hierarchal genetic stratigraphy a framework for paleoceanography a detailed genetic stratigraphic framework for paleoceanographic studies can be derived by describing correlating interpreting and predicting stratigraphic sequences relative to a hierarchy of their constituent time stratigraphic transgressive regressive units t r units t r unit hierarchies are defined and correlated using lithostratigraphic and paleoecologic data but correlations can be enhanced or checked tested to confirm or deny with objective biostratigraphic magnetostratigraphic or chemostratigraphic data such chronostratigraphies can then be bracketed by radiometric ages so that average periodicities for t r units can be calculated and a hierarchal geochronology derived t r units are inferred to be the net depositional result of eustatic cycles of sea level change and can be differentiated from autocyclic deepening shallowing units because the latter are noncorrelative intrabasinally boundaries between t r units are conformable or unconformable genetic surfaces of two types transgressive surfaces and climate change surfaces the latter are useful for correlating minor transgressive phases through nonmarine intervals thereby deriving information linking paleoclimatic and paleoceanographic processes permo carboniferous sequences can be analyzed relative to a hierarchy of six scales of genetic t r units having periodicities of 225 300 m y first order 20 90 m y second order 7 13 m y third order 0 6 3 6 m y fourth order 300 500 10 years fifth order and 50 130 10 years or less sixth order paleogeographic maps for the time of maximum transgression transgressive apex of successive fifth order t r units 5 25 m thick in the glenshaw formation upper pennsylvanian northern appalachian basin delineate delta lobes embayments islands and linear seaways relative extent of marine inundation on the fifth order maps was used to delineate fourth order t r units and the fourth order t r units constitute the transgressive half of a third order t r unit this third fourth and fifth order hierarchy is correlated more than 1200 km 750 miles to the western interior basin and is confirmed with limited objective biostratigraphy

search for milankovitch patterns among oolitic ironstones the stratigraphic record of about 175 oolitic ironstones is sparse yet it portrays several meaningful patterns repeated ironstone episodes occurred in only about 10 major sedimentary basins which were marked by relative tectonic stability or subdued orogeny intervals between episodes varied but were mostly a few to several million years long repetitions on this scale are commonly construed as global rise and fall of sea level the pattern persisted for a few tens of million years in fore deeps several tens of million years on unstable cratons and microcontinents and more than 100 m y in intracratonic basins within the congenial habitats an ironstone developed locally between each of several successive shallow marine upward shoaling detrital sequences these asymmetric units normally a few meters to a few tens of meters thick recurred on average every 250 to 500 kyr commonly fewer than 10 ironstone bearing sequences are involved during a very long lapse in normal sedimentation between such sequences stacked ironstones accumulated on the same short time scale speculation about short time scale patterns is poorly constrained but several other repetitive stratigraphic successions with a several hundred thousand year cadence have been attributed tentatively to the 400 000 year milankovitch climate cycle it is unclear how this would exert a eustatic control without the waxing and waning of continental glaciers

tectono stratigraphy of the orhaniye basin turkey implications for collision chronology and paleogene biogeography of central anatolia abstract located along the izmir ankara erzincan suture iaes the maastrichtian paleogene orhaniye basin has yielded a highly enigmatic yet poorly dated paleogene mammal fauna the endemic character of which has suggested high faunal provincialism associated with paleogeographic isolation of the anatolian landmass during the early cenozoic despite its biogeographic significance the tectono stratigraphic history of the orhaniye basin has been poorly documented here we combine sedimentary magnetostratigraphic and geochronological data to infer the chronology and depositional history of the orhaniye basin we then assess how our new data and interpretations for the orhaniye basin impact 1 the timing and mechanisms of seaway closure along the iaes and 2 the biogeographic evolution of anatolia our results show that the orhaniye basin initially developed as a forearc basin during the maastrichtian before shifting to a retroarc foreland basin setting sometime between the early paleocene and 44 ma this chronology supports a two step scenario for the assemblage of the central anatolian landmass with incipient collision during the paleocene early eocene and final seaway retreat along the iaes during the earliest late eocene after the last marine incursion into the foreland basin our dating for the orhaniye mammal fauna 44 43 ma indicates the persistence of faunal endemism in northern anatolia until at least the late lutetian despite the advanced stage of iaes closure the tectonic evolution of dispersal corridors linking northern anatolia with adjacent parts of eurasia was not directly associated with iaes closure and consecutive uplifts but rather with the build up of continental bridges on the margins of anatolia in the alpine and tibetan himalayan orogens

seismic imaging of melanges pieniny klippen belt case study discussion we appreciate the attempts of marzec et al 2019 to investigate the geological structure of the pieniny klippen belt pkb by means of seismic reflection profiling but in our opinion the authors main conclusions contradict the results of previous studies without being constrained by the new data below we comment on some of the problems that led to the misinterpretation

an example of an accretionary forearc basin from northern central anatolia and its implications for the history of subduction of neo tethys in turkey deformed sedimentary sequences of late cretaceous middle eocene age located between the sakarya continent and the anatolian complex have been interpreted as the fill of a forearc basin the history and structure of this basin are critical for understanding the evolution of the neo tethyan subduction in the middle east i test and elaborate upon this interpretation on the basis of three basic outcrop areas of upper cretaceous lower tertiary sedimentary sequences confined to a northeast southwest trending belt in north west ankara these are the alci kinik and orhaniye areas they expose two different sedimentary sequences called alci and orhaniye in the alci area the sequence starts at the base with the continental red clastic rocks on the erosional surface of an underlying ophiolitic melange and continues upward into the shallow marine reefal buildup of the late maastrichtian age the upper half of the alci sequence is separated from its lower half by a local disconformity and dominated by the continental debris flow deposits composed mostly of volcanic material by contrast both the kinik and orhaniye areas are characterized by a thick continuous and coarsening upward sequence overlying conformably the underlying ophiolitic melange the lower half of the orhaniye sequence is dominated by a deep marine flysch its middle part by continental clastic material and the topmost part by the shallow marine reefal buildup lower contact relationships lithologic composition facies distribution internal structures and the regional tectonic settings of both sequences strongly suggest that the above mentioned three outcrops preserve the remnants of a peripheral accretionary forearc basin forming the north northwestern margin of the haymana polath accretionary forearc basin during middle campanian middle eocene time this peripheral basin is here named orhaniye accretionary forearc basin

reassessment of the age and depositional environments of the eocene cayraz formation a reference unit for tethyan larger benthic foraminifera haymana basin central turkey abstract the cayraz formation a reference unit for tethyan ypresian middle late lutetian larger benthic foraminifera haymana basin central turkey is a thick 350 m shallow marine mixed carbonate siliciclastic sequence divided into lower middle and upper units the lower and upper units predominantly consist of rhythmic intercalations of limestone and marly silty beds with abundant larger benthic foraminifera lbf and the middle unit is composed of massive fine siliciclastic sediments mostly barren in lbf and macrofossils by studying three sections caya cayb and ye encompassing the lower unit we show that the cayraz formation ca 100 m thick displays notable vertical and lateral variability in benthic fauna and facies along an se nw transect at its type locality near cayraz village the distribution of lbf and facies patterns indicate a general shallowing upward trend with more open marine environments in the easterly section caya and restricted shallow marine to continental environments with low diversity fauna in the westerly section ye a depositional setting ranging from outer to inner ramp with continental influence only in the westerly section is proposed key orthophragminid and alveolinid taxa from the lower unit of the cayraz formation indicate shallow benthic zones sbz 9 10 for its lower part and sbz 12 for its upper part suggesting a late ypresian age the massive marly silty section of the middle unit of the cayraz formation overlies the alveolina bearing limestones in all sections and yielded abundant planktonic foraminifera suggestive of p9 zone this implies a sharp environmental transition from platform to basin across the ypresian lutetian boundary

