depositional history and sequence stratigraphy of the precambrian cambrian boundary stratotype section chapel island formation southeast newfoundland abstract facies relationshps in the vendian to lower cambrian chapel island formation of southeast newfoundland are used to establish a sequence stratigraphic framework for this important boundary stratotype section the formation consists of five members of sandstone mudstone and minor limestone deposited in a variety of shoreline to shelf environments peritidal sandstone and shale units in member 1 are overlain by sandstone and silstone deltaic and shelf deposits of member 2 these make up a transgressive system tract in which small scale changes in relative sea level are superimposed on autocyclic deltaic processes the thickness 400 m of nearshore and inner shelf sediments resulted from high sediment accumulation rates which for member 2 nearly kept pace with subsidence upper member 3 and member 4 consist of inner shelf mudstone and peritidal limestone that were deposited in a low energy oxygen stratified basin these deposits are arranged in three large scale shoaling cycles representing three foresteping parasequences of one highstand systems tract an extensive limestone bed at the tope of member 4 contains a sequence boundary associated with or shortly postdating development of this surface is a significant epeirogenic event that resulted in basin reorganization increased subsidence and progradation of a thick clastic sequence represented by member 5 the deposits of this upper member consist of an upward coarsening storm dominated shelf to shoreface succession of sandstone and silstone deposits of nearly identical character are also found in new brunswick and suggest that these sediments and the underlying sequence boundary could be significant for interregional correlation global correlation of the paleobathymetric curve developed for the chapel island formation is considered unfeasible given the long history of epeirogenic movements during the vendian and early cambrian in this region

impact of relative sea level and rapid climate changes on the architecture and lithofacies of the holocene rhone subaqueous delta western mediterranean sea abstract the modern rhone delta in the gulf of lions nw mediterranean is a typical wave dominated delta that developed after the stabilization of relative sea level following the last deglacial sea level rise similar to most other deltas worldwide it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation sediment supply and autogenic processes on the architecture of a wave dominated delta the interpretation of a large set of newly acquired very high resolution seismic and sedimentological data well constrained by 14c dates provides a refined three dimensional image of the detailed architecture seismic bounding surfaces sedimentary facies of the rhone subaqueous delta and allows us to propose a scenario for delta evolution during the last deglaciation and holocene the subaqueous delta consists of parasequence like depositional wedges a few metres to 20 30 m in thickness these wedges first back stepped inland toward the nw in response to combined global sea level rise and overall westward oceanic circulation at a time when sediment supply could not keep pace with rapid absolute eustatic sea level rise at the younger dryas preboreal transition more rapid sea level rise led to the formation of a major flooding surface equivalent to a wave ravinement surface after stabilization of global sea level in the mid holocene accommodation became the leading factor in controlling delta architecture an eastward shift of depocentres occurred probably favoured by higher subsidence rate within the thick messinian rhone valley fill the transition between transgressive backstepping geometry and regressive prograding geometry para sequences resulted in creation of a maximum flooding surface mfs that differs from a classical mfs described in the literature it consists of a coarse grained interval incorporating reworked shoreface material within a silty clay matrix this distinct lithofacies results from condensation erosion which appears as an important process even within supply dominated deltaic systems due to avulsion of distributaries the age of the mfs varies along strike between ca 7 8 and 5 6 kyr cal bp in relation to the position of depocentres and climatically controlled sediment supply the last rapid climate change of the holocene the little ice age 1250 1850 ad had a distinct stratigraphic influence on the architecture and lithofacies of the rhone subaqueous delta through the progradation of two deltaic lobes in response to changes in sediment supply linked to rapid climate changes and to anthropic factors the rhone delta evolved from wave dominated to fluvial dominated and then wave dominated again

cambrian depositional history of the zanskar valley region of the indian himalaya tectonic implications a well preserved cambrian section in the zanskar valley of northern india has previously been interpreted to record the transition from a passive to an active tectonic margin related to cambrian ordovician orogenesis this interpretation has been used to support the tectonostratigraphic interpretation of other successions across the tethyan himalaya our detailed paleoenvironmental analysis significantly revises the tectonic and depositional history of these cambrian deposits no definitive record of impending cambrian ordovician orogenesis is recorded in these late middle cambrian rocks a critical transition from an 125 m thick stromatolite bearing carbonate deposit the karsha formation into shale and sandstone of the kurgiakh formation was interpreted to represent tectonically induced drowning of a carbonate platform siliciclastic strata of the kurgiakh formation were thought to record deep water flysch deposition in a tectonically active foreland basin next to an arc trench system this interpretation was based on sandstone beds with classic bouma sequences we show that these event beds in the kurgiakh instead contain hummocky cross stratification quasi planar lamination and combined flow ripple stratification all of which reflect deposition in shallow marine storm influenced environments thus although the karsha carbonate platform may have been drowned it did not culminate in deep sea flysch deposition and this in turn eliminates a major line of evidence linking kurgiakh deposition to the onset of cambrian ordovician orogenesis other aspects of cambrian ordovician deposits of northern india also shed doubt on the proposed link between kurgiakh sedimentation and the cambrian ordovician orogenic event first our improved biostratigraphic database suggests that the transition from the karsha carbonate to the kurgiakh formation may have predated the main phase of cambrian ordovician orogenesis as recorded by overlying ordovician molasse by as much as 20 30 my second published data from the ordovician molasse indicate northward paleocurrents which are parallel to those recorded by siliciclastic deposits of the parahio formation below the karsha and thus are at odds with standard models of foreland basin development for the cambrian ordovician event our sedimentological analysis of depositional cycles of the parahio formation indicates that these strata record storm influenced environments from offshore marine to shoreface to fluvial settings this is at odds with previous paleoenvironmental interpretations that ranged from deep sea flysch to intertidal deposits paleocurrent data for marine and fluvial facies of the parahio formation in both zanskar and the spiti valley to the south indicate northeast sediment transport this supports the view that the parahio and overlying carbonate of the karsha formation record the ancient northern passive margin of india during the cambrian and that these strata may be distal equivalents of the younger cambrian deposits of the lesser himalaya

