how to explain a decapod crustacean diversity hotspot in a mid cretaceous coral reef article the mid cretaceous late albian decapod crustacean fauna from the koskobilo quarry in spain is the most diverse decapod fauna known thus far from the cretaceous this may be related to the coral reef environment in which these decapods were found within the aldoirar patch reef this diversity hotspot was further inves tigated by a detailed paleoecological study focusing on variation in lithology throughout the quarry using car bonate rock hand samples thin sections and acetate peels and by studying decapod rich sites within the quarry the northern and stratigraphically oldest part of the koskobilo quarry contained mostly wackestones and biomicrites the middle to southern part contained floatstones and biosparites or biomicrites with many sponge remains whereas the southernmost and stratigraphically youngest part consisted of coral rich boundstones and biolithites fossils were more abundant and generally larger in the southern part of the quarry decapod rich siteswere restricted to the southern part of the quarry possibly inpartbecauseofanincreasedpossibility for shelter and food in a coral rich area in the southernmost part of the quarry water depth was estimated to be between 20 and 80 m for at least the southern part with energy levels apparently increasing from the northern to the south ern part of the quarry systematic collecting was performed at four decapod rich sites in the quarry to investigate differences in decapod diversity composition and size width the decapod fauna from the site within the coral rich boundstones and biolithites appears to be the most diverse based on several diversity measures has a statistically different faunal composition contains species that were not found in other parts of the quarry and con sists of smaller decapods compared to other sites more specimens of species with a smaller maximum width were found here as well as fewer specimens with a large maximum width smaller presumed juvenile specimens of the crab goniodromites laevis were also excavated here this shows that decapod size can vary within a reef paguroids hermit crabs were mostly restricted to this coral rich site some of the many decapods at this site may have been obligatory associates with the mostly branching corals one site within the floatstone and biosparite zone contained hardly any decapods which may be related to the abundance of hard to eat corallinacean red algae a site in the olazagutia quarry in the same patch reef consisting of massive colonial corals did not yield any decapods presu mably because of the inaccessible nature of the coral framestone leaving few places as shelter for decapods the results suggest that different decapod sub and microenvironments existed within this patch reef thereby explaining at least in part the high diversity of decapods known from the koskobilo quarry this is one of the first times that a detailed paleoecological study has been performed for decapods in a fossilized coral reef these results concur with modern reefs in that decapod communities also differ among subenvironments the methodologies introduced herein for studying fossil decapods in reef environments can be used as well to study the paleoecology of decapods as well as other invertebrate sf rom other periods in earth s history

oldest scleractinian coral reefs on the north american craton upper triassic carnian northeastern british columbia canada abstract bioclastic accumulations composed of crinoids brachiopods molluscs spongiomorphs and scleractinian corals occur within upper triassic strata of the lower baldonnel formation at pardonet hill in northeastern british columbia canada these small buildups 100 to 500 m3 have planar bases and broadly convex tops these mounds are interpreted as small patch reefs composed of packstone bioclastic floatstone rudstone and carbonate breccia intercalated with mixed siliciclastic carbonate sediments deposited in a shallow subtidal setting i e above fairweather wave base amalgamated hummocky cross stratified to current ripple laminated quartz dominated sandstone beds and numerous sharp based normally graded bioclastic commonly encrinitic packstone grainstone quartz sandstone couplets characterize inter reef lithologies conodont biostratigraphy indicates that the pardonet hill patch reefs occur within strata dated as earliest upper carnian lower nodosus zone the pardonet hill patch reefs originated and developed during an interval of regional sea level lowstand strata within which these patch reefs occur represent the westernmost migration of the triassic shoreline in western canada disappearance of coral reefs in the study area may have been affected by rapid marine transgression and failure of reef faunas to recolonize the new shore zone further to the east the pardonet hill locality occurred on the western margin of the north american craton during the triassic prior to their discovery reef like structures dominated by corals in the western panthalassa were limited to allochthonous terranes now part of the cordillera the pardonet hill patch reefs occur at approximately 30 triassic paleolatitude in modern settings this is at the extreme latitudinal margin of subtropical zooxanthellate reef development the presence of benthic faunas characteristic of low paleolatitude settings on the northwestern coast of pangea has significant implications in paleotectonic and paleoenvironmental reconstructions

quantitative compositional analysis of a triassic carbonate platform southern alps italy abstract we have estimated abundance and distribution of automicrite marine cements and skeletal grains in the triassic sella massif an isolated platform flanked by steep 25 35 clinoforms 108 samples were taken at constant intervals from measured sections of the major zones of the platform edifice the platform top margin upper slope and lower slope in a first step carried out in the field and on hand specimen purely detrital deposits were separated from automicrite facies i e beds with automicrite cement filled primary vugs and admixtures of skeletal carbonate and lithoclasts in the second step samples with automicrite facies were thin sectioned and point counted the categories used for point counting were a automicrite b vugs and cement c microspar or neomorphic spar d skeletal grains and e internal sediments at the platform top 46 of samples are pure detrital deposits 27 consist of automicrite facies and 27 are too strongly altered by dolomitization to allow classification at the margin upper slope 68 of samples consist of automicrite facies 22 are pure detrital sediments and 10 are strongly altered at the lower slope 63 are detrital deposits 10 automicrite facies and 27 are extensively dolomitized the most important contributors to the automicrite facies are automicrite 41 on the platform top 29 on the margin upper slope 28 on the lower slope and early marine cement 35 on the platform top 48 on the margin upper slope 27 on the lower slope the amount of skeletal grains is less than 10 the automicrite facies stabilized the platform margin and upper slope automicrite abundant early marine cements and micro organisms such as tubiphytes formed a rigid framework thus substituting for the lack of a metazoan reef on the upper slopes the framework of automicrite facies stabilized the slope but intermittently the automicrite layers are frequently dissected by sediment filled fractures or are broken into clasts we assume that they slid on the layers of loose detritus bigger slides turned into rubbly debris flows that formed metre thick breccias at the lower slope and the proximal basin floor the planar shape and steep angle of the clinoforms indicate that the large scale geometry of the slope was not controlled by the automicrite but rather by non cohesive layers of sand and rubble piled up to the angle of repose the production mode of the sella is comparable of that of a mud mound factory this factory was highly productive in 1 ma the platform aggraded over 300 m and prograded over 2000 m in all directions

significant southern ocean warming event in the late middle eocene a prominent middle eocene warming event is identified in southern ocean deep sea cores indicating that long term cooling through the middle and late eocene was not monotonic at sites on maud rise and the kerguelen plateau a distinct negative shift in 1 8 o values 1 0 is observed ca 41 5 ma this excursion is interpreted as primarily a temperature signal with a transient warming of 4 c over 600 k y affecting both surface and middle bathyal deep waters in the indian atlantic region of the southern ocean this isotopic event is designated as the middle eocene climatic optimum and is interpreted to represent a significant climatic reversal in the midst of middle to late eocene deep sea cooling the lack of a significant negative carbon isotope excursion as observed during the paleocene eocene thermal maximum and the gradual rate of high latitude warming suggest that this event was not triggered by methane hydrate dissociation rather a transient rise in pco 2 levels is suspected possibly as a result of metamorphic decarbonation in the himalayan orogen or increased ridge arc volcanism during the late middle eocene

