high resolution surface and subsurface sequence stratigraphy of late middle to late ordovician late mohawkian cincinnatian foreland basin rocks kentucky and virginia the late middle to late ordovician late mohawkian to cincinnatian supersequence in kentucky and virginia was deposited in a tectonically active foreland basin during a transition from the ice free early ordovician to the glacial late ordovician this sequence was deposited in less than 12 m y is 250 500 m thick and is composed of four large third order sequences each 40 150 m thick that are regionally correlative in outcrops cores and gamma ray logs smaller scale third order parasequence sets up to 20 m thick and component parasequences 1 8 m thick make up the larger sequences and are only locally correlative subtidal dominated parasequences comprise the basal part of each sequence whereas shallower subtidal or peritidal dominated parasequences compose upper parts of sequences each large third order sequence is asymmetric and marked by lowstand transgressive and highstand systems tracts with unique lithologic and gamma ray log response characteristics ramp margin wedges rmw are poorly developed and consist of marine siltstone or grainstone packstone sheets extending into deep ramp settings these sheets have high gamma ray values in their base and lower blockier gamma ray responses in their tops transgressive systems tracts tst are thin composed of high energy locally phosphatic grainstone copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 7 1996 revised manuscript received may 27 1997 final acceptance june 16 1997 2department of geology virginia tech blacksburg virginia 24061 0420 present address department of earth atmospheric and planetary sciences massachusetts institute of technology cambridge massachusetts 02139 3department of geology virginia tech blacksburg virginia 24061 0420 this study was supported by nsf grant ear 9316057 to j f read a grant from mobil oil company and grants in aid of research from the geological society of america and appalachian basin industrial associates to mike pope we thank john haynes brian keith and rick major for thorough and insightful reviews of an earlier version of this manuscript

endolithic biodegradation of cool water skeletal carbonates on scott shelf northwestern vancouver island canada abstract biodegradation of shell material is widespread in the cool water skeletal carbonate deposits on scott shelf northwestern vancouver island and is especially evident in the large aragonitic bivalves glycymeris and humilaria major primary sediment contributors ten types of endolithic microborings have been identified in the shells including representatives of green algae e g ostreobium quekettii blue green algae e g plectonema terebrans scytonema sp fungi bacteria and clionid sponges as well as macroborings of phoronids polychaetes and naticid gatropods microcrystalline carbonate is not precipitated in vacated bores boring physically weakens the shells rendering them more prone to mechanical abrasion during sediment transport and bioturbation and to biological abrasion by grazing benthos tumbling experiments demonstrate that the rate of carbonate mud production is much greater for bored as compared to fresh bivalve shells and that mud production rates decrease with tumbling time because most endolithic microborings are confined to the periphery of grains boring also increases significantly the porosity and surface area of skeletal grains and destroys their organic matrix making them susceptible to maceration and dissolution on cool water shelves fostered by the generally low rates of carbonate production and accumulation many aragonitic bivalve shells on scott shelf have become thoroughly degraded through a combination of endolithic microboring maceration and dissolution within about 1000 years in ambient sea water in geologic terms such selective taphonomic loss of skeletal material may be considerable in ancient temperate shelf limestones and should be evaluated when interpreting their paleoecology and paleoenvironments

revised sequence stratigraphy of the upper katian stage cincinnatian strata in the cincinnati arch reference area geological and paleontological implications abstract the upper ordovician cincinnatian series is a critical upper katian reference succession previously six 3rd order depositional sequences c1 to c6 have been recognized and frequently used as regional time slices recent research however indicates a need for revision and additions including the recognition of additional 3rd and 4th order sequences we propose amendments based upon high resolution correlations using a combination of regional disconformities cycle stacking patterns bioevents marker beds and chemostratigraphy several disconformities including a large regionally angular mid richmondian unconformity are newly recognized or reinterpreted in addition distinctive depositional patterns aid in the recognition of systems tracts with a thick proximal laminated peritidal facies representing early transgressive systems tracts tsts or lowstands in part lsts b shell rich limestone packages representing later tsts and overlain by c more shale prone highstand systems tracts hsts themselves overlain locally by d siliciclastic dominated falling stage systems tract fsst deposits that are commonly removed beneath substantial unconformities sequence boundaries at present we recognize eight 3rd order cincinnatian sequences designated c1 through c8 and 16 4th order subdivisions and their component systems tracts a younger hirnantian sequence may be present at some localities as the enigmatic centerville formation and or basal belfast member of the brassfield formation the implications of these new correlations and sequence interpretations include a new standard for relative sea level changes and insights into basin dynamics this framework also permits a more nuanced history of biotic changes that include geologically brief pulses of immigration associated with the transgressions of the c1 lower kope formation c5c clarksville member of waynesville formation and c7a basal whitewater formation