paleoenvironmental analysis of the ichnogenus zoophycos in the lower devonian tempestite sediments of the longmenshan area sichuan china abstract the trace fossil zoophycos is characteristic of the lower devonian in the longmenshan area of southeastern china three distinct storm generated or induced types of sedimentary sequences bearing zoophycos have been identified in shallow marine deposits of the bailiuping formation and the yangmaba formation the type a deposit is composed of siltstones with shell concentrations and wave ripples and small zoophycos at the top the type b deposit is characterized by fine graded sandstone with long wavelength hummocky cross stratification and black gray mudstone as well as the largest and densest zoophycos at the top the type c deposit has graded bioclastic limestone with short wavelength hummocky cross stratification muddy wackestone and large zoophycos at the top based on the features of the types of zoophycos the distribution zone of the zoophycos ichnogenus that preserved in tempestite sequence was built between the fair weather wave base and storm wave base in the lower devonian this research suggests that the distribution patterns of zoophycos formed in storm induced deposits may not provide significant clues for the estimation of relative water depths the hydrodynamic conditions and sedimentation rate are two important environmental factors of the development of the zoophycos in the lower devonian shallow marine deposits where it was mainly affected by storms between the fair weather and storm wave bases the abundance of zoophycos at the top of locally frequent storm deposits could indicate a fairly opportunistic behavior and they were formed in the early hst deposit which had a relatively stable environment with low energy and higher sedimentation rate

origin of shore normal channels from the shoreface of sable island canada a suite of modern shore normal channels was discovered on the southern shoreface of sable island canada repetitive multibeam and sidescan surveys of these features as well as box coring and sampling showed that the depressions were perennial features of the shoreface they occurred in fine and medium sand and were most abundant in depths less than 20 m they were up to 1 m deep and 50 m wide increased in size seawards and generally followed the seabed slope the channels dominated the inner shoreface becoming wider and deeper seawards to depths in excess of 40 m there is a continuum of scales in width and depth of these channels the smallest of which are equated with gutters preserved in the geological record the internal structure of the shoreface sediments where the gutters are found is characterised by normally graded tempestites composed of cut and fill structures overlying an erosion surface thus the environmental setting internal structure and scale are similar to ancient counterparts gutters have been interpreted to result from downwelling over palaeo shorefaces during ancient storms myrow 1992b the composition of gutter infill as well as the stability evolution associated bedforms and hydrodynamic conditions under which they formed were examined to verify genetic interpretations of the ancient counterparts the multi sensor benthic lander ralph was deployed within a field of shore normal channels for 17 days during late winter 1998 ralph burst sampled flow at hourly intervals whilst imaging the seabed resulting sequential imagery revealed the genesis of a group of five gutters during storm spin down that was coincident with the formation of large scale wave ripples this was followed by infilling of the gutters and wave ripple destruction within 20 hours by longshore sand transport the gutters were located within and parallel to a larger channel 50 m wide and 0 50 m deep they were formed by coastal set up and subsequent downwelling that was triggered by the rotation of storm winds from seawards onshore wind to landwards offshore wind the gutters formed within 2 to 3 hours during spin down of a winter storm under live bed conditions of sand transport wave height and mean tidal flows were well below those of the storm peak and so they were not directly responsible for creating the gutters the mechanism we propose for the evolution of gutters supports the geological interpretations that is a storm driven downwelling event as described by swift and niedoroda 1985 however the downwelling event appeared to take place suddenly rapid acceleration in flow briefly few hours duration and within narrow corridors guided by wider and deeper channels of the shoreface high turbidity during the time of gutter formation leads us to believe that the phenomenon of inner shelf turbidity currents as suggested by walker 1985 exists and may be instrumental in channel formation

analysis of flute forming conditions using ice sheet reconstructions and field techniques basal shear stress and sediment strength associated with the development of glacial flutes exposed during the 20th century in the saskatchewan glacier valley alberta canada were determined by comparing reconstructed ice thicknesses basal shear stresses and field properties of sediments with the morphologically similar kiwa glacier valley british columbia canada where flutes are absent reconstructed subglacial conditions in these two valleys were compared to understand why flutes were developed in the former and not the latter using an existing topographic map of each glacier equations for a series of longitudinal profile lines were determined to represent the existing ice surface a previous ice surface identified by trimlines along the valley walls was reconstructed by applying the equations of longitudinal profile lines from the existing ice surface to a previous terminus between 5 and 10 km downvalley after subtracting the elevation of the land surface determined from topographic maps from the reconstructed glacier surface and calculating former ice surface slope ice thickness and basal shear stress distributions were determined sediment texture and the location of flutes on a morainal topographic high downglacier from a proglacial lake basin allowed high porewater pressures to develop as glaciers extended to terminus positions in the saskatchewan glacier valley sediment strength was reduced sufficiently below values of reconstructed shear stress plots to allow deformation creating flutes the absence of a similar topographic high and different sediment textural characteristics in the kiwa glacier valley resulted in lower porewater pressures and consequently less reduction in sediment strength preventing the development of glacial flutes despite higher shear stress values here results indicate that the degree to which sediment characteristics and porewater pressure allow reduction of subglacial sediment strength relative to basal shear stress is important in determining conditions when flutes may develop

effects of bioturbation on carbon and sulfur cycling across the ediacaran cambrian transition at the gssp in newfoundland canada the initiation of widespread penetrative bioturbation in the earliest phanerozoic is regarded as such a significant geobiological event that the boundary between ediacaran and cambrian strata is de

sedimentology and sequence stratigraphy of a pronounced early ordovician sea level fall on baltica the bjorkasholmen formation in norway and sweden abstract the bjorkasholmen formation consists of interbedded carbonates shales and glauconitic beds and is characterized by heavy bioturbation and few preserved sedimentary structures the unit shows five facies shale glauconitic packstone and three predominantly mud dominated carbonate facies carbonates and shales are arranged in small scale deepening upward cycles a minimum of fourteen of these small scale cycles are recognized in the bjorkasholmen formation they are arranged in stacks of 3 to 5 forming a total of four medium scale cycles separated by decimeter thick shale units based on the predominance of mud rich facies the succession is interpreted to have been deposited in an overall tranquil setting during one mayor sea level fall and subsequent initial rise of third order time estimates suggest that the 14 small scale cycles fall into the milankovitch band of precessional forcing and the overriding medium scale cycles likely represent short eccentricity the sequence stratigraphic interpretation shows that the bjorkasholmen formation is characterized by falling stage lowstand and initial transgressive systems tracts consequently the contact between the bjorkasholmen and the underlying alum shale formation represents the basal surface of forced regression the maximum regressive surface is defined by a hiatus in the oland sections and by shallow marine packstones within mud rich distal ramp carbonates in norway the top of the bjorkasholmen formation represents a flooding surface at the base of the transgressive systems tract a comparison of time equivalent successions worldwide suggests that the bjorkasholmen formation represents a tectonically enhanced lowstand with two overriding short term milankovitch eustatic signals although deposition of the bjorkasholmen formation coincides with the initiation of a foreland basin in the caledonides of norway it remains unclear how these tectonic movements may have lead to the widespread bjorkasholmen lowstand during the early ordovician it is suggested in this study that a combination of compressional forces from avalonia and the caledonian margin may have acted in concert to produce an uplift of larger parts of the baltica plate for a time span of approximately 0 5 myr