early history of scleractinian corals and its geological consequences conventional views have implied that scleractinian corals were hermatypic and thus were potentially reef building from the onset of their appearance in early mesozoic time in shallow shelf carbonate environments however for almost 25 m y they held rather subordinate positions and generally did not participate in extensive ecologic reef framework evidence from both north america and europe demonstrates that triassic corals had ecologic preferences quite different from those in the cenozoic a key step in the evolutionary success of these corals may have been the advent of a symbiotic association with algae this association believed to have developed at the end of the triassic could have been responsible for thrusting scleractinians into prominent positions as reef builders and may account for their dramatic radiation in mesozoic time

paleogene calcite compensation depth in the eastern subtropical pacific answers and questions 1 ocean drilling program leg 199 drilled a north south transect across the eocene paleoequator in the eastern pacific permitting reconstruction the calcite compensation depth ccd since earliest eocene time the ccd was relatively shallow near the early eocene pacific equator 3200 m and unlike modern latitudinal ccd gradients deepened to the north to 3600 m paleolatitude 10 n at 41 ma the ccd underwent a brief sharp transient deepening of 700 m then remained shallow until the eocene oligocene boundary at the e o boundary the ccd deepened by 1200 m in less than 300 kyr this rapid deepening served to more than double the area of seafloor subject to caco3 deposition sea level fall associated with ice volume buildup and ensuing shelf basin fractionation is unlikely to be the sole cause of the increased deep ocean caco3 burial rather a sudden rapid increase in the amount of ca entering the ocean appears necessary to explain the observations

silica burp in the eocene ocean the eocene was a time of greatly increased silica accumulation in the ocean and the peak was in the early middle eocene at about 50 ma the responsible geohistorical configuration included the following elements extensive volcanism about 4 m y earlier as part of the chron 24 plate reorganization early eocene warming with deep weathering to high latitudes and accumulation of the released silica in a sluggish ocean and sharp cooling in the earliest middle eocene stimulating oceanic upwelling and biosilicification it is possible on the evidence of carbon and oxygen isotopic patterns that the trigger for the exhalation of silica was a reverse greenhouse effect

reef fabrics biotic crusts and syndepositional cements of the latemar reef margin middle triassic northern italy the latemar reef buildup of the central dolomites northern italy provides a rare opportunity to examine an in place middle triassic upper anisian to lower ladinian platform margin that is not strongly deformed or dolomitized the margin lies between the flat lying platform interior and steeply dipping foreslope clinoforms across this transition the depositional profile relates directly to a consistent lateral facies pattern 1 restricted biota grainstone of the platform interior 2 tubiphytes rich boundstone and 3 diverse biota grainstone that grades into 4 foreslope breccia beds the boundstone and diverse biota grainstone facies comprise the platform margin the boundstone facies consists of a framework of small 10 cm skeletal remains 10 by volume with associated biotic crusts internal sediments and syndepositional cements crusts and cements constitute most of the rock volume and created the boundstone fabric biotic crusts exhibit gravity defying geometries and range from a light grey structure grumeleuse rind to dark grey micritic laminae both cements and biotic crusts occur as redeposited talus in the foreslope talus deposits indicating a syndepositional origin the diverse biota grainstone facies primarily consists of skeletal peloidal grainstone with a diverse open marine biotic assemblage in contrast to the restricted biota grainstones of the platform interior that have a low diversity restricted marine biota metre scale hexacoral boundstone and centimetre scale sponge boundstone and microbial boundstone occur as isolated patches tens to hundreds of metres apart within the diverse biota grainstone facies the depositional profile facies zonation and biotic constituents all indicate that the latemar buildup had a shallow water reef margin in contrast to previous interpretations that these were upper slope reefs the syndepositional biotic crusts and inorganic cementation played key roles in stabilizing the boundstone fabric to form a wave resistant reef fabric

depth transect of an upper triassic rhaetian reef from gosau austria microfacies and community ecology abstract in the late triassic 235 201 3 ma scleractinian corals and hypercalcified sponges built large diverse reef ecosystems the most famous of which are the dachstein reefs this study presents a depth transect along an upper triassic lower rhaetian dachstein reef from the gosausee margin of the dachsteingebirge gosau austria the gosausee microbial sponge coral reef is a complete barrier reef with an almost continuous fore reef to lagoon transect preserved a very rare occurrence for the triassic and thus provides a window into depth zonation of dachstein type reef facies and biotic succession the gosausee reef facies exhibit strong depth control and five classic reef facies or zones are identified the fore reef reef front reef crest back reef and lagoon facies thin rare microbial fabrics and a high abundance of fine grained mud rich skeletal wackestones transported reef debris characterize the deepest fore reef as the reef shallows muddy sediments decrease in abundance and are replaced by microbial fabrics corals and cements abundant sponges microbial crusts and thick marine cements typify the reef crest whereas microbialite coated phaceloid corals are dominant in the back reef facies heavily cemented oncoids or microbial sponge bindstones are characteristic of the lagoon based on their compositional and biotic similarities the gosausee reef was likely part of the same barrier reef systems as the source reef for the gosaukamm reef breccia one of the classic norian rhaetian dachstein reefs the reef zones of the gosausee margin can be used to interpret the depth or reef zone of less well preserved reef fragments can inform models of community ecology and niche utilization in the late triassic and highlight the need for additional research into the environmental factors that controlled biotic distribution in upper triassic reefs

platy coral patch reefs from eastern panthalassa nevada usa unique reef construction in the late triassic abstract upper triassic lower norian reefal buildups near mina nevada represent some of the earliest scleractinian coral reefs from eastern panthalassa the small patch reefs 20 40 m high and 50 150 m wide obvious metre scale elevation above the surrounding sediments are from the luning allochthon and grew on an inner to middle ramp or in a deep lagoon the mina patch reefs were constructed by several different coral ecomorphotypes platy tabular domal massive and branching corals interpreted to have had zooxanthellate symbionts and record subtle coral zonation within the reefs based on modern coral ecomorphotypes platy to tabular corals at mina grew in the lower euphotic zone stressed by low light conditions and the massive or domal corals inhabited shallower water possibly above fair weather wave base and were stressed by wave energy unlike most other late triassic reef ecosystems where phaceloid branching corals or calcareous sponges constitute the principal bioconstructors the platy to tabular corals were the primary builders in the mina patch reefs the mina reefs are also unique because cryptic and cavernous internal environments epibionts cryptobionts and thick microbial crusts are rare or absent the combination of platy coral dominance with the lack of epibionts cryptobionts microbial crusts suggests that the norian reefs from mina nevada represent a unique form of scleractinian reef construction from the late triassic