sequence stratigraphy of a carbonate clastic ramp the cincinnatian series upper ordovician in its type area the cincinnatian series consists of five depositional sequences each is composed of a thin transgressive systems tract and a much thicker shallowing upward highstand systems tract whereas the highstand systems tracts are relatively poor in micrite but rich in terrigenous shale the transgressive systems tracts are composed of cleaner carbonate facies ranging from coarse grained calcarenites to micrite rich wackestones and micstones this alternation of carbonate and terrigenousfacies types resulted from the trapping of clastic sediment near its presumed source in the appalachians during a relative sea level rise and it may be a feature common to sequences in other mixed carbonate clastic settings these depositional sequences were produced by eustatic fluctuations as shown by the limited extent to which the sequences can be traced into more proximal portions of the appalachian basin the recognition of depositional sequences clarifies the regional paleogeography and simplifies regional lithostratigraphic nomenclature within current biostratigraphic resolution sequences in the cincinnatian series appear to have chronostratigraphic significance and thereby offer an additional means of intrabasinal correlation in the upper ordovician

sequence stratigraphy and relative sea level history of the middle and upper ordovician of the nashville dome tennessee abstract eleven depositional sequences are present in the middle and upper ordovician of the nashville dome all but one lack lowstand systems tracts and many display evidence of subaerial exposure such as paleokarst or regional erosional truncation at their sequence boundaries which are combined with transgressive surfaces features formed during the transgression such as hardgrounds are more prominent at most sequence boundaries than are those features related to subaerial exposure all sequences have maximum flooding zones with aggradational stacking rather than discrete maximum flooding surfaces condensation features are much more common at transgressive surfaces than within the maximum flooding zone the expression of these parasequences and sequences changes with the onset of the taconic orogeny although parasequences from equivalent depositional environments can be recognized before and after the onset of the orogeny their facies composition changes completely sequences following the orogeny display fewer paleokarst features more pyritized and iron stained hardgrounds at flooding surfaces and transgressive surfaces and more phosphatic lags and mineralization at transgressive surfaces than those preceding the orogeny a relative sea level curve for the nashville dome has a long term 5 m y component presumably dominated by subsidence and a short term 1 3 m y component consisting of 10 50 m fluctuations that is primarily the result of eustasy

rare colonial corals from the upper ordovician kope formation of kentucky and their role in ephemeral invasions in the edenian abstract a large colonial rugose coral was recently discovered as float partially buried beneath several inches of sediment in the kope formation of northern kentucky corals are unreported in the kope assemblage not appearing until much later during the c4 and c5 sequences during the richmondian invasion a period in which the area was inundated with invasive taxa migrating from the midcontinent the slab contains the remains of several other species that are diagnostic of the kope formation such as the brachiopods sowerbyella rugosa and zygospira cincinnatiensis the large colonial rugose coral is composed of corallites ranging in diameter from 3 to 5 mm containing 10 14 twisting major septa with crenulated walls which is consistent with cyathophylloides cf c burksae new taxa or new occurrences in a well sampled formation such as the kope formation are unexpected especially for large skeletonized taxa and highlights the rarity of coral within the assemblage the richmondian invasion is linked to a transgressive event that increased connectivity between marine biogeographic provinces disrupted ecosystem structure as well as acted as a significant evolutionary driver during the late ordovician in the cincinnatian faunal assemblages isolated dispersal events may have brought planktonic larva onto the cincinnati arch much earlier during transgression in the c1 sequence the failure of the coral to become established might be linked to the low abundance of larva entering the region or non ideal environmental conditions the discovery of this coral in the kope formation further indicates the occurrence of rare and ephemeral dispersal events that have recently been reported within brachiopods

the use of faunal gradient analysis for intraregional correlation and assessment of changes in sea floor topography in the type cincinnatian abstract in paleobiology and stratigraphy there is a growing need to develop high resolution chronostratigraphic frameworks at regional scales which would permit unprecedented assessments of spatiotemporal variation in preserved biotas here we present an intraregional correlation for the kope and lower fairview formations of the type cincinnatian on the basis of detrended correspondence analysis dca of faunal census data we believe that the method also holds promise as a tool of correlation in other fossiliferous venues the data were collected directly in the field at closely spaced stratigraphic intervals but with relatively coarse taxonomic and quantitative data resolution this approach is independent of lithologic assessments and does not require the delineation of sequence stratigraphic architecture in the study area faunal curves were constructed for each locality on the basis of stratigraphic changes in sample scores for dca axis 1 the curves were smoothed to reveal a long term signal of