syneresis cracks subaqueous shrinkage in argillaceous sediments caused by earthquake induced dewatering abstract syneresis cracks often confused with subaerial desiccation phenomena are traditionally ascribed to subaqueous shrinkage whereby salinity changes caused deflocculation of clay this and other previously proposed mechanisms fail to account for their occurrence in low energy typically non evaporitic facies stratigraphically sporadic distribution intrastratal formation under shallow burial depths variation in morphology degree of contraction generation of sedimentary dikelets as crack fills and deformation of dikelets and enclosing layers instead it is suggested that ground motion from strong synsedimentary earthquakes caused argillaceous sediments to dewater interbedded sands and silts to be almost simultaneously liquefied and injected into the resulting fissures and then these dikelets to be distorted comparative rarity of syneresis cracks in phanerozoic versus precambrian marine strata is considered to be primarily an evolutionary consequence of theological changes caused by increased organic binding of clay flocs in the water column greater input of organic matter into the sediment and the diversification of sediment dwelling bacteria and meiofauna in phanerozoic deposits

alluvial fan to storm dominated shelf transition in the mesoproterozoic singhora group chattisgarh supergroup central india abstract mesoproterozoic siliciclastic strata at the basal part of the singhora group central india provide an example of a pre vegetation alluvial fan and braid delta depositional system detailed process based facies and paleoenvironmental analysis have led to the identification of 15 facies types grouped under four different facies associations which record paleoenvironmental settings ranging between continental alluvial fan and distal marine shelf two formations investigated are the rehtikhol formation formed in a conglomeratic or coarse arenaceous alluvial fan braid plain and delta setting and the overlying saraipalli formation which preserved the sedimentation record of a storm infested inner to distal shelf setting the preponderance of granular and sandy sediment gravity flow products with subordinate rock fall deposits within the alluvial fan system together with a pervasive west northwesterly paleocurrent is suggestive of a gently sloping beveled source area in the east southeast distal to the inferred fan a braid plain system developed with the decrease in the depositional slope streams within the braid plain had widths up to several hundred meters the braid plain system at the margin of the marine basin developed a delta with the deposition of wave reworked fluvial dominated sediments the crest trends of wave generated bedforms within the inferred delta sediments depict the northeast southwest shoreline interpreted for the singhora sea the prodeltaic basinal part of the singhora braid delta was storm infested the inner shelf acted as a zone of throughput with high velocity storm flows eroding deep narrow scours gutter casts and is interpreted as a zone of bypass operation of geostrophic currents on the singhora shelf has been inferred from the directional relationship of gutters with the inferred orientation of the shoreline a proximal distal relationship has been established within the shelf products based on the relative dominance of erosional and depositional features the singhora alluvial fan and braid delta facies are arranged in a fining upward sequence denudation of the source area increasing bathymetry with relative rise in sea level or a combination of both is inferred both extrabasinal and intrabasinal forcings possibly contributed to the deepening upward trend

the structural glaciology of kongsvegen svalbard and its role in landform genesis mapping of the structural glaciology of kongsvegen svalbard reveals evidence for four main deformational structures these are stratification longitudinal foliation thrusts and crevasse traces these structures are considered in terms of their contribution to debris entrainment transport and subsequent landform development stratification is associated with small amounts of supraglacial debris that has been folded with flow parallel axes longitudinal foliation in places incorporates basal glacial sediments along folds with flow parallel axes and thrusts transport basal debris to the glacier surface crevasse traces are not significant in terms of debris entrainment the entrainment of basal debris along longitudinal foliation is not a universally recognised process at kongsvegen this process is attributed to the development of a transposition foliation in combination with incorporation of debris rich basal ice or soft basal sediment in the fold complex mapping of the landforms in the proglacial area shows that debris incorporated along longitudinal foliation is released as foliation parallel ridges and that transverse ridges mark debris bearing thrusts the role of longitudinal foliation in landform development has never been documented in this manner although the preservation potential of such ridges may be limited recognition of foliation parallel ridges in the pleistocene landform record has important implications for the interpretation of the dynamics of former ire masses

deep structure of the scottish caledonides revealed by the moist reflection profile the moine and outer isles seismic traverse moist is a deep crustal reflection profile shot at sea off the north coast of scotland in 1981 spectacular reflections are observed from the moho and from thrust zones within the caledonian fold belt and foreland deep reflection profiling of the continental crust of the united states under the direction of the cocorp group has amply demonstrated the value of this technique when applied to suitable geological problems see for example refs 1 2 a similar group the british institutes reflection profiling syndicate birps has now been set up in the uk to organize such projects funds are provided by the natural environment research council nerc through the core group based at cambridge university however a preliminary experiment of which moist is the result was organized through the institute of geological sciences igs

glaciotectonic deformation within a flute from the isfallsglaciaren sweden the internal structure of a glacial flute in an area of fluted moraine outside the glacier isfallsglaciaren in the kebnekaise massif lapland northern sweden has been observed along a series of sections the till in the flute is underlain by glaciofluvial or glaciolacustrine sediment that has been subject to extensive glaciotectonic deformation the flute forming process is discussed and it is suggested that the flute was initiated beneath the warm based part of the glacier by the sediment moving into the low pressure area in the lee side of a clast associated with a deforming bed it is suggested that deformation increased both down the lee and outwards from the centre line these results were compared with fabric data from two other flute sites from norway where similar deformation patterns were observed it is suggested that because the deformation pattern in the flutes formed beneath both cold toe and warm based glaciers are similar then the warm based deforming bed model is valid for both followed by either passive freezing by the frozen toe moving over them or active freezing by the release of pressure from the surrounding ice causing the water saturated till in the cavity to refreeze to the basal ice

