living on the edge evaluating the impact of stress factors on animal sediment interactions in subenvironments of a shelf margin delta the mayaro formation trinidad abstract integrating sedimentological and ichnological characteristics of the gelasian mayaro formation along the se coast of trinidad allows recognition of a river dominated and wave influenced shelf edge deltaic succession of the paleo orinoco river developed under strong slope instability four main sedimentary settings and twelve subenvironments developed on and beyond the outer shelf i e at the shelf margin have been identified extreme paleoenvironmental conditions make the succession rarely and sporadically colonized ichnologic evidence suggests that shelf edge deltas are among the most stressful marine environments due to a combination of physicochemical factors in response to the intrinsic sedimentary processes and the relative hierarchy of their influences specific to every subenvironment within any particular subenvironment the relative dominance of the fluvial feeder system the action of waves and rare influence of tides and slope instability determine the combinations and ranking of stress factors river dominated shelf edge delta subenvironments demonstrate the extreme influence of stress factors related to channel activity e g salinity changes high sedimentation and erosion rates flocculation of mud seasonal variations of fluvial flux whereas subenvironments dominated by waves storms and oceanic swells away from the axial feeder s are mostly influenced by barform morphodynamics and its effects on local physiography the paleo orinoco delta is represented not only by the delta lobe s developed at the shelf edge but by delta lobe s formed on the outer shelf as well outer shelf deltaic subenvironments manifest typical ichno sedimentological signatures of a normal wave influenced in this case inner shelf delta being susceptible to extensive gravitational instabilities the delta system suffered from canyonization and smaller gullying and subsequent filling n b hereafter we use the term canyon for both canyons and smaller gullies the shelf edge delta system was also associated with shelf attached mass transport systems such depositional subenvironments dominated by slope instability and sediment gravity flows appear to be the most unconducive for benthic colonization resulting in almost complete absence of bioturbation characterization of the stress factors as the functions of parameters arising from specific sedimentary and or oceanographic processes chemical conditions and preservational constraints specific to each subenvironment leads to the construction of a comprehensive ichnological and depositional analog model for shelf edge deltas in general and for the accommodation driven low latitude shelf edge deltas at an active oblique foreland setting in particular

spatangoid produced ichnofabrics bateig limestone miocene spain and the preservation of spatangoid trace fossils a spatangoid produced ichnofabric is described from the miocene bateig limestone se spain this ichnofabric is characterized by the dominant presence of large meniscate burrows bichordites produced by irregular echinoids this constitutes an unusual mode of occurrence for spatangoid bioturbation as their traces are most typically preserved in bases and tops of sandstone event beds in fact despite their important role as burrowers in modern settings that can be extended back to the early cretaceous based on their body fossil record spatangoid trace fossils scolicia and bichordites are comparatively rare several factors play an important role in their preservation mechanism of burrowing sediment characteristics early diagenesis and presence absence of deep tier burrowers spatangoid produced ichnofabrics such as those from the bateig limestone characterize depositional settings with intermittent deposition of event beds where there is an absence of deeper tier bioturbation

trace fossils biology and taphonomy 1990 special topics in palaeontology 3 280 pp e17 95 pbk e40 00 hbk unwin hyman london isbn 004445 6867 pbk 3035 hbk

organism substrate interactions and astrobiology potential models and methods abstract organism substrate interactions and their products biogenic structures are important biosignatures on earth this study discusses the application of ichnology the study of organism substrate interactions to the search for present and past life beyond earth three main questions are addressed 1 why to look for biogenic structures i e traces and ichnofabrics beyond earth 2 what biogenic structures to expect on other planets moons and asteroids 3 how to study extraterrestrial biogenic structures review of terrestrial evidence highlights a set of properties that make traces and ichnofabrics important for the search of potential extraterrestrial life trace fossils preserve the activity of soft bodied organisms biogenic structures are resilient to processes that obliterate other biosignatures i e mechanical and chemical degradation diagenesis tectonism and metamorphism traces are very visible biosignatures traces indicate environment and behaviour traces can be universal biosignatures i e biosignatures ideally suited for detecting any type of life a model of organism substrate interactions beyond earth is here proposed expected extraterrestrial traces are those that manifest behaviours that allow to maintain homeostasis excavations meandering traces and biodeposition structures most of the existing rovers and orbiters provide basic instruments for searching these traces it is here suggested that the search for extraterrestrial biogenic structures by rovers would also benefit from artificial adjustable lighting gpr lidar and drilling equipment with optical televiewer in this study open access databases of rover and orbiter imagery have been searched for traces and ichnofabrics but no unquestionable evidence of biogenic structures beyond earth has been found besides those produced by humans this sounds along the lines of the famous fermi paradox if the universe is teeming with aliens where are their traces results of this search show that habitable environments are not the only place to look for biogenic structures non habitable environments such as moons without atmosphere can favour the preservation of shallow tier traces the better preservation potential of traces compared to other biosignatures greatly widens the issue of planetary protection including the interaction between astronauts or vehicles and the substrate may produce disturbances although this study highlights a new direction of study with the tools and concepts of ichnology dialogue between the astrobiological and ichnological communities is needed to use its full potential and possibly answer one of the major questions of science does life exist beyond earth

