facies mosaics across the persian gulf and around antigua stochastic and deterministic products of shallow water sediment accumulation abstract among broadly different types of sedimentary successions those that accumulate in nearshore settings are perhaps unique in that a very wide range of rock types recurs with high frequency over relatively short stratigraphic intervals this vertical lithofacies heterogeneity suggests that deposition of any sedimentary unit at any site was short lived that many different sediment types existed within a complex mosaic over the depositional surface and that this facies montage repeatedly moved across surfaces of accumulation in response to eustatic sedimentologic and or tectonic forcing data on numbers and thicknesses of lithofacies units from several dozen such sequences define the size frequency distribution expected if horizons of lithologic change occur randomly within sedimentary successions walther s law suggests that the amount of vertical lithologic heterogeneity manifest in a sedimentary sequence should reflect the degree of lateral heterogeneity in sediment composition that existed across depositional surfaces if so this repetition should also be manifest in sizes and areal distributions of sediment patches constituting the depositional mosaic in order to examine size frequency relations of sediment bodies across surfaces of sediment accumulation we tabulated numbers and areal extents of lithotopes across two rather dissimilar settings across the persian gulf and around the caribbean island of antigua although compositions and lateral extents of different sediment types exhibit broad lateral variation across interior to margin transects in either area lithotope abundances and areal extents define frequency distributions that are in excellent agreement with those anticipated for a facies mosaic of elements whose mean linear widths constitute an exponential frequency distribution these are the size frequency distributions one would expect if mosaic element boundaries occur randomly across regions of sediment accumulation and suggest that distributions of lithotope areas from holocene surfaces are directly analogous to lithofacies thickness frequencies from ancient successions in addition to the fact that both of the size frequency distributions attest to the importance of stochastic processes during sediment deposition they also afford numerical descriptors of abundances and areal extents of holocene lithosomes that can then be used as controlling parameters in computational models of sediment accumulation importantly results derived from such simulations are based not on inference of water depth varying in response to change in subsidence sea level and rate of sediment accumulation but on statistical attributes intrinsic to modern and ancient marginal marine successions

paleoecological interpretation and age of an interstadial lake bed in western new york abstract pollen assemblages from a 6 6 m exposure of pleistocene lake silt in central western new york consist of anomalous mixtures dominated by spruce pine and sedge but with a significant representation of deciduous forest elements leaves of dryas integrifolia and plants of the terrestrial moss distichium from the lake silt yielded ams ages of 24 900 1000 and 24 180 900 yr b p indicating that the silt was deposited during the middle wisconsinan plum point interstade and that the pollen of beech hickory and other deciduous trees was recycled from an interglacial deposit caution therefore must be exercised in the paleoecological interpretation of interstadial lake deposits plant macrofossil assemblages seeds fruits mosses from the silt also probably are mixtures of primary and secondary fossils scanning electron microscopy of surface features of fruits and seeds revealed two classes of preservation the best preserved fossils had intact surface microfeatures and are considered of primary origin those with the outer cell layer degraded or absent probably have been recycled the distributions of species represented in the latter category center on the great lakes region and southward whereas those of the primary fossils are more northern and indicate tundra and spruce jack pine forest the late wisconsinan kent ice margin advanced across central western new york after ca 24 500 yr b p into a mosaic of tundra and conifer forest

widespread prolonged late middle to late ordovician upwelling in north america a proxy record of glaciation late middle to late ordovician subtidal ramp carbonates of new mexico texas and oklahoma contain abundant spiculitic chert to 70 chert by volume and phosphate 1 5 wt indicating that these rocks formed in an extensive upwelling zone upwelling began in the late middle ordovician ca 454 ma and persisted until the end of the ordovician late ordovician cherty carbonates also occur along the u s cordilleran margin in board of organic rich graptolitic shale and chert the widespread occurrence of late ordovician cherty and phosphatic carbonates on southern and western laurentia in addition to phosphate rich cool water carbonates over much of the north american midcontinent suggests vigorous thermohaline circulation related to prolonged 10 14 ma gondwana glaciation

methodological advances in the use of faunal gradient analysis for regional high resolution correlation in the type cincinnatian series upper ordovician abstract historically strata of the type cincinnatian series have not been correlated with precision because of an assumption that individual beds are not regionally persistent in an effort to establish a regional chronostratigraphic framework for the cincinnatian a technique has been developed recently that uses gradient analysis of fossil abundance data to compare vertical trends in biotic composition among five localities that span a distance of 65 km using faunal data to establish correlations below the meter scale has been problematic because variability in the lateral expression of many beds has made it difficult to sample equivalent fossiliferous strata at all localities here this correlation technique is modified in an attempt to draw meter scale correlations of the kope and lower fairview formations this modification involves grouping fossil census samples into stratigraphic intervals such that the stratigraphic spacing of samples is identical at all localities samples are binned using two protocols one that groups samples into 0 5 m thick intervals and another that groups samples by lithologically delineated meter scale cycles gradient analysis of binned samples using both protocols produces curves in which patterns in faunal composition below the meter scale can be correlated with success only for limited intervals at select localities the inability to consistently correlate at high resolution might indicate that correcting for regional variations in the expression of strata is not enough alternatively the ability to correlate some intervals below the meter scale suggests that other problems such as fine scale lateral variations in biotic composition might be impeding correlation in addition gradient analysis techniques are employed at a new locality to extend the lateral breadth of the existing broader scale chronostratigraphic framework by approximately 40 km although interpreted to be in an up ramp direction from previously measured localities this new locality does not have an overall shallower water faunal assemblage until just below the kope fairview contact

chemical mineralogical and textural properties of the kope formation mudstones how they affect its durability abstract the kope formation is a rock unit that extends over southwest ohio and adjacent areas of kentucky and indiana usa it is characterized by meter scale cycles of mudstones and limestones where thick mudstone is sandwiched between thin limestone layers kope formation mudstones are less durable than the mudstones in the area they cause abundant slope failures in areas of their outcrops this study evaluates chemical mineralogical and textural properties of kope mudstones to determine why it is less durable the two cycle slake durability index id 2 was measured on thirty mudstones belonging to three consecutive cycles of the kope formation chemical composition and mineralogy of kope mudstones do not show significant relationship with the id 2 instead a relationship to fabric was found kope mudstones with two main fabric types were observed in the field laminated mudstones and non laminated mudstones detailed micro fabric analysis on kope mudstones was done using the scanning electron microscope laminated mudstones with turbostratic fabric showed higher id 2 and lower moisture content than the non laminated mudstones with matrix fabric the difference in the id 2 of laminated mudstones and non laminated mudstones is statistically significant both mudstone types exist in many cycles of the kope formation thus core samples should be selected from both types for preliminary tests in geotechnical practice to obtain more accurate estimations of the geotechnical properties of the kope mudstones the results and data interpretations of this study can be correlated with the mudstones and shale in different areas of the world specifically a great attention should be paid to the macro and micro textural properties of any rock type regardless of their classification

bed load grain velocities and sediment transport rates theoretical consideration of the dynamics of bed load sediment transport leads to expressions for bed grain velocity and sediment transport rate as respectively ub a u u c and ib a tan u u c 0 c agreeing in form with many previous analyses the grain velocity equation agrees well with all experimentally determined velocities of single grains moving over fixed rough beds if a is allowed to vary with bed roughness and saltation height values of u c for such overriding grains are substantially less than normally accepted values the sediment transport rate equation predicts plane bed experimental data well over five orders of magnitude of ib values of a tan increase significantly from lower to upper stage plane beds due to an increase in a with suspended sediment concentration but also due to a decrease in tan with increasing transport stage and grain size as predicted by bagnold

climatic and tectonic controls on alluvial fan and axial fluvial sedimentation in the plio pleistocene palomas half graben southern rio grande rift abstract six steep 0 6 4 3 short radial length 1 5 5 km deeply incised pliocene to early pleistocene paleofans and associated axial fluvial strata are preserved adjacent to the footwall of the palomas half graben in the southern rio grande rift two different scales of interbedding of lithofacies are evident in the exposed basin fill sediment the footwall derived alluvial fan strata are arranged into 3 10 m thick cyclothems representing three events 1 development of calcic paleosols that were contemporaneously or subsequently truncated by channels up to 4 m deep 2 infilling of channels by turbulent flow horizontally bedded and cross bedded conglomerates and 3 deposition of hyperconcentrated flow pebbly sandstones these cyclothems probably resulted from paleoclimatic changes on the scale of 150 kyr on a larger geographic and temporal scale the axial river ancestral rio grande which primarily deposited cross bedded pebbly sand experienced kilometer scale lateral movement toward the footwall block resulting in one thick 80 m axial fluvial lithosome in the northern part of the basin and two or three thinner 8 25 m axial fluvial lithosomes in the south a protracted period of fault movement and consequent basin tilting was the probable driving force behind lateral movement of the river and toe cutting of the fans by the river was the dominant process

paleobiology of the sand beneath the valders diamicton at valders wisconsin abstract previously undescribed pollen plant macrofossils molluscs and ostracodes were recovered from a 2 5 m thick glaciolacustrine unit of silty sand and clay at valders wisconsin the interstadial sediment was deposited about 12 200 14 c yr b p after retreat of the green bay lobe that deposited diamicton of the horicon formation and before advance of the lake michigan lobe that deposited the red brown diamicton of the valders member of the kewaunee formation fluctuations of abundance of candona subtriangulata cytherissa lacustris and three other species define four ostracode biozones in the lower 1 7 m suggesting an open lake environment that oscillated in depth and proximity to glacial ice pollen is dominated by picea and artemisia but the low percentages of many other types of long distance origin suggest that the terrestrial vegetation was open and far from the forest border the upper part of the sediment a massive sand deposited in either a shallow pond or a sluggish stream contains a local concentration of plant macrofossils the interpretation of a cold open environment is supported by the plant macrofossils of more than 20 species dominated by those of open mineral soils arenaria rubella cerastium alpinum type silene acaulis sibbaldia procumbens dryas integrifolia vaccinium uliginosum var alpinum armeria maritima etc that in north america occur largely in the tundra and open tundra forest ecotone of northern canada ice wedge casts occur in the sand