flat pebble conglomerate its multiple origins and relationship to metre scale depositional cycles carbonate flat pebble conglomerate is an important component of precambrian to lower palaeozoic strata but its origins remain enigmatic the upper cambrian to lower ordovician strata of the snowy range formation in northern wyoming and southern montana contain abundant flat pebble conglomerate beds in shallow water cyclic and non cyclic strata several origins of flat pebble conglomerate are inferred for these strata in one case all stages of development of flat pebble conglomerate are captured within stormdominated shoreface deposits of hummocky cross stratified hcs fine carbonate grainstone a variety of synsedimentary deformation structures records the transition from mildly deformed in situ stratification to buckled beds of partially disarticulated bedding to fully developed flat pebble conglomerate these features resulted from failure of a shoreface and subsequent brittle and ductile deformation of compacted to early cemented deposits failure was induced by either storm or seismic waves and many beds failed along discrete slide scar surfaces centimetre scale laminae within thick amalgamated hcs beds were planes of weakness that led to the development of platy clasts within partly disarticulated and rotated bedding of the buckled beds in some cases buckled masses accelerated downslope until they exceeded their internal friction completely disarticulated into clasts and transformed into a mass flow of individual cm to dm scale clasts this transition was accompanied by the addition of sand sized echinoderm rich debris from local sources which slightly lowered friction by reducing clast clast interactions the resulting dominantly horizontal clast orientations suggest transport by dense viscous flow dominated by laminar shear these flows generally came to rest on the lower shoreface although in some cases they continued a limited distance beyond fairweather wave base and were interbedded with shale and grainstone beds the clasts in these beds show no evidence of extensive reworking i e not well rounded or condensation i e no rinds or coatings a second type of flat pebble conglomerate bed occurs at the top of upward coarsening metre scale cycles the flat pebble conglomerate beds cap these shoaling cycles and represent either lowstand deposits or in some cases may represent transgressive lags the clasts are well rounded display borings and have iron rich coatings the matrix to these beds locally includes glauconite these beds were considerably reworked and represent condensed deposits thrombolites occur above the flat pebble beds and record microbial growth before initial transgression at the cycle boundaries a third

clastic dykes of the devono carboniferous horton bluff formation nova scotia storm related structures in shallow lakes abstract clastic dykes are common in the late devonian to early carboniferous horton bluff formation of nova scotia where they occur in wave dominated shoreline deposits of lacustrine shoaling upward cycles the dykes typically less than 25 cm wide and 40 cm in vertical extent project downward into clayshale from broad loads at the base of elongate isolated lenses of hummocky cross stratified siltstone ptygmatic folding of the dykes reflects a shale siltstone compaction ratio of 2 3 times and maximum depth of dyke penetration prior to compaction was 1 m dyke orientation parallels the orientation of wave ripple crests and the elongation direction of the siltstone lenses dyke formation was penecontemporaneous with sedimentation dyke and load formation was probably initiated in shallow water during storms which promoted sediment failure through cyclic wave loading microseisms and rapid deposition of hcs bearing siltstone lenses reversed density gradient and uneven sediment loading from silt lenses probably promoted downward emplacement loads reflect ductile failure of surficial water rich mud whereas dykes reflect downward injection of silt following brittle failure of underlying more compacted mud the depositional slope provided a tensional stress that controlled the fracture direction orthogonal to the slope of the failed sediment

sequence stratigraphy and sedimentology of the neoproterozoic kuibis and schwarzrand subgroups nama group southwestern namibia abstract the kuibis and schwarzrand subgroups of the nama group form a succession of shallow marine and minor fluvial sedimentary rocks that is exposed over much of central and southern namibia ediacaran type body fossils and the stratigraphic carbon isotope variability indicate a vendian age for much of these strata the precambrian cambrian boundary is in the uppermost part of the schwarzrand subgroup radiometric dating of abundant volcanic ash beds which span much of the vendian and extend into the cambrian part of the section could make the nama group the best calibrated reference section for vendian chronostratigraphy here we describe the sedimentology and sequence stratigraphy of exposures of the kuibis and schwarzrand subgroups in southwestern namibia we place tighter environmental constraints on the paleontology and geochemistry and we identify seven depositional sequences the boundaries of the depositional sequences correspond to the more important disconformities in the kuibis and schwarzrand subgroups their identification is crucial for defining rates of organism evolution and isotopic differentiation

grain size distribution and cementation of the cretaceous mzamba formation of eastern cape south africa a case study of a storm influenced offshore sequence abstract the late cretaceous mzamba formation of the eastern cape south africa is a storm influenced succession deposited in an offshore marine environment the succession is composed of two fundamental lithofacies very fine sandstone and packstone shell bed lithofacies the former represents background sedimentation in a relatively deep water low energy offshore environment whereas the latter represents storm deposits occurring with variable periodicity within the quiet offshore environment the storm generated packstone lithofacies shows a bimodal grain size distribution with two saltation fractions on the cumulative frequency diagrams together with negative skewness parameters and a relatively wide kurtosis of grain size distribution these characteristics are indicative of offshore storm generated sediments initial cementation of the storm influenced sediments occurred in a marine phreatic environment when isopachous rims of phosphate isopachous fibrous rims of smectite and micrite calcite cements were formed these cementation textures also support the offshore tempestite origin of the mzamba sediments the original marine phreatic diagenetic environment of the mzamba sediments changed to a meteoric phreatic environment probably at the end of mesozoic following deposition of the overlying cainozoic sediments the mzamba formation entered a burial diagenetic environment where the sediments were affected by elevated temperature and pressure finally the sediments were entered into a meteoric vadose zone due to tectonic uplift or sea level fall new dissolution pores and pendant calcite cement were created

the vaca muerta quintuco system tithonian valanginian in the neuquen basin argentina a view from the outcrops in the chos malal fold and thrust belt the vaca muerta quintuco system uppermost lower tithonian lower valanginian is a thick shallowing upward sedimentary cycle consisting of dark bituminous shales marlstones limestones and sandstones cropping out in the neuquen basin west central argentina this paper analyzes three outcrop sections in chos malal area northem neuquen province detailed facies analysis allows us to differentiate six facies associations representing basinal to proximal outer ramp facies of a homoclinal carbonate ramp system vaca muerta formation and basinal to shoreface facies of a mixed carbonate siliciclastic shelf system quintuco formation prograding westward from the eastern margin of the basin two sequence hierarchies were recognized 5 composite depositional sequences third order and 15 high frequency sequences fourth order fluctuations in organic matter content within the vaca muerta formation suggest a relationship with depositional sequences finding the highest values associated with transgressive systems tract whereas the transition to the quintuco formation shows a strong decrease in total organic carbon the x ray diffraction studies show an increase of clay minerals and quartz in the transgressive systems tract of the vaca muerta formation and an increase in the content of calcite in highstand systems tracts this pattern is reversed in the quintuco formation our sequence stratigraphic approach contributes to the understanding of the relationship between organic matter clay minerals facies stacking pattern and relative sea level changes in this exceptional shale oil and shale gas unconventional reservoir this study may be helpful for a better postulate of petrophysical and geomechanical models for unconventional exploration

