratory long term study damages to natural building stones induced by the action of frost are considered to be of great importance commonly the frost resistance of building stones is checked by standardised freeze thaw tests before using corresponding tests normally involve 30 50 freeze thaw action cycles in order to verify the significance of such measurements we performed long term tests on four selected rocks over 1 400 freeze thaw action cycles additionally numerous petrophysical parameters were analysed to compare the behaviour of rocks in the weathering tests according to the current explanatory models of stress formation by growing ice crystals in the pore space the long term tests yield more information about the real frost sensibility of the rocks a clear deterioration cannot be determined in most cases until 50 weathering cycles have been completed in the freeze thaw tests the samples are also stressed by changing temperature and moisture indicating that different decay mechanisms can interfere with each other thus thermohygric and moisture expansion are important damage processes

granite fracture index to check suitability of granite outcrops for quarrying a correct knowledge of fracture patterns previous to quarrying is important for economical exploitation this work comprises the general characterization of the discontinuities of 10 granite rock masses in ne portugal during the study some discontinuity characteristics such as orientation persistence aperture trace length and spacing were evaluated the differences in the characteristics of the selected granites were described and the most important exploration factors were identified in the granites studied most of the joints are oriented from n10 e to n50 e which is compatible with the regional fracture pattern concerning joint termination the xx type is common while the rr type is rare the persistence index ranges from 3 5 to 25 4 closed joints are predominant in the granites studied n 72 4 and openings of the others are about 1 2 mm as a result of superficial displacement of the granite blocks the percentage of filled joints usually by quartz and pegmatite is different from one granite to another but most are b 20 the average joint length ranges from 11 1 m in post tectonics granites to 4 6 m in syntectonic granites joint spacing varies from 0 98 to 2 8 m with higher values in post tectonic granites joint space distributions of the granites studied are close to log normal and exponential distributions volumetric joint count jv ranges from 0 8 to 2 1 joints m 3 and is used for categorizing the places of each granite the relationships between jv and other joint characteristics such as length spacing and number of joint sets were investigated a granite fracturing index gfi is introduced computed on the basis of volumetric joint count number of joint sets and true joint spacing the gfi classification of studied places allows us evaluate the suitability for profitable exploitation 2007 elsevier b v all rights reserved

holocene development of the southeastern texas coast sabine lake area from foraminiferal biofacies abstract foraminifera were analyzed in cores of holocene sediments from the southeastern texas coast to better understand the post glacial evolution of the texas chenier plain and incised valley of the sabine and neches rivers foraminifera are rare to absent in highstand interfluve marsh and in incised valley fluvial floodplain deposits whereas nearshore marine estuarine and chenier plain deposits contain abundant foraminifera overall foraminiferal diversity is low and sample assemblages are dominated by ammonia parkinsoniana and elphidium gunteri these species comprise about 78 of the fauna the remaining taxa include elphidium spp miliolids brizalina spp bucella hannai and palmerinella palmerae samples are characterized by mixtures of well preserved and poorly preserved tests this along with the presence of cretaceous foraminifera suggests that many of the microfossils are reworked small adult foraminifera are common in cores from the chenier plain and are generally associated with fine grained sediments deposited as mudflats between the sand rich beach ridges agglutinated foraminifera are surprisingly rare probably because geochemical conditions do not favor the preservation of agglutinated tests below about 2 m foraminiferal biofacies include a very low diversity brackish marsh assemblage a moderate diversity beach assemblage a moderate diversity shallow marine assemblage and a relatively high diversity slightly deeper but still nearshore marine assemblage these biofacies are consistent with those described from the louisiana chenier plain the faunal associations diversity abundance and preservation provide insight to the paleoenvironments and depositional processes of the chenier plain

bottom water anoxia inoceramid colonization and benthopelagic coupling during black shale deposition on demerara rise late cretaceous western tropical north atlantic 1 the bulk rock geochemistry and inoceramid isotopic composition from cenomanian to santonian finely laminated organic rich black shales recovered during ocean drilling program leg 207 on demerara rise western tropical north atlantic suggest persistent anoxic free h2s conditions within the sediments and short term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a 15 ma time interval in addition to being organic rich the 50 90 m thick sections examined exhibit substantial bulk rock enrichments of si p ba cu mo ni and zn relative to world average shale these observations point to high organic burial fluxes likely driven by high primary production rates which led to the establishment of intensely sulfidic pore waters and possibly bottom waters as well as to the enrichments of cr mo u and v in the sediments at the same time the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not have been continuously anoxic the 13c and 15n values of the inoceramid shell organics provide no evidence of chemosymbiosis and are consistent with pelagic rain as being a significant food source demerara rise inoceramids also exhibit well defined regularly spaced growth lines that are tracked by 13c and 18o variations in shell carbonate that cannot be simply explained by diagenesis instead productivity variations in surface waters may have paced the growth of the shells during brief oxygenation events suitable for benthic inoceramid settlement these inferences imply tight benthopelagic coupling and more dynamic benthic conditions than generally portrayed during black shale deposition by invoking different temporal scales for geochemical and paleontological data this study resolves recent contradictory conclusions e g sulfidic sedimentary conditions versus dysoxic to suboxic benthic waters drawn from studies of either sediment geochemistry or fossil distributions alone on demerara rise this variability may be relevant for discussions of black shales in general

anatomy of shelf deltas at the edge of a prograding eocene shelf margin spitsbergen although shelf edge deltas are well imaged seismic features of holocene and pleistocene shelf margins documented outcrop analogues of these important sand prone reservoirs are rare the facies and stratigraphic architecture of an outcropping shelf edge delta system in the eocene battfjellet formation spitsbergen is presented here as well as the implications of this delta system for the generation of sand prone shelf margin clinoforms the shelf edge deltas of the battfjellet formation on litledalsfjellet and hogsnyta produced a 3 5 15 km shelf edge attached slope apron 70 m of sandstones proximally tapering to zero on the lower slope the slope apron consists of distributary channel and mouth bar deposits in its shelf edge reaches passing downslope to slope channels chutes that fed turbiditic lobes and spillover sheets in the transgressive phase of the slope apron estuaries developed at the shelf edge and these also produced minor lobes on the slope the short headed mountainous rivers that drained the adjacent orogenic belt and fed the narrow shelf and the shelf edge position of the discharging deltas made an appropriate setting for the generation of hyperpycnal turbidity currents on the slope of the shelf margin the abundance of organic matter and of coal fragments in the slope turbidites is consistent with this notion evidence that many of the slope turbidites were generated by sustained turbidity currents that waxed then waned includes the presence of scour surfaces and thick intervals of plane parallel laminae within turbidite beds in the slope channels and thick spillover lobes with repetitive alternations of massive and flatlaminated intervals the examined shelf edge to slope system now preserved mainly below the shelf break and dominated by sediment gravity flow deposits has a threefold stratigraphic architecture a lower progradational part in which the clinoforms have a slight downward directed trajectory a thin aggradational zone and an upper part in which clinoforms backstep up onto the shelf edge a greatly increased density of erosional channels and chutes marks the regressive to transgressive turnaround within the slope apron and this zone becomes an angular unconformity up near the shelf edge this unconformity with both subaerial and subaqueous components is interpreted as a sequence boundary and developed by vigorous sand delivery and bypass across the shelf edge during the time interval of falling relative sea level the studied shelf margin clinoforms accreted mostly during falling stage sea level below the shelf edge but the outer shelf later became estuarine as sea level became re established above the shelf edge