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

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

pliocene and quaternary history of the rio grande the axial river of the southern rio grande rift new mexico usa abstract the history of the rio grande the axial river of the southern rio grande rift new mexico may be divided into an aggradational phase 5 to 0 8 ma during which time about 100 m of fluvial sediment was deposited in eight basins and a degradational phase 0 8 ma to present when the river alternately incised and partially backfilled its basins reversal magnetostratigraphy dated volcanic rocks and vertebrate biostratigraphy allow correlation of sediment of the aggradational phase with the gilbert gauss and matuyama chrons while the degradational phase primarily encompasses the brunhes chron tectonics was the primary control on river behaviour during the aggradational phase in half grabens multistorey channel sands were deposited in narrow belts near the footwall uplifts in response to tilt of the basin floor towards the border fault and smaller footwall catchments and their alluvial fans compared to those of the hanging wall mountains in contrast the river traversed almost the entire width of full grabens depositing interbedded channel and floodplain sediment with moderately mature palaeosols condensed sections dominated by floodplain sediment with very mature palaeosols developed in basins largely abandoned by the river due to preferential tilting of the basin floor lateral growth or renewal of fault activity or alternating flow of the river between adjacent basins the degradational phase was dominated by net basin erosion related to glacial climate cycles despite continued activity on many of the basin bounding faults

does altonian drift exist in pennsylvania and new jersey abstract from new jersey to southwestern new york altonian colluvium and fluvial gravel have been recognized beneath woodfordian drift but the existence of altonian till near or beyond the woodfordian border has not been demonstrated reworking of weathered materials by woodfordian ice has produced some drift with an altonian appearance soil criteria applied without regard for parent material differences have been incorrectly used to infer an altonian age for illinoian deposits that have a redbed provenance the currently mapped distribution of altonian till and the occurrence of undisturbed illinoian deposits within areas of inferred altonian ice cover are incompatible with the behavior of ice sheets

using species distribution models in paleobiogeography a matter of data predictors and concepts article i nfo the increasing interest in the effects of climate changes on species distributions has been followed by the development of species distribution models sdms although these techniques are starting to be used to study the location and dynamics of past species distributions a sound theoretical framework for their use in paleoecology is still lacking in this paper we are reviewing the main challenges for constructing paleo species distribution models to describe and project the past distribution of species namely data limitations selection of predictors and choice of a biologically relevant modeling procedure we also review and discuss the current state of the art in paleo sdms providing a series of recommendations for their use and proposing future research lines to improve the use of these techniques in paleobiogeography

analysis of sample level properties along a paleoenvironmental gradient the behavior of evenness as a function of sample size abstract the assessment of fossil biodiversity is influenced by a range of sampling effects such as sample size evenness and lithological character many paleontologists have worked to understand and mitigate for such biasing effects generating standardized assessments of local regional and global biodiversity however when assessing biodiversity among individual communities with small sample sizes such as those from lithified paleozoic samples it is important to understand how these properties relate to one another qualitatively and quantitatively here the properties of richness and evenness were investigated at the sample level along an ecological gradient within a stratigraphically and geographically constrained interval the fulton submember of the kope formation upper ordovician of kentucky and ohio using a replicate subsampling procedure analogous to rarefaction evenness values were generated using four metrics j pie ess and essmin simulations using real and simulated data revealed that the pie metric generates the most stable assessments of evenness at very small sample sizes and relative evenness can be assessed at any sample size provided that replicate subsampling is performed comparisons of richness evenness and lithology revealed no directional trend along the ecological gradient but two distinct groups of samples were identified by differences in evenness as well as the number of sampled individuals such differences in abundance structure influence perceptions of biodiversity when samples from low evenness and high evenness assemblages are aggregated increasing the sampling intensity in low evenness communities may help to mitigate for these differences and more thoroughly capture the richness contained within small samples

unconventional distribution of facies in a continental rift basin the pliocene pleistocene mangas basin south western new mexico usa the pliocene early pleistocene mangas basin in sw new mexico usa was a n nw trending full graben that changed southward to an eastward tilted half graben unlike the facies distribution predicted in existing models the half graben part of the mangas basin was characterized by broad alluvial fans derived from the footwall scarp smaller hangingwall derived alluvial fans and a shallow closed lake lake buckhorn that locally lapped onto the hangingwall hills the distribution of facies within the full graben part of the mangas basin was also unlike that predicted in current models primarily because of a broad belt of alluvial fan sediment derived from the eastern footwall scarp and a narrow belt of axial fluvial sediment adjacent to the western footwall scarp the distribution of facies in the mangas basin does not appear to have been controlled by the eastward tilt of the floor of the half graben or see saw motion of the floor of the full graben as predicted by existing models but rather by the large size of the alluvial fans on the eastern side of the basin these fans were derived from large high relief catchments on the footwall scarp of the mogollon mountains the uplift of which began during early miocene this example illustrates how earlier uplift and drainage development in a mountain range may influence facies distribution in a younger extensional basin

cycle anatomy and variability in the storm dominated type cincinnatian upper ordovician coming to grips with cycle delineation and genesis although parasequence and sequence are scale independent terms they are frequently applied only to specific scales of cycles for example meter scale cycles are commonly assumed to be parasequences or pacs in the upper ordovi cian kope and fairview formations of northern kentucky we examined a succession of 50 meter scale cycles that have been variously interpreted as deepening upward shallowing upward or showing no relationship with water depth our analysis shows that these cycles characterized by shifts in storm bed proximality are highly variable in their thickness and internal construction most cycles are best considered high frequency sequences because deepening upward intervals are common and many cycles contain evidence of abrupt basinward shifts in facies as expected at sequence boundaries a minority fit the parasequence model of shallowing upward cycles bounded by flooding surfaces larger 20 m scale cycles are defined by systematic thickening and thinning trends of meter scale cycl

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

lack of impact of hurricane michelle on tidal flats andros island bahamas integrated remote sensing and field observations abstract major storms commonly are cited as important geomorphic and sedimentologic agents and their significance is perhaps most emphatically noted in interpretations of modern and ancient tidal flats the purpose of this study was to assess the impact of hurricane michelle on the carbonate tidal flats of andros island bahamas by coupling remote sensing data and field observations although regional modis remote sensing data reveal that the passage of hurricane michelle suspended sediments across the shallow bank integrating ultra high resolution remote sensing data with field observations demonstrates that the hurricane had almost no impact on the andros island tidal flats this lack of impact is surprising because the storm still had hurricane force winds as it passed immediately over some of the focal areas with this hurricane storm strength and intra storm interval were probably not limiting factors instead several influences combined to minimize the storm s impact on both sedimentation and erosion including the low level of water on the bank resulting from ebb tides and in the northwestern area from offshore storm winds and the short duration of the storm resulting from its high forward velocity given the apparent prevalence of widespread storm effects on ancient tidal flats but the spatially limited major geomorphic impacts of storms on many modern systems we suggest that the geologic evolution and preservation of ancient tidal flat successions may have been shaped by mega storms that simply cannot form in the present global climate nonetheless understanding tidal flat dynamics and changes on human timescales will require continued monitoring and assessment of low impact storms such as michelle as well the more sensational hurricanes that produce widespread death destruction and deposition

poisson processes of carbonate accumulation on paleozoic and holocene platforms abstract cambro ordovician carbonate lithofacies units in the elbrook and conococheague formations exposed at wytheville virginia as well as those in many other phanerozoic peritidal sequences exhibit exponential thickness frequency distributions that is occurrence frequency decreases exponentially with linear increase in unit thickness such distributions are characteristic of waiting times between independent poisson events this relative frequency of spaces of different size between horizons of lithologic change is what one would expect if the horizons were distributed randomly throughout carbonate successions abundances of different lithologies both as net stratigraphic thickness and as number of occurrences also decreases exponentially among successively rare sediment types with each lithology being about 60 as plentiful as the next more abundant rock type relations between net thickness and number of occurrences for each facies define a linear trend coincident with a mean thickness for all wytheville units of 0 48 m a relation indicating that thickness distribution is independent of facies type similar relations are apparent for the horizontal extent of carbonate sediment bodies from the holocene florida bahama platform areal extents of individual facies units lithotopes are described by a frequency distribution in agreement with that anticipated for a population of equidimensional facies elements whose diameter distribution follows an exponential frequency distribution although regional gradients in sediment texture and composition are also apparent along most transects from platform margin to interior such frequency distributions indicate that lateral extents of individual sediment reflect a largely stochastic distribution of facies boundaries across this holocene surface lithotope abundances also yield trends of exponentially decreasing dominance among successively subordinate facies with each being about 70 as extensive the next more abundant sediment type relations between areas and abundances for all lithotopes define a covariant trend corresponding to a mean area of 2 2 103 km2 for all florida bahamas lithotopes we consider several numerical models of stochastic carbonate accumulation although not demonstrably unique scenarios incorporating the sequential superposition of randomly placed coniform lithotopes result in thickness and area frequency distributions that are the same as those observed in ancient and modern platform deposits such simulations of poisson processes of sediment accumulation are in general agreement with stochastic models of lithologic heterogeneity that have been more widely applied to petroleum reservoirs and groundwater aquifers to the as yet unknown degree that peritidal lithofacies area and thickness are correlated data from paleozoic and holocene platforms suggest that carbonate units should exhibit length height ratios of approximately 105 given the decimeter scale over which facies are designated in most paleozoic peritidal successions these relations predict mean lateral extents on the order of several tens of kilometers a value in general agreement with the few data that exist on spatial continuities of peritidal lithotopes in paleozoic carbonate sequences