quantitative evaluation of the reservoir potential and controlling factors of semi deep lacustrine tempestites in the eocene lijin sag of the bohai bay basin east china abstract ancient lacustrine storm deposits that act as petroleum reservoirs are seldom reported the lijin sag which is located in the southeastern corner of the bohai bay basin in east china is a ne sw trending cenozoic half graben basin some of its eocene deposits bindong deposits were interpreted as lacustrine tempestites the bindong tempestites which developed in the lower part of the upper fourth member of the shahejie formation es41 constitute a new kind of petroleum reservoir and are novel petroleum exploration targets in the bindong area however the characteristics of the es41 bindong tempestite reservoirs and their controlling factors are poorly understood point count analyses of thin sections scanning electron microscope image analyses x ray diffractometry data and the petrophysical parameters of the bindong tempestite reservoirs were utilized to estimate the reservoir quality the reservoirs have undergone significant diagenetic alteration which can be divided into negative and positive aspects the negative alteration includes compaction authigenic minerals and cementation such as carbonates clay minerals and overgrowths of quartz and feldspar the uneven distribution of carbonate cement increased the reservoir s heterogeneity with carbonate cement commonly precipitating along the sandstone mudstone contacts the primary porosity was severely reduced because of compaction and extensive carbonate cementation positive alteration includes dissolution carbonate cementation undercompaction and fractures carbonate cementation exhibited both positive and negative effects on the reservoir quality overall the objective reservoir quality is quite poor a quantitative evaluation of the reservoirs potential was conducted the cutoff values of several of the reservoir s parameters were calculated the lower limits of the porosity and permeability are 8 35 5 85 and 1 2587 0 2753 10 3 m2 respectively depending on the depth the upper limits of the carbonate and mud content are approximately 18 5 and 9 10 respectively a fundamental understanding of these characteristics will provide necessary information for extracting hydrocarbons from analogous subsurface reservoirs

geology and taphonomy of the l espinau dinosaur bonebed a singular lagoonal site from the maastrichtian of south central pyrenees abstract the l espinau site is a dinosaur bonebed from the upper cretaceous of the south central pyrenees north eastern spain that have provided hundreds of bone remains attributed to hadrosauroids together with a rich assemblage of herpetofauna fish and microflora magnetostratigraphy calibrated the site with the early late maastrichtian and the combined sedimentology stable isotope geochemistry and palaeoecology revealed that this fossil site formed in a lagoon in which a mixed freshwater brackish palaeoenvironment was developed this setting displays a south north charophyte zonation from freshwater clavator brachycerus dominated assemblage to brackish or eurihaline conditions feistiella malladae dominated assemblage revealing a palaeoenvironment change towards the coast sedimentology and taphonomy bidirectional arrangement of long bones abrasion and disarticulation indicate that the l espinau site is the result of a cohesive mass flow event originated very close to the sea this process entrained and mixed fauna from both the terrestrial and the brackish marine environment of a lagoon an increasing of the water runoff e g by intense rainfall reworking poorly consolidated sediments is considered here as the most probable triggering mechanism mass flow hosted bonebeds are commonly linked to fluvial palaeoenvironments so our study case is a rare example of bones accumulating near the sea this study adds evidence that hadrosauroids inhabited littoral environments during the maastrichtian in the southern pyrenean area

cambrian stratigraphy and depositional history of the northern indian himalaya spiti valley north central india recent work on himalayan tectonics indicates that prior to the cenozoic collision of india and asia an enigmatic cambrian ordovician event may have strongly infl uenced the regional geology of the himalaya stratigraphic and sedimentological analyses of well preserved cambrian deposits are critical for understanding the nature of this early tectonic event and its infl uence on the later tectonic evolution of the himalaya the parahio formation defi ned herein of the parahio valley spiti region in the tethyan himalaya of india is the best biostratigraphically resolved section of cambrian strata in the entire himalaya this formation consists of 1350 m of dominantly siliciclastic deltaic deposits the formation ranges from uppermost lower cambrian lungwangmiaoan stage to middle middle cambrian hsuchuangian stage representing a time span of 5 10 m y it contains numerous mediumscale shoaling cycles that range from storminfl uenced offshore deposits to thick trough cross bedded fl uvial facies many thin carbonate beds with abundant trilobite fossils directly overlie the fl uvial facies and represent transgressive systems tract deposits the cycles are interpreted to have resulted from delta lobe switching based on a lack of systematic stratigraphic changes in cycle or facies thicknesses this paleoenvironmental reconstruction contradicts previous interpretations of this unit that range from deep sea fl ysch to shallow marine tidalites in addition our paleoenvironmental analysis and paleocurrent data suggest that the uppermost lower to middle cambrian deposits of the lesser and tethyan himalaya are parts of the same ancient northward prograding fl uvial deltaic depositional system of the paleo tethys margin of india an angular unconformity with overlying ordovician conglomeratic rocks has considerable local relief with meter scale scours and a valley fi ll 100 m thick the scours have northeast southwest orientations which parallel both the paleocurrents in the underlying parahio formation as well as published paleocurrent readings from the coarse red beds of the overlying ordovician strata the cambrian ordovician unconformity is of regional extent and our recent biostratigraphic database indicates that the minimum hiatus associated with the unconformity in spiti is 15 m y our sedimentological analysis and associated paleocurrent data from the parahio formation along with additional data from units both above and below the unconformity indicate that published models portraying foreland basin development at this time with southward directed thrusting are problematic an alternate possibility that uplift took place south of the tethyan himalaya is also problematic because no published stratigraphic or structural evidence exists for such an uplift to the south for either the greater or the lesser himalaya lithotectonic zones