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

proximal distal ichnofabric changes in a siliciclastic shelf early pliocene guadalquivir basin southwest spain abstract the lower pliocene deposits cropping out along the atlantic coast of cadiz in the conil cabo roche area formed on a shelf gently deepening towards the w nw up to five types of facies can be recognized distributed in belts from proximal to distal parts of the shelf 1 coarse grained sandstone with trough cross stratification facies on the most proximal parts of the shelf inner shelf deposits 2 medium grained sandstone with low angle planar cross stratification facies deposited in a more distal position due to storm currents transporting sediment offshore this facies intercalates with the previous trough cross bedded sandstone 3 massive fine grained sandstone and siltstone facies laterally and vertically related with the previous facies type and representing sediments formed in the middle shelf close to the storm wave base 4 tabular sandstone bed facies corresponding to storm bed deposits intercalated within the two previous facies 5 greenish bluish shale facies accumulated on the outer shelf below storm wave base three ichnofabrics associated with these facies are recognized 1 the two cross bedded facies are dominated by a macaronichnus ichnofabric characterized by macaronichnus and bichordites traces that represent colonization of a shifting sandy substrate by polychaetes macaronichnus tracemakers and by sea urchins bichordites producers 2 a rosselia ichnofabric consisting of vertical traces of rosselia cross cutting macaronichnus characterizes the interval of massive fine grained sandstone and silt facies and interbedded tabular sandstones this ichnofabric formed under high sedimentation rates with rosselia traces exhibiting stacked patterns that indicate vertical readjustment following deposition 3 massive fine grained sandstone and silt facies are distinguished by a cylindrichnus ichnofabric this fabric was produced by the activity of a moderately diverse community dominated by sessile burrow dwelling probably superficial detritus feeding polychaetes rosselia and cylindrichnus tracemakers and vagile deposit feeding polychaetes planolites producers in addition infaunal deposit detritus feeders producing spreiten structures teichichnus are found in distal areas pervasive indistinct mottling of the sediment of this facies was probably due to the activity of very shallow burrowers in the uppermost sediment tiers this proximal distal replacement of ichnofabrics reflects the change of benthic communities across the shelf this distribution does not fit the traditional seilacherian ichnofacies model for soft ground shallow marine settings in which proximal vertical dwelling burrows of the skolithos ichnofacies dominate high energy environments in the pliocene of cadiz shallow tier burrows of deposit detritus feeders characterize the high energy facies instead which fit better with the cruziana ichnofacies this deviation can be related with the particular palaeoenvironmental conditions thus vagile opportunistic deposit feeders colonized the dune foreset when the dunes were stable and the progradation of the structure favored the preservation of the traces

a multidisciplinary study of ecosystem evolution through early pleistocene climate change from the marine arda river section italy the arda river marine succession italy is an excellent site to apply an integrated approach to paleoenvironmental reconstructions combining the results of sedimentology body fossil paleontology and ichnology to unravel the sedimentary evolution of a complex marine setting in the frame of early pleistocene climate change and tectonic activity the succession represents a subaqueous extension of a fluvial system originated during phases of advance of fan deltas affected by high density flows triggered by river floods and overlain by continental conglomerates indicating a relative sea level fall and the establishment of a continental environment an overall regressive trend is observed through the section from prodelta to delta front and intertidal settings the hydrodynamic energy and the sedimentation rate are not constant through the section but they are influenced by hyperpycnal flows whose sediments were mainly supplied by an increase in apennine uplift and erosion especially after 1 80 ma the arda section documents the same evolutionary history of coeval successions in the paleo adriatic region as well as the climatic changes of the early pleistocene the different approaches used complement quite well one another giving strength and robustness to the obtained results