evidence of orbital forcing in lake level fluctuations in the middle eocene oil shale bearing lacustrine successions in the mudurnu goynuk basin nw anatolia turkey abstract mudurnu goynuk basin of the sakarya zone in nw anatolia comprises ca 1500 m thick paleocene eocene terrestrial to shallow marine succession overlying the late cretaceous deeper marine progradational fore arc sediments formed in a foreland setting in relation to southerly situated izmir ankara suture zone this terrestrial succession regionally known as kizilcay group comprises a thin

symmetrical and upward shallowing cycles in the middle devonian of new york state and their implications for the punctuated aggradational cycle hypothesis the middle devonian eifelian and givetian hamilton group in western and central new york composed largely of fossil rich marine shelf and slope facies is subdivisible into repetitive facies sequences of varying thicknesses minor cycles include 1 to 3 m thick upward coarsening shale to siltstone hemicycles resembling sixth order punctuated aggradational cycles pacs in central new york probably correlative 0 5 1 0 m shale to argillaceous nodular limestone couplets occur in western areas major cycles in western new york include subsymmetrical 3 to 5 m thick packages with medial limestone beds analogous to upper limestones of pennsylvanian cyclothems the center of each cycle marks a regressive maximum and grades vertically above and below into black shale or dark gray mudstone corresponding in a facies sense to cyclothemic core shales in the midcontinent pennsylvanian these widespread units appear to be allocyclic in nature and approximate fifth order transgressive regressive cycles based upon average unit thickness relative to the encompassing well zoned hamilton sequence correlations show that most key regressive events marked by limestones in western new york are expressed by equivalent siltstone or fine sandstone units in central new york most cycles which are nearly symmetrical in western new york grade eastward into 5 to 20 m upward coarsening pac motif hemicycles these asymmetric cycles apparently reflect rapid sediment aggradation to limits imposed by wave energy in a region of abundant sediment supply further minor shallowing was accompanied by winnowing and bypass of fine grained sediments generating condensed capping deposits of coarser silt and sand reworked shells and commonly phosphatic nodules ensuing sea level rises were accompanied by initial sediment starvation followed by sedimentation in deeper water hence asymmetrical upward shallowing hemicycles pacs appear to grade offshore into thin but symmetrical cycles both pac and symmetrical motifs are local responses to the same probably allocyclic sea level fluctuations we suggest that the pac motif is partially facies controlled being largely restricted to shallow shelf settings with relatively high rates of sediment accumulation

cyclicity and paleoenvironmental dynamics rocknest platform northwest canada the superbly exposed rocknest formation northwest territories canada contains 140 to 160 shallowing upward cycles 1 to 15 m thick that contain distinctive marker beds and can be correlated for 200 km parallel to strike and 120 km perpendicular to strike cycles are grouped according to cycle base lithology which reflects paleogeographic position on the platform shale based cycles of the distal inner shelf pass westward into dolosiltite based cycles then into tufa based cycles of the shoal complex and then into grainstone based cycles of the outer shelf cycles are bounded by erosional surfaces that become less pronounced away from the shoal complex cycles formed in response to small asymmetric rapid rise slow fall eustatic oscillations in sea level 10 m during sea level rise rapid transgression and submergence of tidal flats occurred along the eastern margin of the shoal complex followed by eastward expansion of the shoal complex and slow progradation of tidal flats over lagoonal facies during sea level fall a glacio eustatic model for cyclicity accounts for the data favoring asymmetric eustatic sea level oscillations subaerial exposure and vadose diagenesis of platform during sea level falls arrested progradation and incomplete shoaling of many cycles and cycle periods of 20 000 to 100 000 yr 18 000 to 30 000 yr for rocknest inner shelf slopes ranged from 8 cm km average at high sea level stand to 2 cm km average at low sea level stand tidal flat progradation rates were 7 to 9 km 1 000 yr interaction of inner shelf slope sea level fall rate and sedimentation rate generates complete condensed or expanded cycle profiles one dimensional computer modeling reveals that sedimentation rates of shoal complex facies were 250 cm 1 000 yr that lag times in sedimentation following transgression may have ranged from zero on the shoal complex to 2 000 yr on the distal inner shelf and that subtidal sedimentation rates may have ranged from 80 cm 1 000 yr for the proximal inner shelf to 20 cm 1 000 yr for the distal inner shelf

stratigraphy and depositional environments of the kanawha formation middle pennsylvanian southern west virginia u s a abstract the kanawha formation of southern west virginia consists of up to 620 m of lithic sandstone and mudrocks with subordinate coal and impure limestone that accumulated in a subsiding foreland basin the formation contains 26 of the state s 62 minable coal seams it accounts for about 43 of the coal currently produced in west virginia component sedimentary facies from 46 outcrop localities reflect alluvial paludal lacustrine paralic and shallow marine environments internal and architectural facies attributes indicate more evidence for coastal and tidal estuarine deposition than traditional deltaic models evidence for tidal processes includes bipolar paleocurrents rhythmic textures and structures and associated biogenic structures a new two part model is presented that relates facies to changing coastal morphology during transgressive regressive cycles eustatic sea level changes played a major role in basin wide development of major coal zones and marine units lowstandss of sea level caused incisement of fluvial channels whereas rising sea level led to expansion of tidal plains and estuaries shoreface retreat produced ravinement surfaces and transgressive lags that now separate coastal plain and marginal marine facies from shallow subtidal facies coastal progradation began during highstands after estuarine sediment sinks had filled and may have been intensified during falling sea level

stratigraphic architecture and hierarchy of fluvial overbank splay deposits splay deposits represent an important sand prone component of the otherwise fine grained stratigraphic record of fluvial overbank systems this work presents a hierarchical approach to the classification and palaeoenvironmental interpretation of ancient preserved splay deposits supported by the analysis of the stratigraphic architecture of 11 exhumed examples from the jurassic morrison formation and the cretaceous mesaverde group western usa and analysis of the morphology of splays from nine modern fluvial systems a hierarchical arrangement of splay deposits is proposed categorized into lithofacies beds elements and complexes recognition criteria for each tier of the hierarchy include identification of bounding surfaces thinning and fining trends of splay elements and complexes and palaeocurrent variability progradational and compensational stacking trends control the stratal architecture of splay deposits and these are influenced by the following factors 1 the rate of local accommodation generation which influences the erosive power of floodwaters and whether splay elements are laterally offset owing to compensational stacking 2 the nature of the topographic confinement of the floodplain 3 the preservation potential linked to migration direction of channel splay bodies can contribute volume to fluvial reservoirs and may form significant connectors that link otherwise isolated primary channel bodies thereby enhancing reservoir connectivity supplementary material thickness and facies types with global positioning system gps coordinates length and width v thickness and modern data and coordinates are available at https doi org 10 6084 m9 figshare c 4461026