pioneer reef communities within a middle triassic anisian to upper triassic carnian mixed carbonate siliciclastic ramp system from the star peak group south canyon central nevada abstract reef patterns change drastically between the late paleozoic and early mesozoic due to the effects of the end permian mass extinction reef communities follow an ecological transition from the stabilization stage in the anisian to the colonization stage in the carnian through norian to the final diversification and domination stages in the norian through the rhaetian most eastern panthalassa reef studies focused on documenting framework supported reef structures elevated from the seafloor during the late triassic diversification stage however to fully understand reef development we also need to record the precursor stages here we examine field based and microfacies data using a sequence stratigraphic lens to develop a quantitative assessment of non skeletal and skeletal carbonate grains our results indicate that a reef mound and biostromes developed during an overall transgressive sequence due to substrate cementation caused by flooding events although taxonomic differences between biostromes and the reef mound change through time we conclude that these taxonomic changes do not record true first occurrence data instead these fossil accumulations probably occurred due to random chance of larval recruitment even though the reef types found here preserve similar taxa that have been shown to promote high reef growth e g calcified demosponges calcareous algae and bivalves low reef growth structures are found at our site thus reefs containing large amounts of micrite built by low growing binding and encrusting organisms typify this middle and upper triassic section confirming that this section records the colonization stage of reef recovery

pattern of first and last appearance in diatoms oceanic circulation and the position of polar fronts during the cenozoic 1 first and last occurrences of 389 diatom species from the first global cenozoic record are used to reconstruct the position of major oceanographic boundaries first appearances and extinctions group in three latitudinal bands middle to high northern latitudes equatorial region and high southern latitudes sparse paleogene occurrences were limited to southern high latitudes along the equivalent of the modern antarctic polar front its late middle eocene to middle miocene position varied within 10 and within a 20 band from middle miocene to present suggesting an association with global cooling first and last occurrence events appear in the two remaining latitudinal regions during the eocene and increase in a stepwise fashion mimicking significant cooling events at about 16 ma first and last appearances shift from the north atlantic to the north pacific low latitude data suggest low surface water productivity prior to 40 ma while increased abundance from the middle miocene correlates with expansion of the east antarctic ice sheet

nonskeletal peloidal precipitates in upper triassic reefs yukon territory canada abstract peloidal sediments and crusts form up to 75 percent of framework limestones in upper triassic reefs in the yukon territory the peloids are spherical to irregular in shape 20 250 m in size and are commonly surrounded by one or more rims of sparry calcite the peloidal sediments occur in confined cavities and in open spaces between reef framebuilders the peloidal crusts generally coat calcareous sponges and tabulozoans internal evidence suggests that the peloids are not detrital grains or fecal pellets and comparisons with mg calcite peloids and peloidal crusts in modern environments suggest that they are precipitates possibly resulting from bacterial activity

late eocene diatomite from the peruvian coastal desert coastal upwelling in the eastern pacific and pacific circulation before the terminal eocene event previously undocumented late eocene diatomaceous sediments are present near fundo desbarrancado fd in southern peru these sediments are similar to miocene diatomite from the same area but unlike the miocene diatomite the fd sediments contain cherty layers are enriched in caco sub 3 have a diverse and abundant radiolarian fauna and possess varved massive and millimeter and meter scale biogenic terrigenous alternations the fd sediments are part of an eocene sequence that includes the clastic sediments of the paracas formation and they are correlative to the chira formation of northern peru the paleogene biogenic sediments of western south america show that coastal upwelling developed in the eastern pacific before the latest eocene argue for the existence of a proto humboldt current at this time and suggest that the terminal eocene event was the culmination of gradual changes and not a catastrophic event at the eocene oligocene boundary

paleogene tropical pacific clues to circulation productivity and plate motion 1 stratigraphic data from 63 deep sea drilling project and ocean drilling program odp sites that sample the lower neogene and paleogene sediments of the tropical pacific have been compiled and put on the biostratigraphic and paleomagnetic timescale refined by odp leg 199 scientists sediment accumulation rates have been calculated for ten intervals ranging in age from 10 to 56 ma and have been plotted for the midpoint of each interval at the associated paleoposition for each site used a fixed hot spot model was used for reconstruction of the pacific lithospheric plate all such reconstructed intervals show the development of a tongue of high accumulation rates associated with the oceanographic divergence at the geographic equator the development of this equatorial band is weakest between 46 and 56 ma the time of the peak warmth in paleogene climate possible motion of the hawaiian hot spot or true polar wander between 46 and 56 ma appears to have had little effect on the plate rotation estimate of the position of the equator in addition to temporal changes in the calcite compensation depth and in productivity the biggest change in the patterns of sediment accumulation rates in the eastern tropical pacific was the development of a relatively strong divergence between 6 and 10 n near the region of divergence between the modern north equatorial current and the north equatorial counter current changes in the equatorial circulation appear to be associated in time with the opening and closing of oceanic gateways particularly the complex closing of the caribbean pacific gateway

the descriptive nomenclature and classification of growth fabrics in fossil scleractinian reefs abstract framework sensu stricto is a concept originally relating to modern reefs and is defined by structural ecological and sedimentological criteria however in the geological literature the term framework has come to be applied to almost any organically influenced in situ accumulation including non calcareous non rigid facies associated with sea grasses this drastic departure from the original meaning is misleading and scientifically unhelpful the concept of wave resistance is integral to that of framework but in the geological record it is not easy to evaluate and the term may be of little comparative use between reef environments it is suggested that the term growth fabric be generally applied as a descriptive term for the presence of aggregated in situ corals or other organisms in growth position within a facies the term growth fabric should be used as an alternative to framework as a purely descriptive term the term framework should be restricted to its original definition and used only where the criteria for framework can be clearly demonstrated two end member types of scleractinian growth fabric genesis are recognised termed superstratal and constratal terms adapted from gili e masse j p skelton p w 1995 rudists as gregarious sediment dwellers not reef builders on cretaceous carbonate platforms palaeogeogr palaeoclimatol palaeoecol 118 245 267 in a superstratal growth fabric the constituent organisms collectively projected decimetres to metres above the substratum creating positive topographic relief in contrast constratal growth is where vertical organic accretion occurred at a similar rate to sediment accumulation hence the majority of the skeletal material remained continuously embedded in the sediments and only a small proportion of the skeleton projected centimetres above the sediment surface the architectural palaeoecological sedimentological and diagenetic implications of different types of growth fabric genesis is discussed a review of the classification of reef fabrics suggests that there is currently no adequate system to describe fossil scleractinian growth fabrics the most commonly used classification of reefal fabrics is that of embry and klovan 1971 embry a f klovan j e 1971 a late devonian reef tract on northeastern banks island northwest territories bull can pet geol 33 730 781 there are a number of shortcomings in this scheme which may be grouped into three categories 1 the interpretative nature of the classification 2 problems in interpreting biological effect from form and 3 insufficient categories to adequately describe mesozoic and cenozoic growth fabrics moreover there appears to be a lack of a standardised nomenclature for growth fabrics which has hindered meaningful comparisons of scleractinian growth fabrics through time and space a descriptive system based on a modification and expansion of the embry and klovan system 1971 is proposed and a revised nomenclature for growth fabrics presented the system is designed to be flexible in its application it can be used simply to describe a growth fabric or through the use of genetic and non genetic modifiers to imply types of reef building processes and growth fabric heterogeneity although the concepts and terminology discussed in this paper relate to scleractinian growth fabric they are equally applicable to fabrics comprising other organisms