optimized extraction of dimension stone blocks the profitable production of dimension stone mainly depends on the extractable block size the regularity and volume of the blocks are of critical importance and are controlled by the three dimensional pattern of the discontinuity system therefore optimization of block size has to be the aim when quarrying for natural stone this is mainly connected to the quantification of joints and fractures i e their spacing and orientation the problem of finding unfractured blocks within arbitrarily oriented and distributed planes can be solved effectively by a numerical algorithm the main effects of joint orientations on block sizes and shapes will be presented in this article quantification of unfractured blocks with the aim of optimization is illustrated by detailed studies on several quarries the algorithm used in this study can be applied as a powerful tool in the planning of a quarry and the future exploitation of dimension stone application of the described approach is demonstrated on practical examples of quarrying natural stones namely sandstone granite rhyolite etc block quarrying can be optimized by using the new 3d blockexpert approach the quantification of unfractured rock masses is also shown to contribute to a more ecological protection and the sustainable use of natural resources

rock mass block quality designation for marble production abstract discontinuity spacing measurements are generally carried out along scan lines and or along the rock mass exposures quarry benches and or bore cores for assessing the rock mass quality rock mass block quality designation ratio bqd has been defined for assessment of the block production capacity of rock mass as bqd s 1m l where s 1m cumulative of the discontinuity spacing equal and or greater 1 0 m l scan line length m assessment of the discontinuity spacing measurements made along 2198 m long the scan lines in 6 working and five abandoned limestone quarries in karaburun area in western turkey have shown that while the working quarries had bqd ratios 50 and the abandoned quarries had bqd ratios

biostratigraphy of the upper jurassic lower cretaceous bivalves buchia and aucellina of eastern heilongjiang northeast china the biostratigraphic significance of the bivalves buchia and aucellina in northeast china is assessed buchia is abundant in four assemblages of the dong anzhen formation spanning the jurassic cretaceous boundary b russiensis b fischeriana middle volgian b fischeriana b unschensis upper volgian b volgensis b cf subokensis b cf okensis b unschensis berriasian and b pacifica lower valanginian aucellina is common in two middle barremian aptian assemblages a caucasica a aptiensis a jeletzkii in the lower part of the upper yunshan formation longzhaogou group and in the lower part of the chengzihe formation jixi group a cf caucasica a cf aptiensis in the upper part of the upper yunshan formation these assemblages can be correlated on a global scale and are particularly significant in dating the early cretaceous coalbearing measures of eastern heilongjiang

cretaceous inoceramid biogeography a review abstract cretaceous inoceramid bivalves were widely distributed they did not thrive in very shallow or very warm seas and are therefore rare in tethyan shallow deposits in the berriasian barremian interval they occured mainly in the temperate seas and thier distribution is often bipolar in the albian cenomanian interval inoceramids were varied and numerous especially in clays and chalks but rare in the greensand type strata most inoceramid groups were cosmopolitan during this interval from the turonian onwards the north pacific province is characterized by endemic inoceramid faunas following the opening of the south atlantic ocean in the turonian new inoceramid lineages in the southern hemisphere from brazil to madagascar evolved in co occurrence with other cosmopolitan groups many coniacian and santonian species were widely distributed and short lived but in the campanian and maastrichtian a homogeneous fauna was apparently confined to eastern north america and western eurasia few of the last inoceramid species in the upper cretaceous have stratigraphic value and in contrast to the lower cretaceous they are common in warm water deposits for example in libya nigeria and tunisia

late turonian climate variability in the bohemian cretaceous basin a sclerochronological study of inoceramus hercules shells from the upohlavy quarry czech republic abstract the 18o record of well preserved shells of the inoceramid inoceramus hercules from the upohlavy working quarry czech republic provides an insight into the climate variability in the late turonian benthic environment of the bohemian cretaceous basin similar to modern bivalves this inoceramid species built its shell near equilibrium with the oxygen isotope value of the ambient water due to the nearly year round shell growth sequentially sampled 18o values allowed to estimate the narrowest sub annual temperatures fluctuations that prevailed during lifetime of the organisms in accordance with previous studies reconstructed temperatures suggest colder water conditions 19 0 0 9 c during the earliest late turonian coinciding with the hyphantoceras event also known as hitch wood event than during the later part of the substage 20 9 1 1 c climate warming however did not affect the sub annual temperature fluctuations evenly but predominantly affected the warmest part of the year at least 4 0 c on the contrary the coldest recorded temperatures remained more or less invariant varying not much more than 1 0 c across the studied time interval the observed changes in the benthic temperature estimates likely reflect shifts in seasonal sea surface temperature amplitudes in response to climate forcing given the widespread distribution of i hercules in the upper turonian lower coniacian hemipelagic strata of europe the present study sets the basis for future continent wide sub annually resolved climate reconstructions

jurassic sedimentary cycles and eustatic sea level changes in southern tibet abstract the marine jurassic sequence in southern tibet is well exposed has an abundant fossil record and provides a good basis for the study of paleoeustasy from measured sections nine lhtho facies representing four broad sedimentary environments inner and outer shelves slope and bathyal can be recognised their vertical ranges show that shelf deposits are mainly present in the lower and middle jurassic whilst outer shelf slope and bathyal environments dominate in the middle and upper jurassic on the basis of these after comparison of the two main approaches used in analysing sea level movements i e the exxon eustatic curve and eustatic cycles jurassic eustatic sea level changes in southern tibet are described the resulting curve is seen to correspond closely with earlier published global curves the cause of these sea level changes is thought to lie in the breakup of gondawanaland and the northwards drift of the indian subcontinent and associated microplates