sedimentary evidence of the neogene evolution of se spain the neogene sediments of se spain are dominated by gravity flow deposits ranging from millimetre scale dilute turbidites to kilometre scale olistholiths details of the neogene sequences at finestrat alcoy and fontanars provide examples of responses to periodic tectonic events in a variety of background settings the main control on sedimentation in each area was the episodic rise of triassic gypsiferous mudstone diapirs this probably resulted from periodic regional extension and compression due to contraction and spreading of the alboran sea marginal basin

an ichnofabric approach to the depositional interpretation of the intensely burrowed bateig limestone miocene se spain abstract the foraminiferal rich pelagic bateig limestone forms several varieties of the important building stones quarried at bateig hill in southeastern spain three principal ichnofabrics bichordites mottled palaeophycus and mottled ophiomorpha are recognized which are present in at least two possibly up to four repeated successions cycles each succession begins with an erosional event the bichordites ichnofabric represents a new type of facies formed as thin turbidity grain flow stratiform units derived from sediment slips off a fault into deep water each slipped unit became almost completely bioturbated by infaunal echinoids colonizing by lateral migration because of the thinness of the units successive colonizations tended to truncate the underlying burrows giving rise to a pseudo stratification as the bichordites ichnofabric accumulated on the fault apron thus reducing the effective height of the fault scarp the substrate gradually came under the influence of currents traversing the shelf this led to a change in hydraulic regime and to the mottled palaeophycus and mottled ophiomorpha ichnofabrics in sediment deposited under bed load transport and associated with laminar and cross stratified beds and local muddy intervals reactivation of the fault triggered erosion and channeling and a return to grain flow sedimentation and to the bichordites ichnofabric of the succeeding cycle the highest unit of the bateig limestone is formed entirely of cross stratified calcarenites with occasional ophiomorpha ophiomorpha primary lamination ichnofabric and is similar to many shallow marine facies but they still bear a significant content of pelagic foraminifera the sedimentary setting bears resemblance with that described for the pleistocene monte torre paleostrait and the modern strait of messina italy where the narrow morphology of the depositional area enhanced tidal currents and allowed for high energy sandy deposition in relatively deep areas more data on the miocene paleogeography of the bateig area should provide further testing for this hypothesis the ichnofacies and stacking of the bateig limestone differ from the classic seilacherian model in that they reflect changes in hydraulic process and are associated with faulting and subsidence and changes in sediment supply recognition of the unusual ichnofabrics and their relationships provides a clear indication of the overall dynamic setting

the oldest deep sea ophiomorpha and scolicia and associated trace fossils from the upper jurassic lower cretaceous deep water turbidite deposits of sw bulgaria deep sea trace fossils of the nereites ichnofacies occur in the uppermost kimmeridgian berriasian deep water turbidite deposits of the kostel formation in sw bulgaria the trace fossil assemblage contains tithonian ophiomorpha isp and ophiomorpha annulata which are the oldest deep sea representatives of this ichnogenus they indicate much older invasion of ophiomorpha into deep sea which was hitherto dated as to mid cretaceous it is not clear whether the invasion failed or ophiomorpha survived in deep sea refuge and became widespread after improving oxygenation of the deep seas after the cenomanian turonian anoxic event tithonian scolicia produced by irregular echinoids exhibits a similar distribution pattern

atmospheric summer circulation and coastal upwelling in the arabian sea during the holocene and the last glaciation accumulation rates of biogenic and lithogenic components were studied in 39 turbidite free well dated sediment cores from the northern indian ocean to define the proportions of fluvial and eolian input and to reconstruct quaternary patterns of coastal upwelling the majority of dust deposited in the western arabian sea during the holocene about 100 106 t yr 1 is advected from arabia by northwesterly winds which overlie the low level southwest monsoon the glacial increase in dust flux to 160 106 t yr 1 culminated in the northern arabian sea most probably due to i entrainment of dust rich in chlorite dolomite and lithogenic carbonate in the then dry persian gulf and ii a southward shift of the mean position of the southwest monsoon during glacial summer this shift is recorded in reduced accumulation rates of biogenic opal and increased rates of marine carbonate off somalia and oman both the terrigenous and biogenic sediment records show that the northwesterly winds and the southwest monsoon persisted over the last 27 000 yr as well as the asian continental summer heat low however the glacial seasonal time span of the southwest monsoon season was much reduced most likely because of a delay in the seasonal onset of the southwest monsoon