eocene biogenic silica accumulation rates at the pacific equatorial divergence zone 2 the eocene biosiliceous oozes of the tropical pacific are an easily recognizable sediment type having a reddish brown color and sugary texture these sediments are dominated by radiolarian tests with traces of terrigenous debris hydrothermal oxides a few diatoms and little if any carbonate the paucity of carbonate is a result of the very shallow pacific calcite compensation depth ccd of the eocene 3300 m rea and lyle 2005 and references therein the dominance of radiolarian tests over those of diatoms is an enigma in that diatoms usually dominate siliceous rich sediments of the oligocene and neogene the opal rich character of these eocene sediments is commonly associated with the development of cherts within the sections 3 these unusual characteristics of eocene radiolarian oozes have prompted some authors to puzzle over how so much silica could have been delivered to the sea floor during

isotopic characterization of late neogene travertine deposits at barrancas blancas in the eastern atacama desert chile abstract here we explore the potential of spring related surface and subsurface carbonates as an archive of paleoenvironmental change at barrancas blancas located in the broadest and driest sector of the atacama desert at 24 5 s from these deposits we present a new stable isotopic record of paleoenvironmental conditions over portions of the past 11 5 ma u pb dates from the carbonates both surface and subsurface demonstrate that springs have discharged at this location over much of the last 11 5 ma attesting to the exceptional geomorphic stability of the central atacama many of the sampled vein systems line vertical fissures and formed within the aquifer before groundwater discharged at the surface carbonates in such circumstances should not undergo off gassing and kinetic fractionation prior to formation simplifying the interpretation of their isotopic composition oxygen isotopic compositions of carbonates are generally high 5 vpdb and using paleospring water temperatures of 3 13 c reconstructed from clumped isotopes point to strongly up to 50 evaporated water isotope values like those associated with the hyperarid core of the atacama desert today carbon isotopic compositions are also high 3 pdb reflecting a recharge area essentially devoid of plants and dominated by volcanic co 2 as is the case today our isotopic results are very similar to those from the calama basin to the north suggesting that the western face of the andes between 21 and 25 s has been highly evaporative and nearly plantless when these springs discharged over the last 11 5 ma the spring carbonates at barrancas blancas strongly resemble those found at devils hole and furnace creek in death valley usa and as such warrant further exploration as potential archives of climate change

environmental significance of microbialites in reef environments during the last deglaciation in situ microbialites occurring in reef rocks dredged between 80 and 130 m water depth on the modern fore reef slopes of tahiti and the marquesas islands yield ages ranging from 17 100 2900 to 4410 2250 years bp suggesting that they played a prominent role during the last deglacial sea level rise microbialites developed in both shallow and deep water depositional environments where they characterize various zones of the reef tracts reef crests upper reef slopes deep fore reef slopes reflecting contrasting scenarios of microbialite development involving reefal microbialites in shallow water settings and slope microbialites that formed in environments deeper than 10 20 m and extending down to more than 100 m reefal microbialites correspond to a late stage of encrustation of the dead parts of coral colonies or more commonly of related encrusting organisms red algae and foraminifers thus forming surface crusts slope microbialites generally form the ultimate stage of a biological succession indicating a deepening sequence whereby shallow water corals and associated encrusting organisms are replaced by deeper water assemblages of red algae and foraminifers before microbialite growth the precipitation of phosphatic iron manganese crusts and the deposition of planktonic micritic limestones on the microbialites characterize a deepening upward sequence the widespread development of microbialites in reef sequences from the last deglaciation characterizes a period of environmental degradation consequential on the rapid sea level rise and abrupt climatic changes of that time the reported biological succession reflects changes in water quality and especially an increase in nutrients in shallow water settings increased alkalinity and nutrient availability in interstitial waters were related to surface fluxes and terrestrial groundwater seepage while slope environments were exposed to continuous upwelling of nutrient rich deeper waters during the last deglacial sea level rise the age differences between corals and overlying slope microbialites range from 1600 to 8400 years based on high precision u series age measurements of both corals and microbialites and indicates that a significant time several thousand years elapsed between the development of the coralgal frameworks and the growth of slope microbialite crusts microbialites cannot be considered as part of the drowning event some 14 000 years ago that resulted in the demise of reef frameworks in the 90 110 m present depth range but are substantially younger

the survival recovery and diversification of metazoan reef ecosystems following the end permian mass extinction event abstract the triassic period records important ecological transitions in the aftermath of the end permian mass extinction and is a key interval in the evolution of modern coral reefs there have been several critical developments in our understanding of triassic reef evolution over the past decade the timing of events and duration of stages have changed dramatically the discovery of metazoan reefs in the early triassic details about the environmental perturbations that drove the extinction the relationship between tectonic activity and platform margin reef proliferation and additional proxy evidence for the co evolution of coral reef builders and their photosymbionts here we provide an up to date synthesis of reef collapse and recovery dynamics following the end permian extinction specifically integrating recent discoveries the evolution of reef ecosystems can be divided into five phases based on their composition 1 microbial metazoan reefs represent survival communities that characterize the immediate extinction aftermath 2 the re establishment of reefs built by metazoans small sponge biostromes and bivalve buildups is observed in oxygenated settings in the olenekian early triassic 3 towards the end of the olenekian and into the anisian middle triassic low diversity tubiphytes dominated reefs formed which represent the first triassic platform margin reefs platform margin reefs however are not widespread until the late anisian 4 late anisian reefs also record a composition change and increase in species richness with sponges and tubiphytes as the main reef builders 5 the first scleractinian corals which are the main reef builder in modern marine reef ecosystems evolved during the anisian but are not reported as dominant reef builders until the late triassic the radiation of coral reefs is posited to be coupled to the acquisition of photosymbionts e g zooxanthellae there is clearly a stepwise evolution of reef types during the triassic however once each reef type appears it persists throughout the remainder of the triassic the survival recovery and diversification of reef ecosystems is therefore more complex than previously outlined particularly with respect to the earliest post extinction ecosystems these recent advances highlight the need to thoroughly document the faunal compositions of understudied reef systems as well as to continue the exploration of triassic ecosystems in underrepresented regions