time richness and phosphatic microsteinkern accumulation in the cincinnatian katian ordovician usa an example of polycyclic phosphogenic condensation abstract millimeter scale phosphatic steinkern preservation is a feature of the taxonomically enigmatic early cambrian small shelly faunas but this style of preservation is not unique to the cambrian it is ubiquitous if infrequently reported from the phanerozoic record the polycyclic phosphogenic condensation ppc model envisions both the genesis and concentration of phosphatic microsteinkerns as natural outcomes of shell bed genesis through episodic sediment starvation this model predicts that more reworked and condensed shell bed limestones will contain more phosphatic microsteinkerns but that even the least reworked limestones may contain some phosphatic particles we test this model through examination of vertical thin sections densely collected through a 10 meter interval from the classic cincinnatian upper katian middle maysvillian north american stage upper fairview formation miamitown shale and lower grant lake formations at four localities near cincinnati ohio for each of approximately 50 distinguishable limestone depositional units in each locality a 2 2 cm square was selected for study each square was assigned a textural classification mud content of intergranular space and a breakage rank pristine to comminuted phosphatic particle distribution was quantified both by visual estimation and by particle counting with counts ranging from none detected to over 1000 per 4 cm2 our analyses show a strong positive relationship between phosphate content and both textural maturity and fragmentation this positive relationship is consistent with the ppc model and confirms that textural maturity can reflect the degree of condensation as well as depth related environmental energy this finding suggests that shell bed processes of repeated deposition and reworking make a significant contribution to the generation and accumulation of phosphatic particles if local scale sedimentary processes and conditions can control this accumulation temporal changes in phosphatic sediment deposition rates may be linked to earth changes more complexly than through changing ocean chemistry on a global scale

coordinated biotic and abiotic change during the great ordovician biodiversification event darriwilian assembly of early paleozoic building blocks abstract the ordovician period records an extraordinary biodiversity increase known as the great ordovician biodiversification event gobe which coincided with a series of environmental changes to the earth system notably a cooling global ocean increased oxygenation and increased nutrient supply from volcanism and continental weathering the co evolution of earth and its biota during this interval has been studied in various contexts on multiple paleocontinents emerging patterns depend on the lens of investigation here we summarize the current state of understanding by reviewing and synthesizing the fossil and sedimentary records recent paleontological studies mainly focused on rhynchonelliform articulated brachiopods bryozoa cephalopods trilobites graptolites echinoderms and reef organisms have documented details of diversification body size increase development of ecosystem complexity and intensification of inter continental dispersal from the late cambrian through late ordovician biomass increased markedly between the early and middle ordovician furthermore diversification rates increase statistically during the mid darriwilian age both globally and regionally coincident with these biotic changes geochemical proxies record significant changes to earth s physical system oceanic temperatures decreased and atmospheric oxygen levels increased to near modern levels in concert with the middle ordovician diversification of shelly fauna anoxic pulses ceased and evidence for deep ocean ventilation prevails in middle ordovician strata furthermore a major middle late ordovician change in oceanic strontium isotopic composition indicates increased weathering of juvenile volcanic rocks and delivery of nutrients to marine settings this multi proxy dataset records near simultaneous changes in fossil rich shallow marine environments during exactly the interval of greatest diversification by integrating biotic and geochemical datasets a clear picture of the co evolution of earth and its biota emerges indicating that the darriwilian was the critical interval facilitating increased capacity of ecosystems we therefore recommend restricting the term gobe to indicate this short interval of rapid diversification and ecosystem change and using ordovician radiation when referencing the sum of diversifications that occurred throughout the ordovician period

stratigraphic relationships and detrital composition of the medial ordovician flysch of western new england implications for the tectonic evolution of the taconic orogeny a reply to rodgers we present new stratigraphic and petrographic data on the easterly derived medial ordovician flysch sequence of western new england and eastern new york state a conformable relationship exists between the flysch and underlying early paleozoic continental rise sediments within the western taconic allochthon farther east in the allochthon we observe a possibly disconformable relationship contrary to previous interpretations these facts suggest that at any place within this paleogeographic realm the sediments were undeformed and untransported at the initiation of flysch deposition at least three sources contributed detritus to the flysch 1 taconic sequence sediments 2 deformed and metamorphosed pelitic psammitic and volcanic lithologies and 3 igneous rocks of dominantly mafic ultramafic affinities these three sources are respectively interpretable as continental rise accretionary prism and ophiolitic volcanic arc assemblages which are recognized in the regional geology of western new eng