the bowing potential of granitic rocks rock fabrics thermal properties and residual strain the bowing of natural stone panels is especially known for marble slabs the bowing of granite is mainly known from tombstones in subtropical humid climate field inspections in combination with laboratory investigations with respect to the thermal expansion and the bowing potential was performed on two different granitoids cezlak granodiorite and flossenburg granite which differ in the composition and rock fabrics in addition to describe and explain the effect of bowing of granitoid facade panels neutron time of flight diffraction was applied to determine residual macro and microstrain the measurements were combined with investigations of the crystallographic preferred orientation of quartz and biotite both samples show a significant bowing as a function of panel thickness and destination temperature in comparison to marbles the effect of bowing is more pronounced in granitoids at temperatures of 120 c the bowing as well as the thermal expansion of the cezlak sample is also anisotropic with respect to the rock fabrics a quantitative estimate was performed based on the observed textures the effect of the locked in stresses may also have a control on the bowing together with the thermal stresses related to the different volume expansion of the rock forming minerals

phenomena of pulsation tectonics related to the breakup of the eastern north american continental margin abstract new data from the recent ipod drilling of dsdp site 534 in the blake bahama basin give a definite age for the spreading center shift involved in the breakup of the north american atlantic margin a basal callovian age 155 m y is determined for the blake spur magnetic anomaly marking this spreadingcenter shift that signals the birth of the modern north atlantic ocean this is some 20 m y younger than previously thought an implication of this younger age for the blake spur event is that very high spreading rates are now required for the jurassic outer magnetic quiet zone along the north american margin this association of a relatively high spreading rate with a magnetic quiet zone is similar to that for the mid cretaceous and implies a link between the processes controlling plate spreading which are in the upper mantle and the processes controlling the magnetic field which are in the outer core a theory of pulsation tectonics involving the cyclic eruption of plumes of hot mantle material from the lowermost mantle could explain the correlation plumes carry heat away from the core mantle boundary and later reach the asthenosphere and lithosphere to induce faster spreading the pulse of fast spreading in the jurassic apparently followed the breakup of continents bordering the north atlantic ocean other pulses of fast spreading appear to correlate with major ocean openings on various parts of the globe implying that this might be a prevalent process rifting of passive margins may be controlled by the more fundamental global processes described by the theory of pulsation tectonics

the development and application of the alteration strength index equation abstract we have developed an alteration strength index asi equation to address the effect of hydrothermal alteration on mechanical rock properties this equation can be used to estimate a range of rock strengths comparable to uniaxial compressive strength ucs based on rapid analysis of mineralogy and microstructure we used rock samples from three geothermal fields in the taupo volcanic zone tvz to represent a range of alteration types these are sedimentary intrusive and extrusive rocks typical of geothermal systems from shallow and deep boreholes 72 measured depth md to 3280 md the parameters used in asi were selected based on literature relating these aspects of mineralogy and microstructure to rock strength the parameters in asi define the geological characteristics of the rock such as proportions of primary and secondary mineralogy individual mineral hardness porosity and fracture number we calibrated the asi against measured ucs for our samples from the tvz to produce a strong correlation r2 of 0 86 and from this correlation we were able to derive an equation to convert asi to ucs because the asi ucs relationship is based on an empirical fit the ucs value that is obtained from conversion of the asi includes an error of 7 mpa for the 50th percentile and 25 mpa for the 90th percentile with a mean error of 11 mpa a sensitivity analysis showed that the mineralogy parameter is the dominant characteristic in this equation and the asi equation using only mineralogy can be used to provide an estimated ucs range although the error or uncertainty becomes greater this provides the ability to estimate strength even when either fracture or porosity information are not available for example in the case of logging drill cuttings this research has also allowed us to provide ranges of rock strengths based solely on the alteration zones mineralogy and depth of lithologies found in a typical geothermal field that can be used to update conceptual models of geothermal fields

geochemistry and petrology of a middle tithonian limestone marl rhythmite in the neuquen basin argentina depositional and burial history

sea level fall below the shelf edge without basin floor fans a fall of sea level to below the shelf edge formation of type 1 sequence boundary increases greatly the likelihood of sand delivery into deep water basin floor areas although an unusually high sediment supply can bring significant volumes of sediment to the shelf edge at any time an eocene ypresian data set from seismic scale mountainside outcrops of shelf slope clinoforms illustrates that a fall of sea level below the shelf edge produces significant sand accretion on the shelf margin but brings no sand out onto the basin floor fall and subsequent rise of relative sea level are documented by the style and topographic position of successive shelf edge to slope clinoforms each representing a shelf edge delta with its greatly extended slope apron of turbidite lobes sheets and chutes a downslope shift of clinothems at the shelf edge and a headward cannibalization of the oldest perched slope deltas are the criteria for recognition of 1 the time interval of sea level fall and 2 the position of sea level below the shelf edge the lowest sea level is recorded by the most basinward clinothem set with a high density of erosive turbidite chutes at its upper surface the sequence boundary wave eroded terraces at its updip near shelf edge end identify the shoreline position at lowest sea level aggradation and landward stepping of clinothems reflect subsequent rise of relative sea level the fall to rise configuration and especially the occurrence of peak erosion at the time of lowest sea level are compelling evidence for placing the type 1 sequence boundary at the fall to rise turnaround and not along the surface onto which the clinothems downlap the excellent exposure downdip as well as along strike of the clinoform complex demonstrates the absence of sand accumulation beyond the base of slope the slope turbidites were produced from dilute nonignitive flows and caused significant shelf margin accretion the data show that such slopes can be extremely sand prone and that sea level fall below the shelf edge does not necessarily result in basin floor sand deposits beyond the base of slope particularly where canyons have not been eroded into the slope

tectonic forcings of maastrichtian ocean climate evolution a global compilation of deep sea isotopic records suggests that maastrichtian ocean climate evolution tvas tectonically driven during the early maastrichtian the atlantic intermediate deep ocean was isolated from the pacific indian and southern oceans deep water formed in the high latitude north atlantic and north pacific at the early late maastrichtian boundary a major reorganization of oceanic circulation patterns occurred resulting in the development of a thermohaline circulation system similar to that of the modem oceans a combination of isotopic and plate kinematic data suggests that this event was triggered by the final breaching of tectonic sills in the south atlantic and the initiation of north south flow of intermediate and deep water in the atlantic the onset of laramide tectonism during the mid maastrichtian led to the concurrent draining of major epicontinental seaways together these events caused cooling increased latitudinal temperature gradients increased ventilation of the deep ocean and affected a range of marine biota