an undulatory discontinuity surface on a gently inclined muddy ramp possible evidence of secondary helical flow from the geological record an unusual somewhat cryptic undulatory discontinuity has been recognized near the basal contact of the wanakah shale member of the middle devonian ludlowville formation in western new york it is in part marked by undulating diagenetic limestone beds and concretionary horizons but can be traced continuously by subtle surfaces of fossil and pyritic lags this surface marks the top of parallel elongate mud ridges trending approximately n s perpendicular to the inferred e w depositional strike of the appalachian basin in western new york these ridges are observed in the field as irregularly spaced mud swells which have up to 1 5 m of relief and vary from 30 to 50 m or more in width the intervening broad flat channel floors are characterized by dense concentrations of diminutive brachiopods with gastropods and styliolinids which are gradually replaced by thin styliolinid horizons with abundant pyrite nodules and pyritized burrows over the tops of the swells traceable shelly horizons are observed to pinch out over the swells suggesting a period of relatively undisturbed sediment filling following the formation of the channellized surface the interval of nearly barren shale below this irregular surface however contains concretionary horizons and rare styliolinid pavements which are themselves irregular possibly indicating a changing topography for this surface through time previous taphonomic and palaeoecological studies of the lower wanakah shale member have disclosed a well defined regressive transgressive cycle with more subtle superimposed subcycles the undulatory surface described here occurs within the early regressive part of this cycle and appears to record an accentuated regressive kick of a lower order subcycle the formation of this surface is therefore interpreted to be a consequence of regressive submarine erosion and sediment bypass together with redeposition from suspension the development of the channels and parallel longitudinal mud ridges was probably controlled by helical flow cells within offshore directed bottom currents they may be the first recorded instance of sedimentary furrows described from the geological record taphonomic and biofacies data indicate relative depths below average storm wave base suggesting that sediment winnowing and redeposition occurred at depths only rarely affected by the direct impact of storm wave agitation

millennial to secular time scale impacts of climate and sea level changes on mangroves from the doce river delta southeastern brazil this work integrates geomorphological sedimentological and palynological data with radiocarbon dating as well as 13c 15n and c n from sedimentary organic matter to provide a model of mangrove dynamics during the evolution of a wave dominated delta in southeastern brazil mangrove dynamics are analyzed within the context of millennial and secular climatic and sea level changes tidal flats positioned at highest limit of the intertidal zone along the edge of a lagoon sheltered by beach ridges were occupied by wetlands represented by mangrove and herbaceous vegetation during the mid holocene high sea level after considering the relative sea level fall and relatively higher fluvial sediment discharge during the last 6350 years progradation took place along this shoreline resulting in extensive beach ridge deposits that overlie transgressive muds this process led to loss of mangrove area similar dynamics were repeated at 3043 cal yr bp although in a relatively more distal i e seaward posi

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

punctuated aggradational cycles implications for stratigraphic analysis application of the hypothesis of punctuated aggradational cycles pacs a model of episodic stratigraphic accumulation has yielded results fundamentally in conflict with those predicted and generated by gradualistic models the assumption that stratigraphic accumulation is controlled principally by rapid small scale base level fluctuations in the milankovitch band leads to the adoption of the pac a thin time stratigraphic unit as the fundamental unit of stratigraphic description and interpretation the thicker generally diachronous formation is inadequate for stratigraphic analysis because it is an artifact of stratigraphic gradualism correlation of stratigraphic sections is accomplished by matching patterns of facies change particularly the abrupt changes at the synchronous surfaces that mark pac boundaries this kind of physical event correlation is far more accurate than traditional biostratigraphic methods focus on synchronous pac boundaries separating environmentally disjunct facies reveals discontinuities that preclude application of walther s law across those surfaces when viewed from this episodic perspective the manlius formation of the helderberg group in new york state becomes a highly ordered set of time stratigraphic cycles rather than a disordered mosaic of facies representing short term autogenic processes in a single nearshore environment not only was manlius deposition episodic with no gradual upward deepening as is predicted by stratigraphic gradualism but also the manlius coeymans formational boundary is interpreted as a small scale unconformity rather than a paleoenvironmental boundary created by gradual transgression each of these interpretations is the direct result of assuming and applying a model of episodic stratigraphic accumulation

shallowing upward sequences in purbeckian peritidal carbonates lowermost cretaceous swiss and french jura mountains purbeckian carbonates in the swiss and french jura goldberg formation lower berriasian comprise shallow subtidal intertidal supratidal low energy high energy marine brackish freshwater and hypersaline facies these facies are arranged in small 0 2 1 5 m thick sequences which display a dominant shallowing upward component and which form the fundamental units of the highly structured purbeckian sedimentary record six types of small scale sequences can be recognized a intertidal to supratidal overprinting of shallow lagoonal facies b algal marsh sequence with frequent dolomitization c sabkha sequence often associated with collapse breccia d tidal flat sequence with desiccation features e lacustrine sequence f terrestrial overprinting of subtidal or intertidal facies episodic event deposits such as tempestites are superimposed thin transgressive beds which rework elements of the underlying facies are frequently found at the base of the sequences green marls and black pebbles are common at the top and indicate long subaerial exposure the sequences are often incomplete as subtidal facies may be absent or their upper part can be eroded lateral facies changes are common which is due to the very shallow and partly emergent purbeckian platform where various depositional environments were juxtaposed however many sequence boundaries are well developed and can be correlated over large parts of the study area the purbeckian shallowing upward sequences were generated by climatically controlled sea level changes autocyclic processes occurred locally but were overprinted by drops of sea level affecting the entire platform the small scale sequences are most probably related to the 20 000 year cycle of the precession of the equinoxes larger sequences with usually well developed emersion surfaces are attributed to the 100 000 and 400 000 year eccentricity cycles of the earth s orbit identification and correlation of sequence boundaries makes it possible to set up a framework of isochronous surfaces which often cut across facies boundaries and thus to interpret in detail the palaeogeographic sedimentological and diagenetic evolution of the purbeckian peritidal carbonate environments