a new trace fossil assemblage from the middle permian broughton formation southern sydney basin southeastern australia ichnology and palaeoenvironmental significance abstract the permian triassic sedimentary succession of the southern sydney basin in southeastern australia contains a wealth of well preserved trace fossils that are important for systematic ichnological palaeoecological and palaeoenvironmental interpretations in this study a new ichnofossil assemblage comprising macaronichnus palaeophycus psammichnites protovirgularia rosselia and teichichnus is documented from the tide influenced shoreface deposit of the middle permian jamberoo sandstone member of the broughton formation two distinct ichnofabrics are recognized i the psammichnites ichnofabric characteristic of the upper middle shoreface deposit and ii the crowded rosselia ichnofabric cri representing the lower shoreface the psammichnites dominated ichnofabric is interpreted to have resulted from opportunistic behaviours of unknown trace makers whereas the cri is interpreted to represent possible strategic behaviours of stress tolerant polychaetes e g terebellid spionid and cirratulid polychaetes in a distal shoreface with high sedimentation rate thus the psammichnites crowded rosselia ichnofabric succession can be considered to represent a response to an environmental shift from proximal to distal shoreface as such this study highlights the utility of these two ichnofabrics as stressed environmental indicators

sequential colonization of muddy turbidites in the eocene beloveža formation carpathians poland abstract a 100 350 m thick succession of centimeter thick fine grained turbidites form the lower mud dominated part of a prograding deep sea fan in the eocene belove a formation in the carpathian mountains of poland these strata contain over 50 ichnotaxa only six of which are common phycosiphon nereites chondrites scolicia halopoa ophiomorpha polished slabs and examination of cross cutting relationships show that post event colonization was sequential using modern analogues it can be shown that the colonization of different depth levels in the sediment at different times reflects changing geochemical conditions especially the re adjustment and re establishment of the redox boundary modern analogues allow an assessment of the timing of each colonization phase the phycosiphon producers entered first and occupied the well oxygenated muds 5 40 mm below the sediment surface as the redox boundary reformed nereites producers entered and probably utilized microbial matter just above the redox boundary about 15 30 mm below the sediment surface subsequently chondrites producers penetrated down to the oxygen deficient layers of the event bed or even deeper levels the halopoa producers entered with phycosiphon but reworked coarser layers contemporaneously with this sequential colonization deep permanent bioturbators which were unaffected by the event cross cut the post depositional suite the variability of the resultant ichnofabrics can be attributed in part to a patchy distribution of the benthos and the relative frequency of turbidite events five ichnofabrics which reflect the successive colonization episodes are recognized each was modified by elements of the permanent infauna

quaternary glacial history of nw garhwal central himalayas a first account of the quaternary glacial history is presented for northwest garhwal central himalaya on the basis of sediments and landforms one glacial stage has been recognised this is called the bhagirathi glacial stage when extensive valley glaciers advanced down the bhagirathi valley to jhala 40 5 km from the snout of gangotri glacier the ela depression during this stage was ca 640 m the bhagirathi glacial stage is constrained by optically stimulated luminescence dates of ca 63 ka and 5 ka bp and this glaciation is considered equivalent to the last glaciation elsewhere in the world the maximum extent of ice occurred ca 63 ka bp this however does not correlate with the last glacial maximum for the northern hemisphere ice sheets 20 18 ka bp a series of sharp crested moraines are present between 1 to 3 km beyond the snouts of most of the present glaciers these moraines formed during the mid holocene 5 ka bp termed here the shivling glacial advance small moraines are inset into these and are dated at about 200 to 300 bp the bhujbas glacial advance ca 300 to 200 bp and considered equivalent to the little ice age in other parts of the world ela depressions of between 40 100 m and 20 60 m occurred during the shivling and bhujbas glacial advances respectively since the bhujbas glacial advance there has been progressive retreat of glaciers initially by downwasting and retreat and then by simple retreat this retreat has accelerated during the last few decades impressive paraglacial fans are associated with deglaciation representing very rapid resedimentation during and soon after ice retreat