late jurassic coral microbial reefs from the northern paris basin facies palaeoecology and palaeobiogeography abstract during the late middle oxfordian patch reefs grew on the northern margin of the paris basin according to the facies analysis of the reef and inter reef sediments the environment was a warm clear and agitated sea with highly episodic sedimentation the bioherms were a short lived phenomenon during the third phase of regional reefal development sequence stratigraphically they are associated with a highstand system tract volumetrically and trophically dominant organisms were microbes now represented by massive clotted leiolite stalactitic hemispheroids with purely thrombolitic texture are restricted to open caves corals were of structural reef building importance due to their rapid upward growth the patch reefs are characterised by thickets of ramose corals which developed a very open framework in the vicinity of these patch reefs though in hydrodynamically higher energy environments grew thickets of more stoutly branched corals however they are rarely preserved in situ and are generally represented as abundant coral rubble the reef taxa are characterised by the notable absence of several groups e g oysters serpulids bryozoans pectinids occurring at other localities where reefs of similar age developed in similar environmental conditions the reefs also have strikingly modern aspects to them in particular the presence of cryptic elements within caves and a sponge dominated borer association dwellers belong to various life form types although encrusting taxa are exceedingly rare this may be explained by the presence of soft microbial films on most surfaces the palaeoecological analysis suggests that the major controls on faunal composition and high diversity were elevated nutrient levels highly episodic sedimentation and probably seasonal environmental disturbances structural and functional aspects of the reef community grazers trigger framebuilders borers trigger binders binders hamper borers allow ecological comparisons to be made with contemporaneous as well as recent reefs the unique combination of ecological factors resulted in a specialised previously undescribed community which differs from both tethyan and northern localities in various aspects these include cavities with cryptofauna prominence of grazing gastropods and high faunal diversity in a microbially dominated build up

shelf and open ocean calcareous phytoplankton assemblages across the paleocene eocene thermal maximum implications for global productivity gradients abrupt global warming and profound perturbation of the carbon cycle during the paleocene eocene thermal maximum petm ca 55 ma have been linked to a massive release of carbon into the ocean atmosphere system increased phytoplankton productivity has been invoked to cause subsequent co2 drawdown cooling and environmental recovery however interpretations of geochemical and biotic data differ on when and where this increased productivity occurred here we present high resolution nannofossil assemblage data from a shelf section the u s geological survey usgs drill hole at wilson lake new jersey and an open ocean location ocean drilling program odp site 1209 paleoequatorial pacific these data combined with published biotic records indicate a transient steepening of shelf offshelf trophic gradients across the petm onset and peak with a decrease in open ocean productivity coeval with increased nutrient availability in shelf areas productivity levels recovered in the open ocean during the later stages of the event which coupled with intensified continental weathering rates may have played an important role in carbon sequestration and co2 drawdown

late early triassic microbial reefs of the western united states a description and model for their deposition in the aftermath of the end permian mass extinction abstract research in the western united states to reinvestigate and characterize the previously reported stromatolites of the latest early triassic spathian virgin limestone member of the moenkopi formation has shown that these microbial build ups formed patch reef mounds detailed field analysis of these reef mounds and the surrounding beds has established that they attained 1 2 m of topographic relief above the seafloor a petrographic study of these microbial mounds illustrates that they consisted of microbial fabrics as well as voids with early marine cements and formed in the absence of in situ metazoans these reef mounds formed during the aftermath of the end permian mass extinction that spanned the early triassic due to the devastation of marine metazoans at this extinction the early triassic has often been deemed a reef gap because no metazoan reefs are found at this time whereas colonial metazoan reefs are globally absent from lower triassic strata microbial build ups similar to these described from the western united states have been found in south china armenia southern turkey and greenland a regional early permian to late early triassic unconformity exists in the study region however analysis of these microbial reefs within a global context suggests that conditions favouring microbial reef development must have existed as long as 4 8 m y after the end permian mass extinction a depositional model of these microbial mounds indicates that flooding of the shelf with anoxic and or co2 rich deep waters may have fostered their occurrence

paleoceanography and paleoclimatology an earth system perspective abstract the purpose of this paper is to provide an overview of paleoceanography and paleoclimatology as a framework for other papers dealing with the earth system geochemical perspectives an introduction to both paleoceanography and paleoclimatology is followed by examples of the temporal changes through the phanerozoic the important and interactive role of the biosphere is emphasized many important changes in the earth system have affected the coupled ocean atmosphere system and many in turn have been reflected in biotic events many such changes can be tracked through time using geochemical signatures as proxy indicators whereas the scale of past paleoceanographic and paleoclimatic changes have been generally appreciated for some time the recognition of periodic rapid change in the ocean climate state and the ability to study and measure these precisely is only a recent accomplishment the potential for such rapid change in the ocean climate biosphere of the earth system raises concerns for events in the near future that may be forced by anthropogenic activities that enhance natural variability

paleogeographic trends in late triassic reef ecology from northeastern panthalassa the late triassic was a pivotal period in reef evolution but the majority of information about reef ecology during this time comes from buildups in the alps e g the tethys ocean recent studies of reefs in western north america have recognized unique ecologies along the eastern margin of the panthalassa ocean although there are numerous twenty five localities with putative reef builders only four buildups had syndepositional relief and a rigid framework i e true reefs the most paleo northern true reefs were microbial patch reefs with only a few large skeletal bioconstructors hypercalcified sponges and spongiomorphs built the mid latitude reefs with secondary microbial encrustation and branching phaceloid retiophyllia corals corals are the primary bioconstructors in panthalassa s most paleo equatorial reefs and calcareous microbes are sparse when all reefal deposits are analyzed the n s gradient is also present with microbial and bivalve deposits in the north sponge coral deposits in the mid latitudes and coral deposits near the equator this ecological gradient is not apparent in the tethys ocean tethyan reefs thrived in oligotrophic tropical waters without strong latitudinal gradients by contrast paleoceanographic considerations suggest that cool nutrient rich waters swept south along the western north american borderlands in the late triassic the eastern boundary current is interpreted to have created a strong north south differentiation of environments in northeastern ne panthalassa that was manifested in both the biotic and abiotic characteristics of eastern panthalassic reefs reefs from equatorial panthalassa are similar to tethyan reefs warm water photozoan coral reef structures whereas higher paleo latitude reefs from panthalassa are interpreted as cool water heterozoan buildups with abundant calcareous microbes diminutive biocalcifiers and few large framework building corals