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

controls on geochemical expression of subaerial exposure in ordovician limestones from the nashville dome tennessee u s a abstract stable isotope and trace element data from 301 samples in six stratigraphic sections largely support previous inferences of subaerial exposure at third order sequence boundaries in mohawkian and cincinnatian limestones of the nashville dome they also reveal the presence of previously unrecognized surfaces of subaerial exposure for example evidence of subaerial exposure at the tops of parasequences suggests that at least some of the latter are better interpreted as high frequency sequences clusters of surfaces of subaerial exposure near some previously interpreted sequence boundaries suggest that the latter may represent sequence boundary zones some surfaces of subaerial exposure are at neither recognized sequence boundaries nor parasequence boundaries and may represent missed beats in which sea level fluctuations are preserved geochemically but not recognized on stratigraphic criteria recognition of these unexpected surfaces of subaerial exposure may in part depend on the close spacing of samples used in this study different sequence boundaries exhibit different degrees of geochemical alteration and more extensive alteration appears to characterize sequence boundaries of greater temporal significance overprinting of exposure surfaces is controlled by accommodation rate in that meteoric alteration as suggested by low c isotope composition and sr concentration is seemingly pervasive in an interval of slow accommodation but not in an interval of rapid accommodation 18o values show little relationship to exposure surfaces in these strata so that sr 13c plots are more useful than 18o 13c plots in recognizing meteoric diagenesis in aggregated data in this data set 13c excursions interpreted to result from pedogenic processes are at most 2 4 and extend at most only 1 5 meters below exposure surfaces less than the extent of such signatures in younger carbonates such minima are best developed in paleo lowland and paleo coastal settings and they are essentially unrecognizable in paleo inland settings where more section was removed by lowstand and transgressive erosion

eustatic and far field tectonic control on the development of an intra platform carbonate shoal complex upper tongue of the tanglewood member upper ordovician lexington limestone central kentucky u s a abstract the lexington or trenton limestone is an upper ordovician chatfieldian edenian upper sandbian lower katian temperate water unit averaging about 60 m thick that was deposited in relatively shallow waters across the lexington platform in east central united states during the taconian orogeny lexington trenton shallow water deposition ended across most of the platform in late chatfieldian time and from that point deepened upward into the more shale rich clays ferry point pleasant and kope formations due to apparent sea level rise in central kentucky however deposition of the lexington limestone continued into early edenian time and includes up to 50 m of additional coarse calcarenites and calcirudites at the top which form the tanglewood buildup and reflect locally regressive conditions apparently related to local structural uplift consequently in central kentucky the lexington is more than 100 m thick and lexington deposition on the buildup continued into early edenian time as an intra platform shoal complex that tongues out into deeper water units in all directions in an attempt to understand how this shoal complex developed we examined the last major body of coarse skeletal sands in the central kentucky lexington limestone the upper tongue of the tanglewood member a 12 m thick succession of fossiliferous calcarenite and calcirudite that occurs across an area of 5200 km 2 near the center of the lexington platform although relatively homogeneous the upper tanglewood is divisible into five small scale fining upward sequence like cycles which contain prominent widespread deformed horizons facies analysis indicates that four lithofacies which reflect distinct depositional environments comprise the sequences across the shoal complex lithofacies were correlated across the shoal complex by integrating cyclicity and widespread deformed horizons in order to delineate the locations of major depositional environments facies analysis shows that the thickest and coarsest parts of each sequence and the shallowest depositional environments coincide with basement fault blocks which are known to have experienced uplift during earlier lexington limestone deposition the occurrence of thick coarse facies on the same blocks suggests that the blocks continued to experience uplift into shallow water where tides and waves redistributed sediments during upper tanglewood deposition although eustasy apparently controlled cyclicity taconian far field forces generated by orogeny in the east seem to have influenced facies distribution in each cycle through reactivation of basement fault zones as synsedimentary growth faults the example of the upper tanglewood member shows that tectonic far field forces can exert important influences on the development of carbonate depositional environments even in distal intracratonic settings like the lexington platform

geobiology and paleobiogeography tracking the coevolution of the earth and its biota abstract paleobiogeographic research is an important area of geobiology that involves the study of the coevolution of the earth and its biota by considering how tectonic and climatic changes have affected the evolution and distribution of organisms the intellectual heritage of the discipline stretches back well before darwin phylogenetic approaches to paleobiogeography have played an important part in the expansion of the field and recent analyses have incorporated geographic information systems gis each of these approaches by enhancing the precision of paleobiogeography helps make the discipline more relevant to geobiology the interaction occurring between the geological and biological sciences in paleobiogeography is apparent in several areas first there is the emergence of new techniques such as the ability to analyze ancient dna sequences also paleobiogeographers and biogeographers have realized that geo dispersal a biogeographic process first identified through studies of the fossil record can powerfully influence the evolution and distribution of biotas finally biogeographers have recognized that paleontological incompleteness and extinction constrain our ability to reconstruct biogeographic patterns in the fossil record and the extant biota respectively each of these developments suggests that further growth in paleobiogeography will involve important interactions between studies involving the fossil record and the extant biota and this along with the discipline s commitment to studying how tectonic and climatic changes have influenced evolution reaffirms the validity of the synthetic field that is geobiology

late oligocene and miocene faulting and sedimentation and evolution of the southern rio grande rift new mexico usa abstract the distribution of nonmarine lithofacies paleocurrents and provenance data are used to define the evolution of late oligocene and miocene basins and complementary uplifts in the southern rio grande rift in the vicinity of hatch new mexico usa the late oligocene middle miocene hayner ranch formation which consists of a maximum of 1000 m of alluvial fan alluvial flat and lacustrine carbonate lithofacies was deposited in a narrow 12 km northwest trending northeast tilted half graben whose footwall was the caballo mountains block stratigraphic separation on the border faults of the caballo mountains block was approximately 1615 m an additional 854 m of stratigraphic separation along the caballo mountains border faults occurred during deposition of the middle late miocene rincon valley formation which is composed of up to 610 m of alluvial fan alluvial flat braided fluvial and gypsiferous playa lithofacies two new north trending fault blocks sierra de las uvas and dona ana mountains and complementary west northwest tilted half graben also developed during rincon valley time with approximately 549 m of stratigraphic separation along the border fault of the sierra de las uvas block in latest miocene and early pliocene time following deposition of the rincon valley formation movement continued along the border faults of the caballo mountains dona ana mountains and sierra de las uvas blocks and large parts of the hayner ranch and rincon valley basins were segmented into smaller fault blocks and basins by movement along new largely north trending faults analysis of the hayner ranch and rincon valley formations along with previous studies of the early oligocene bell top formation and late pliocene early pleistocene camp rice formation indicate that the traditional two stage model for development of the southern rio grande rift should be abandoned in favor of at least four episodes of block faulting beginning 35 ma ago with the exception of two northwest trending border faults of the caballo mountains block that may be reactivated along eocene compressional structures the majority of border faults and complementary basins throughout the history of the southern rio grande rift were north trending which challenges the conventional idea of a clockwise change in stress through time

the action of wind and water in a mid cretaceous subtropical erg margin system close to the variscan iberian massif spain aeolian processes and ephemeral water influx from the variscan iberian massif to the mid cretaceous outer back erg margin system in eastern iberia led to deposition and erosion of aeolian dunes and the formation of desert pavements remains of aeolian dunes encased in ephemeral fluvial deposits aeolian pods demonstrate intense erosion of windblown deposits by sudden water fluxes the alternating activity of wind and water led to a variety of facies associations such as deflation lags desert pavements aeolian dunes pebbles scattered throughout dune strata aeolian sandsheets aeolian deposits with bimodal grain size distributions mud playa ephemeral floodplain pebble sand and cobble sand bedload stream pebble cobble sand sheet flood sand bedload stream debris flow and hyperconcentrated flow deposits sediment in this desert system underwent transport by wind and water and reworking in a variety of sub environments the nearby variscan iberian massif supplied quartzite pebbles as part of mass flows pebbles and cobbles were concentrated in deflation lags eroded and polished by wind driven sands facets and ventifacts and incorporated by rolling into the toesets of aeolian dunes the back erg depositional system comprises an outer back erg close to the variscan highlands and an inner back erg close to the central erg area the inner back erg developed on a structural high and is characterized by mud playa deposits interbedded with aeolian and ephemeral channel deposits in the inner back erg area ephemeral wadis desiccated after occasional floods were mud cracked and overrun episodically by aeolian dunes subsequent floods eroded the aeolian dunes and mud cracked surfaces resulting in largely structureless sandstones with boulder size mudstone intraclasts floods spread over the margins of ephemeral channels and eroded surrounding aeolian dunes the remaining dunes were colonized occasionally by plants and their roots penetrated into the flooded aeolian sands upon desiccation deflation resulted in lags of coarser grained sediments a renewed windblown supply led to aeolian sandsheet accumulation in topographic wadi depressions synsedimentary tectonics caused the outer back erg system to experience enhanced generation of accommodation space allowing the accumulation of aeolian dune sands ephemeral water flow to the outer back erg area supplied pebbles eroded aeolian dunes and produced hyperconcentrated flow deposits fluidization and liquefaction generated gravel pockets and recumbent folds dune damming after sporadic rains the case of the namib desert monsoonal water discharge thar desert and meltwater fluxes from glaciated mountains taklamakan desert are three potential non exclusive analogues for the ephemeral water influx and the generation of hyperconcentrated flows in the cretaceous desert margin system an increase in relief driven by the aptian anti clockwise rotation of iberia led to an altitude sufficient for the development of orographic rains and snowfall which fed melt water fluxes to the desert margin system quartzite conglomerates and sands dominantly consisting of quartz and well preserved feldspar grains which are also observed in older cretaceous strata indicate an arid climate and the mechanical weathering of precambrian and palaeozoic metamorphic sediments and felsic igneous rocks unroofing of much of the cover of sedimentary rocks in the variscan iberian massif must therefore have taken place in pre cretaceous times