colonization of rugose corals by diverse epibionts dominance and syn vivo encrustation in a middle devonian givetian soft bottom habitat of the holy cross mountains poland abstract middle devonian givetian rugose corals from the holy cross mountains miloszow poland have been analysed with respect to epibiont colonization patterns solitary microconchid tubeworms and colonial bryozoans hederelloids and ascodictyids numerically dominate on the coral hosts moreover the same taxonomic groups of epibionts dominate both the larger heliophyllum acanthophyllum stringophyllum ceratophyllum cystiphylloides and smaller thamnophyllum corallites indicating the true pattern of epibiosis was achieved the presence of common bioclaustrated epibionts constricted and rejuvenated coral calyces as well as epibionts growing concordantly with the host s growth direction indicate that at least some corals were colonized during life the observed low number of overgrowth cases of various epibionts on coral hosts suggests that competition for hard substrate was negligible most probably due to abundant coral substrates on muddy sea bottom of the givetian sea at miloszow this epibiont community is similar to other known devonian encrusting communities which likely developed in a more nutrient rich palaeoenvironments and differs markedly from taxonomically poor assemblages developing in a more oligotrophic conditions the presence of rothpletzella encruster which is considered to be related to green algae indicates that the miloszow coral community dwelled within the limits of the photic zone

comparative sequence stratigraphy of two classic upper ordovician successions trenton shelf new york ontario and lexington platform kentucky ohio implications for eustasy and local tectonism in eastern laurentia abstract comparison of the classic upper ordovician mohawkian to lower cincinnatian caradoc to lower ashgill black river and trenton groups in new york state southern ontario with the tyrone lexington formations exposed in the jessamine dome southern cincinnati arch in north central kentucky and southern ohio reveals striking similarities previous emphasis on complex local facies mosaic has obscured widespread regional patterns biostratigraphy and k bentonites provide broad constraints on inter regional correlations however an allostratigraphic approach permits higher resolution correlations and a partial test of eustatic vs strictly local tectonic models to explain stratigraphic patterns upper mohawkian to lower cincinnatian 455 449 ma depositional sequences previously recognized for the jessamine dome and nashville dome areas are correlated between the two main study areas and further refined chatfieldian rocklandian to shermanian or cobourgian of traditional terminology sequences m5 and m6 of previous workers are interpreted to be composite sequences and are each subdivided into three smaller scale sequences which also have counterparts in the new york ontario strata in turn these correlations indicate at least partial allocyclic control on sedimentary cycles complex lateral variations within depositional sequences especially in the late shermanian to edenian indicate that tectonically controlled patterns of basinal subsidence and uplift of crustal blocks perhaps reflecting forebulge migration exerted a strong influence on the local facies and motif of depositional sequences these tectonic features however did not obliterate the underlying allocyclic pattern indeed high resolution sequence stratigraphy enables detailed resolution of shifting patterns of minor uplift and subsidence

record of microendoliths in different facies of the upper ordovician in the cincinnati arch region usa the early history of light related microendolithic zonation abstract this study provides the first documentation of microendolithic borings made by cyanobacteria algae and fungi in invertebrate skeletons from the late ordovician of eastern north america samples from the upper mohawkian to cincinnatian series katian stage caradoc to lower ashgill of traditional usage limestones and calcareous shales of ohio indiana and kentucky were selected for study because of the excellent preservation of fossil shell material the substrates mostly are brachiopods and corals strata of the mohawkian lexington limestone and cincinnatian kope formation maysville and richmond groups have been recently studied in terms of facies sequence stratigraphy and paleoenvironments which facilitates a reliable comparison of the distribution of microborings and inferred environmental settings especially relative paleobathymetry this paper reports the first occurrence of 10 ichnospecies plus various conchocelis traces in late ordovician cincinnatian marine shells these traces have been previously observed in shells from younger geological periods their modern counterparts are produced by species of cyanobacteria green algae red algae and heterotrophic microendoliths considering the bathymetric index ichnocoenoses of microendoliths defined for the later phanerozoic it appears that only one or two light related bathymetric zones can be recognized in a few samples from the upper ordovician cincinnatian of ohio and kentucky but not in all deposits where they might have been expected the shallow euphotic zone iii and with less certainty the deep euphotic zone on the contrary our samples from the underlying lexington formation contain only borings of worms macrotubular form and some forms with unknown producers although they were collected in facies realms comparable to the younger samples given the present state of knowledge the best explanation for the appearance of these 10 ichnospecies and the first bathymetric index ichnocoenoses within the late ordovician is that they represent the early evolution of microendolithic ichnospecies and early emplacement of ichnocoenoses