upper triassic shallow water carbonates from the naizawa accretionary complex hokkaido japan new insights from panthalassa abstract due to their accretion on the circum pacific area during the jurassic and the cretaceous upper triassic carbonates from the panthalassa occur very scarcely and with relatively poor preservation in accretionary complexes however they represent a unique opportunity to improve our knowledge of the depositional conditions in tropical regions of the panthalassa recognized as a cradle of life shallow water carbonates are also of great importance to understand of how life evolved out of the tethyan domain during the triassic since 2007 several sedimentological and biostratigraphic studies focused on the upper triassic shallow water limestone from the circum pacific area have been carried out as part of the reefcade project at the university of geneva carbonates were thus reported in the southern part of japan and in the russian far east hokkaido island in northern japan represents the missing link between those two areas to fill this gap five limestone outcrops so far poorly described in the literature were identified and sampled in the pippu and esashi areas central and northern part of hokkaido island respectively their related microfacies are presented in detail as well as their foraminiferal associations the obtained age based on foraminiferal biostratigraphy from both areas is defined as carnian and the facies similarities associated with specific modes of occurrence identify the outcrops from the two areas as part of the same depositional system based on microfacies interpretations a hypothetical depositional model is presented it corresponds to a intra oceanic depositional system developed on the flanks of an emergent volcanic seamount the strong similarity with synchronous systems from the sambosan accretionary complex southwestern japan is discussed

early triassic stromatolites as post mass extinction disaster forms aftermaths of mass extinctions have been thought to be characterized by relaxation of ecological constraints accompanied by increased prominence of opportunistic generalists such taxa termed disaster forms have been shown to increase dramatically in range and abundance after several mass extinction events the cambrian ordovician stromatolite decline in normal marine level bottom environments has been explained as a direct or indirect consequence of increases in ecological constraints such as greater levels of predation and or bioturbation of microbial communities caused by early paleozoic benthic invertebrate evolution and diversification thus one would predict that in post ordovician strata stromatolites might appear in normal marine level bottom environments as disaster forms in the aftermaths of mass extinction particularly devastating to the benthic biota such as during early triassic time mounded stromatolites are present in two beds up to 1 5 m thick of the lower triassic spathian virgin limestone member moenkopi formation in the southwestern spring mountains of nevada stromatolites from level bottom normal marine subtidal environments have also been described from other lower triassic strata in north america europe and asia these stromatolites unusual in level bottom normal marine settings may have developed locally during the long aftermath 4 5 m y of the permian triassic mass extinction because of partial relaxation of the ecological constraintsmore that typically restricted them from unstressed subtidal normal marine level bottom environments less

distribution of paleogene planktonic foraminifera analogies with the recent abstract distribution patterns and morphologies of modern and paleogene planktonic foraminifera in the atlantic ocean were compared although many paleogene and modern planktonic foraminifera are homeomorphs they are not ecomorphs morozovellid homeomorphs of the modern higher spired globorotaliids inhabited warmest layers of the mixed layer the planorotalitids homeomorphic with modern low trochospiral globorotaliids have different geographic ranges they predominated at temperature and higher latitudes where they grew to largest sizes the cool water low spired subbotinids little resemble the non spinose modern neogloboquadrinids which dominate polar faunas today spinosity of paleogene polar forms indicates that they could have been carnivorous or omnivorous rather than herbivorous like the modern neogloboquadrinids early paleogene polar seas may have been relatively oligotrophic for at least part of the year some paleogene genera may have been ecomorphic with their modern analogues the dentoglobigerinids and globoquadrinids occupied equatorial and offshore upwellings much as neogloboquadrina dutertrei does today because the globorotaloids and catapsydracids deposited calcitic crusts and register most enriched oxygen isotope values they may have lived within and below the thermocline like some modern globorotaliids globorotaloids and catapsydracids may have been strictly herbivorous as are most modern non spinose species their predominance in later paleogene lower latitude upwellings but their near exclusion from polar regions indicates that subeuphotic equatorial waters may have been more eutrophic paleogene type warming in zones p1d p3a p5 p6 7 late p12 late p16 late p19 and early p22 involves proliferation evolutionary diversification and poleward migration of thermophilic forms but decreased species abundance at low latitudes and diminished numbers of fertility indices the guembelitrids biserial heterohelicids globigerinathekids globoquadrinids or dentoglobigerinids neogene type warmings in zones p4 and probably p alpha and p21a involved diversification of cooler water taxa retreat of thermophilic forms from higher latitudes and their concentration in lower latitudes and proliferation of fertility indices under these conditions oxygen isotope records include lower latitude warming but cooling of temperature and higher latitudes and tropospheric waters planktonic foraminiferal diversity and population structure reflect changes in oceanic fertility and the depth of the thermocline cooling and eutrophication resulting in a contraction of the trc trophic resource continuum in atlantic surface waters from late middle eocene through mid oligocene time explain the low diversities extinctions of morphologically complex thermophilic species increased dominance of opportunistic subeuphotic and temperature species proliferation of euphotic and subeuphotic fertility indices and geographic expansion of siliceous primary producers

barrier holes and trench application to reduce blast induced vibration in seyitomer coal mine in this research experimental applications have been performed to reduce blast induced vibrations in open pit mines for this purpose artificial discontinuity zones such as barrier holes and trench were opened in a dragline panel of seyitomer lignite enterprise kutahya turkey peak particle velocities in front of and behind them were measured by seismographs in this way their effect against vibration was observed and compared barrier holes were opened 24 m deep through 3 parallel lines and aligned at 1 m spacing on the other hand the trench had 8 m depth and 4 m width during the research 209 measurements were taken belonging to 105 explosions twenty eight explosions were carried out in the barrier holes experiments and 77 explosions were carried out in the trench experiments a decrease in vibration of 14 3 18 5 was obtained behind the barrier holes while a decrease of 24 8 58 1 was provided by the trench

chert in the pacific biogenic silica and hydrothermal circulation abstract data on sections drilled by dsdp and odp in the pacific have been compiled for 187 sites 105 of which contain chert the spatial pattern of siliceous deposits in the pacific generally follows the pattern of biologic productivity there is some evidence that enhanced vertical diffusivity in the ocean during the eocene warm climate gave rise to siliceous deposits on and near bathymetric highs and basin margins the most common occurrence of chert is in eocene and older sections however cherts do occur in sections as young as 7 ma in the sites investigated over half of the youngest chert occurrences in sedimentary sections are within 150 m of basement nearly all the chert occurrences on crust younger than 60 ma are within 150 m of basement the deficit in heat flow over ocean crust younger than 60 ma is explained as the result of heat advection by hydrothermal waters circulating in the upper part of the ocean crust these waters appear to dissolve biogenic silica and deposit it as chert in the lower parts of sedimentary sections diffusion of these waters into the lower sediment section is enhanced by small scale faulting this faulting may be associated with intra plate stresses that develop during ridge jumps and reorientations of plate motion the relatively warm bottom waters of the early cenozoic may have also enhanced the dissolution of biogenic silica during hydrothermal circulation in the upper oceanic crust and basal sediment section

triassic carbonate development and reefbuilding in western north america the cordilleran region of western north american contains numerous examples of middle to upper triassic carbonate sequences many of these developed as broad shallow water platforms associated with island arcs these platforms however were not characterized by extensive reef structure shallow water facies in many sequences contain abundant corals spongiomorphs sponges and a variety of rich invertebrate faunas most of these are endemic with the exception of the corals which show much similarity with the tethyan faunas small local reefoid buildups occur within many sequences especially those of norian age and contain local organic framework