salt bursting tests on volcanic tuff rocks from mexico during the pre colonial period all the architectural constructions of the maya and the later aztec culture were made from different types of rocks available in the nearby surroundings of the settlements later the architecture characterizing the spanish colonization utilized volcanic tuff rocks for ashlars and masonry facades volcanic tuffs were used in large quantities and are still the main natural building rock used in most of the country tuffs are mostly soft and porous rocks that can be easily cut and reworked they are however very susceptible to the effects of weathering especially the deterioration caused by salt crystallization seventeen volcanic tuff samples from mexico used as natural building stones were studied these tuffs show highly variable compositions and different porosities and textural properties as well as very different behaviors in regard to salt crystallization the petrographic petrophysical mineralogical and geochemical properties of the 17 samples were analyzed before and after a large number of salt bursting tests in order to try and determine the main factors leading to the weathering caused by salt crystallization some factors appear to have a real importance in regard to the resistance against salt crystallization two of the most important are the water vapor diffusion value and the pore radii distribution however microporosity also becomes a relevant factor for rapid salt destruction if it reaches more than 50 of the pore volume all these effects related to the salt crystallization are dependent on the presence of water in any form so the climatic conditions must also play a principal role

differences in the quality of polishing between sound and weathered granites aesthetic characteristics are important when rocks are used as construction materials among all the surface finishes available the polished finish is the one which best enhances the rock attractiveness colour c roughness r and gloss g are surface properties usually used to assess the rock polishing in this research the crg properties were assessed in polished samples of three ornamental granites with different textures and physical mechanical properties one weathered and two sound c was evaluated in cie l a b and cie l c abhab systems r with ra and rz parameters and g using the 20 60 and 85 geometries the weathered granite presents a noticeable colour variation especially in the b parameter while the sound ones have a more homogeneous colour sound and more textural homogeneous granites have a low surface roughness and high gloss which are uniformly distributed the weathered granite shows a higher surface roughness and lower gloss with scattered distribution the mineral contacts are the main cause of the surface irregularities the results show the interdependence between the crg properties and stress the importance of the polishing process for enhancing the aesthetic characteristics of the granites crg properties could be used for quality control in granite processing plants thus avoiding noticeable differences in the facades of buildings particularly when weathered granites are used

paleo environments and tectonic setting of the mesozoic thung yai group in peninsular thailand with a new record of parvamussium donaiense mansuy 1914 abstract the thung yai group extends over a large area of peninsular thailand along the eastern margin of the shan thai block bound by angular unconformities 300 m thick dominantly detritic brackish to non marine deposits with few intercalated limestone beds between triassic marine and tertiary non marine sediments represent the thung yai group that comprises four formations khlong min lam thap sam chom and phun phin formations in the ao luk plai phraya alpp area the khlong min and lam thap formations yield marine brackish water and non marine fossil assemblages these include trace fossils and for the first time in peninsular southern thailand the bivalve parvamussium donaiense mansuy 1914 based on fossil determinations the thung yai group has a late early jurassic to early cretaceous age our new observations help unravel the tectonic history of mesozoic peninsular thailand after the complete closure of the paleotethys in the late triassic renewed inundation from the late early jurassic to the early middle jurassic brought a regime of shallow to open marine and lagoon sedimentation over northwestern western and southern peninsular thailand in the eastern part of sundaland bordering the mesotethys to the west

late mesozoic sedimentation in the northern antarctic peninsula and its relationship to the southern andes two distinct phases of island are evolution are recognized in late mesozoic sedimentary rocks of the northern antarctic peninsula during late jurassic kimmeridgian tithonian times alternating radiolaria rich mudstones and ash fall tuffs were deposited under shallow marine euxinic conditions in association with restricted volcanic centres the name nordenskjold formation is proposed for this lithostratigraphic unit subsequently during the early cretaceous a major episode of volcanism and uplift led to the construction of an emergent are terrane simultaneous development of a retro arc basin resulted in the accumulation of coarse volcaniclastic detritus along the eastern side of the arc retro are sedimentation and intermittent volcanism continued into the late cretaceous and early tertiary although the pattern of sedimentation in the northern antarctic peninsula is broadly comparable to that of the southern andes an active marginal basin has not been recognized in the former area interbedded mudstones and tuffs identical to those of the nordenskjold formation were deposited in the southern andes and south georgia during the late jurassic early cretaceous

discontinuity modelling and rock block geometry identification to optimize production in dimension stone quarries abstract evaluating the reserves of commercial blocks in dimension stone quarries requires determining in situ block geometry furthermore to extract blocks the planes need to be cut and the intersection between the fracture network and the cutting patterns forms smaller blocks the optimization of the cutting patterns can increase quarrying efficiency resulting in less environmental damage in this paper a numerical algorithm was selected from various algorithms and was developed for in situ block identification the optimization approach was adopted to increase quarry productivity and to investigate quarrying direction on a large scale however on a small scale this approach was employed for checking the distance between the cutting planes according to the algorithms developed 3d quarryoptimizer was programmed in the matlab environment to determine the geometry of the blocks and to optimize extraction based on the quality classification of the blocks formed the algorithms developed have such advantages as the optimization approach and taking the geometry of the blocks into consideration this methodology was applied in a marble quarry and a granite quarry research conducted in the granite quarry showed that the program is a practical tool to determine the geometry of in situ blocks and their quality classification the marble quarry was studied for the optimization phase the large scale optimization indicated a maximum difference of 17 in the yield among several quarrying directions on a small scale however a 120 increase in quarry yield was achieved with the optimal interval between the cutting planes

paleobiogeography of campanian maastrichtian foraminifera in the southern high latitudes abstract distributions of planktonic and benthic foraminifera have revealed antarctic land sea distributions oceanic surface gyre configurations and changes in the configurations of the tethyan transitional and austral realms during campanian maastrichtian time poleward changes in the diversity of total and keeled planktonic species of the southern hemisphere are compared for the early and late campanian and early and late maastrichtian latitudinal diversity gradients were weakest during the early campanian and more pronounced during the late campanian and maastrichtian shallow marine seaways within west antarctica are suggested by similarity of late cretaceous nearshore benthic and open ocean planktonic assemblages from southern high latitude land and drill sites and by the occurrence of recycle cretaceous marine microfossils from antarctic interior and continental margin localities development of a major water mass boundary between cool surface waters south of about 50 s paleolatitude and warmer surface waters to the north in the south atlantic and indian ocean may have caused biogeographic isolation of austral realm assemblages during late campanian and early maastrichtian time several planktonic foraminifera show significant diachroneity in their latitudinal distributions magnetobiostratigraphic data suggest that abathomphalus mayaroensis migrated from high to low latitudes whereas pseudotextularia elegans globigerinelloides subcarinatus globotruncanella citae globotruncanella petaloidea globotruncana bulloides and globotruncana subcircumnodifer made time transgressive poleward migrations the distribution of a mayaroensis is in agreement with isotopic evidence for late maastrichtian climatic cooling while that of p elegans correlates with a latest maastrichtian warming event about 66 8 66 6 ma delayed first occurrences of the other taxa cannot be explained by paleoclimatic factors alone variations in global eustatic sea level and orogeny between southern south america and west antarctica may have also influenced the taxonomic composition of southern high latitude foraminiferal assemblages