multiple sources supply eolian mineral dust to the atlantic sector of coastal antarctica evidence from recent snow layers at the top of berkner island ice sheet the sr and nd isotopic composition of dust extracted from recent snow layers at the top of berkner island ice sheet located within the filchner ronne ice shelf at the southern end of the weddell sea enables us for the first time to document dust provenance in antarctica outside the east antarctic plateau eap where all previous studies based on isotopic fingerprinting were carried out berkner dust displays an overall crust like isotopic signature characterized by more radiogenic 87sr 86sr and much less radiogenic 143nd 144nd compared to dust deposited on the eap during glacial periods differences with eap interglacial dust are not as marked but still significant indicating that present day berkner dust provenance is distinct at least to some extent from that of the dust reaching the eap the fourteen snow pit sub seasonal samples that were obtained span a two year period 2002 2003 and their dust sr and nd isotopic composition reveals that multiple sources are at play over a yearly time period southern south america patagonia in particular likely accounts for part of the observed spring summer dust deposition maxima when isotopic composition is shifted towards younger isotopic signatures in the spring possible additional inputs from australian sources would also be supported by the data most of the year however the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in east antarctica which carry old crust like isotopic fingerprints whether the restricted east antarctic ice free areas produce sufficient eolian material has yet to be substantiated however the fact that large 5 mu m particles represent a significant fraction of the samples throughout the entire time series supports scenarios that involve contributions from proximal sources either in patagonia and or antarctica possibly including snow free areas in the antarctic peninsula and other areas as well this also indicates that additional dust transport which does not reach the eap must occur at low tropospheric levels to this coastal sector of antarctica

paleobathymetric implications of microborings in tertiary strata of alaska usa abstract microboring algae bacteria and fungi that lived under non tropical conditions are abundantly present in four richly fossiliferous marine strata of paleocene to miocene age in alaska by comparing their boring trace communities with endolithic guide ichnocoenoses characterizing various photic zones which have been previously defined mainly in tropical and subtropical environments the alaska strata can be placed in bathymetric zones as follows the lower upper paleocene prince creek formation in the dysphotic zone the lower oligocene stepovak formation in the shallow euphotic zone shallow euphotic zone iii and the upper miocene tachilni formation in the deep euphotic zone these interpretations agree very well with bathymetric reconstructions inferred from other criteria a fourth formation the lower middle miocene narrow cape formation contains only heterotrophic microborers as if it had been deposited in the aphotic zone in contrast to previous reconstructions in this formation the periostracum of the mollusc shells is exceptionally well preserved this may explain the absence of boring algae because only heterotrophs can penetrate through organic shell layers the absolute depth ranges of these ichnocoenoses zones are inferred from their ranges in comparable latitudes of the modern north atlantic the most important features of bathymetrically controlled tropical and subtropical guide ichnocoenoses are also present at the non tropical alaskan sites although some boring algae that are widespread in tropical realms are absent

fracture mapping with electrical core images naturally fractured reservoirs often contain a range of different fracture types and networks fractures that are relatively permeable and relatively impermeable unconnected and connected to the part of the fracture network that carries fluid flow and naturally occurring or drilling induced consequently in terms of their fluid connectivity fractures may be open or closed while individual fractures may be isolated or well connected we have adapted our approach to imaging sedimentary fabric in the laboratory where we related electrical core images to properties such as porosity permeability grain size and cementation to enable electrical imaging of fractures in core our approach uses similar principles to those employed in down hole electrical imaging the results demonstrate an ability to image conductive fractures in fully saturated low porosity water bearing core these fractures being electrically connected from the flat measurement surface through to the outer surface of the core published results for numerical modelling of down hole electrical imaging tools show the electrical response is related to fracture depth and fracture aperture our experimental results on fractured core in the laboratory support these numerical observations increased current flowing into the fracture as the aperture increases the finite size of the electrode however means that this technique cannot distinguish between a single fracture and smaller groups of fractures intersecting the electrode

microendolithic structures from the fort payne formation lower mississippian kentucky and tennessee implications for the paleoenvironment of carbonate mud mounds abstract resin cast embedment and naturally occurring internal molds have revealed an assemblage of microendoliths from the lower mississippian fort payne formation microendoliths produced by the heterotrophs orthogonum lineare orthogonum giganteum and saccomorpha clava dominate this unit as well as the phototroph produced traces ichnoreticulina elegans and fascichnus dactylus a chlorophyte ostreobium quekettii and cyanobacterium hyella caespitosa respectively they were found within a variety of fossil substrates including solitary corals bryozoans brachiopods and gastropods with a notable absence in all trilobites and echinoderms the fort payne from the lake cumberland dale hollow region of southern kentucky northern tennessee contains a suite of fossiliferous green shale deposits with isolated locations of enigmatic carbonate mud mounds the latter commonly referred to as waulsortian mounds in other geographical areas have been the center of much speculation in the past few decades and the paleoenvironmental parameters behind their formation remain controversial using the aforementioned microendoliths a sense of the light availability within the illinois basin can be determined the assemblage of ichnotaxa uncovered is representative of light conditions spanning from dysphotic to aphotic using previously constrained depth parameters that indicate a depth of no more than 100 m a dysphotic environment suggests that the water column was eutrophic presumably due to high productivity within the illinois basin this would seem to corroborate several other inferences about the early mississippian including the growing number of suspension feeding echinoderms the restructuring of phytoplanktonic communities and increased nutrient flux from a developing terrigenous floral weathering regime in the early mississippian