planktonic foraminiferal biostratigraphy microfacies analysis sequence stratigraphy and sea level changes across the cretaceous paleogene boundary in the haymana basin central anatolia turkey abstract the cretaceous paleogene k pg boundary in the haymana basin central anatolia turkey was delineated using planktonic foraminiferal biostratigraphy microfacies analysis and sequence stratigraphy an 29 m outcrop consisting of limestone and marl was measured and four planktonic foraminiferal biozones were identified spanning the boundary planktonic foraminiferal extinction across the k pg boundary was catastrophic and abrupt the extinction level is overlain by a unit zone p0 showing an increase in echinoid fecal pellets and authigenic clay minerals such as glauconite suggesting low sedimentation rates in the early danian ten microfacies types were identified indicating inner ramp to basinal paleoenvironments based on the sedimentological characteristics and microfossil and macrofossil assemblages maastrichtian carbonates contain large benthic foraminifera calcareous red algae bryozoans fragments of echinoderms and mollusks and planktonic foraminifera overlying maastrichtian danian silty marls and silty limestones have common planktonic and benthic foraminifera progradation of carbonates into the basin took place during the highstand systems tract and deposition of a silty marl succession occurred during the transgressive systems tract the k pg boundary is in the upper part of the transgressive systems tract below a maximum flooding surface sequence stratigraphic analysis of a second section campo pit new jersey usa showed that the k pg boundary occurs within a transgressive systems tract in new jersey as well suggesting a global sea level rise across the k pg boundary

reply to the seismic imaging of melanges pieniny klippen belt case study discussion we welcome the discussion by jurewicz et al 2020 whose main criticism focused on the fact that the authors main conclusions contradict the results of previous studies however this statement refers perhaps to the geological setting since we are not aware of any previous studies providing seismic imaging of melanges in the pieniny klippen belt pkb we did not consider the critical remarks by plasienka et al 2017 because we believe that sufficient answers were provided by golonka et al 2017 we are grateful to jurewicz et al 2020 for pointing out the erroneous term tectonic olistolith that we will correct it in future work the discussion is based on two sets of problems regional geology and interpretations of seismic data

brachiopod geochemical records from across the carboniferous seas of north america evidence for salinity gradients stratification and circulation patterns abstract stable isotopic analyses of 100 well preserved carboniferous brachiopod shells representing two time slices from across north america reveal systematic regional changes in environmental conditions for both of the time slices studied the chesterian latest mississippian and the virgilian latest pennsylvanian 18o and 13c show a stepwise decrease moving across the continent from modern day west to east higher 18o in the west reflects greater water depths less freshwater input and more direct upwelling influence from cool open marine waters than in the east modelling based on these regional isotopic data indicates salinity reductions on the order of 1 4 psu in the appalachian basin relative to the midcontinent basin for the virgilian time interval over a range of reasonable thermal gradient and 18ofw assumptions the magnitude of this gradient is similar to those of modern day hudson bay and the panama bight which exhibit permanent haloclines driven by freshwater discharge considering existing paleoecological evidence for freshening the lack of more dramatic benthic freshening suggests that the depth of a regional halocline was shallower than the depths inhabited by thick shelled stenotopic brachiopods although other lines of evidence are necessary to verify the strength of the halocline estimated 18o temperatures for appalachian basin brachiopods are 3 5 c cooler than those of coeval conodonts due to either slightly warmer fresher surface waters or uncertainty in the phosphate 18o paleothermometer despite discrepancies in calculated temperatures the magnitude of the regional isotopic gradient derived from brachiopod and conodont proxies is similar after making appropriate glacioisotopic and water depth corrections a decreasing 13c trend toward the east southern paleolatitude likely reflects greater restriction and terrestrial influence near the sea s tropical shoreline trace element trends are less consistent and are affected by species and metabolism erratic variations in mg ca concentrations even among pristine samples of the same genera with similar 18o values and unrealistic mg ca derived temperatures justify continued caution in applying existing mg ca thermometer equations to paleozoic brachiopods

walchian conifers from the mid late pennsylvanian conemaugh group in the appalachian basin stratigraphic and depositional context and paleoclimatic significance abstract walchian conifers are indicators of seasonally dry habitats of the euramerican subtropics and tropics and are of considerable value in tracking both short term and long term pennsylvanian permian paleoclimatic changes in central pangea walchian conifer macrofossils first appeared in north america during the middle pennsylvanian but are rare in central pangean coal basins until the permian an abrupt climate change occurred near the desmoinesian missourian boundary that was characterized by global warming stronger seasonality and shorter wet phases this change coincided with the regional extinction of most tree lycopsids and the appearance of widespread high chroma calcic vertisols and aridisols only four occurrences of walchia have been reported from the pennsylvanian of the appalachian basin 1 7 11 mine of eastern ohio 2 rennersville in southwest pennsylvania and 3 charleston and 4 cedar run both in southern west virginia this paper uses recently acquired outcrop data to more fully document and reevaluate the depositional and stratigraphic context of the west virginia assemblages and their paleoclimatic and paleogeographic implications the cedar run walchia assemblage occurs in olive mudshale of an abandoned fluvial channel fill 15 8 16 9 m above the base of the ames limestone indicating an early virgilian age it consists of compressions and impressions of branches and branchlets of walchia lepidophylloides cordaites and rare neuropteroid pinnules the channel fill at this location is a component of the grafton sandstone incised valley fill previously described from the study area correlation of paleosol bounded marine cored cyclothems in the study area with their nonmarine cyclothem equivalents at charleston west virginia indicates the walchia previously reported at the mahoning coal horizon occurs between the brush creek and bakerstown coals and is therefore missourian not late desmoinesian and similar to the revised age for the 7 11 mine walchia reported from eastern ohio late pennsylvanian upland or dryland conifer communities were comprised of walchia cordaites and sigillaria which produced a forest with seed ferns as an understory the cedar run assemblage was probably transported into the valley from adjacent well drained coastal plain uplands formed during valley incision and deposited within the early transgressive systems tract it is also possible that walchia expanded into the valleys when drainage became ephemeral during more arid climatic phases the revised correlations of appalachian basin walchia horizons indicate their appearance closely followed rather than predated the abrupt climate change and extinctions at the desmoinesian missourian boundary

depositional environments and sequence stratigraphy of the late carboniferous early permian coal bearing successions shandong province china sequence development in an epicontinental basin abstract this study focuses on the late carboniferous early permian coal bearing successions in shandong province north china in order to understand the depositional processes and sequence stratigraphic framework in an epicontinental basin based on detailed analysis of eleven facies five facies assemblages fas were recognized in the studied succession fa1 3 are present mainly in the benxi and taiyuan formations and consist of mixed siliciclastic and carbonate lithofacies representing eluvial lagoon barrier lagoon and tidal flat environments fa4 occurs in the shanxi formation and consists mainly of interbedded medium to fine sandstone siltstone mudstone and coal lithofacies representing river dominated deltaic environments fa5 is characterized by interbeds of trough cross stratified coarse sandstone and silty mudstone mainly in the lower shihezi formation which was deposited in meandering river channel and floodplain three third order sequences were established based on the vertical arrangement of facies assemblages and identification of physical surfaces i e subaerial unconformity transgressive surface and regressive surface each sequence comprises a transgressive systems tract tst and a highstand systems tract hst tst of sequence 1 is composed of eluvial lagoonal deposits fa1 whereas hst formed in lagoon barrier and tidal flat settings fa2 and fa3 tst of sequence 2 formed in a barrier lagoon system fa2 whereas hst is characterized by repetitive accumulation of interbedded limestone sandstone mudstone and coal deposited under lagoonal and tidal flat settings fa2 and fa3 tst of sequence 3 comprises fa2 and hst mainly fa4 deposited in a river dominated shallow water delta system sequence 3 is overlain by a fluvial sequence fa5 the three third order sequences in the shandong region are generally correlated with those in the taebaeksan basin south korea the eastern part of the north china block the relative sea level curves established in the two regions show a generally similar long term rising trend