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

storm related sedimentation influenced by coastal configuration in the stratigraphic record of a tectonically active shelf upper pleistocene le castella terrace italy abstract analysis of patterns of coastal circulation and sediment dispersal is an essential step for the study of controlling factors influencing the long term dynamics of coastal systems modern settings offer the possibility to monitor relevant parameters over relatively short time spans however geological examples complement this perspective by providing a time averaged record where longer trends and stratigraphically significant processes can be evaluated this study investigates the shallow marine deposits of le castella terrace upper pleistocene southern italy to document how patterns of circulation influenced by coastline configuration can affect the preserved millennial scale depositional record of a progradational shoreline system the regressive portion of the le castella terrace deposits developed during a relative sea level highstand and falling stage consists of a progradational wedge mainly composed of redistributed skeletal particles of a coeval shallow water carbonate factory preservation of the morphology of the paleocoastline and abundant current related sedimentary structures allow reconstruction of the predominant sediment dispersal dynamics responsible for the formation of this sedimentary wedge facies and paleocurrent analysis indicate offshore and alongshore sediment transport modes consistent with coastal circulation driven by storms normally incident to the shoreline and a sharp change in coastline orientation this coastal inflection influenced circulation patterns causing flow separation and eddy formation in the lee of the curved coastline syndepositional tectonic deformation also affected the architecture of the preserved deposits controlling the nucleation and development of a clinostratified body and determining localized lateral stratigraphic variability this study illustrates how transient but recurrent circulation patterns associated with changes in coastal orientation and related to high energy storm events can leave a predominant signature in the stratigraphic record of microtidal shallow marine successions

distribution ecology and taphonomy of the organism trace scolicia in northeast atlantic deep sea sediments abstract the organism burrow scolicia was studied in deep sea sediment cores from several regions of the northeast atlantic including the iceland faeroe ridge rockall plateau and reykjanes ridge the data comprised sedimentological and physical measurements and x ray radiographs scolicia generally can be observed only in radiographs grain size and sorting of sediments control the distribution of the echinoids that produce scolicia if developed under optimum ecological conditions in well sorted coarse silts to fine sands scolicia dominates the biogenic structures with its very characteristic ichnofabrics its distribution pattern is influenced mainly by bottom currents sedimentation rate and the faunal association indirectly a dependence on water depth also seems to exist the preservation and recognition of scolicia in lithified sediments needs special conditions these include restricted competition by organisms of the deeper burrowing tiers its generation within the optimum sediment grain size or its production at the sand silt mud interface

sedimentary facies during early stages of flooding in an extensional basin the breche rouge de carboneras late miocene almeria se spain the intramontane basins of the betic cordil leras se spain formed subsequent to the main phase of orogenic deformation during the middle miocene in a close genetic relation to the trans alboran shear zone left lateral movements along a local branch carboneras fault zone cf strike ne sw of this zone played a major role in controlling the formation and dynamics of the nijar carboneras basin to the south of the fault a major phase of strike slip faulting is recorded during the late tortonian the expression of this event is the brche rouge de carboneras brc which seals a deep denudational surface on top of dislocated fault blocks formed by volcanics of the cabo de gata complex and early tortonian shallow marine calcarenite the sedi mentary facies of this widely distributed unit in the carboneras subbasin mirror the submarine topography and the distribution of the fault zones along strike slip fault zones autoclastic breccias and neptunian dikes preferentially oriented nw se and ne sw occur which are interpreted to represent the near surface expression of the faults red limestone forms the groundmass of the autoclastic breccia and infills of neptunian dikes which exhibit multiple phases of opening of fissures gravita tional sedimentary infill lithification and renewed cre ation of cracks steep relief probably along fault scarps was mantled by epiclastic volcanic conglomerate with a red carbonate matrix well lithified coarse skeletal lime stone rich in planktonic foraminifera formed pavements along sediment starved rocky surfaces in deep water laterally within topographic depressions the pavement limestone grades into thick accumulations of skeletal rudstone composed of fragmented azooxanthellate corals and stylasterid hydrozoans which were concentrated by powerful bottom currents and gravitiy flows within the shallow water zone of dip slope ramps cross bedded calcarenite and calcirudite formed based on textures fabrics and biota rocks of the brc were grouped into nine genetic lithofacies which document cryptic deep aphotic and shallow photic environments typical of a sediment starved extensional basin