missing organic carbon in eocene marine sediments is metabolism the biological feedback that maintains end member climates 1 ocean chemistry is affected by pco2 in the atmosphere by increasing the dissolution of solid calcium carbonate and elevating the dissolved inorganic carbon concentrations in seawater positive feedbacks between the ocean and atmosphere can maintain high atmospheric pco2 and affect global climate we report evidence for changes in the oceanic carbon cycle from the first high quality organic carbon corg data set of eocene sediments beneath the equatorial pacific upwelling region leg 199 of the ocean drilling program eocene corg mass accumulation rates mars are 10 times lower than holocene rates even though expected corg mars estimated from biogenic barium mars an indicator of biological production equal or exceed modern fluxes what happened to the missing corg recent advances in ecology and biochemical kinetics show that the metabolism of nearly all animals marine and terrestrial is positively correlated by first principles to environmental temperatures the approximately 10 c abyssal temperature difference from eocene to holocene should have radically reduced pelagic corg burial as we observe we propose that higher basal metabolism and nutrient utilization recycling rates in the eocene water column and surface sediments precluded corg sediment burial in the pelagic ocean increased rates of metabolism nutrient utilization and lowered corg sedimentation caused by increased temperature may have acted as a biological feedback to maintain high atmospheric pco2 and hothouse climates conversely these same parameters would reverse sign to maintain low pco2 when temperatures decrease thereby maintaining icehouse conditions during cold climate regimes

regional correlations across the internides externides front northwestern rif belt morocco during the late cretaceous early burdigalian times palaeogeographical and palaeotectonic implications

paleoceanographic and paleoclimatic constraints on the global eocene diatom and silicoflagellate record abstract eocene diatom and silicoflagellate biostratigraphy are summarized and correlated with the most recent geologic time scale as well as with the global oxygen isotope and eustatic sea level curves the global distribution of eocene diatom silicoflagellate bearing sediments varies considerably reflecting changing oceanic gateways and paleoceanography with changing patterns that are punctuated by four major depositional events event 1 49 million years ago ma at the end of the early eocene climatic optimum eeco saw the cessation of diatom silicoflagellate deposition in epicontinental regions of the north sea region and in the northern russia and the onset of biosilica deposition in the arctic event 2 46 ma which coincided with intensification of the middle eocene cooling trend marked the widespread expansion of diatom silicoflagellate deposition in both the north and south atlantic a shift of diatom silicoflagellate deposition from the atlantic to the pacific began at event 3 at the end of the middle eocene climatic optimum meco 40 ma that was likely tied to the initial opening of the drake passage between antarctica and south america event 4 39 ma coincided with a major sea level fall and a widespread deep sea hiatus in the latest middle eocene late eocene diatom silicoflagellate deposition became more concentrated in middle to high latitude regions and coastal upwelling regions particularly in the pacific ocean tabulation of the first and last occurrences of 132 biostratigraphically important diatoms suggests increased species turnover during the latest paleocene to earliest eocene that may be in part due to a monographic effect an increasing rate of evolution of new diatom species between 46 and 43 ma and after 40 ma coincides respectively with the widespread expansion of diatom deposition in the atlantic and with an increased pole to equator thermal gradient that witnessed the expansion of diatoms in high latitude oceans and coastal upwelling settings

oligocene magnetostratigraphy from equatorial pacific sediments odp sites 1218 and 1219 leg 199 abstract an oligocene magnetostratigraphy from odp sites 1218 and 1219 equatorial pacific has been obtained by measurements made on u channel samples augmented by about 221 discrete samples u channel samples were measured at 1 cm intervals and were stepwise demagnetized in alternating fields af up to a maximum peak field of 80 mt the magnetization directions were determined at 1 cm intervals by principal component analysis of demagnetization steps in the 20 to 60 mt peak field range a similar treatment was carried out on the discrete samples which confirmed the results obtained with u channel measurements sites 1218 and 1219 were precisely correlated based on multisensor track paleontological and shipboard magnetostratigraphic data this correlation is substantiated by u channel measurements although the magnetostratigraphy obtained from the u channels is similar to the interpretation deduced from shipboard measurements based on blanket demagnetization at peak af of 20 mt the u channel results are substantially more robust since many interpretative uncertainties are resolved by the stepwise demagnetization and higher stratigraphic resolution the temporal resolution of u channel based magnetic stratigraphy in the oligocene section of sites 1218 and 1219 is better than 5 kyr and it is therefore suitable for detection of brief polarity subchrons however in spite of the high resolution we did not find any reversals corresponding to the numerous cryptochrons identified in this time span by cande and kent s c cande d v kent revised calibration of the geomagnetic polarity time scale for the late cretaceous and cenozoic j geophys res 100 1995 6093 6095

geochemical characteristics of oil and source rocks and implications for petroleum systems talara basin northwest peru in the first comprehensive study of the talara basin petroleum system of onshore and offshore northwest peru we test oil source rock correlation through molecular biomarker analysis of oil samples from wells scattered throughout the basin as well as purported source rocks the new data presented in this manuscript suggest that the oils constitute one oil family and that the source rock was a predominant marine clay deposited in an oxic to suboxic environment substantial relative amounts of oleanane in each oil sample indicate a notable input of terrestrial organic matter deposited in a mixed marine and terrestrial environment probably deltaic the high ratio of 24 norcholestanes to 27 norcholestanes and c25 highly branched isoprenoid hbi alkanes suggests a significant upwelling component in the source rock depositional environment in addition the high oleanane indices oleanane hopane of the oils are not paralleled in any alternative source rock candidate in this study the values are as expected for tertiary source rocks and are at levels that exceed any reported cretaceous or older source rock or oil this result in concert with high nordiacholestane ratios norcholestane ratios and hbi concentrations indicates a tertiary age source rock possible source rocks were selected and analyzed from different outcrops and wells and compared with the oils a negative correlation suggests that upper cretaceous intervals of limestone marl and black shale previously believed to be important source rocks can be discounted as an important contributor to talara basin oils instead the new data suggest a tertiary source rock eocene oligocene comparable to that of the progreso basin however no such source rock strata have yet been identified within the talara basin certain upper cretaceous samples with good source potential could support another petroleum system not yet identified in the coastal areas of peru