record of glacial eustatic sea level fluctuations in complex middle to late pennsylvanian facies in the northern appalachian basin and relation to similar events in the midcontinent basin abstract pennsylvanian cycles in the northern appalachian basin nab were historically considered to result from delta lobe switching and more recently from sea level fluctuation with sandy deltas prograding during highstand these interpretations are revised using new data from cores and outcrop exposures thick 5 m channel deposits with a marked erosion surface at their base cutting down across previous cycles are re interpreted as incised valley fill ivf deposits in paleovalleys because the basal erosion surfaces are widespread and thus reflect a record of lowstand most common are simple paleovalleys that contain mainly sandy fluvial deposits compound paleovalleys with sequence boundaries above the basal erosion surface contain terrestrial estuarine and marine deposits early to late highstand deposits in interfluvial parts of the cycles are dominated by shale and mudstone with paleosols coals and local non marine limestone which reflect floodbasin to lacustrine conditions these reinterpretations are applied to previously and newly recognized cycles in ascending order upper kittanning lower freeport upper freeport leader new upper freeport piedmont new mahoning mason interval locally includes upper new galilee in the north and brush creek across a 300 km arc in the northern appalachian basin these deposits accumulated in a high shelf setting that experienced fewer marine transgressions and were interrupted by more frequent exposure and downcutting in contrast to the thicker and more complete succession with more numerous marine units in the midcontinent magnitudes of highstand transgressions into this basin deduced from the up dip extent of marine and brackish fossil assemblages were greatest for the brush creek less so for the upper kittanning and mahoning and least for the lower freeport upper freeport leader piedmont and mason the anomalous basin wide fresh water roofshales and equivalents of the upper freeport coal may reflect ponding of fresh water to the north by an elevated area that prevented marine encroachment at the southern opening of the basin along the kentucky ohio border maximum thicknesses of ivf deposits in each cycle are used as a proxy for estimating the minimum depth of lowstand incision preceding transgression while the thickness of ivf deposits in most cycles ranges from 6 to 20 m the two thickest are 30 m thick one associated with the pre mahoning paleovalley and the other with the immediately post mahoning paleovalley the extent of transgression of each cycle in the nab is roughly equivalent to those of their age correlative major marine cyclothems pawnee through swope in the midcontinent moreover the amount of incision between them is also roughly equivalent to the amount of regression between each of the roughly coeval cyclothems in the midcontinent with the deepest incisions in the nab pre mahoning and post mahoning corresponding to the greatest southward withdrawals of the sea in the midcontinent memorial and seminole hepler during this same interval

tracing the interaction of acid mine drainage with coal utilization byproducts in a grouted mine strontium isotope study of the inactive omega coal mine west virginia usa abstract in order to ameliorate acidic discharge the inactive omega coal mine west virginia was partially filled by injection of a grout consisting of 98 coal utilization byproducts cub including fluidized bed combustion ash and fly ash and 2 portland cement in this study discharge chemistry and sr isotope ratios were determined to identify and quantify the extent of interaction between mine waters and the cub cement grout eight sampling sites were monitored around the downdip perimeter of the mine the major and trace element chemistry of the discharges was generally not sufficient to distinguish between discharges that interacted with grout and those that did not elements that showed the most separation include k and as which were elevated in some waters that interacted with cub cement grout in contrast the sr isotope ratios clearly distinguished discharges from grouted and non grouted areas discharges that bypassed the grouted portions had 87 sr 86 sr ratios ranging from 0 71510 to 0 71594 while two discharges that interacted with grout had ratios in the range of 0 71401 0 71456 the treatment inlet which includes both grouted and ungrouted discharges yielded intermediate isotopic ratios leaching experiments on cub cement grout coal and surrounding rocks are consistent with the isotopic trends observed in the discharges based on these results waters that interacted with grout received 30 40 of their sr from the cub cement grout material these results suggest that the grout material is chemically eroding at a rate of approximately 0 04 per year this novel application of the sr isotope system illustrates its ability to sensitively track and quantify fluid interaction with coal and cub based grout

cyclicity in the middle eocene cayraz carbonate formation haymana basin central anatolia turkey abstract the haymana basin in central anatolia turkey developed on a fore arc accretionary wedge during the late cretaceous and the middle eocene turbidite deposits fill the center of the basin and grade northwestward into shallow marine clastics and carbonates which in turn pass into lacustrine and fluvial deposits toward the margin the middle eocene cayraz formation represents the youngest paleotectonic unit of the haymana basin it is composed of two shelf systems ss each formed by a package of nummulitic banks and intervening calcareous mudstones 150 250 m thick overlying 70 100 m thick monotonous mudstones within each of the two shelf systems two orders of coarsening upward and shallowing upward sequences are recognized the smaller order sequences 3 10 m thick are termed basic units bu four types of basic units have been distinguished these are made up of either calcareous mudstone overlain by a nummulitic bank or silty mudstone overlain by sandy to conglomeratic beds each basic unit represents a specific depositional environment ranging from quiet lagoon or open marine to more energetic bank or sandy bar basic units are vertically associated to form three types of 15 35 m thick basic sequences bs which represent the time and space evolution of the shelf systems owing to their small scale their lateral association and the condensed nature of their bounding surfaces basic units are considered to be allocyclic transgressive regressive cycles tuned to milankovitch bands at the scale of basic sequences bs and shelf systems ss the lateral and vertical distribution of the sequences and the presence of onlap structures strongly suggest sea level changes the sequential organization thicknesses of basic units and basic sequences and an estimated sedimentation rate favour sea level changes controlled by milankovitch climatic cycles amalgamation or condensation of basic units in basic sequences and the existence of locally accentuated onlaps suggest a coupled effect of discontinuous subsidence

sedimentary cyclicity in the marine pliocene pleistocene of the wanganui basin new zealand sequence stratigraphic motifs characteristic of the past 2 5 m y earth s climatic history since 2 5 ma has been controlled by milankovitch variations in the planetary orbit comprising alternate periods of glaciation and interglaciation with a dominant frequency of 41 000 yr concomitantly eustatic sea level has fluctuated 70 to 130 m causing rapid transgressions and regressions of the shoreline across the world s continental shelves the resulting sedimentary record is cyclothemic each cyclothem corresponding to a single climate and sea level cycle the wanganui basin new zealand contains a 2 km thick almost complete composite record since isotope stage 100 ca 2 5 ma in the form of 47 superposed cyclothems of shelf origin each cyclothem corresponds to an unconformity bound stratigraphic sequence and typically contains a transgressive systems tract sometimes a mid cycle shell bed a highstand systems tract and sometimes a regressive systems tract no advantage accrues from using transgressive regressive units rather than cyclothems and or sequences in description of the succession six basic sequence motifs represent deposition in locations between the shoreline and offshore shelf i e the hawera birdgrove turakina seafield castlecliff and rangitikei motifs a seventh the nukumaru motif which includes dominant coquina limestone represents deposition in shallow water areas of reduced terrigenous sediment on the flank of the basin the sequence motifs represented in any section change systematically in sympathy with basin scale changes in subsidence and sediment supply in contrast with the 41000 year length of individual glacioeustatic sequences these basin wide tectonic cycles have a periodicity of many hundreds of thousands to a few million years i e that of third or fourth order sequences of the exxon type this coupled with the restriction of strongly cyclothemic sediments to geological periods of known glacio eustasy permiancarboniferous pliocene pleistocene suggests that tectonic subsidence cycles rather than glacio eustasy are the driving forces behind the development of the third and fourth order unconformity bound sequences that are reported to occur throughout the stratigraphic record