timing of multiple late quaternary glaciations in the hunza valley karakoram mountains northern pakistan defined by cosmogenic radionuclide dating of moraines moraines and associated landforms in the upper hunza valley karakoram mountains northern pakistan provide an excellent record of multiple glaciations during the late quaternary glaciers advanced at least eight times by using 10 be and 26 al surface exposure dating on moraine boulders and scoured bedrock we determined the timing of glaciation for four of these glacial advances ca 54 7 43 2 ka borit jheel glacial stage ca 25 7 21 8 ka ghulkin i glacial stage ca 18 4 15 3 ka ghulkin ii glacial stage and ca 10 8 9 0 ka batura glacial stage for two of the older advances the yunz and shanoz glacial stages our data set a limit of 60 ka although at present the uncertainties in dating make it impossible to describe unequivocally the climate processes controlling glaciations in the hunza valley the results suggest that precipitation changes related to oscillations in the southwest asian monsoonal system combine with cooling that is broadly associated with heinrich events to cause glacial advances in this region

pliocene pleistocene sequences bounded by subaerial unconformities within foramol ramp calcarenites and mixed deposits salento se italy nine discrete metre scale sequences of early pliocene to middle pleistocene age were deposited in the small novoli graben salento peninsula puglia s italy they consist of carbonate and mixed carbonate siliciclastic sediments deposited on a slowly subsiding foreland ramp skeletal concentrations and intervening less fossiliferous intervals have been examined to provide information on major environmental parameters and infer the dynamics of their changes taphonomic and palaeoecological analyses indicate that storm induced waves and currents reduced sediment input and settling behaviour of components were the main factors controlling the features of the various shellbed types the concentrations were formed below fair weather wave base in low stress inner to outer shelf environments and are often associated with surfaces or intervals that are characterized by sedimentary condensation vertical change in the fossil content within individual cycles indicates water depth changes that were parallel to climatic fluctuations hence may result from glacio eustatic sea level changes most sequences are bounded by subaerial karstic unconformities because of the regional setting of low subsidence rate the record of the relative sea level fluctuations is incomplete episodes of subaerial exposure and concomitant effects of vadose diagenesis are documented by i diagenetic changes leading to hardening of unconformity horizons ii local subvertical solution pits developed in the vadose zone below unconformity surfaces iii networks of polygonal cracks below unconformities and iv infilling of solution pits and polygonal cracks with vadose silt and marine sediment inwashed during transgressions following the subaerial stages lower sequences are characterized by tighter cementation and significant increase in moldic and vuggy porosity due to superimposition of the diagenetic effects of repeated high amplitude sea level fluctuations

composite ichnofabrics and tiering of burrows infaunal communities in marine environments typically are tiered that is different taxa live at different depths within the sediment tiered suites of biogenic structures yield complex biogenic sedimentary fabrics ichnofabrics with the traces of deep burrowing organisms overprinted on those of shallow burrowing organisms careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities it is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier thus they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers on which the deeper traces are juxtaposed

catastrophic landslide deposits in the karakoram himalaya in july 1986 three catastrophic landslides deposited about 20 x 106 cubic meters of debris on bualtar glacier in the karakoram himalaya a sudden acceleration and superficial breakup of the glacier provided an opportunity to examine the fresh deposits in depth beneath a surface layer of large boulders finer materials mainly sand and silt made up half of the total volume the fine materials were formed during the rock avalanche from mostly intact massive rock of the source zone velocity estimates suggest that this disaggregation occurred in less than 2 minutes coarse materials remained in bands of uniform lithology but the fine materials had diffused throughout the landslides a small amount of carbonate appears to have been calcined by frictional heating presumably at the base of the initial sliding masses these observations are relevant to understanding the mechanisms of catastrophic landslides other nearby rock avalanche deposits indicate that landslides are an important geomorphic process in the area and that they pose a continuing risk to human activity