estimation of uniaxial compressive strength of rock materials by index tests using regression analysis and fuzzy inference system abstract this paper presents a comparative evaluation of efficacies of different index tests and analysis techniques i e regression analyses and fuzzy inference system in predicting uniaxial compressive strength ucs of granite schist and sandstone ucs and indices such as block punch index point load strength schmidt rebound hardness ultrasonic p wave velocity and physical properties effective porosity and density were determined for the concerned rocks from simple regression analyses it was apparent that for granite and sandstone performances of all six indices are reasonably good in predicting ucs in case of granite block punch index and point load strength are the best indices whereas effective porosity point load strength and schmidt rebound hardness are the most efficient indices for sandstone in case of schist however ultrasonic p wave velocity does not seem to be a competent index unlike other indices where point load strength proves to be the best one from the critical analysis of the tests results it was demonstrated and subsequently concluded that index test results of different rock types with different geology should not be clubbed together for statistical correlation with any rock mechanical parameter like ucs both multiple regression analyses and the fuzzy inference system exhibited better predictive performances for ucs than simple regression analyses in addition to the coefficient of correlation the variance account for vaf and the root mean square error rmse were also calculated to check the predictive performances of these two models and it was found that the predictive performances of both models are comparable however one should be cautious while employing multiple regression analysis in predicting ucs as there is always a chance of cumulating plausible errors that might have remained within individual index test results on the other hand fuzzy inference system seems to be an efficient tool in predicting ucs of rock materials from indices because of its efficacy in handling uncertainties in the test results with transparency

elastic anisotropy and pore space geometry of schlieren granite direct 3 d measurements at high confining pressure combined with microfabric analysis pore space geometry of granitic rocks and its evolution with depth are key factors in large scale seismics or in projects of enhanced geothermal systems or of deep hazardous waste repositories in this study we studied macroscopically anisotropic schlieren bearing granite by experimental p wave velocity v p measurements on spherical sample in 132 directions at seven different confining pressures in the range 0 1 400 mpa in order to discriminate the phenomena affecting the rock elastic properties we analysed the orientation of microcracks and of grain boundaries and we measured the anisotropy of magnetic susceptibility of the rock three sets of microcracks were defined with two of them linked to the massif exfoliation process and one to cooling contraction of the massif during pressurization the measured mean v p and v p anisotropy degree at ambient pressure and at highest confinement 400 mpa yielded 3 3 km s 1 and 24 per cent and 6 2 km s 1 and 3 per cent respectively the associated v p anisotropy pattern was transversely isotropic and governed by the schlieren with a minimum v p direction perpendicular to them and a girdle of high v p directions parallel to them the highest change in v p was observed between 0 1 and 10 mpa suggesting a significant closure of porosity below depths of 500 m change of the v p anisotropy pattern to orthorhombic together with increase of mean v p and v p anisotropy degree during depressurization was attributed to inelastic response of one of the sets of microcracks to the loading unloading cycle

tectonic and magmatic evolution of the andes of northern argentina and chile abstract two orogenic cycles both with different evolution are developed in the western margin of the south american continent in northern argentina and chile the paleozoic hercynic cycle and the meso cenozoic andean cycle the hercynic cycle a wide marine basin extending westward of the cordillera oriental which developed in cambrian ordovician times marks the beginning of this cycle in contrast to peru and bolivia where this basin developed between two precambrian blocks the western margin of this basin in northern argentina and chile is still unknown the ordovician sedimentation and accompanied volcanism ends with the ocloyic deformation phase and its synkinematic granitic plutonism two basins were developed in the silurian devonian separated by the puna arc uplifted during this ocloyic phase the shallow water marine terrigeneous sediments which were deposited in them were deformed by a new tectono magmatic associated phase chanic phase carboniferous to lower permian marine carbonates were deposited west of the puna arc and red beds east of it later on during the permian to triassic a magmatic belt was developed along the cordillera occidental the rhyolites ignimbrites and the granitic to granodioritic related intrusives are well represented in chile although the overall geologic history of this period is known many problems concerning its origin and relations to plate tectonics are still unsolved the andean cycle during this cycle a series of magmatic arc systems related to the subduction of the pacific crust was built up along the western margin of south america huge volumes of calc alkaline lavas and related plutons were emplaced since the jurassic along belts parallel to the present coastline showing a general eastward migration trend up to the lower cretaceous an ensialic back arc basin was formed east of this magmatic arc thousands of meters of marine and continental sediments were deposited in it this basin disappeared during the middle cretaceous probably as a result of the final opening of the atlantic and the active westward movement of the south american plate since middle cretaceous times the magmatic arc has been the fundamental paleogeographic element the arc progressively migrated stepwise eastward each step marked by a tectonic phase subduction related crustal erosion could explain the lack of fore arc petrotectonic assemblages the eastward magmatic polarity which characterizes this section of the andes could also be explained by such a mechanism

the evolution of late cretaceous deep ocean circulation in the atlantic basins neodymium isotope evidence from south atlantic drill sites for tectonic controls 1 the south atlantic basins during the late cretaceous were characterized by overall expansion and the opening of deep water connections eventually permitting deep ocean circulation with the indian and north atlantic basins however the evolving pattern of deep ocean circulation through the late cretaceous particularly the timing of the connection between various basins is not well constrained here we present new neodymium isotope data from five sites in the south atlantic to reconstruct water mass chemistry and circulation patterns the new data combined with previously published data indicate deep water formation occurred in the high latitude south atlantic throughout the late cretaceous tectonic boundaries restricted the circulation of southern component water until the opening of the equatorial atlantic gateway and the subsidence of rio grande rise between 79 and 75 ma subsidence of these features permitted the northward flow of southern component water which then ventilated the deep north atlantic nd isotope data indicate that the south atlantic water column during the cenomanian to santonian was vertically stratified between intermediate and deep waters with increased mixing evident during the campanian and maastrichtian