sedimentary environment dynamics and the formation of coal in the pennsylvanian variscan foreland in the ruhr basin germany western europe during the pennsylvanian formation of coal was a phenomenon that was spread over many continents it is the aim of this paper to illustrate factors that led to the formation of coal seams in paralic clastic sedimentary environments in the ruhr basin german variscan foreland during the pennsylvanian in terms of sequence stratigraphy and the structural evolution of the basin lithostratigraphic sections from exploration wells in the currently explored zone of the coal basin allowed the generation of volumetric lithofacies models using geostastical methods these models support the analysis of sedimentary facies and a sequence stratigraphic interpretation of the successions that are widely correlated throughout the basin we then evaluate the relation of the sequence stratigraphic elements derived from the facies models with the abundance of coal seams

holocene book reviews global climates since the last glacial maximum edited by h e wright jr j e kutzbach t webb iii w f ruddi man f a street perrott and p j bartlein minneapolis university of minnesota press 1993 569 pp us 59 95 hardback isbn 0 8166 2145 4 distributed in the uk by university college london press 1994 50 00 hardback

depositional controls in a bedload dominated fluvial system internal architecture of the lee formation kentucky abstract sandstones of the early pennsylvanian lee formation central appalachian foreland basin were deposited in a low sinuosity bedload dominated fluvial system the internal architecture of the sandstones consists of a six fold hierarchy of bounding surfaces which are evaluated with respect to depositional controls minor first second and third order surfaces generally less than a few hundred meters in extent separate deposits of small to intermediate scale bedforms third order surfaces which dip gently in the downflow direction represent reactivation surfaces of downstream accreting macroforms major surfaces fourth fifth and sixth order are hundreds of meters to kilometers in extent fourth order surfaces separate deposits of individual macroforms fifth order bounding surfaces are erosional boundaries of major system scale channels individual sandstone members of the lee formation are bound by sixth order surfaces erosional at the base and gradational at the top deposits overlying major surfaces contain fining upward sequences the trends are more apparent with increased scale of the deposit these sequences represent responses of the fluvial system to various mechanisms that controlled sedimentation both fourth and fifth order surfaces are interpreted as results of autocyclic controls the nature of the lee formation fluvial system was such that a solitary major channel was relatively stable in one position within the alluvial plain for a significant period of time during this time the channel aggraded with the passage of one or more downstream accreting macroforms creating a fourth order erosional surface the channel eventually diverted its flow to another portion of the alluvial plain by avulsion creating a fifth order surface a gross fining upward trend and upward change in fluvial style for individual sandstone members both characteristic of paleovalley fills indicate that sixth order surfaces were controlled by allocyclic processes these characteristics and the stair step positioning of the sandstone members younger away from the alleghenian mountains to the east suggest that tectonic processes were the ultimate control on the system

correlation of carboniferous strata using a hierarchy of transgressive regressive units carboniferous strata can be described interpreted and correlated using six scales of allocyclic transgressive regressive t r units these t r units are inferred to be the net result of deposition during cycles of sea level change all pennsylvanian and lower permian strata constitute one second order t r unit or synthem the pennsylvanian system contains third fourth fifth and sixth order t r units that can be correlated across both marine and nonmarine facies in the appalachian basin this permits differentiation of allocyclic t r units from autocyclic t r units or fluvial autocyclic units the hierarchical approach is also useful for predicting the location of marine horizons coals claystones and various types of stratigraphic breaks a hierarchical scheme of allocyclic t r units could be combined with biostratigraphic radiometric and magnetostratigraphic data to form a practical chronostratigraphic framework for the carboniferous

earthquakes recorded stratigraphically on carbonate platforms the longest records of earthquake activity1 may be preserved near the edges of carbonate platforms where reefs have bordered active faults because the carbonate sediments build up almost to low tide level because their character and lithification are very sensitive to deviations from that datum and because they commonly lithify soon after deposition2 strata can precisely record changes in lithospheric flexure3 which in turn record the buildup and release of elastic strain energy during stick slip faulting the approximate stratigraphy is predictable for a given history of faulting comparison of predictions with observations leads to an explanation for some of the hemicyclic sedimentary sequences common4 6 on carbonate platforms these records are important for characterizing the seismicity of atlantic type continental margins in general after rifting faults evidently remain active7 but major earthquakes are so rare that their recurrence times cannot be established from direct observations

the upper mississippian bluefield formation in the central appalachian basin a hierarchical sequence stratigraphic record of a greenhouse to icehouse transition abstract the upper mississippian chesterian bluefield formation is the basal unit of the predominantly siliciclastic mauch chunk group in the appalachian basin this formation developed in a northeast southwest oriented foreland trough fronting the alleghanian highlands to the southeast regional cross sections and isopach maps of the bluefield formation in southeastern west virginia southwestern virginia and southeastern kentucky define a depocenter in the southeastern part of the study area and a paleovalley system along the basin margin to the northwest at most localities facies that make up the bluefield formation are stacked into 1 15 m thick upward shallowing parasequences each of which is capped by a flooding surface these parasequences are stacked into four regionally correlatable depositional sequences on the margins of the depocenter incised valleys and fewer meter scale parasequences characterize the depositional sequences stacking of parasequences into sequences reflects a hierarchy of greenhouse type fifth order and icehouse type fourth order sea level cycles superimposed on a differential subsidence history related to early alleghanian thrust loading the bluefield depocenter experienced greater total accommodation which prevented incision during lowstands instead lowstands are typified by preservation of fifth order coal bearing parasequences in the depocenter basin margin areas experienced less total accommodation which resulted in development of fourth order lowstand valleys and erosion of parasequences this study demonstrates that both tectonic and eustatic forcing mechanisms controlled stratigraphic evolution of the bluefield formation