development of equatorial delta front patch reefs during the neogene borneo abstract miocene patch reefs formed in turbid waters associated with high siliciclastic input at the seaward margin of the equatorial mahakam delta in eastern borneo se asia patch reefs were initiated on unstable substrates on localized low relief bathymetric highs associated with delta front channels or distributary mouthbars in the process of abandonment patch reefs developed only in shallow waters formed low relief buildups lacked rigid frameworks and had gently sloping margins although the biodiversity of the patch reefs may be comparable with that of clear water systems all the organisms present were adapted to turbid water areas associated with siliciclastic and sometimes nutrient influx the patch reefs were transient features and their demise was influenced by increased siliciclastic and nutrient input perhaps at times associated with deepening carbonate production and bioherm or patch reef development can occur in turbid water delta front areas as localized or more regionally extensive units during any phases of eustatic sea level however development and preservation of turbid water carbonates is most likely during relative transgression or perhaps late lowstand periods this is in contrast with common highstand carbonates from clear water shelves where nearly pure carbonates interdigitate with siliciclastics it is the interplay between factors such as tectonics eustasy delta lobe switching shelf currents and amount and size fraction of siliciclastic influx that ultimately controlled carbonate development and preservation

comparative radiocarbon dating of terrestrial plant macrofossils and aquatic moss from the ice free corridor of western canada in order to assess the reliability of aquatic moss for radiocarbon dating sup 14 c analyses were performed on a stratigraphic series of terrestrial plant macrofossils and samples of drepanocladus crassicostatus from a small hard water lake ph 8 2 in the ice free corridor of alberta all sup 14 c dating was done by using accelerator mass spectrometry mazama ash provided an independent chronological control the aquatic bryophyte samples consistently produced sup 14 c ages significantly older than the terrestrial macrofossils the relation between the radiocarbon dates from the macrofossils and the moss was not linear and age differences ranged from approximately 1400 to 6400 yr the sup 14 c content of d crassicostatus growing in the lake at present was less than 85 modern despite the apparent inability to take up sup 14 c deficient carbon by the direct incorporation of bicarbonate the bryophytes clearly do not provide reliable material sup 14 c dating the sup 14 c deficiency of aquatic mosses may be explained by the generation of sup 14 c deficient co sub 2 through isotopic exchange the formation of co sub 2 from bicarbonate by chemical processes and metabolic co sub 2 production these results demonstrate the potential unreliability of sup 14 c dates from aquatic mosses and raise serious concernsmore about the deglaciation dates from the ice free corridor that were obtained from aquatic drepanocladus less

depositional processes of the zhushadong and mantou formations early to middle cambrian shandong province china roles of archipelago and mixed carbonate siliciclastic sedimentation on cycle genesis during initial flooding of the north china platform to understand the depositional processes and environmental changes during the initial flooding of the north china platform this study focuses on the lower to middle cambrian zhushadong and mantou formations in shandong province china the succession in the jinan and laiwu areas comprises mixed carbonate and siliciclastic deposits composed of limestone dolostone stromatolite thrombolite purple and grey mudstone and sandstone a detailed sedimentary facies analysis of seven well exposed sections suggests that five facies associations are the result of an intercalation of carbonate and siliciclastic depositional environments including local alluvial fans shallowing upward carbonate siliciclastic peritidal cycles oolite dominant shoals shoreface and lagoonal environments these facies associations successively show a transition from an initially inundated tide dominated carbonate platform to a wave dominated shallow marine environment in particular the peritidal sediments were deposited during a large number of depositional cycles these sediments consist of lime mudstone dolomite stromatolite and purple and grey mudstones these shallowing upward cycles generally resulted from carbonate production in response to an increase of accommodation during rising sea level the carbonate production was however interrupted by frequent siliciclastic input from the adjacent emergent archipelago the depositional cycles thus formed under the influence of both autogenetic changes including sediment supply from the archipelago and allogenic control of relative sea level rise in the carbonate factory a low relief archipelago with an active tidal regime allowed the development of tide dominated siliciclastic and carbonate environments on the vast platform siliciclastic input to these tidal environments terminated when most of the archipelago became submerged due to a rapid rise in sea level this study provides insights on how a vast cambrian carbonate platform maintained synchronous sedimentation under a tidal regime forming distinct cycles of mixed carbonates and siliciclastics as the system kept up with rising relative sea level during the early stage of basin development in the north china platform

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

sedimentation and tectonic geomorphology adjacent to major active and inactive normal faults southern greece the active psatha skinos normal fault is uplifting a contrasting variety of lithologies in its footwall including mesozoic limestones ophiolitic peridotites and poorly consolidated plio pleistocene sediments of the inactive megara basin in the latter basin linear marginal uplands border the sedimentary fill and are interpreted as degraded and segmented scarp lines which exhibit features such as facetted spurs drainage domains are defined as groups of drainage basins sharing a common tectono geological substrate contrasting domains in the footwall of the active fault have given rise to spectacular differences in drainage basin growth and form in the uplifting footwall raised coastal terrace levels are present at about 10 and 40 m the latter have yielded corals dated at between 90 126 ka and have enabled us to calculate uplift and erosional rates extrapolation of these rates indicate that some 350 m of footwall relief has been produced over approximately 1 ma most of the sediment eroded from the uplifting footwall is presumed to have been re sedimented into the alkyonides gulf basin plain during this time the prominent footwall unconformity so produced forms a fine modern analogue to features seen in ancient syn rift tilt blocks such as the viking graben footwall uplift has also backtilted the former depositional surface of the megara basin and caused reversal of flow in its axial drainage domain a variety of depositional environments are documented in the subsiding hangingwall to the coastal fault including syn quake talus cones alluvial fans intra fan marshes and swamps truncated fans transgressive barriers and spits

lateral erosion toe cutting of alluvial fans by axial rivers implications for basin analysis and architecture abstract we document the neglected phenomenon of lateral erosion toe cutting of alluvial fans by non incising axial river channels field examples from the holocene of the big lost river basin idaho and the plio pleistocene of the rio grande rift new mexico help to establish architectural models with more general application to basin analysis the process of toe cutting can lead to complete fan destruction and may be a response to climate change tectonic tilting fault propagation or a combination of these variables it gives rise to near horizontal erosion surfaces cut in fan sediment steep fan margin scarps progressive up fan incision from the scarp by a network of channels soil formation up fan away from the incised channel network a deposit of axial alluvium that overlies the erosion surface and onlaps the scarp once avulsion occurs to take the axial channel away from the bajada margin distinctive healing wedges of fan alluvium prograde across abandoned axial river channel and floodplain deposits gradually onlapping the eroded scarp and its upstream network of incised channels toe cutting has important stratigraphic basin analysis and economic consequences bajada deposits subject to the process exhibit appreciable extra groundwater and petroleum reservoir potential in the intercalations of more porous and permeable axial fluvial sediments

carbonate deposition in restricted basins a pliocene case study from the central mediterranean northwestern apennines italy abstract carbonate depositional models are often informed by the study of platforms of good lateral continuity and sizable thickness because of their significance in petroleum geology however spatially restricted and more ephemeral carbonate accumulations can be an important but frequently overlooked component of otherwise siliciclastic dominated or mixed carbonate siliciclastic systems pliocene successions of tuscany and the tyrrhenian shelf northern apennines italy record a regional pulse of nontropical carbonate deposition across several restricted basins that has not yet been precisely constrained in its genesis and correlation this study investigates the stratigraphic expression of these carbonates to extract general aspects applicable to carbonate sedimentation across tectonically structured and physiographically complex shelves analyses of the extension composition facies and sequence stratigraphic architecture of the studied piacenzian carbonate units are complemented by new biostratigraphic and magnetostratigraphic data which document the slightly diachronous development of the carbonates within mediterranean planktonic foraminifera subzones mpl4b and mpl5a and magnetic polarity chron c2an the carbonate units are part of a regionally defined tectonically controlled sequence and represent the first transgressive unit overlying the basal sequence boundary but are also found in the regressive portion of the sequence collectively the units document the establishment of a shallow marine carbonate factory dominated by calcareous red algae the larger benthic foraminifer amphistegina and heterozoan skeletal components along the margins of a complex archipelago like coastal domain a review of the studied successions and other examples from the literature indicates that carbonate accumulations in settings with varied coastal physiography and active partitioning of depocenters are generally characterized by a spatial discontinuity b an overall skeletal association consistent across separate basins but with local variability in dominant skeletal components c preferential accumulation along basin margins or over isolated structural highs not in direct proximity to a hinterland with major drainage systems d predominance of low to moderate energy facies e preferential onset of deposition during transgression with possible development of mixed carbonate siliciclastic facies and f differing internal stratigraphic architecture tied to the specific subsidence and uplift history of coeval individual basins these observations built upon the study of mid piacenzian carbonate units from the central mediterranean contribute to the refinement of carbonate facies models and their application in the fields of sequence stratigraphy and basin analysis