probe permeametry is it worth the effort abstract an overview is given of the wide variety of current applications for probe permeameter technology and data in light of recent key advances in reservoir characterization the future trends in applications and tool development are discussed by examining the procedures and costs associated with data acquisition quality control and general information enhancement and by comparing these factors to more conventional methods for obtaining permeability it is concluded that probe permeametry is indeed worth the effort

gradients and patterns of sclerobionts on experimentally deployed bivalve shells synopsis of bathymetric and temporal trends on a decadal time scale bivalve shells deployed experimentally in a variety of environments of deposition eods and over a wide range of depths from 15 to 570 m in the bahamas and gulf of mexico were assessed for encrusting and endolithic bionts sclerobionts sensu taylor and wilson 2002 that accumulated over 1 2 8 and 12 13 year intervals data include percent coverage and when possible identification to generic or species level taxonomic categories data were binned into two further categories based on guilds and whether or not sclerobionts were judged to be preservable each study site shows substantial variability in both percent coverage and species richness composition which we attribute to partial burial of different individuals or parts of arrays average values of taxonomic richness guild number and percent coverage for a given eod represent a combination of exposed and buried shells as would be typical of a time averaged fossil assemblage maximally covered shells give the potential coverage for each site in both study areas there are characteristic patterns in terms of overall percentage of shells covered by sclerobionts numbers and extent of coverage by different guilds as well as by different taxa for most eods there is a progressive though non linear increase in both species richness and areal coverage through the twelve years exceptions are in the 30 m site in the bahamas and parker bank and flower garden sites in the gulf of mexico which show a significant decline in areal coverage though not in richness this effect may result from differences in sediment cover over time these sites showed a tendency to have many or all experimental bags completely sediment covered in the later sampling cluster analysis and non metric multidimensional scaling nmds of various shell substrate species at all eods from the bahamas and gulf of mexico reveal discrete groupings that are related to both depth light gradient and other factors such as variations in sedimentation and salinity similar numbers of guilds are found at various eods although the specific guild types represented differ in general highest average richness values are recorded for carbonate 70 90 m wall and deep reef sites 69 to 70 taxa and lowest are for the efg brine pool no sclerobionts other than bacterial films after 12 13 years and deeper dysphotic to subphotic sites max values 25 taxa surprisingly shallow water sites 30 m yield only moderate diversities of 40 50 taxa this results in part from the fact that certain encrusters especially the foraminifer gypsina and coralline algae tend to overgrow others and dominate space in addition to burial effects certain taxa notably the serpulid pseudovermilia are ubiquitous while other taxa e g larger foraminifera vermetid gastropods and many bryozoans are largely restricted to shallower depths a combination of species richness average coverage and key taxa permits discrimination of groups of eods and potentially in tandem with other evidence of depth gradients

dust provenance in antarctic ice during glacial periods from where in southern south america 1 the origin of dust deposited in east antarctica is not fully understood yet this study demonstrates that contrary to nd sr isotopes are strongly fractionated in the finest sized material representing potential dust sources in south america analysis of nd isotopes suggests that argentine loess southern ocean sediments and antarctic dust may all have a related origin or can represent comparable mechanisms of eolian sediment transport and deposition this analysis also concludes that the patagonian signature can explain a high proportion of the isotopic composition of dust trapped in antarctic ice during glacial periods the puna altiplano plateau emerges as the second possible important sediment contributor explaining the crustal like signature found in east antarctic dust and should be considered as a potential source area when quaternary paleoclimate is reconstructed from argentine loess antarctic dust and south atlantic sediment records

shell bioerosion in high latitude low energy environments firths of clyde and lorne scotland abstract the agents of bioerosion in the firths of clyde and lorne include endolithic algae cliona phoronids acmaea virginea lepidopleurus asellus and regular echinoids which directly and indirectly cause shell disintegration and the production of calcareous sediments algae and acmaea are very effective in shell erosion but are confined to the photic zone where over 90 of the shells have suffered from their attack other bioerosion agents are not depth restricted but individually affect a lesser number of shells the photic limit approx 30 m is estimated from the disappearance of the deepest growing algae conchocelis and ostreobium the density of algal boring is high due to the low energy at the bottom it is shown that algal borings and acmaea grazing are also important as palaeobathymetric tools

visual identification and quantification of milankovitch climate cycles in outcrop an example from the upper ordovician kope formation northern kentucky