non uniform across shelf variations in thickness grain size and frequency of turbidites in a transgressive outer shelf the middle pleistocene kakinokidai formation boso peninsula japan abstract across shelf variations in thickness grain size and frequency of sandstone beds in a transgressive outer shelf succession were investigated from the middle pleistocene ca 0 7 ma kakinokidai formation on the boso peninsula japan the transgressive deposits are generally muddy and contain slumps and slump scars the intercalated sandstone beds are interpreted to have been formed from turbidity currents as a response to erosion and resuspension of sandridge complex deposits in the southwestern upslope area during storm events mapping of volcanic ash beds and a transgressive surface in the base of the formation permits detailed bed by bed correlation of the outer shelf sandstone beds although overall thickness grain size and frequency of sandstone beds decrease in the downslope direction some sandstone beds locally thin out and coarsen in association with slump scars in the surrounding muddy deposits these sandstone beds subsequently thicken and fine and finally thin out in the farther downslope area in addition to the local thinning of sandstone beds the frequency of sandstone beds first decreases and then increases in the farther offshore direction from this evidence we concluded that these non uniform patterns of across outer shelf variations in thickness grain size and frequency of sandstone beds were caused by the local increases in flow speeds and subsequent expansion and reduced speeds of turbidity currents along with a local increase in the seafloor gradient that was induced by the development of slump scars in the transgressive outer shelf floor these physiographic features in the outer shelf are interpreted not to have permitted monotonous downslope thinning and fining of sandstone beds compared with the bed shape models of depletive turbidity currents and with the proximality trend of shelf sandstones from modern and ancient highstand stage shelf systems

lower carboniferous ramp sedimentation of the central alborz basin northern iran integrated sedimentological and rock magnetic studies the lower carboniferous mobarak formation in the alborz basin northern iran was deposited along the northeastern margin of gondwana in a carbonate ramp setting this paper focuses on the tournaisian stratigraphic interval of this formation that crops out at the jaban section in the southwestern central alborz basin the following facies associations representing different ramp palaeoenvironments have been identified 1 mudstone wackestone outer ramp facies 2 crinoidal to skeletal grainstone packstone mid ramp facies 3 peloidal to crinoidal grainstone packstone inner ramp facies and 4 coastal facies which include a variety of microbial laminated to oncoidal grainstones and mudstones with evaporitic pseudomorphs this ramp profile was affected by frequent storms that were responsible for the formation of several skeletal to non skeletal shoals in the distal mid ramp to the most proximal inner ramp areas the development of the skeletal to non skeletal shoals along the sea side of the ramp formed a semi enclosed lagoon sensitive to the influence of both high tides and storm surges the magnetic susceptibility xin of all the samples was measured and compared with that of the facies from which the sample was taken there is a clear link between xin and the facies the average xin values were higher for the distal facies than for the proximal facies the xin profile of this lower carboniferous carbonate sequence reflects stratigraphic variations in response to relative changes in sea level and the input of detrital materials in the context of the sequence stratigraphic framework the average xin values for lowstand and transgressive systems tract deposits are higher than for the highstand systems tract deposits the clear link between xin and facies indicates at least a partly preserved primary xin signal related to the detrital inputs however to obtain a better understanding of the nature and origin of the minerals carrying the xin we performed hyster esis measurements on selected samples it appears that the xin signal is mainly carried by low coercivity ferromagnetic minerals such as magnetite with a mixture of relatively coarse grains detrital fraction and ultra fine grains probably formed during diagenesis

the formation of glacial flutes assessment of models with evidence from lyngsdalen north norway abstract flutes are a distinctive type of glacial landform and comprise closely spaced streamlined ridges and furrows usually developed on till surfaces and aligned parallel to ice movement direction several models proposed to explain their formation involve at least in part post depositional deformation or transfer of subglacial sediments others involve primary deposition or erosion the flutes on several glacier forelands in the mountains of the southern lyngen peninsula in north norway are associated with glaciers with cold based margins to explain the formation of the flutes three main sets of variables are investigated 1 the landforms and their shapes dimensions and field relationships 2 the physical properties of the materials comprising the flutes and 3 the glacier properties and in particular the basal thermal regime and ice debris relationships at the glacier margin existing models of flute formation which involve post depositional deformation or transfer of subglacial sediments do not explain satisfactorily several aspects of the flutes found in lyngen instead a model is proposed in which the flutes are primary features formed by deformation of the basal ice layer around subglacial boulders or other obstacles

terminal cambrian and lowest ordovician succession of mexican west gondwana biotas and sequence stratigraphy of the tinu formation the tinu formation of oaxaca state is the only fossiliferous lower palaeozoic unit between the laurentian platform in northwest mexico and gondwanan successions in andean south america the tinu traditionally has been referred to the lower ordovician tremadoc and regarded as having a provincially mixed fauna with laurentian avalonian and gondwanan elements bio and lithostratigraphic re evaluation demonstrates that the tinu is a gondwanan passive margin succession it includes a lower thin to 16 m condensed uppermost cambrian yudachica member new the yudachica nonconformably overlies middle proterozoic basement as a result of very high late late cambrian eustatic levels the yudachica changes from storm dominated but slightly dysoxic shelf facies fossil hash limestone and shale in the south to an upper slope facies with debris flows 50 km to the north three biostratigraphically distinct depositional sequences comprise the yudachica the yudachica has gondwanan aspect trilobites with low diversity conodonts characteristic of unrestricted marine temperate facies the upper tinu or rio salinas member new is a lower ordovician tremadoc depositional sequence that records strong early but not earliest tremadoc eustatic rise marked by graptolite and olenid bearing dysoxic mudstones higher strata shoal upward into shell hash limestones and proximal tempestite sandstones with upper lower tremadocian unrestricted marine temperate conodonts new taxa include orminskia rexroadae landing gen et sp nov from the cordylodus andresi zone this euconodont is related to hyaline coniform genera best known from ordovician tropical platform successions cornuodus clarkei landing sp nov resembles the coeval upper lower tremadoc tropical species scalpellodus longipinnatus ji barnes

eifelian givetian middle devonian high paleolatitude storm and wave dominated shallow marine depositional systems from the bidouw subgroup bokkeveld group of south africa abstract the sedimentology of the eifelian givetian middle devonian bidouw subgroup in the clanwilliam sub basin of south africa has been reassessed four distinct lithofacies associations are recognized a d and are representative of the deposits of offshore os offshore transition zone to distal lower shoreface otz dlsf proximal lower shoreface plsf and upper shoreface beach usf beach paleoenvironments these paleoenvironments are arranged as several t r controlled storm and wave dominated shallow marine depositional systems the presence of storm and wave dominated shallow marine depositional systems in the bidouw subgroup as well as the preceding emsian eifelian early middle devonian ceres subgroup provides an alternative explanation to storm and wave dominated delta and mixed wave and tide dominated delta models that have previously been proposed for the bokkeveld group sequence stratigraphic analysis of the bidouw subgroup suggests that although sedimentation occurred during two large scale second order transgressive events the succession was predominantly regressive third order and fourth order transgressive regressive t r sequences are more numerous with respect to the preceding ceres subgroup suggesting that the driver for t r cyclicity and relative sea level change was more active during the eifelian givetian than in the emsian eifelian of south africa these data are important since relative sea level change and its effects on paleoenvironmental change at high paleolatitudes during the devonian period are poorly known