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

fluvial morphology and sediment flux steering of axial transverse boundaries in an experimental basin abstract the distinction between depositional belts associated with the basin axis and flanking piedmont streams is a fundamental attribute of the stratigraphic architecture of intracontinental rift basins spatiotemporal distributions of these lithofacies associations are sensitive to a combination of factors including basin geometry subsidence rate and sediment discharge however most studies have focused on one or two controls and one depositional component axial or tributary of the basin fill succession a new perspective on how these depositional belts develop under simple but precisely controlled boundary conditions of steady subsidence sediment flux and water discharge is achieved through the creation of an experimental stratigraphic succession the experimental earthscape run in 2006 xes06 focused on the geomorphic evolution of sedimentary successions within an asymmetrically subsiding basin analogous to a simple half graben containing four interacting supply points of sediment and water under the imposed conditions the experimental system self organized into an axial stream flanked by transverse fans imposition of various combinations of longitudinal and lateral sediment flux showed that the locations and widths of the axial and transverse systems were strongly controlled by relative sediment fluxes flux steering and less influenced by the location of the subsidence maximum and subsidence rate the axial drainage was dominated by transversely sourced sediment through toe cutting of the transverse fans except during the highest axial sediment discharges footwall fans persisted even under conditions of very large axial sediment discharge aided by topographic inheritance of the steeper transverse depositional slopes

recognition of facies bounding surfaces and stratigraphic patterns in foreland ramp successions an example from the upper devonian appalachian basin u s a abstract a detailed stratigraphic study of the upper devonian lock haven formation in the appalachian basin provides new interpretations applicable to understanding sedimentation and stratigraphic architecture in the foreland ramp setting the common occurrence of graded beds hummocky cross stratification and shell lags indicates that storm processes played an important role in deposition gradational based coarsening upward shoreface sequences of interbedded sandstone and mudstone formed during gradual fall in relative sea level in contrast sharp based regressive sequences consist of laminated sandstone facies overlying a submarine erosion surface that developed in response to more rapid fall in relative sea level transgressive sequences become finer grained upward from conglomerate lag which was deposited on a basal transgressive surface to heterolithic facies and mudstone facies a combination of eustasy and tectonic subsidence of the foreland ramp produced changes of relative sea level these fluctuations provided a means for transporting sand onto the ramp and for producing repetition of stratigraphic patterns in the lock haven formation the upper devonian clastic succession which includes both the lock haven formation and the catskill formation represents northwestward progradation of shoreline to nonmarine environments as sediment supply to the foreland ramp exceeded the rate of formation of accommodation compared to passive margin shelves thick fine grained successions such as the lock haven formation are more likely to form in foreland basins where tectonic subsidence provides a mechanism for creating accommodation sediment influx from uplifted areas and absence of a slope break on the foreland ramp results in a higher rate of fine grained clastic sedimentation than occurs on shelves of passive margins

discontinuity surfaces on a shallow marine carbonate platform berriasian valanginian france and switzerland discontinuities in sedimentation are commonly expressed as surfaces in outcrop sections and are due to rapid and substantial environmental changes on shallow marine carbonate platforms most such surfaces represent hiatuses below biostratigraphic resolution and detailed analysis is necessary to identify and evaluate the environmental change involved surfaces in nine sections of the lower cretaceous of the french and swiss jura platform are characterized on the basis of eight universally applicable criteria geometry lateral extent morphology biological activity mineralization facies contrast diagenetic contrast and biostratigraphy nine different surface types are distinguished by their common features and environment of formation all of them are related to environmental changes in the form of subaqueous erosion subaerial exposure subaqueous omission or changes in texture and facies the distribution of surface types in the studied sections shows that condensation and exposure related surfaces tend to occur repetitively in certain intervals calibrated by biostratigraphy these surface zones can be correlated across the platform from proximal to distal positions in comparison with the global sequence stratigraphic framework hardenbol et al 1997 most exposure zones correlate with third order sequence boundaries condensation zones fall in between in the studied sections third order eustatic sea level drops appear to be represented rather by zones of small scale discontinuities than by widespread and well marked single sequence boundaries this is explained by the superposition of high frequency low amplitude sea level fluctuations on a larger scale sea level trend under greenhouse conditions the lateral extent of the surface zones varies through time and indicates important changes in platform morphology changes in local subsidence rate indicated by variable thicknesses of the deposits in comparison with second and third order sea level trends suggest an evolution of the french jura platform from a ramp type morphology in the late middle berriasian to a flat topped platform in the late berriasian the early valanginian again is characterized by increased differential subsidence and well marked platform morphology this study demonstrates that 1 small scale and short lived discontinuities can reflect large scale variations of relative sea level 2 on shallow platforms characterized by small topographic variations and lateral facies changes third order sequence stratigraphic surfaces are not necessarily expressed by one widespread single surface but by zones of surfaces indicating repeated environmental changes surface zones can serve as an additional tool for correlation and interpretation of platform evolution and 3 small scale discontinuities form an integral part of the stratigraphic record and should receive the same attention as the sedimentary deposits they delimit

100 kyr sedimentary record of marginal gangetic plain implications for forebulge tectonics abstract the gangetic foreland is a consequence of continent continent collision and formation of the himalayan thrust and fold belt in the more distal part of the peripheral gangetic foreland basin the late quaternary sedimentary architecture analysis from 17 stratigraphic successions together with optically stimulated luminescence dating osl divulge interaction of peripheral bulge tectonics and climate over the past 100 kyr these sections exhibit three sedimentary packages formed under different environmental conditions detailed vertical and lateral sedimentary architecture delineates nine lithofacies that are grouped into three facies associations i flood plain facies association ii channel facies association and iii interfluve facies association the basal package i 114 ka old was deposited by sandy meandering channels and overlying to this with a hiatus of 30 ka is package ii 80 54 ka deposited by gravelly rivers the sediments of both the packages i ii are derived from rocks exposed in the peripheral bulge region overlain package iii deposited by small meandering channels consist of the sediments derived from the himalaya the results indicate that the duration of 80 54 ka was a period of forebulge uplift when gravelly fans prograded basinward below the fan sediments lies a peripheral bulge unconformity marked by regionally significant pedogenic horizon this pedogenic horizon qualifies as to be termed as peripheral bulge uncomformity after 54 ka the fine himalayan sediments onlap the cratonic sediments implying rather a stable forebulge tectonics coupled with fluctuating climatic conditions occasionally bringing micaceous gray coloured sand silt of himalayan origin

astronomically forced cyclicity in the upper ordovician and u pb ages of interlayered tephra oslo region norway abstract the late ordovician world experienced a series of huge volcanic eruptions recorded as the big deicke millbrig and kinnekulle bentonites together with numerous thinner beds the kinnekulle event can be traced across northwestern europe u pb zircon ages are here presented of both the kinnekulle k bentonite and the uppermost recorded tephra layer in the upper ordovician of the oslo region norway the tephras are located in the upper part of the arnestad formation sandbian south of oslo and gave ages of 454 52 0 50 ma the kinnekulle k bentonite and 453 91 0 37 ma the upper grimstorp k bentonite the dated tephras are separated by a 7 m thick shale succession with subordinate nodular limestone beds although the two u pb ages overlap within errors statistical considerations indicate a most likely time interval of about 600 kyr between the tephras high resolution magnetic susceptibility logging in the same section shows cycles that likely represent changes in sediment supply in response to astronomical forcing spectral analysis shows the presence of long 400 kyr and short 100 kyr eccentricity bands and obliquity components in the 30 kyr band precessional cycles are not detected based on this method it is possible to estimate a time interval of 766 kyr between the two tephra events and the radiometric dating therefore does not exclude a milankovitch interpretation of the cycles this opens new possibilities for understanding the evolution of one of the world s best preserved ordovician marine systems

eustatic and tectonic control on the distribution of marine seismites examples from the upper ordovician of kentucky usa abstract widespread zones of soft sediment deformation are not ubiquitous throughout the rock record rather they are associated with orogenic sediments and are concentrated in specific portions of depositional sequences characterized by deformation prone facies upper ordovician soft sediment deformation features exposed in kentucky are here interpreted as the result of seismically induced thixotropic fluidization of muds resulting in foundering of denser silts and carbonate sands and corresponding diapiric injection of muds severity of soft sediment deformation is associated with sediment density gradients bed thicknesses and varying magnitudes of triggering events the widespread nature 5000 km 2 of multiple deformation horizons argues for a seismic trigger resulting from reactivation of multiple basement faults eight large scale 3rd order depositional sequences were examined for the presence of specific deformation features and stratigraphic position of those intervals the regular distribution of deformation prone facies throughout the upper ordovician seems to have been regulated by eustatic fluctuations seismicity generated by far field tectonics provided the triggering mechanism to disrupt deformation prone strata the record of seismites and their co occurrence with k bentonites provides a meter of intensity and timing of tectophases of the taconic orogeny

upper cambrian carbonate platform evolution elvinia and taenicephalus zones pterocephaliid ptychaspid biomere boundary northwestern wyoming abstract the pterocephaliid ptychaspid biomere boundary is an upper cambrian extinction horizon that can be used to correlate mixed carbonate siliciclastic strata in northwestern wyoming the biomere boundary is defined by the change between the elvinia and taenicephalus zones of the standard north american trilobite zonation it is also signaled chemostratigraphically by a positive trend in carbon isotope ratios thus both biostratigraphic horizons and carbon isotope data are used to constrain the position of the biomere boundary in northwestern wyoming study of 21 stratigraphic sections reveals the presence of distinct facies belts for the middle and upper elvinia zone and lower taenicephalus zone these are interpreted to reflect deposition in three distinct paleoenvironments 1 oolitic shoal 2 intrashelf basin and 3 inner platform margin following a major hiatus in sedimentation in wyoming during much of pterocephaliid biomere time a healthy shallow water carbonate factory was reestablished during elvinia zone time this produced abundant deposits of oolitic and skeletal packstone in the shoal environment and an areally extensive thrombolite boundstone facies in the intrashelf basin setting approximately coincident with the biomere boundary extinction event irvingella major time ooid production was terminated and the thrombolites were drowned the correlation of this major change in the pattern of sedimentation allows for the recognition of parts of two depositional sequences in the study area this drowning event sequence boundary may also be coeval with the accumulation of transported shallow water carbonate deposits in an inner platform margin environment during early taenicephalus zone time sedimentation rates were apparently reduced and the entire study area is marked by thin concentrations of trilobite and brachiopod shells the nonskeletal carbonate factory was never reestablished in the former shoal environment where thick successions of homogeneous lime mud accumulated during the rest of taenicephalus zone time flat pebble conglomerate and shale accumulated in the storm influenced intrashelf basin during this time sea level change and changes in seawater chemistry likely both played roles in the drowning event across the elvinia taenicephalus boundary a positive trend in carbon isotope values across the pterocephaliid ptychaspid biomere boundary is observed in the six sections analyzed this is consistent with previous studies that indicated that the mass extinction occurs within a regional shift towards positive values and this may reflect the development of low oxygen conditions on the shelf the global significance of these isotopic trends changes in relative sea level and the mass extinction has not been confirmed although recent study of the extinction event at the base of the pterocephaliid biomere has revealed a similar trend towards positive carbon isotope values that is worldwide