the lower triassic cyclic deposition in chaohu anhui province china abstract the lower triassic strata developed in chaohu anhui province of east central china including the yinkeng helongshan and nanlinghu formations is about 268 m thick and consists of carbonate rocks such as micrite limestone and nodular limestone as well as shale and argillaceous mudstone the deficiency of sedimentary structures and bioclastic particles and presence of pyrite and high ratios of v v ni suggest that the lower triassic strata formed in a quiet open marine basin environment bordering carbonate slope and lower slope within the lower triassic the cyclic deposits include two orders of thickening and coarsening upward successions respectively called basic unit bu and basic sequence bs which represent shallowing upward cycles five basic units are recognized and they are mostly composed of shale argillaceous mudstone calcareous mudstone and nodular limestone and overlying nodular limestone and micrite limestone about 0 25 1 4 m thick the shale and mudstone mainly formed in a deep water basin and the nodular limestone and micrite limestone formed on the rise of basin margin or the base of slope thus the basic units are interpreted to reflect cyclic sedimentation from the deep water basin to the rise of basin margin or from the rise to base of slope the basic units are combined with medium to thick bedded micrite limestones and thus form four types of basic sequences average 6 5 14 62 m thick likewise they are interpreted to be shallowing upward cycles with long period for example from the deep water of basin through the rise of basin margin to the base of slope farther reaching to lower slope the various orders of cycle in the lower triassic are laterally very extensive regionally which suggests that the fluctuation of sea level was likely a control on the origin of the cycles these small scale transgressive regressive cycles possibly reflect milankovitch cyclicity the associations of basic sequences constitute two transgressive regressive cycles which comprise strata of yinkeng helongshan and nanlinghu stages respectively which is similar to the carbon isotope cycles of the lower triassic tectonic activities can control the origin of the cycles the collision of south china block and north china block in the lower middle triassic may have resulted in the development of the two cycles and caused the shallowing upward sequence of the lower triassic from deep water basin to slope

composite sequence stratigraphic patterns in alluvial to shallow marine successions examples from the piacenzian of the valdelsa basin central italy abstract the sequence stratigraphic analysis of continental and shallow marine successions is a helpful tool for investigating the cyclicity of the sedimentary record a similar approach is adopted in the present study to illustrate the composite cyclothemic facies architecture that characterizes the piacenzian strata of the southern valdelsa basin central italy specifically we integrated facies analysis paleopedology paleobiology of marine mollusk assemblages and biostratigraphy to assess the response of geomorphic sedimentary and biotic systems to piacenzian multifrequency relative sea level fluctuations this integrated approach resulted in the definition of a composite sequence stratigraphic framework that includes a hierarchy of units ranging from the elementary to the composite depositional sequences referred to the 5th to 3rd order cycles of sea level fluctuations respectively a correlation with the piacenzian oxygen isotopic signature of glacial and interglacial stages and related sea level fluctuations associates the cyclic development of fluvial coastal and shallow marine depositional systems to the mid piacenzian warm period and to the subsequent transition to the gelasian thus the glacio eustatic control prevailed on the development of the described multi scale cyclical pattern of sedimentation compared to the role played by the deformation of the northern apennines orogen

periodicity of mesoscale phanerozoic sedimentary cycles and the role of milankovitch orbital modulation data on more than 200 mesoscale sedimentary cycles indicate that phanerozoic cycle periods are randomly distributed with respect to the four major milankovitch orbital parameters except late mississippian through late pennsylvanian cycles which show positive clustering about the 413 000 yr eccentricity period cycle periods calculated from average thicknesses and accumulation rates are strongly dependent on the former correlation coefficient 0 802 but relatively independent of the latter correlation coefficient 0 360 hence calculated period is largely a function of average cycle thickness and milankovitch range periods will be preferentially calculated for cycles with average thicknesses between 1 m and 20 m regardless of actual causes of cyclicity for individual cyclic sequences arguments for milankovitch control based solely on average period are unfounded comparison of short term holocene sedimentation rates and long term phanerozoic accumulation rates for cyclic peritidal and delta

discussion of olistostromes of the pieniny klippen belt northern carpathians d plasienka j michalik j sotak r aubrecht comment in their recent paper golonka et al 2015 described the cretaceous and palaeogene olistostromes and other types of mass transport deposits occurring within the pieniny klippen belt pkb of the western carpathians after a short introduction into the olistostrome concept and an overall description of the pkb structure the authors presented their views on the composition and evolution of the pkb with olistostromes as the leading phenomenon although novel in some aspects the model they present is largely oversimplified and partly erroneous in our opinion in the following we shall comment on the several most disputable statements and interpretations offered in the discussed paper

cyclicity in the middle eocene yamak turbidite complex of the haymana basin central anatolia turkey the haymana basin in central anatolia turkey formed on a late cretaceous to middle eocene fore arc accretionary wedge a sequential model is proposed for the 1 km thick lutetian yamak turbidite complex ytc which is the youngest paleotectonic unit of the basin the ytc represents a prograding submarine fan subdivided into three depositional sequences ds each several hundred meters thick each depositional sequence consists of a turbidite system ts with sandstone and conglomeratic sandstone beds alternating with mudstones overlain by basin plain mudstones in each turbidite system the sandstone and mudstone sequential organization allows the distinction of smaller subdivisions namely basic sequences bs and basic units bu with each basic sequence being composed of several basic units this subdivision associated with a two dimensional geometric reconstruction of the ytc leads to a better understanding of the evolution in time and space of the submarine fan system lower to middle fan depositional lobes and upper fan and slope channels are represented as a whole the ytc progressed from a sand poor to a sand rich system depositional sequences ds of the ytc may correspond to third order sea level cycles of tectonic origin accordingly fourth and fifth order cycles might be proposed for the bs and bu respectively however partly because of the limited extent of exposures the allocyclic origin of these finer subdivisions remains problematic

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

episodic accumulation and the origin of formation boundaries in the helderberg group of new york state at any single locality in the helderberg group of new york state most formation and member boundaries coincide with boundaries of punctuated aggradational cycles in each case of coincidence the boundary is a discontinuity that was produced by a rapid rise of relative base level rather than a facies contact representing gradual migration of contiguous paleoenvironments apparently diachronous formation boundaries in the sequence are not single continuous surfaces instead each diachronous boundary is actually a stratigraphic series of isochronous surfaces that are separate punctuated aggradational cycles pac boundaries produced by distinct geologically instantaneous base level rises these conclusions about the origin of formation boundaries suggest that the concept of the formation as a fundamental unit of stratigraphic description and interpretation may need revision if the stratigraphic record accumulated episodically on a small scale

facies sequences on a carbonate ramp the carboniferous limestone of south wales during early carboniferous times a major sea level rise led to the development of an extensive carbonate ramp over what is now south wales differential subsidence and sea level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho tectonic settings inner mid and outer ramp the inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence the sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments the peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing up cycles the sequence contains many subaerial breaks and tectonic uplift resulted in base level changes and fluvial incision the mid ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base sedimentation periodically exceeded sea level rise and subsidence and regressive progradational oolitic sand bodies developed the thickest of which are stacked units with up to four individual sand bodies storm processes were of major importance in this setting the outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major waulsortian reef mounds also developed none of the shallowing phases seen in the other ramp zones can be detected in this sequence subsidence and eustatic sea level rise seem to have been the major controls on deposition but the recognition of eustatic sea level falls is difficult the detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record