relationship between bowl shaped clastic injectites and parent sand depletion implications for their scale invariant morphology and composition 3d seismic reflection data provides a means to assess the impact of injection on parent sands and to quantify the character of the resulting injectite networks the morphology of a series of large injectite structures hosted in the palaeocene lower lista formation were mapped using broadband 3d seismic data from the north sea to investigate their relationship with parent sands fourteen bowl shaped structures were identified within the lista formation in the study area 60 85 m in height and 200 900 m in width sand is absent below resolution below these large scale bowls suggesting that the parent sand is the underlying maureen formation and sand welds formed rather than sand prone channelised deposits within the lista formation identification of injectite networks can be ambiguous which impacts geological model development observations from exhumed systems and core offers high resolution insights into the complexity of injectite networks to advance our understanding of this scale gap we argue for injectites being scale invariant in their shape and grain size this permits the application of outcrop scale knowledge to seismic scale interpretation the demonstrable depletion of parent sands and their scale invariance can be applied to basin fills worldwide to reduce uncertainties of the impact of sand injectites on hydrocarbon reservoirs

core permeability imaging its relevance to conventional core characterization and potential application to wireline measurement abstract core imaging provides a new perspective in conventional core characterization recent work using permeability imaging on apparently featureless sandstones from a variety of depositional settings has shown that the primary depositional fabric is usually revealed suggesting that truly massive sandstones are in fact extremely rare permeability imaging therefore provides a complement to visual facies description ensuring improvements in the interpretation of depositional models such imaging is therefore particularly relevant in submarine fan settings where substantial portions of sandstone units can appear massive in core or outcrop samples permeability imaging is extremely sensitive to subtle changes in pore characteristics such images therefore provide important insights into the distribution of cements and their relationship to primary fabric this information offers a scale bridge between facies description from cores and microscopic description from thin sections thin section sampling can be focused on the relevant parts of the sample conventional image analysis techniques can be applied to such data comparison of borehole microresistivity image data and core permeability images often reveal a striking similarity due to the approximate equivalence in rock volumes investigated by these techniques quantitative applications arising from this relationship are considered

tectonic synthesis of the taconian orogeny in western new england a tectonic synthesis based on stratigraphic and structural analysis of western new england is proposed for the ordovician taconian orogeny it emphasizes arc continental collision in which ocean floor continental margin and ensialic rift rocks were imbricated westward in a repeatedly deformed accretionary wedge continued compression displaced segments of the north american sialic crust to the west and deformed the earlier emplaced slices of the taconic allochthons which were derived from the continental margin critical arguments for this synthesis are 1 the west to east stratigraphic relations among the basal rift clastic rocks of the dalton pinnacle and hoosac formations of late precambrian to early cambrian age 2 the stratigraphic and sedimentological similarities between the rocks of the lower taconic sequence and rocks in the pinney hollow and underhill slices to the east and north of the green mountain massif 3 the environmental similarities between the cambrian and lower ordovician section of the giddings brook slice and the age equivalent section in the st albans synclinorium 4 the presence of carbonate platform rocks as slivers between each of the successively higher and younger premetamorphic slices groups 1 and 2 of the taconic allochthons 5 the presence of synmetamorphic fault related structures in the youngest and highest slices group 3 of the taconic allochthons 6 the recognition of extensive thrust zones in the pre silurian eugeoclinal sequence east of the middle proterozoic basement of the housatonic berkshire green mountain and lincoln massifs 7 the location of the taconic root zone within the pre silurian eugeoclinal sequence 8 the recognition of numerous faults in the serpentinite belt 9 the similarity between the rocks of the moretown formation and modern fore arc basin sequences 10 the recognition that the volcanic arc continental complexes of the ascot weedon and bronson hill have been displaced westward over the moretown and or hawley formations along such faults as the bristol and coburn hill thrusts 11 the allochthonous and internally imbricated nature of the north american basement in the berkshire massif 12 the proposition that the housatonic green mountain and lincoln massifs as well as the middle proterozoic cored domes of southeastern vermont are also thick sialic slices of north american basement 13 the recognition of medium high to high pressure metamorphic mineral assemblages in the pre silurian eugeoclinal rocks of vermont and 14 the recent synthesis of isotopic age data by sutter and others 1985 on the basis of an analysis of the foregoing arguments and relationships a chronological sequence of seven structural sections between albany new york and the bronson hill anticlinorium in central massachusetts is used to depict the evolution of the taconian orogeny retrodeformed distances are based on structural overlap and restoration of the taconic slices to their depositional setting along the ancient north american continental margin these easterly younging diverticulated slices formed as a result of horizontal compression rather than gravity sliding this palinspastic analysis implies the following 1 approximately 1 000 km of shortening has occurred during the emplacement of the taconic allochthons and the subsequent imbrication of north american basement as thick sialic slices approximately 330 km of this shortening is attributed to multiple cleavage generations 2 repeated movement along such major surfaces as the cameron9s line whitcomb summit belvidere mountain thrust zone has buried the taconic root zone we suggest that the northern extension of this root zone is exposed to the east of the lincoln massif in vermont where the underhill pinney hollow and hazens notch formations are exposed these formations here considered thrust slices disappear along the belvidere mountain whitcomb summit thrust zone as it is traced southward into western massachusetts and western connecticut 3 taconian metamorphic rocks particularly the older medium high pressure rocks in northern vermont have been transported westward on such reactivated surfaces as the belvidere mountain thrust 4 the anticlinorial form of the middle proterozoic basement in the green mountain and lincoln massifs may have resulted from fault bend folding on deep mantle involved thrusts that developed late in the taconian orogeny