storms versus tsunamis dynamic interplay of sedimentary diagenetic and tectonic processes in the cambrian of montana the upper cambrian deadwood formation of north central montana is composed mainly of fine grained calcareous sandstone and intercalated silty shale and contains scattered intraclastic flat pebble conglomerate these rocks typical of many mixed carbonate siliciclastic subtidal shelf successions of proterozoic through early ordovician age are distal storm deposits in which the conglomerates are conventionally thought to record occasional very high energy events that scoured incipiently cemented layers in the deadwood formation most sandstone beds have a linear to crudely reticulate pattern of vertical cracks filled with injected silt and clay the cracks exhibit a consistent northwest southeast trend and are very shallow burial deformation structures caused by the passage of seismic waves possibly originating from strong earthquakes in idaho most conglomerates are composed of angular to subangular sandstone intraclasts the polygonal plan view of which is similar in outline to the areas between cracks in the sandstones the deformation implied by the cracks sporadic distribution of conglomerates high degree of scouring indicated and angularity of the intraclasts argue that rather than storms the conglomerates were generated by occasional tsunamis the sweep of these tsunamis across the shallow intracratonic sea created extraordinarily strong oscillating bottom currents at the deeper reaches of storm wave base tsunamites are therefore identified with confidence virtually for the first time in shallow subtidal shelf deposits

magnetostratigraphy susceptibility of the upper ordovician kope formation northern kentucky abstract as a test of the utility of magnetic susceptibility ms measurements for correlation among lithified marine sequences samples were collected from well studied shale and limestone outcrops of the upper ordovician kope formation northern kentucky the bulk initial low field ms of these samples is compared among two litho and biostratigraphically correlated sections containing the same beds the results of this comparison demonstrated an excellent correlation among equivalent beds thermomagnetic susceptibility analysis supports previous xrd work indicating that illite is primary and is the main paramagnetic mineral responsible for the ms variations observed in this study a composite of ms results for a sequence of 31 named shale limestone couplets is used to build a composite section of kope sequences for the area these ms variations permit division of the various sections into a set of 28 ms cycles within the kope formation covering 50 m of section these cycles suggest a systematic control by climate on the influx of detrital material that formed these sedimentary sequences and support other work indicating kope climate cyclicity

a systematic analysis of eight decades of incipient motion studies with special reference to gravel bedded rivers data compiled from eight decades of incipient motion studies were used to calculate dimensionless critical shear stress values of the median grain size t c 50 calculated t c 50 values were stratified by initial motion definition median grain size type surface subsurface or laboratory mixture relative roughness and flow regime a traditional shields plot constructed from data that represent initial motion of the bed surface material reveals systematic methodological biases of incipient motion definition t c 50 values determined from reference bed load transport rates and from visual observation of grain motion define subparallel shields curves with the latter generally underlying the former values derived from competence functions define a separate but poorly developed field while theoretical values predict a wide range of generally higher stresses that likely represent instantaneous rather than time averaged critical shear stresses the available data indicate that for high critical boundary reynolds numbers and low relative roughnesses typical of gravel bedded rivers reference based and visually based studies have t c50 ranges of 0 052 0 086 and 0 030 0 073 respectively the apparent lack of a universal t 50 for gravel bedded rivers warrants great care in choosing defendable t c50 values for particular applications

stratigraphy and correlation of glacial deposits from indiana to new york and new jersey the quaternary glacial history of part of the region from indiana to new york and new jersey fig 1 was outlined in three summaries prepared for the vii congress of the international union for quaternary research wayne and zumberge 1965 goldthwait et al 1965 muller 1965 subsequent regional summaries by white 1969 1982 white et al 1969 ray 1974 and coates 1976 reviewed the entire succession of tills in parts of kentucky northeastern ohio pennsylvania and new york other syntheses and discussions by dreimanis and goldthwait 1973 evenson and dreimanis 1976 dreimanis 1977 fullerton 1980 mayewski etal 1981 and mickelson et al 1983 were concerned only with late wisconsin tills the glacial history of the region fig 2 and chart 1 is much more complex than was assumed in 1965 much of the new information is in unpublished theses and dissertations and other publications of limited distribution and it has not been summarized correlations in chart 1 are based primarily on stratigraphic relationships of tills and paleosols and secondarily on radiometric ages paleomagnetic polarity data and relativeage data this summary serves as an expanded explanation of chart 1 glacial events are discussed within a framework of time divisions from older to younger and by glacial lobes as shown in chart 1 paleomagnetic polarity data in chart 1 are from harrison and terasmae 1961 bleuer 1976 and pers commun johnson 1976 this volume and pers commun hoyer 1977 1983 and pers commun bonnett et al 1978 and teller and last 1981 sources of data related to named tills in indiana ohio pennsylvania new york and new jersey are listed in appendix 1 the term glacial lobe here is applied both to a regional physiographically controlled pattern of ice dispersal and to the geographic region influenced by such movement huron erie lobe glaciation includes ice movement from the georgian bay region ontario into the lake erie basin as well as ice movement through the lake huron basin into the lake erie basin fig 3 illinoian and pre illinoian tills throughout the region have not been well studied and they have no radio

cherty carbonate facies of the montoya group southern new mexico and western texas and its regional correlatives a record of late ordovician paleoceanography on southern laurentia abstract the upper ordovician montoya group in southern new mexico and westernmost texas records predominantly subtidal deposition on a gently dipping carbonate ramp that was subsequently nearly entirely dolomitized the medial unit of the montoya group the aleman formation is unique because it contains abundant chert 10 70 by volume the chert occurs as 1 thin continuous beds of sponge spicules within mudstone or calcisiltite 2 discontinuous lenses or nodules within skeletal wackestones and packstones or 3 as a replacement of skeletal grains and burrows coeval skeletal grainstones and muddy peritidal facies contain little chert phosphate up to 5 wt occurs within the underlying upham formation and the aleman formation as replacement of fossils and peloids the abundance of chert and phosphate in these subtidal facies indicates they formed within a region of strong upwelling regional correlation with upper ordovician cherty units along the periphery of southern laurentia and other low latitude continents suggests that upwelling was widespread and long lived during the late ordovician the upwelling is interpreted to record vigorous oceanic circulation produced by the onset of glaciation on gondwana during this period late ordovician relative sea level curves around the periphery of laurentia indicate correlative third order 1 3 my duration fluctuations that may provide a means for high resolution global correlations however the mechanism s that produced these long term fluctuations are unclear

hinge modifications and musculature of strophomenoid brachiopods examples across the ordovician silurian boundary anticosti island quebec six modifications to the hinge occur in strophomenoid brachiopods from anticosti island 1 overhanging socket ridges 2 posterolateral socket ridges along the interarea articulate with grooves on the posterior of teeth 3 anteromedian dental notches articulate with the crests of socket ridges 4 dental crenulations on the surfaces of teeth mesh with socket ridges 5 denticles extend laterally to the cardinal extremities and 6 the margin of the ven tral interarea fits into a long socket along the dorsal interarea forming a lateral tooth denticulate hinges and dental notches that typify silurian and devonian strophomenids begin in the fauna of the ellis bay formation thus the most important interval of strophomenid faunal turnover was at the base of the gamachian the base of the hirnantian and not at the ordovician silurian boundary muscle attachment pads in the delthyrial cavity do not correspond to the posi tions of either the adductor or diductor muscle scars pedicle adjustor muscles in modern brachiopods occupy this posi tion the round gap between the median fold of the pseudodeltidium and groove on chilidium is proposed as the point of emergence of the pedicle muscle the tiny foramen commonly sealed early in growth is suggested to be part of a neanic water intake system active before the growth of the cardinal process in ephebic shells once the cardinal pro cess appeared the foramen was blocked recurring types of strophomenid ornamentation such as posteriorly steepened rugae and checkerboard ornamentation may have served as a plow to redistribute sediment as the shell was pulled backwards along the pedicle