birps deep seismic reflection studies of the british caledonides the western isles north channel winch traverse fig 1 an extension of the successful moist profile1 was recorded in 1982 at sea along the west coast of britain for birps british institutions reflection profiling syndicate by the geophysical company of norway geco the purpose of the winch traverse was to study crustal structure of the caledonian foreland to cross the caledonian orogen and to establish the three dimensional geometry of mantle reflectors originally seen on moist we describe here the data first emphasizing british caledonian structures and then discussing features of the deep crust of wider significance the data are of very good quality and contain clear moho and upper mantle reflections the lower crust is surprisingly reflective deeply penetrative thrusts are observed and there is firm evidence that several of the mesozoic basins round the shores of the united kingdom were formed by reactivation of older features

the early paleozoic development of bioturbation evolutionary and geobiological consequences abstract bioturbation the physical and chemical mixing of sediments by burrowing animals is a critical engineering process in modern seafloor environments and exerts an important control on not only benthic ecology and sediment properties but also ocean wide biogeochemical cycling well mixed sediments have long been assumed to appear at the precambrian cambrian boundary with the first occurrence of the index fossil and three dimensional burrow treptichnus pedum however field based analyses synthesizing ichnological stratigraphic sedimentological and taphonomic data collected from lower paleozoic successions worldwide indicate that sediment mixing in marine shelf environments remained limited until at least the late silurian 120 million years after the precambrian cambrian transition in spite of early advances in complex modes of infaunalization mixed layer development had a much more gradual trajectory and did not occur in step with the first appearance of three dimensional burrows the delayed appearance of modern style intensities of sediment reworking postdating both the cambrian explosion and the great ordovician biodiversification event may be due to the late stage radiation of mobile infaunal deposit feeders biological bulldozers the organisms which are in modern marine settings the most efficient bioturbators the protracted development of the sediment mixed layer holds important implications for contemporaneous biogeochemical cycling and oxygenation of the ocean atmosphere system the delayed development of intensive sediment mixing may have also mediated exceptional preservation of both fossilized soft tissues and shallow tier trace fossils and may therefore have contributed to the anomalous preponderance of konservat lagerstatten and exceptionally preserved shallow tier trace fossils and bioglyphs characteristic of the lower paleozoic stratigraphic record

seismic profiling the continental lithosphere deep seismic reflection profiling is successfully being used worldwide to study the structure of the continental crust1 7 the moist8 profile recorded by birps british institutions reflection profiling syndicate was the first to show that the structure of the upper mantle could also be imaged given a powerful source and long recording times birps has recently acquired an ultra deep seismic reflection line drum deep reflections from the upper mantle the drum line was designed specifically to investigate the reflectivity of the lower continental lithosphere and was therefore recorded to a two way time twt of 30 s giving a depth of penetration into the lithosphere of 110 km this profile has now revealed strong reflections which are unequivocally from the lower lithosphere well below the base of the crust and which are as far as we are aware the deepest and most continuous structures imaged in the upper mantle by multi channel seismic reflection profiling

stable isotope geochemistry and palynology of the late precambrian to early cambrian sequence in newfoundland a sequence of clastic sediments in southeastern newfoundland straddling the precambrian cambrian boundary has been investigated for its stable isotope geochemistry of carbon and sulfur and acid resistant organic walled microfossils a detailed study of the chapel island formation which includes the boundary interval has revealed fluctuations in the isotopic composition of organic carbon these are largely interpreted as caused by differences in the depositional environments highly variable sulfur isotopic compositions indicate bacterial sulfate reduction as a pyrite forming process sometimes under sulfate limited conditions palynological results are quite limited with respect to diagnostic microfossils

wave modified turbidites combined flow shoreline and shelf deposits cambrian antarctica sandstone tempestite beds in the starshot formation cen tral transantarctic mountains were deposited in a range of shoreline to shelf environments detailed sedimentological analysis indicates that these beds were largely deposited by wave modified turbidity currents these currents are types of combined flows in which storm generated waves overprint flows driven by excess weight forces the interpreta tion of the tempestites of the starshot formation as wave dominated turbidites rests on multiple criteria first the beds are generally well graded and contain bouma like sequences like many turbidites the soles display abundant well developed flutes they also contain thick divisions of climbing ripple lamination the lamination however is dominated by convex up and sigmoidal foresets which are geometries identical to those produced experimentally in current dominated com bined flows in clear water finally paleocurrent data support a tur bidity current component of flow asymmetric folds in abundant con volute bedding reflect liquefaction and gravity driven movement and hence their orientations indicate the downslope direction at the time of deposition the vergence direction of these folds parallels paleocur rent readings of flute marks combined flow ripples and a number of other current generated features in the starshot event beds indicating that the flows were driven down slope by gravity the wave component of flow in these beds is indicated by the presence of small to large scale hummocky cross stratification and rare small two dimensional ripples wave modified turbidity currents differ from deep sea turbidity cur rents in that they may not be autosuspending and some proportion of the turbulence that maintains these flows comes from storm waves such currents are formed in modern shoreline environments by a com bination of storm waves and downwelling sediment laden currents they may also be formed as a result of oceanic floods events in which intense sediment laden fluvial discharge creates a hyperpycnal flow event beds in the starshot formation may have formed from such a mechanism oceanic floods are formed in rivers of small to medium size in areas of high relief commonly on active margins the starshot formation and the coeval douglas conglomerate are clastic units that formed in response to uplift associated with active tectonism sedi mentological and stratigraphic data suggest that coarse alluvial fans formed directly adjacent to a marine basin the geomorphic conditions were therefore likely conducive to rapid fluvial discharge events asso ciated with storms the abundance of current dominated combined flow ripples at the tops of many starshot beds indicates that excess weight forces were dominant throughout deposition of many of these beds