empirical ratio of dynamic to static stiffness for propped artificial fractures under variable normal stress abstract the stiffness coefficient is a key parameter of rock fractures that controls the properties and behavior of a rock mass according to the displacement discontinuity theory the dynamic stiffness of rock fractures can be back analyzed using stress wave propagation this study aims to measure the dynamic stiffness of rock fractures then develop an empirical ratio to describe the relationship between dynamic and static stiffness propped artificially fractured shale and granitic rock samples are employed mechanical and ultrasonic tests are conducted on two artificial rock fractures during uniaxial loading and unloading as normal stress changes from 1 mpa to 50 mpa the average dynamic normal stiffness of shale and granitic rock fractures changes from 330 gpa m to 1960 gpa m and from 90 gpa m to 2320 gpa m respectively for both artificial fractures the dynamic stiffness is higher than the static stiffness but approaches the static stiffness with increasing normal stress the ratio of dynamic to static normal stiffness is approximately 2 0 at a normal stress of 15 mpa this ratio approaches 1 0 with increasing normal stress and varies widely under low normal stress this study provides a method for evaluating the static or dynamic stiffness of rock fractures which has important applications for seismic surveys or acoustic logs in the field of geological engineering

thermal stress induced microcracking in building granite abstract microcracking induced by wide fluctuations in temperature affects granite quality and durability making the stone more vulnerable to decay determining the extent of that effect is not always straightforward however given the excellent durability of these materials four types of construction granite quarried in the region of madrid spain and frequently used in both the built heritage and in de novo construction alpedrete cadalso de los vidrios colmenar viejo and zarzalejo were exposed to 42 thermal cycles 105 20 c une en 14066 2003 petrographic and petrophysical properties were analysed using both destructive and non destructive techniques microcracking generated in the granite stones by 42 thermal cycles had barely any impact on their petrophysical properties which are the parameters normally assessed to establish material quality and durability their petrographic properties which are not generally assessed in this type of studies were affected however this study contends that petrographic analysis is needed to objectively quantify the actual quality and durability of the most highly resistant materials when petrophysical studies are inconclusive petrographic and fluorescence microscopy along with fractography are among the most prominent techniques for petrographic exploration thanks to the deployment of these techniques mineral microcracking could be monitored throughout the present tests conducted the microscopic findings revealed substantial micro textural and microstructural change in and around the granite minerals which play a prominent role in decay the findings showed that pre existing microcracks coalesced and generated further microcracking as decay progressed microcracking was most intense in zarzalejo granite due to its textural characteristics determined by its high feldspar content microscopic observation revealed that the microstructure of feldspar minerals with their crystallographic anisotropies and secondary mineral phases favoured microcrack development zarzalejo granite exhibited lower quality and durability than colmenar viejo and cadalso de los vidrios granites which were more resistant to heat treatment

early cretaceous aucellina bivalvia from the dajiashan area northeastern china abstract aucellina is described systematically for the first time from the dajiashan formation of the dajiashan area earlier it had been identified as otapiria based on the occurrence of aucellina caucasica aucellina aptiensis aucellina acuminata assemblage the age of the dajiashan formation is revised from early jurassic to early cretaceous and probably ranges from late barremian to early albian in addition the distribution of aucellina as well as the differentiation between aucellina and buchia are discussed briefly in this paper

the jurassic succession in west central argentina stratal patterns sequences and paleogeographic evolution abstract jurassic rocks in west central argentina are predominantly marine and marginal marine siliciclastics associated with prominent but volumetrically subordinate carbonates and evaporites facies developments were ruled by paleogeographic persistence within the southern infratropical latitude belt within 40 50 s and by siliciclastic derivation from the patagonian hinterland to the southwest minor volcanic and volcaniclastic supply arrived from the west out of a magmatic belt related to circum pacific convergence timing of the main marine flooding events and general correspondence with the high rank stratal packaging recorded in western north america suggest that global eustasy was also a factor in controlling the local stratigraphic record early jurassic sedimentation occurred within a series of semi isolated depocentres linked to fault bounded triassic troughs the sinemurian toarcian deposits record depocentre expansion and coalescence these trends were coeval with progressively more widespread marine invasions from the northwest and west leading to an elongate marine seaway which connected central patagonia with the pacific domain during the aalenian bajocian the region was subject to a more subdued tectonism and the foreland side of the basin became fringed by an extensive clastic embankment bathonian and early callovian were times when coarse clastics prograded into the basin while the marine embayment shrank as a result of stepwise forced regressions during late callovian to oxfordian globally rising sea level the depocentre witnessed the appearance of cosmopolitan invertebrates and a stratal pattern of basin widening and depositional underbalance that promoted cratonward onlap and inception of widespread carbonate deposition ooidal coralline carbonate development was terminated after a relatively sudden messinian style event that desiccated a large tract of the andean basin and favored massive precipitation of anhydrite in the course of the kimmeridgian the evaporite basin was largely flooded by siliciclastics and turned into a broad and featureless mudflat salina complex linked to a widespread erg and to an ephemeral drainage system by the tithonian at a period of peak oceanic stand marine connection was reinstated and recorded as the most widespread jurassic transgression across the neuquen aconcagua embayment shelfal deposition consisted of molluscs and ooid dominated carbonate terraces that grew in pulses tuned to eustatic fluctuations like in other prolific petroleum provinces around the world the tithonian basinal strata involve widespread euxinic deposits featuring unusually high organic content

characterisation of monzogranitic batholiths as a supply source for heritage construction in the northwest of madrid abstract the church of the assumption of our lady in valdemorillo madrid spain is almost entirely built with granitoids the studies and analyses were focused on the oldest part of the building ghosts corner which will be restored and rehabilitated in the near future homogeneous monzogranite is the predominant granitoid used in the ghosts corner followed by granitic porphyry porphyrytic monzogranite gneiss and leucogranite the original quarries that supplied homogeneous monzogranites for the first construction stages correspond to blocks present in the monument s surroundings quarries that supplied the granitic porphyries correspond to the dykes located to east southeast of valdemorillo which are oriented n s in relation to their intrusion direction the combined use of ultrasonic velocity and schmidt hammer techniques allowed first selection of the most representative blocks and ashlars for sampling this reduced sampling to a minimum but yielded representative results for the whole building second the combined values were used to compare results for the building stones of the church to rocks from the surrounding quarries stones from the building showed lower ultrasonic and schmidt hammer values and higher porosity and water saturation values compared to the original quarry rocks the anisotropy indices are directly related to the decay processes in the stone spalling of homogeneous monzogranite and grain disintegration in granitic porphyries finally the methods applied are inexpensive easy to use and non destructive techniques very advisable properties when working with built heritage

global cretaceous paleogeography international geologic correlation program project 191 abstract five global cretaceous paleogeographic maps within a plate tectonic framework are illustrated based on the ten contributions in this special volume