continental drift and phanerozoic carbonate accumulation in shallow shelf and deep marine settings knowledge of past rates of transfer of rock forming materials among the principal geologic reservoirs is central to understanding causes and magnitudes of change in earth surface processes over phanerozoic time to determine typical rates of global sediment cycling we compiled information on area volume and lithology of shallow water sediments by epoch for both terrigenous clastics and marine carbonates data on amounts of surviving continental terrigenous rock as opposed to deep oceanic and including terrestrial marginal marine and marine deposits exhibit positive age area trends wherein greatest areas and volumes of conglomerate sandstone and shale are represented by younger sequences global volumes of terrigenous clastic sediment yield a mean cycling rate of 0 00124 m yr similar to that determined for eurasian 0 00127 north american 0 00058 a b ronov 0 00352 t d cook and a w bally african 0 0017 and south american 0 0021 clastic sequences surficial erosion results in the mean destruction of 0 124 of terrigenous rock volume per million years of reservoir age in contrast surviving epicratonic and shelf margin carbonate sequences yield negative cycling rates of about 0 164 m yr surviving areas and volumes increase with sequence age that is the amount of limestone and dolostone preserved in shallow water settings increases back in time to maximal areal extents in the middle and upper cambrian mass age data on terrigenous clastic successions indicate generally constant rates of crustal erosion over phanerozoic time decrease in size of the shallow marine carbonate reservoir forward in time therefore suggests generally invariant rates of global limestone accumulation and a shift in sites of accumulation from shallow cratonic to deep oceanic settings over much of the past 540 m yr causes of this eon scale depositional translocation of carbonate sediment from shallowto deep marine settings cannot be satisfactorily linked to either changes in global sea level or the evolution of carbonate producing plankton because neither exhibits a pattern of unidirectional change in position or abundance since the early phanerozoic however tabulation of long term variation in areas of continental shelves from paleogeographic maps reveals a generally uniform decrease in low latitude 30 platform area with decreasing age over most of the phanerozoic moreover rate of change of low latitude shelf area km 2 m yr is almost exactly

modern flood deposition erosion and fan channel avulsion on the semiarid red canyon and palomas canyon alluvial fans in the southern rio grande rift new mexico u s a abstract in the summer of 2006 large floods occurred on the red canyon footwall derived and palomas canyon hanging wall derived alluvial fans which are located on opposite sides of the rio grande floodplain in the palomas half graben of the southern rio grande rift the initial phase of the red canyon flood took place on the active central fan lobe but subsequent avulsion of the main channel shifted the flood to the south where it eroded all but two small relicts of the former inactive toe cut lobe before depositing up to 2 m of coarse gravel deposition of 0 5 m of gravel size detritus by the palomas canyon flood was largely confined to the active incised channel and to gravel bars that built into the river although floodwater spilled over the southern bank of the channel near its mouth depositing a thin 15 cm veneer of fine sand on the floodplain measurements of mean and maximum grain size of the flood deposits channel bed slopes and flood depth based on vegetative high water marks allow estimates of mean flood velocity red canyon 8 6 m s 1 palomas canyon 7 4 m s 1 floodwater discharge red canyon 971 m3 s 1 palomas canyon 179 m3 s 1 and volume of flood deposits red canyon 3 19 105 m3 palomas canyon 1 72 104 m3 mapping of the modern floodplain and outcrop analysis of the palomas formation pliocene lower pleistocene in the palomas basin provide insight into facies architecture in half grabens footwall derived alluvial fan detritus consists principally of shallow multistory gravel conglomerate channels produced by channel avulsion across the surface of the small fans asymmetrical basin tilting causes toe cutting of the footwall derived fans by the axial river and incision of hanging wall derived alluvial fan channels the latter resulting in ribbon shaped gravel conglomerate channels interbedded with finer grained distal fan sediment the red canyon and palomas canyon floods changed the location width and depth of the rio grande causing flooding of the western floodplain for 1 km upstream of the constriction because the rio grande has been dammed since 1916 it no longer has the stream power to effectively redistribute large volumes of fan detritus and must be dredged in order to avoid upstream flooding by the river

tectonic and climatic controls on holocene channel migration incision and terrace formation by the rio grande in the palomas half graben southern rio grande rift usa in order to evaluate potential effects of tectonics and climate change on the behaviour of the axial rio grande in the rio grande rift a 16 5 km stretch of modern floodplain and holocene terraces were mapped in the tectonically active palomas half graben south central new mexico usa in addition 51 cores and natural exposures were logged and 20 radiocarbon dates were obtained from charcoal bulk organic matter mollusc shells and pedogenic calcite the holocene alluvium comprises four terraces above the modern floodplain each of which formed by a period of river incision followed by stability and renewed floodplain construction to a level below that of the previous terraces estimated times of incision between terraces i and ii ii and iii and iii and iv are after 12 400 8040 to 5310 and 760 to 550 yr bp respectively whereas the incision between terrace iv and the modern floodplain occurred within the last 260 years although there is some evidence for tectonic control on river behaviour in the southern part of the basin terrace formation is interpreted as being related to climate change with periods of incision corresponding to times of increased aridity and low sediment water discharge ratio in the rio grande this process may have resulted from a reduction in intensity and magnitude of summer storms which supply sediment to the axial river coupled with an increase in spring discharge peak caused by snowmelt in upstream mountain catchments

high resolution sequence stratigraphy of the upper ordovician montoya group southern new mexico and western texas outcrop analog of an unconventional chert and carbonate reservoir the upper ordovician montoya group crops out in southern new mexico and westernmost texas and records predominantly subtidal deposition on a gently dipping carbonate ramp that was subsequently almost entirely dolomitized the montoya group is a third order composite sequence composed of six regionally correlative shallowing upward third order depositional sequences m0 m5 sequence m0 has sandstone at its base that is overlain by skeletal packstone grainstone sequence m0 occurs only locally and was likely deposited in a topographic low formed during regional development of the unconformity following el paso group deposition sequence m1 marking the initial widespread transgression over the ellenburger unconformity consists of sandstone updip that passes downramp into skeletal packstone the highstand systems tract hst of m1 consists of a prograding skeletal grainstone that was subaerially exposed upramp sequence m2 which contains the second order maximum flooding surface has abundant subtidal cherty carbonate at its base which shallows upward into a widespread prograding coral packstone grainstone in the hst sequence m3 also contains abundant downramp chert that passes upramp into an aggrading crinoidal shoal and farther upramp into peritidal mudstone sequence m4 records an extensive basinward shift in facies as peritidal burrowed and cryptalgalaminated mudstone prograded over subtidal carbonate sequence m5 is only locally developed downramp and consists of crinoidal grainstone with abundant evidence of subaerial exposure a regional unconformity separates the montoya group from the silurian fusselman dolostone or younger units parasequences meter scale cycles recording low to moderate amplitude relative sea level fluctuations are ubiquituous features at individual outcrops but are difficult to correlate regionally the abundance of syn or early depositional chert in the subtidal facies indicates that the montoya group was deposited within a region of strong regional upwelling along southern laurentia this early formed chert was the reservoir facies in a successful upper ordovician gas play in ward and reeves counties texas

orogeny and stratigraphy numerical models of the paleozoic in the eastern interior of north america a computer model is used to estimate patterns of lithospheric deformation caused by obduction and removal of loads within orogenic belts regions of lithospheric downwarp become sedimentary depocenters and regions of lithospheric upwarp suffer erosion by following the deposition and erosion of sedimentary packages through a number of model time steps it is possible to calculate a synthetic stratigraphy for a given study area this model is applied to the post early ordovician stratigraphy of the eastern interior region of north america the loading that drives lithospheric deformation is associated with the development of the appalachian and ouachita orogens and the independent development of the michigan and illinois intracratonic basins model results are shown to be consistent with presently observed stratigraphy lithology and cumulative erosion and are then used to estimate the configuration of given sediment packages at discrete intervals following their deposition these estimates are presented in the form of isopach maps stratigraphic cross sections and time stratigraphic diagrams as a function of time over the last 470 ma by tracking the burial and erosion history of sedimentary units we are able to establish a cause and effect relationship between particular tectonic events and the extent of preservation of sedimentary units in particular we suggest that the pennsylvanian permian alleghanian orogeny produced major sediment cover over much of the study area

analyzing niche stability and biogeography of late ordovician brachiopod species using ecological niche modeling abstract gauging the potential impacts of environmental change on the geographic distributions of species is a central area of modern biogeographic analysis often involving complex models of species environment interactions the geographic distribution of fossil species can also provide a framework to test the impact of environmental change on biogeography and ecological niches of species yet few paleontological analyses have attacked this question in deep time herein we present a quantitative biogeographic analysis to examine the stability of ecological niches and geographic ranges of rhynchonelliform brachiopods during an interval of sea level change preserved in upper ordovician strata of the cincinnati arch the intensive sampling excellent preservation and numerous prior paleoecological and sedimentological analyses within the tri state region of kentucky indiana and ohio provide a robust framework for detailed paleobiogeographic study quantitative biogeographic modeling methods incorporating gis geographic information systems are utilized in order to spatially analyze the geographic ranges of brachiopod species of the corryville and mt auburn formations of the c3 uppermost maysvillian depositional sequence this study employs the ecological niche modeling program garp genetic algorithm using rule set prediction to predict the geographic distribution of eight brachiopod species during three time slices within the c3 sequence this method estimates a species geographic range by modeling the ecological niche of the species based on a set of known species occurrence data coupled with environmental data inferred from sedimentologic proxies once environmental tolerances for a species are modeled the species is predicted to occur wherever its preferred set of environmental conditions occurs within the study region distributional patterns were reconstructed for three time slices during the c3 sequence recovered range predictions were quantitatively analyzed for evidence of temporal range changes results indicate that average species range within the study area decreased and species tracked their preferred niche with high fidelity during the transition from the early to middle portions of the c3 depositional sequence an interval of rapid relative sea level change however during the transition from the middle to late portions of the sequence gradual shallowing within the basin and development of discontinuous habitat patches correlates with niche evolution of five of the eight species modeled the average area a species occupied within the basin increased during this interval but there is a mixed response including both increases and decreases in range size within the study group in general the species that exhibit niche evolution increased their geographic range size while those that continue to track their niche with high fidelity experience a decrease in geographic range size during the latter half of the c3 sequence previously continuous habitats become fragmented thereby isolating individual populations and providing a mechanism for niche evolution the rate of sea level change and the corresponding fragmentation of previously continuous habitats into isolated patches appear to be the primary controls on both mean geographic range size and relative degree of niche evolution