bypass zone tempestite facies model and proximality trends for an ancient muddy shoreline and shelf member 2 of the late precambrian to lower cambrian chapel island formation of southeast newfoundland was primarily deposited in storm influenced nearshore and shelf environments along a fine grained coastline deposition took place within or adjacent to a deltaic system that supplied abundant silts and clays thin bedded graded sandstone beds hummocky cross stratified beds and a variety of very thin conglomerate units contain evidence for deposition by storm currents sedimentological and stratigraphic evidence is used to reconstruct the relative paleobathymetric position of the three major facies in member 2 the gutter cast facies is a shallow subtidal deposit characterized by very thin sandstone laminae and abundant pot and gutter casts the siltstone dominated facies contains more laterally extensive thin bedded sandstones and fewer erosional features and was deposited in the inner shelf the sandstone dominated facies consists of thin to medium graded and hummocky cross stratified sandstone beds deposited in a more distal shelf setting but above storm wave base the facies model and set of proximality trends developed for member 2 deposits may be applicable to other storm influenced fine grained shorelines in this model the shallow subtidal is a zone of throughput with high velocity sediment laden flows eroding deep narrow scours gutter casts and depositing very little sand outside of these scours as the storm generated flows move into deeper water they decelerate resulting in less erosion of the sea floor and depositing thicker and more continuous sand beds siltstone dominated facies further from shore bed thickness reaches a maximum sandstone dominated facies and hummocky crossstratification is abundant even more distally bed thickness decreases again represented by thinly laminated siltstones of the overlying member 3 analysis of sedimentary structures and paleocurrent data suggests deposition by storm currents that transported sediment nearly perpendicular to shore

sequence stratigraphy and carbonate siliciclastic mixing in a terminal proterozoic foreland basin urusis formation nama group namibia abstract superb three dimensional exposures of mixed carbonate and siliciclastic strata of the terminal proterozoic urusis formation in namibia make it possible to reconstruct cross basin facies relations and high resolution sequence stratigraphic architecture in a tectonically active foreland basin six siliciclastic facies associations are represented coastal plain upper shoreface middle shoreface lower shoreface storm influenced shelf and pebble conglomerate siliciclastic shoreface facies pass seaward into and interfinger with facies of an open carbonate shelf four carbonate facies associations are present mid shelf shelf crest outer shelf and slope facies are arranged hierarchically into three scales of unconformity bounded sequences small scale sequences are one to tens of meters thick and span a few thousand years they consist of shelf carbonate with or without shoreface siliciclastic facies near the bottom medium scale sequences are tens of meters thick and span a few hundred thousand years they consist of shoreface siliciclastic facies in their lower parts which grade upward and pass seaward into shelf carbonate large scale sequences are tens to hundreds of meters thick and span 1 to 2 million years they are identified by widespread surfaces of exposure abrupt seaward shifts in shoreface sandstone patterns of facies progradation and retrogradation and shoreline onlap by medium scale sequences patterns of carbonate siliciclastic mixing distinguish tectonic from eustatic controls on the evolution of large scale sequences characteristics of eustatically controlled large scale sequences include 1 basal unconformities and shoreface sandstone that extend across the shelf to the seaward margin 2 retrograde carbonate and siliciclastic facies belts that onlap the shoreline together symmetrically during transgression and 3 upper shoreface sandstone that progrades seaward during highstand in contrast tectonically controlled sequences feature 1 basal erosion surfaces and upper shoreface sandstone that are restricted to near the landward margin and pass seaward into zones of maximum flooding and 2 asymmetric stratigraphic development characterized by landward progradation of carbonate from the seaward margin coincident with backstepping and onlap of the shoreline by siliciclastic facies a two phase tectonic model is proposed to account for the stratigraphic asymmetry of tectonically controlled sequences increased flexural bending during periods of active thrust loading caused submergence of the seaward margin and uplift of the landward margin rebound between thrusting episodes flattened the basin gradient and submerged the landward margin causing expansion of carbonate facies from the seaward margin and simultaneous transgression of the landward margin although the two phase model should apply to single lithology successions deposited in active foreland basins the mixing of carbonate and siliciclastic facies provides a particularly sensitive record of tectonic forcing the sensitivity may be sufficient for medium and small scale sequences to record higher frequency variations in flexural warping

nontypical birps on the margin of the northern north sea the shet survey summary striking similarities in the reflectivity of the crust and upper mantle on birps profiles has led to the development of the typical birp a model seismic section for the british continental lithosphere the shet survey collected in the region of the shetland islands and the northern north sea fits the general pattern to a certain extent caledonian structures and devonian or younger basins are imaged in the otherwise acoustically transparent upper crust an unexpected and exciting feature imaged on shet is a short wavelength structure on the moho or abrupt moho offset beneath the strike slip walls boundary fault shet differs markedly from the swat typical birp however by showing a poorly reflective lower crust only a narrow zone 1 s at the base of the crust contains high amplitude reflections the shet survey therefore highlights the wide variation in lower crustal reflectivity within the total birps data set rather than the similarities

analysis of marrow cavity fillings as a tool to recognise diverse taphonomic histories of fossil reptile bones implications for the genesis of the lower muschelkalk marine bone bearing bed middle triassic żyglin s poland abstract the bone bearing bed from yglin s poland which likely represents the oldest lower muschelkalk accumulation of reptile remains in the se part of the germanic basin has been investigated in order to determine its genesis the basic methods were supported by petrographic analysis of the marrow cavity and large inter trabecular pore space fillings of fossil bones which was used to check its usefulness to identify the environments where the bones were initially deposited and to decipher taphonomic histories of the remains the bone bearing bed is a composite deposit which consists of three distinct layers from bottom to top micritic limestone mudstone bioturbated autochthonous mud crinoidal limestone grainstone to packstone calcirudite and shell rich limestone packstone to wackstone calcirudite the crinoidal limestone layer the main bone bearing bed is recognised as the proximal tempestite deposited in the mid ramp zone the petrographic analysis of the fillings reveals the prevalence of minute ostracod carapaces accompanied by other grains embedded together with micrite to microspar such compositions suggest that these sediments may have been inserted into the bone pore spaces in lagoons and tidal flat ponds features of some bones record their early diagenetic burial and lithification before the final redeposition the isopachous spar blocky spar and weathered pyrite document changes in the chemical composition of fluids that flowed into the bone interiors the burrow found in the marrow cavity of specimen iguam zov 7 provides evidence that some remains were inhabited by minute or juvenile invertebrates all recognised features indicate that both invertebrate and vertebrate bioclasts included in the tempestite were initially deposited in various settings of the carbonate ramp and in the end redeposited as a result of a heavy storm or a hurricane the examined bone bearing bed represents time averaged assemblage which originated due to hydraulic concentration of the vertebrate bioclasts the petrographic analysis of the fillings is a valuable tool to identify complex taphonomic pathways of vertebrate bioclasts