the effects of out of plane seismic energy on reflections in crustal scale 2d seismic sections abstract crustal scale seismic surveys mostly collect data along single profiles and the data processing has an underlying assumption that the data have imaged two dimension 2d structure striking at right angles to the seismic profile however even small amounts of out of plane topography on a reflector can result in reflections that do not map the reflector shape accurately out of plane energy will migrate within the plane of the section to an apparent depth represented as two way time twt that is greater than the depth of the reflection point out of the plane of the section it will fall within the plane of the section at depths less than equal to or greater than the intersection of the reflector with the plane of the section depending on both the amount of out of plane topographic relief on the reflector and the offset of the topographic relief from the plane of the section reflectors that are a single surface can therefore be manifested in the seismic section as a band of several reflections rather than a single reflection more complex reflectors such as shear zones that have a finite thickness because they are made up of several to many anastomosing layers of altered and anisotropic rock embedded in protolith will appear as laterally short reflections within a laterally continuous reflection band other examples of such reflectors would be the moho in some places and rock with compositional layering with increasing out of plane topographic relief on the reflector the top of the reflection band for both single and multi layer reflectors will be a poor indicator of the top of the reflector in the earth the bottom of the reflection band will always be a poor indicator of the bottom of the reflector because out of plane energy can arrive at twts that are different from those of the reflector in the plane of the section out of plane energy has the potential to interfere constructively or destructively with the in plane energy in synthetic data calculated for a simple model assuming one layer and topographic relief of 250 m over wavelengths of 4 5 km similar to that imaged in a real sub horizontal detachment amplitudes ranged up to 2 6 times the expected amplitude for the layer a model with anastomosing layers built to resemble a thick shear zone rather than a discrete fault surface allowed tuning between layers the effects of out of plane energy when combined with the effects of tuning caused amplitudes up to 3 1 times those expected larger amplitudes could be achieved if a suitable model was contrived the results indicate that care must be taken when calculating impedance contrasts using real data the highest amplitude reflections are likely to yield overestimates of the true impedance contrast

sequences cycles and basin dynamics in the silurian of the appalachian foreland basin abstract field stratigraphic analysis of the early and medial silurian strata of ontario new york and pennsylvania permits recognition of six major sequences reflecting 3rd order cycles in the niagaran llandoverian ludlovian of new york and adjacent regions these sequences correspond approximately to the medina lower clinton middle clinton upper clinton two sequences and lockport groups each is bounded by widespread unconformities produced by the interplay of eustatic sea level drop and local tectonic uplift in general erosional sequence boundaries and transgressive surfaces are merged with no record of the lowstand wedge each sequence is subdivisible into two to five sub sequences that are marked by sharp though generally non erosional basal discontinuities investigation of the clinton and lockport groups corroborates earlier suggestions that carbonate and siliciclassic tongues extended basinward from opposite margins synchronously in response to sea level drops analysis of the thickness and basinward extent of the progradational tongues reveals the existence of multi scale sedimentary cycles sequences and component sub sequences are correlative basinwide and are synchronous within the resolution of bio and event stratigraphy major drops in relative sea level are represented by the sequence bounding discontinutiies these surfaces are overlain by siliciclastic wedges near terrigenous source areas or winnowed carbonate pack and grainstones on the tectonically passive margin overlying highstand deposits typically shales calcareous mudstones and limestones are separated from lowstand or transgressive deposits by thin condensed intervals commonly marked by phosphatic or glauconitic material and or surfaces of maximum sediment starvation the relative highstand deposits of sequences and sub sequences are developed in relatively deep water facies and are at most slightly progradational hence most sequences and sub sequences are sharply bounded roughly upward deepening to slightly shallowing successions of strata in turn sub sequences are further divisible into widespread minor parasequences and parasequence sets probably corresponding to 6th and 5th order cycles respectively the smaller scale units 0 2 5 mthick commonly display an upward shallowing motif the nested relationship of these cycles supports the hierarchical model of transgressive regressive allocycles proposed by busch and rollins 1984 niagaran cycles discussed herein are equivalent to third fourth and fifth order cycles and are traceable circumbasinally depocenters of successive sequences and sub sequences display a pattern of eastward westward eastward basin axis migration through the silurian during early llandoverian the taconic queenston deltaic complex began to subside and the basin axis depocenter and eastern shoreline shifted eastward approximately 200 km over a 6 million year period as the basin axis migrated eastward the western basin ramp forebulge was repeatedly upwarded and eroded resulting in the generation of regionally angular unconformities at the bases of sequences ii iv and vi the pattern of unconformity greatest to the west suggests rise of the algonquin arch concomitant with eastward basin axis migration during the late llandoverian to early wenlockian the algonquin arch subsided slightly concurrently with a reversal in direction of basin axis migration during deposition of upper clinton and lockport vernon strata sequences v vi the basin axis shifted approximately 300 km back to the west eastward migration of the basin axis corresponds with a time of tectonic quiescence and probable thrust load relaxation the abrupt reversal of migration in the late llandoverian may be a signal of renewed thrusting in the hinterland at the onset of the salinic disturbance

thrust ridge paleodepositional model for the upper freeport coal bed and associated clastic facies upper potomac coal field appalachian basin u s a abstract a blind thrust ridge model is proposed to explain the lack of coarse clastic material in the vast minable upper freeport coal bed uf this coal bed contains only fine elastic partings and is overlain by regionally extensive closely spaced channel belt deposits in the upper potomac coal field of the appalachian basin a blind thrust ridge may have formed a sediment trap and prevented c coarse fluvial sediments from entering the swamp during a period westphalian d when the thick upper freeport peat accumulated anticlinal thrust ridges and associated depressions may have existed uninterrupted for about 40 km parallel to the appalachian orogen sediment shed from the breached anticlinal ridges accumulated in the sediment trap and was carried out of the ends of the trap by streams that occupied the shear zone at the ends of the blind thrust ridge the extent parallel to the orogen of thick areally extensive uf is related to the length of the blind thrust ridge that in turn controlled the spacing of the river derived coarse clastic sediments that entered the main basin from the east the thrust plane eventually emerged to the surface of the blind thrust ridge and peat accumulation was terminated when the ridge became eroded and the sediment trapped behind it was released the peat was buried by abundant coarse clastic sediment which formed closely spaced channel belts and intervening flood basins this model has implications for widespread peat deposits now coal that developed in tropical regions a few hundred kilometers from the sea in a tectonically active foreland basin

punctuated aggradational cycles a general hypothesis of episodic stratigraphic accumulation according to the hypothesis of punctuated aggradational cycles presented here the stratigraphic record consists of small scale 1 5 m thick shallowing upward cycles pacs separated by surfaces marked by abrupt change to deeper facies this motif pervasive in time and environment is produced by relatively long periods tens of thousands of years of base level stability punctuated by geologically instantaneous relative base level rises of at least basin wide extent as basin wide lithologic time stratigraphic units pacs are fundamental to all aspects of stratigraphic analysis including correlation paleoenvironmental interpretation and paleogeographic reconstruction of several possible allogenic mechanisms for a pervasively cyclic stratigraphic record glacial eustasy driven by orbital perturbations is preferred the pac hypothesis is presented as a comprehensive model to be tested and modified by examination of the stratigraphic record from an episodic perspective