siltstone a key to cyclicity in mixed siliciclastic carbonate successions example from upper ordovician kope formation ohio indiana kentucky 1 the upper ordovician mid katian kope formation provides an example of how a detailed study of fine grained siliciclastic sediment can provide sedimentological insights the kope formation is an exemplar of mixed siliciclastic carbonate cyclicity however most of the sedimentological research to date has focused on the fossiliferous limestone beds conversely this paper provides a detailed investigation of siltstone within 42 metre scale cycles from 26 locations spanning a large geographic area the objective of the study is twofold i to confirm the mineralogical nature of silt sized sediment currently silt sized sediment is irregularly defined as being either carbonate or siliciclastic rich this paper uses x ray diffraction thin section and elemental analyses to determine the mineralogy of the silt ii to determine the stratigraphic distribution of siltstone beds if a distinctive and reoccurring distribution of siltstone can be found then it can provide additional information about environmental energy changes that led to cyclic fossiliferous limestone formation this study finds that silt within the kope formation is siliciclastic and siltstone therefore records periodic minor pulses of coarser terrigenous sediment predominantly metre scale limestone shale cycles show an increasing abundance of siltstone beds in the upper half of the shale interval with a marked decrease just before the capping limestone this finding supports the idea that limestone formation occurred during slowing sedimentation perhaps at a time of maximum sea level rise furthermore decametre scale fluctuations in siltstone abundance are similar in pattern to previously documented faunal variations indicating that fauna assemblage might be more controlled by turbidity and not depth

using gis to unlock the interactions between biogeography environment and evolution in middle and late devonian brachiopods and bivalves abstract the late devonian was a time of profound evolutionary and environmental change associated with the frasnian famennian biodiversity crisis one way to unravel the faunal dynamics of this complex crisis is to document the spatial and temporal patterns associated with biodiversity decline this analysis investigates the relationship between biogeography relative sea level and environmental changes in laurentian brachiopod and bivalve species during the givetian through famennian stages upper middle to terminal devonian representatives from all major brachiopod and bivalve clades and paleocommunities were examined to provide a cross faunal comparison species ranges were reconstructed both spatially and temporally at the level of conodont zones using gis to understand the timing and extent of species invasions and the importance of geographic range during the crisis interval species geographic ranges were linked closely with both relative sea level change and depositional environment and expanded as relative sea level rose in addition times of interbasinal species invasions corresponded closely with sea level rises that breached tectonic barriers species with larger geographic ranges were more resistant to extinction during the late devonian this relationship is reflected partly in a general trend towards increased extinction resistance in taxa that are found farther offshore in environments that potentially included more area for example there is an increased survival advantage for species that inhabited the middle and outer platform environments though not for species inhabiting the open shelf additionally species whose givetian to frasnian history includes at least one interbasinal invasion event were more likely to survive the late devonian biodiversity crisis than noninvasive species this may have relevance for our understanding of the current biodiversity crisis given the role that invasive species are playing in mediating modern extinctions

depositional controls on mixed carbonate siliciclastic cycles and sequences on gently inclined shelf profiles the interplay between carbonate production and siliciclastic input produces mixed systems that typically contain a very high degree of lateral and vertical facies heterogeneity this heterogeneity complicates the sequence stratigraphic analysis of mixed systems outcrop studies facilitate the deciphering of controls and understanding of facies distributions within sedimentary successions the picun leufu anticline in the neuquen basin argentina offers the opportunity to integrate large scale depositional architecture with detailed facies descriptions of the shelf to basin successions of the upper jurassic lower cretaceous quintuco picun leufu vaca muerta system the strata in the system are mixed and range in depositional environments from shallow marine sandstones and limestones to deep basinal shales these environments are arranged in metre scale shallowing upward cycles and cycle sets with increasing carbonate proportions in regressive hemicycles increased input of siliciclastic material from the volcanic arc area occurred during phases of relative sea level rise and was controlled by the intensity of along shelf currents the shelf transport was driven by the available accommodation space on the shelf and therefore was a function of the eustatic sea level fluctuations within the studied section a pure carbonate depositional system developed because siliciclastic input was shut down either due to long lived highstand settings or a sudden climatic change to more arid conditions carbonate siliciclastic mixing in this setting is a function of siliciclastic dilution of the carbonate sedimentation and differs from the classical reciprocal sedimentation model which typically includes shut off of carbonate production during lowstand periods in the regional context the subsurface strata of time equivalent reservoirs in the eastern neuquen embayment display strong similarities of architecture indicating that similar mixing processes occurred along most of the neuquen basin

glacially redeposited pollen in tills of southern ontario canada according to published opinion based on analytical data the secondary pollen of subglacial till in the eastern baltic region of europe reflect the pollen assemblages of the preceding interstadial or interglacial sediment including abundant thermo philous pollen tills and glaciolacustrine sediments from 10 sites in southern ontario including the don valley brickyard section at toronto where polynologically investigated to compare the pollen content in glacigenic deposits of various ages only one site upper bradtville till contained a secondary pollen assemblage with abundant deciduous pollen like those found in a yarmouthian interglacial deposit in indiana in all the others pine pinus pollen dominate this phenomenon is explained by glacial incorporation of sediments enriched in overproduced pinus pollen which had accumulated during either i a lengthy cool transitional period between the warm phase of the sangamonian interglacial and the first major early wisconsinan glacial advance ii t

taphonomic reworking and stratal organization of tempestite deposition abstract tempestite beds of the ordovician kope formation of northern kentucky provide an interesting subject for numerical simulation and stratigraphic analysis taphonomic characteristics of these shell rich beds suggest that they were formed by multiple reworking and amalgamation events if so then storm driven redepositional processes could have led to temporal condensation within the tempestite beds numerical simulation of tempestite formation indicates that storm bed abundance is maximized by frequent weak storm events whereas shell degradation is increased by frequent strong storms conversely these stratigraphic and taphonomic parameters are insensitive to changes in storm intensity when such events are relatively uncommon additionally the stratigraphic and taphonomic characteristics of tempestite formation are found to be largely insensitive to the abundance of shell material in the undisturbed shale lacunarity analysis of the vertical spacing of kope formation tempestite beds grainstones and packstones demonstrates stratal clustering such clustering was caused by either absolute or relative changes in storm intensity or frequency given the temporal scale of tempestite clustering within the kope changes in water depth across the shallow shelf driven either by changes in sea level or sedimentation rate is a likely mechanism by which such relative changes in storm processes occurred conversely climatologic variability at the scale of tens to hundreds of thousands of years could drive absolute changes in storm intensity leading to stratigraphic clustering of tempestite beds

models for generation of carbonate cycles computer modeling provides a quantitative approach to a better understanding of actual carbonate cyclic sequences to model carbonate cycles the authors can use water depth dependent sedimentation rate for each facies an initial lag time linear subsidence tidal range and period and amplitude of sea level oscillation about a horizontal datum tidal flat capped cycles up to a few meters thick result from low amplitude sea level oscillation of a few meters and short lag times nonerosive caps reflect sea level lowering being balanced by subsidence and basinward migration of the shoreline not exceeding tidal flat progradation rate when higher amplitude sea level oscillations occur the tidal flats are abandoned on the inner shelf during sea level fall because seaward movement of the strandline outpaces progradation rate of flats increased amplitude also results in sea level falling faster than flats can subside so that disconformities with thick vadose profiles develop high amplitude 100 m or more oscillations result in incipient drowning of platforms and juxtaposition of deep water facies against shallow water facies within cycles sea level falls before the platform can build to the sea level highstand and the shoreline migrates much more rapidly than tidal flats can prograde thus cycles are disconformity bounded and lack tidal flat caps 10 references

sequence stratigraphic model for repeated butter shale lagerstatten in the ordovician katian of the cincinnati ohio region usa the butter shale lagerstatten of the cincinnati arch have produced an abundance of articulated trilobites along with assorted bivalves and cephalopods these bluish gray shales are rich in clay poorly calcified and show vague internal bedding in outcrop butter shales form a repetitive motif with similar lithological and paleontological characteristics suggesting conditions existed that can be explained by the interference between different orders of sequence stratigraphic cyclicity the characteristics that define butter shales include rarity of coarser interbeds homogenous fine grain size and abundance of burial horizons the overriding control is siliciclastic sediment supply during third order transgressions sediment supply to the basin is too low to produce thick shale prone intervals conversely during third order falling stages sediment supply is generally too high to favor butter shale deposition butter shales formed preferentially during a third order highstand systems tract and two subtly different variants resulted from the superimposed effects of higher order cycles highstands moderated by small scale transgressions are characterized by lower background sedimentation and fewer thinner mud deposition events superposition of small scale sea level fall on highstands produced increased background sedimentation higher silt and patchy fossil occurrences juxtaposition of various scaled highstand systems tracts provided the optimal butter shale conditions characterized by elevated mud influx and frequent episodic burial events leading to abundant articulated trilobites and associated fauna in these scenarios episodic events provide sufficient mud to smother local faunas and create a soft fine grained substrate that prohibited recolonization by taxa adapted to firm substrates each scenario differs from the others with respect to sedimentology and faunal composition

evolution of the late ordovician plaesiomyid brachiopod lineage in laurentia multivariate analysis of 197 well preserved specimens among 11 species of late late ordovician katian and hirnantian plaesiomyid brachiopods from north america revealed two trends of morphological changes 1 increasing globosity and dorsal convexity from the early to late katian and 2 coarser but fewer ribs in species from the paleoequatorial intracratonic seas compared with species from the mid to high tropical pericratonic shelves and platforms another notable change albeit not quantified was the enlargement of cardinal process in plaesiomyids from early to late katian characterized by a predominantly trilobed cardinal process in the intracratonic species versus a bilobed cardinal process in pericratonic species increases in dorsal convexity and shell globosity are interpreted to have allowed for development of a larger lophophore improving the capacity and efficiency of filter feeding and gas exchange smaller but more frequently bifurcating ribs would have led to more numerous setae nea