a comparison of the ammonite faunas of the antarctic peninsula and magallanes basin ammonite bearing jurassic and cretaceous sedimentary successions are well developed in the antarctic peninsula and the magallanes basin of patagonia faunas of middle jurassic late cretaceous age are present in antarctica but those of patagonia range no earlier than late jurassic although the late jurassic perisphinctid dominated faunas of the antarctic peninsula show wide ranging gondwana affinities it is not yet possible to effect a close comparison with faunas of similar age in patagonia because of the latter s poor preservation and our scant knowledge of them in both regions the neocomian is not well represented in the ammonite record although uninterrupted sedimentary successions appear to be present lack of correspondence between the aptian and albian faunas of alexander i and patagonia may be due to major differences in palaeogeographical setting cenomanian coniacian ammonite faunas are known only from patagonia although bivalve faunas indicate that rocks of this age are present in antarctica kossmaticeratid faunas mark the late cretaceous in both regions in antarctica these have been classified as campanian whereas in patagonia it is generally accepted perhaps incorrectly that these also range into the maestrichtian

bowing of dimensional granitic stones bowing is a well known phenomenon seen in marbles used as building veneers this form of rock weathering occurs as a result of external factors such as temperature humidity the system for anchoring the marble slabs or the panel dimensions under the same external conditions many factors will determine the degree of deformation including petrography thermal properties and residual locked stresses the usual way to solve the problem of bowed marble slabs is to replace them with other materials such as granites in which the deformation still exists but is less common in this study eight ornamental granites with different mineralogy grain size grain shape porosity and fabric were tested in a laboratory to assess their susceptibility to bowing three slabs of granite each cut with a different orientation were studied under different conditions of temperature 90 and 120 c and water saturation dry and wet to investigate the influence of these factors together with that of anisotropy at 90 c only the granite with the coarsest grain size and low porosity exhibited deformation under wet conditions at 120 c and wet conditions three of the granites showed evident signs of bowing again the granite with the coarsest grain size was the most deformed it was concluded that the wide grain size distribution influences microcracking more than other expected factors such as the quartz content of the rock also mineral shape preferred orientation and porosity play an important role in the bowing of the studied granites

paleoclimate of the kimmeridgian tithonian late jurassic world i results using a general circulation model abstract the kimmeridgian tithonian 154 7 145 6 ma middle and late late jurassic was a time of expanded continental rifting increased sea floor spreading and a relatively high eustatic sea level stand these processes collectively caused the fragmentation and flooding of the megacontinent pangea as well as the alteration of the global paleoclimate using a version of the community climate model ccm from the national center for atmospheric research we report two kimmeridgian tithonian paleoclimate seasonal simulations with geologically inferred paleotopography one using a co 2 concentration of 280 ppm pre industrial level and the other 1120 ppm increasing the co 2 four fold warms virtually the entire planet the greatest warming occurs over the higher latitude oceans and the least over the equatorial and subtropical regions simulation of a warmer planet with an elevated greenhouse effect fits the distribution of paleoclimatically sensitive faunas floras and sedimentary rocks model results indicate that sea ice was restricted to the high latitudes of the boreal and austral seas making landfall only in restricted areas the trade winds bring heavy rainfall in december january february to eastern gondwana and in june july august to the tethys sea margins a strong june july august monsoon occurs over southeast asia the distribution of coals correlates to precipitation sufficient to maintain gymnosperm forests and coastal areas where water saturated sediments are a result of eustatic high stands of sea level evaporites are localized to areas of negative precipitation evaporation runoff is restricted to regions of intense precipitation overall the 1120 ppm co 2 simulation provides a reasonable paleoclimate for the kimmeridgian tithonian and provides a standard until a ccm with oceanic heat transport a coupled atmospheric oceanic model or one with a finer grid cell configuration is available the results need further scrutiny in areas with more detailed geologic information

tectono stratigraphic evolution of the andean orogen between 31 and 37 s chile and western argentina fil charrier reynaldo universidad de chile facultad de ciencias fisicas y matematicas departamento de geologia chile universidad andres bello chile

late mesozoic bivalve biostratigraphy of the antarctic peninsula region two groups of bivalves the inoceramids and buchiids are particularly useful zone fossils in the mesozoic sedimentary formations of the antarctic peninsula region in the upper jurassic species of the genera retroceramus malayomaorica buchia and anopaea can be traced considerable distances around the margins of gondwana and as such are especially valuable for regional correlations some of them such as the r haasti subhaasti group can also be employed in detailed local correlations in the lower cretaceous the presence of cosmopolitan inoceramus species such as members of the neocomiensis concentricus and anglicus groups permits correlation with northern hemisphere faunas for the first time other stratigraphically important inoceramids are the i ovatus group in the lower neocomian the i heteropterus group and anopaea trapezoidalis in the upper neocomian and an cf mandibula in the albian the only buchiids present in the lower cretaceous of antarctica belong to the extensive aucellina andina radiatostriata group two types of antarctic upper cretaceous inoceramids that are particularly important for regional correlations are the upper cenomanian i pictus group and the turonian coniacian i madagascariensis ernsti group senonian inoceramids are still poorly known but would seem to offer considerable scope for further studies

pre quaternary sea level changes while the paramount importance of global sea level changes has been widely accepted by quaternary geologists throughout this century it is only within the last decade that such changes in the rest of the phanerozoic have received much attention there are two principal reasons for this arousal of interest first increased exploration of the stratigraphic record across the earth both on land and under the sea and significant improvement in biostratigraphic correlation have drawn attention to what appear to have been globally synchronous events second oceanographic research has demonstrated the importance of tectonically controlled changes in the cubic capacity of the ocean basins notably variations in ridge volume which provide a ready mechanism for sea level changes even at nonglacial times the adjective eustatic was first proposed for global changes of sea level by suess 1906 in his great treatise the face of the earth the corresponding noun is eustasy not eustacy as it is commonly misspelt the unconvinced reader need only think of ecstasy eustatic sea level changes can be inferred as suess recognized by a plotting the temporal spread of marine sediments over the continents and b estimating the depositional depth variations in marine stratal sequences which can be correlated across and between continents to these methods can be added seismic stratigraphy in which biostratigraphically age determined seismic sequences on the con tinental margins are analyzed in terms of cycles of coastal onlap and offiap when the results of these methods are broadly in accord confidence in a eustatic interpretation is increased but the range of confidence can vary considerably it is widely accepted that there was an exceptionally high sea