microbialite morphology structure and growth a model of the upper jurassic reefs of the chay peninsula western france abstract during the early kimmeridgian the northern margin of the aquitaine basin western france is characterised by a significant development of coral reefs the reef formation of the chay peninsula comprises two main reefal units in which the microbial structures can contribute up to 70 of framework the microbial crusts which played an important role in the stabilisation and growth of the reef body show the characteristic clotted aspect of thrombolitic microbialites corals are the main skeletal components of the build ups the bioconstructions of the chay area are thus classified as coral thrombolite reefs four main morpho structural types of microbial crusts are distinguished 1 pseudostalactitic microbialites on the roof of intra reef palaeocaves 2 mamillated microbialites found either on the undersides or on the flanks of the bioherms 3 reticular microbialites in marginal parts of the reefs and between adjacent bioconstructed units and 4 interstitial microbialites in voids of bioclastic deposits thrombolitic crusts developed on various substrates such as corals bivalves or bioclasts the thrombolites formed a dense clotted and or micropeloidal microbial framework in which macro and micro encrusters also occur variations in accumulation rate strongly influenced the reef morphology in particular its relief above the sediment surface the coalescence of the coral microbialite patches created numerous intra reef cavities of metre scale dimensions the direction of microbial growth which defined the macroscopic microbialite forms strongly depended on the position within the reef framework but was also controlled by water energy accumulation rate and light availability

nature and environmental significance of microbialites in quaternary reefs the tahiti paradox drill cores from the bamer reef edge of tahiti exhibit 85 93 m thick coralgal sequences recording at least 13 500 years of continuous reef growth in optimal environmental conditions the cored reef sequences form an overall shallowingupward succession with assemblages of branching or massive colonies of porires at the base overlain by a robust branching community acropom gr dmmi robirstn heavily encrusted by coralline algae sessile vermetid gastropods and arborescent foraminifers which grew at depths less than 6 m microbialites generally form the last stage of encrustation of coral colonies or more commonly of related encrusting organisms thus appearing as a major structural component of the reef sequence where they may locally form 809 of the rock by volume they developed in an open cavity system of the reef framework with freely circulating normal marine water microbialites include laminated crusts and clotted micritic masses commonly associated in compound crusts probably feflecting differences in the composition of the involved biological communities and in biomineralization processes that controlled the accretion of the crusts the isotopic composition of the microbialites 2 05 to 3 92 i they underwent also indivitlual processes of biominrlali2ation besicles the overall decrease in lizht and enqy conditions rttlecting progressive burial by conil growth the widespread development of microbialites within the reef framework may be related to increased alkalinity and niitrient availability in interstitial waters due to temstrial groundwwr seepage and puiodic runoffs the tlevelopment of micrubialites in the cryptic niches of the reef framework ceased about 6000 years

cenozoic marine sedimentation in the sechura and pisco basins peru abstract the central and northern peruvian margin consists of a series of 8 paired forearc basins which may be separated into an inner set of shelf basins and a seaward set of slope basins we have examined the cenozoic stratigraphy of the onshore portions of the sechura basin 5 7 s and pisco basin 13 16 s two shelf basins which have accumulated marine sediment discontinuously since the mid to late eocene cenozoic sediments in the pisco basin were deposited during at least three major transgressive cycles each sequence is preserved as a similar vertical progression of facies including coarse nearshore bioclastic conglomerates and sandstones grading upwards into sandy siltstones and mudstones and capped by biogenic deposits including diatomites diatomaceous mudstones dolomitic horizons and phosphate deposits stratigraphic nomenclature for the pisco basin has recently evolved a stratigraphy presented here includes the eocene caballas fm upper eocene los choros fm upper eocene to lowermost oligocene yumaque fm uppermost oligocene to middle miocene chilcatay fm and upper miocene to pliocene pisco fm major hiatuses in the pisco basin span the late cretaceous to middle eocene early to late oligocene middle miocene and late pliocene pleistocene to recent cenozoic sediments of the sechura basin were deposited within at least 4 major transgressive cycles with hiatuses during the paleocene to middle eocene oligocene early to middle miocene and late miocene based on recent biostratigraphic studies sediments enriched in biogenic components accumulated between about 40 36 ma 24 16 ma and 11 3 ma in the pisco basin and between 40 37 ma and 8 5 4 5 ma in the sechura basin in both basins the most diatomaceous sediments are restricted to the late eocene and late miocene through pliocene the temporal distribution of biogenic sediments suggests that high productivity conditions linked to coastal upwelling have occurred episodically since at least the late eocene the occurrence of diatomites and phosphorites is diachronous between the pisco and sechura basins and between the peruvian forearc and other circum pacific monterey formation analogs a reflection of the strong influence of local tectonism on sedimentation patterns the volume of neogene sediments along the peruvian forearc is nearly twice that of the monterey fm despite basin to basin facies diachroneity these deposits very likely contributed to fluctuations of the late miocene carbon co 2 system by acting as large carbon sinks

microbial framework in upper triassic carnian patch reefs from williston lake british columbia canada abstract the upper triassic carnian patch reefs from pardonet hill british columbia canada are the only known upper triassic reefal buildups from the craton margin of northwestern pangaea these buildups occur within the lower baldonnel formation and are characterized by a moderately diverse assemblage of corals spongiomorphs crinoids echinoderms bivalves gastropods brachiopods and microbialites despite the evidence that these buildups had a rigid structure e g brecciation and hardgrounds and relief above the seafloor visible in outcrop the exact nature and extent of the framework has previously been undetermined this study focuses on the microfacies within these patch reefs and highlights the importance of microbialites in the framework of these diminutive buildups 100 m3 to 500 m3 the pardonet hill patch reefs were mapped in outcrop to determine their structure geometry and the importance of large metazoan framework builders samples of the reefal horizons and surrounding strata were evaluated utilizing point count analyses of organisms cements lithic grains and microbial textures in thin section quantitative analysis of the microfacies in concert with traditional descriptions of reef construction and reef classification allow a more thorough understanding of organism abundance and reef structure despite the presence of corals and spongiomorphs throughout the outcrop they very rarely form a true intergrown framework except at the base of patch reef b instead cemented microbialites form a rigid framework in the core of some patch reefs detailed examination of the microfacies and reef construction demonstrates the importance of non skeletal framework builders in the structural fabric of these small buildups pardonet hill patch reef b is the first true reef with a microbial framework documented from the upper triassic of north america this microbial coral framework bears a striking similarity to some triassic and upper jurassic coral microbial reefs from the tethys although the depositional environment of the pardonet hill patch reefs is likely shallower and more energetic than the tethyan reefs

paleoecology biogeography and evolution of reef ecosystems in the panthalassa ocean during the late triassic insights from reef limestone of the sambosan accretionary complex shikoku japan upper triassic reefs from the panthalassa ocean have been understudied in comparison to their tethyan counterparts and are therefore pivotal to understanding the global reef evolution during the late triassic to fill this gap upper triassic reef limestone from ten localities of the sambosan accretionary complex at shikoku island japan has been investigated biotic assemblages quantitative microfacies analysis and integrated biostratigraphy allow us to characterize two types of reefs those attributed to the ladinian early carnian and those attributed to the late carnian rhaetian at the regional scale our data refine the biostratigraphic framework of the upper triassic sambosan limestone at the global scale multivariate analyses support a strong paleobiogeographic affinity of the western panthalassa reef biota with those of the south tethys ocean during the ladinian carnian and norian rhaetian additionally they indicate connections with east panthalassa reefs during the norian rhaetian