ordovician metre scale cycles implications for climate and eustatic fluctuations in the central appalachians during a global greenhouse non glacial to glacial transition abstract metre scale shallowing upward cycles in ordovician carbonates of the central appalachian basin record climate and eustatic fluctuations during a transition from early ordovician global greenhouse to late ordovician icehouse conditions peritidal facies and shale abundance suggest a long term trend in this area from semi arid early ordovician to more humid middle to early late ordovician conditions with a return to semi arid conditions during the late ordovician the climatic fluctuations were most likely produced by tectonics uplift and erosion related to taconic orogenesis plate motion of north america and the areal extent of water covering the shelf peritidal cyclic facies indicate that high frequency relative sea level fluctuations were of small amplitude 20 m relative sea level fluctuations that decreased into the later ordovician if these sea level changes are eustatic then the increased amplitude may mark the early initiation of continental glaciation on gondwana in the late middle ordovician followed by waning of ice sheets prior to the latest ordovician glaciation

cyclic alteration of proximal and distal storm facies kope and fairview formations upper ordovician ohio and kentucky the upper ordovician kope and fairview formations and the bellevue tongue of the grant lake limestone exposed in the cincinnati ohio region represent storm dominated sedimentation on a prograding intracratonic ramp the upper kopelower fairview transition zone 25 m thick is an outer to intermediate ramp lithofacies and is composed of numerous 1 3 m thick shallowing upward subtidal cycles bedding cycles are composed of two depth controlled facies 1 a shale dominated distal facies and 2 a fossiliferous proximal facies the distal facies records low energy largely single storm events and consists of thin graded shale beds nearly in situ fragile fossil accumulations thin parautochthonous packstones and quartzose siltstone beds siltstones contain abundant storm depositional indicators tool marked soles gutter casts mud filled scours hummocky lamination and hummocky bedforms the proximal facies represents deposition in an energetic storm wave swept environment and consists of amalgamated sets of thick bedded fine to coarse grained skeletal grainstones and packstones with low angle cross lamination megaripples and shale lithoclasts sedimentary structures and paleocurrent patterns from both facies record deposition under a combined flow regime with the unidirectional current vector oriented in the offshore direction cycles are laterally continuous across the 35 km by 32 km study area cycle boundaries flooding surfaces are parallel to a unique storm generated marker bed implying that these surfaces are effective time lines their widespread character and relatively deep subtidal facies assemblage argues against autocyclic processes in cycle formation we propose that the alternation of proximal and distal facies was tied to fluctuations in storm wave base driven by short term glacio eustasy three scales or orders of sedimentary cyclicity are recognized in the study area meter scale bedding cycles are considered fifth order parasequences 20 100 ka duration and stack into genetically related parasequence sets these fourth order units have been previously described as member scale lithostratigraphic tongues analysis of fischer plots suggest that cycle thickness and subfacies composition was controlled by both accommodation and siliciclastic sediment supply these higher order stratal units are super imposed onto the highstand portion of the kope to bellevue depositional sequence and give insight into the high frequency controls on the progradation of the ramp complex

high resolution sequence stratigraphy of a mixed carbonate siliciclastic cratonic ramp upper ordovician kentucky ohio usa insights into the relative influence of eustasy and tectonics through analysis of facies gradients abstract detailed facies analysis and event stratigraphy of an upper ordovician rocklandian edenian cratonic ramp succession in eastern north america yields insights into eustatically driven sequence architecture and localized tectonic instability seven predominantly subtidal mixed carbonate siliciclastic depositional sequences 3rd order are identified and correlated across the length of a 275 km ramp to basin profile within the larger depositional sequences 3rd order at least two smaller orders 4th and 5th of cyclicity are recognizable three systems tracts occur within each sequence transgressive tst highstand hst regressive rst and are considered in terms of their component parasequences 5th order generally tsts are composed of skeletal grainstone rudstone facies hsts are dominated by shaly nodular wacke packstone facies and rsts are mostly calcarenite facies systems tracts sequence boundaries and their correlative conformities maximum flooding surfaces and forced regression surfaces were traced from shallow shelf to basinal settings this high resolution framework also provides insight into the timing of tectonic fluctuations on this cratonic ramp during the taconic orogeny and documents the relative influence of tectonism on lateral facies distributions and eustatically derived cyclicity