ammonite faunas and palaeobiogeography of the himalayan belt during the jurassic initiation of a late jurassic austral ammonite fauna abstract new data obtained in nepal and spiti india on stratigraphy and jurassic ammonite faunas form the basis for a new biogeographical interpretation of the peri gondwanan faunas faunas of the same ages from new guinea new zealand antarctica and south america are also considered from the upper bathonian up to the tithonian berriasian six main successive assemblages are distinguished in nepal and are compared to the faunas described in the above mentioned areas the latter often without accurate stratigraphic support the faunas of nepal show 1 low taxonomic and generic diversity of the ammonites and 2 dominance of one genus or a small number of genera in the same family and the subordinate place of the associated taxa with a few exceptions the classical biogeographical schemes do not recognize the existence of an austral ammonite fauna and or austral province bipolar distributions of several benthic or nekto benthic invertebrates as well as intertropical distribution of calpionellids express a latitudinal pattern of marine faunal distribution austral and tethyan ammonite faunas show less marked contrast than the tethyan and boreal realms and transitional or mixed faunas of subaustral type of relatively high diversity are developed in the indo malagasian trough or seaway and the andean region the austral fauna of low diversity was spread around east and south gondwanaland from the himalaya to patagonia the lack of a geographical trap such as the arctic basin almost completely enclosed by land explains why the austral faunas were never as distinct as the tethyan faunas from the boreal in addition to the role in the differentiation of the boreal faunas the land locked geography of the arctic basin magnified the role of the other environmental factors especially those linked with a high latitude situation seasonal fluctuations of illumination in high latitude resulted in environmental instability which promoted eurytopic taxa with high density and low diversity populations

magmatic intervals transgression regression cycles and oceanic events in the cretaceous and tertiary of southern south america abstract the southern part of south america provides an excellent test area to analyse relationships between transgression regression cycles along a passive continental margin with magmatic activity and tectonic movements of the andean orogen most of the tectono eustatic sea level changes recognized are related to magmatic activity whether calc alkaline or alkaline the magmatic activity depends on whether tectonic convergence or extension forces are dominant

timing of the late jehol biota new geochronometric constraints from the jixi basin ne china abstract the jehol biota is a world famous early cretaceous terrestrial ecosystem in east asia and has revealed exceptionally well preserved fossils which provide significant insights into the origin and evolution of birds and feathers and the early diversifications of mammals and angiosperms after the long lived controversies over the timing of the biota varying from late jurassic to early cretaceous in last century the lifespan of the early middle jehol biota has been precisely dated from barremian to early aptian ca 131 120 ma by a series of recent radiometric analyses however few well constrained ages are available for the late jehol biota hindering our complete understanding of the evolutionary history of the terrestrial ecosystem alternating marine and non marine deposits of the chengzihe formation in eastern heilongjiang have yielded a non marine bivalve assemblage of the jehol biota basal angiosperms and cretaceous marine index bivalves which collectively offer crucial and indisputable clues against the prevailing jurassic time of the biota since 1990s here we present the first discovery of tephra layers from the chengzihe formation dated by zircon u pb geochronology as ca 116 111 ma providing the first quantitative age calibration for the early angiosperms and the jehol bivalve assemblage therefore we demonstrate that the duration of the jehol biota extends to late aptian early albian approximately 4 9 myr younger than the currently accepted age limits

strain determinations using inoceramid shells as strain markers a comparison of the calcite strain gauge technique and the fry method abstract to test the accuracy and reliability of the strain gauge technique for calcite e twin analysis calcite e twin strain and finite strain were determined using a new tectonic marker inoceramid shells macrofossils composed of aggregates of pseudo hexagonal calcite prisms with a honeycomb microstructure although the calcite prisms in the inoceramid shells were not randomly distributed and showed strong crystallographical orientation the strain gauge technique yields principal strain orientations that correlate precisely with those found by the fry method thus this technique can also be used to establish the ellipsoid strain orientation in rocks where calcite grains show strong crystallographical orientation

late cretaceous extinction patterns in antarctica new correlations of marine clastic sedimentary rocks exposed within the james ross basin antarctica have shown that the mid to late cretaceous succession is in excess of 5 km thick plotting the ranges of the principal molluscan macrofossils against the revised stratigaphy indicates that inoceramid bivalves are totally absent and dimitobelid belemnites extremely rare throughout an extensive 1400 m thick maastrichtian succession these early extinction patterns are interpreted to be due to both a regional shallowing event and a pronounced phase of high latitude campanian maastrichtian cooling cool polar bottom waters may have been forming by as early as mid to late campanian times

jurassic ammonite faunas from nepal and their bearing on the palaeobiogeography of the himalayan belt abstract from the upper bathonian up to the tithonian berriasian six main faunas and twelve basic faunal assemblages within them are distinguished in nepal the successive faunas show 1 low taxonomic diversity and 2 the dominance of a small number of genera and the subordinate place of the associated taxa the assemblages include 1 strictly tethyan e g mediterranean or european tethyan species and or genera very few in number and occurring as isolated individuals or discontinuous faunal horizons 2 indo malagasian components some scattered others with a wide occurrence in the sw pacific some as far as antarctica and or patagonia 3 indigenous genera endemic for the himalayas and the sw pacific region faunas of the same age for the sula islands papua new guinea australia new zealand antarctica and south america are also considered in spite of common components the himalayan faunas contrast with the relatively higher diversity of the indo malagasian faunas low diversity and dominance of indigenous genera mean that the faunas extending from the himalayas to antarctica and patagonia represent an actual biogeographical unit the indo pacific faunas and realm indo pacific and tethyan faunas show a less marked contrast than the tethyan and boreal transitional or mixed faunas of subaustral type developed in the indo malagasian and andean regions this is explained by the absence of a geographical trap comparable to the land locked palaeogeography of the arctic basin the palaeogeography of the arctic amplified the role of the other environmental factors among these the high latitude seasonal effects are likely to have resulted in environmental instability controlling trophic resources and therefore the structure of the ecosystems for instance low diversity and high density of the high latitude ammonite faunas

assessment of rock geomechanical quality by quantitative rock fabric coefficients limitations and possible source of misinterpretations abstract rock microfabrics were quantified by image measurement system petrographic image analysis of thin sections along with common measured parameters grain area and size length of major and minor axes and their orientation some quantitative parameters aspect ratio grain boundary smoothness and fabric coefficients micropetrographic quality index k texture coefficient tc indexes of interlocking t and grain size homogeneity g were determined the reliability of these parameters for the evaluation of geomechanical properties was tested on the set of granitic rocks showing pronounced variability in rock mechanical properties none of the tested rock fabric coefficients or parameters proved a close correlation to rock mechanical properties except grain size based on experimental findings the grain size is along with porosity the controlling factor of rock mechanical properties of genetically and mineralogically similar rocks obliteration of the real effects of rock fabric parameters on the mechanical properties of rocks by application of complex fabric coefficients disables their practical use in petrography applied to geomechanics