sand waves echinocardium traces and their bathyal depositional setting monte torre palaeostrait plio pleistocene southern italy stacked cross sets up to 2 5 m thick produced by sand wave migration and meniscate trace fossils produced by echinocardium cordatum both considered in the literature as typical of shallow water marine depositional settings commonly occur in the bathyal plio pleistocene deposits of monte torre calabria southern italy the plio pleistocene sediments form two coarsening upward depositional sequences separated by an unconformity and by a palaeobathymetric gap of at least 300 m the lower sequence passes upwards from hemipelagic marls and thin bedded turbidites to thick bedded sandy turbidites then to sand wave deposits alternated with sandy turbidites and finally to base of slope megabreccias facies characteristics and relationships and the occurrence of deep sea faunal associations indicate deposition in the bathyal zone the facies of the upper sequence reflect a fan delta environment no deeper than a few tens of metres the depositional setting of the lower sequence where the sand wave deposits and meniscate trace fossils occur appears to have been a tectonically controlled seaway connecting the tyrrhenian and ionian seas this seaway became progressively narrower with time evolving into a strait the overall coarsening upward trend reflects the upward transition from a low to a high energy environment possibly caused by the tectonic narrowing of the seaway deposition and erosion from high concentration turbidity currents and from tidal bottom currents were important processes periods of tectonic activity producing first the uplift of the seaway margins and culminating with the uplift of the strait sequence itself are marked by scattered rockfall deposits the strait setting causing the development of powerful oxygenated bottom currents produced optimal conditions in the bathyal zone for the colonization of sandy bottoms by a single infaunal r selected species echinocardium sp

palaeoecology and taphonomy of spatangoid dominated echinoid assemblages a case study from the early middle miocene of sardinia italy abstract the early middle miocene marine sedimentary succession of the borutta formation cropping out at porto torres northern sardinia represents one of the most diverse and well preserved spatangoid dominated sedimentary successions in the miocene of the mediterranean area the echinoid bearing succession is studied with the twofold purpose of firstly reconstructing the palaeoenvironmental setting in which these echinoids occurred and secondly investigating factors influencing the preservation potential of spatangoid echinoids in the fossil record these goals are accomplished by 1 detailed logging of sedimentary facies 2 applying functional morphological interpretations of echinoid skeletons in order to reconstruct their behaviour and life habits 3 quantifying the relative abundance of taxa and taphonomic features of test preservation and 4 analyzing associated trace fossils within the beds the sedimentary succession is composed mainly of fine grained sandstones which are intensely bioturbated by thalassinoides like burrows spatangoid abundance is high throughout the profile declining only in intercalated dm thick rhodolith beds a 20 cm thick bed with a bedding surface of approximately 250 m2 was investigated in detail with respect to relative abundance of spatangoid taxa and taphonomic signatures the echinoids consist almost exclusively of deposit feeding irregular forms with a dominance of the spatangoids ova and brissopsis and the minute clypeasteroid echinocyamus the spatangoids opissaster holanthus metalia and hemipatagus as well as the clypeasteroid clypeaster marginatus are also present a low energy moderately deep outer sublittoral environment with high rates of bioturbation and episodes of sediment deposition by storms is inferred interspecific competition among deposit feeding echinoids appears to be limited by their different burrowing depths feeding strategies and resource partitioning the gregarious behaviour of spatangoid echinoids their habitat in quiet deeper environments and episodes of rapid deposition seem to represent the main factors leading to this spatangoid bearing deposit since both shallow and deep burrowing spatangoid echinoids are well represented as complete specimens mode of life does not appear to play a major role in their preservation potentials

terrestrial 10 be and electron spin resonance dating of fluvial terraces quantifies quaternary tectonic uplift gradients in the eastern pyrenees the 120 km longt et river flows out of the pyrenees to the mediterranean by displaying a mappable sequence of quaternary alluvial units between the pleistocene frontal moraines of the high range and the offshore sedimentary depocentres its 1400 km 2 watershed is well suited to quantifying gradients of topographic uplift five main generations of terrace treads had previously been inferred from constrasts in regolith weathering features but here we present the first radiometric age constraints based on 15 esr sediment burial ages covering the full sequence and 3 vertical tcn age profiles restricted to three mid sequence terraces analytically robust results were obtained for the oldest and uppermost terrace t5 esr age 1099 179 ka for t3b esr age 374 47 ka mis 10 and for t2 esr age 174 44 ka mis 6 these results are consistent with the contrasts in weathering grade of the deposits the tcn profiles only yielded minimum exposure ages but provided precise post depositional denudation rates for the fluvial terrace treads the land to sea geometry of the chronosequence also provided clues about valley incision rates in response to topographic uplift during the last 1 ma based on a critical review of similar data obtained for other mediterranean and atlantic watersheds in the pyrenees the full regional correlation reveals that post orogenic topographic uplift was substantial and relatively uniform throughout the entire mountain range patterns and magnitudes suggest a shared probably subcrustal driving mechanism of neogene and quaternary mountain growth with only subsidiary influence from isostasy and climatic forcing