spatio temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a coral reef lagoon this paper presents the concentration and size distribution of suspended particles in the south west coral reef lagoon of the island of new caledonia data are provided by filtration techniques optical backscattering obs measurements and in situ laser diffraction particle sizing the concentration of suspended particles increased from reef to land a bottom nepheloid layer occurred over the entire lagoon and was more distinct on the nearshore area small particles were more abundant in the bottom nepheloid layer than in the overlying water column the concentration of suspended particles showed more variability over space than over time conversely the particle size distribution of suspended particles showed more variability at a given location over a month time variability than at a given moment over the lagoon space variability analysis showed that aggregates represented a large fraction of suspended particles microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix the relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased the spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to coral reefs the high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance infer that aggregation is induced by the presence of organic ligands unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate dominated system

a tsunami deposit at the cretaceous tertiary boundary in texas at sites near the brazos river texas an iridium anomaly and the paleontologic cretaceous tertiary boundary directly overlie a sandstone bed in which coarse grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple laminated very fine grained sandstone this bed is the only sandstone bed in a sequence of uppermost cretaceous to lowermost paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high the most likely source for such a tsunami at the cretaceous tertiary boundary is a bolidewater impact

multiple impacts across the cretaceous tertiary boundary abstract the stratigraphy and age of altered impact glass microtektites microkrystites ejecta layers from the chicxulub crater are documented in late maastrichtian and early danian sediments in mexico guatemala belize and haiti in northeastern mexico two to four ejecta layers are present in zone cf1 which spans the last 300 ky of the maastrichtian the oldest ejecta layer is dated at 65 27 0 03 ma based on sediment accumulation rates and extrapolated magnetostratigraphy all younger ejecta layers from the maastrichtian and early danian parvularugoglobigerina eugubina zone pla l may represent repeated episodes of reworking of the oldest layer at times of sea level changes and tectonic activity the k t boundary impact event 65 0 ma is not well represented in this area due to widespread erosion an early danian pla l ir anomaly is present in five localities bochil actela coxquihui trinitaria and haiti and is tentatively identified as a third impact event at about 64 9 ma a multiimpact scenario is most consistent with the impact ejecta evidence the first impact is associated with major deccan volcanism and likely contributed to the rapid global warming of 3 4 c in intermediate waters between 65 4 and 65 2 ma decrease in primary productivity and onset of terminal decline in planktic foraminiferal populations the k t boundary impact marks a major drop in primary productivity and the extinction of all tropical and subtropical species the early danian impact may have contributed to the delayed recovery in productivity and evolutionary diversity

the cretaceous tertiary boundary stratotype section at el kef tunisia how catastrophic was the mass extinction abstract the cretaceous tertiary k t boundary stratotype section at el kef tunisia represents the most complete and expanded sedimentary record across this important mass extinction horizon presently known high resolution analysis of planktic foraminifera in two outcrops el kef i stratotype and el kef ii along with comparisons between planktic and benthic foraminifera calcareous nannofossils ostracods pollen and spores and dinoflagellates indicate that major changes across the k t boundary are registered only in benthic and planktic foraminifera and calcareous nannofossils biotic changes in benthic foraminifera are unique to el kef and similarly shallow continental shelf sections and appear to be the result of a sea level regression in the latest maastrichtian followed by a sea level rise across the k t boundary that was accompanied by expansion of the local oxygen minimum zone omz biotic changes in planktic foraminifera appear partly related to these conditions also but in general reflect more global oceanographic changes for instance species extinctions are gradual and selective as observed in k t sections worldwide rather than random and abrupt although there is a 69 decline in species richness between 25 cm below and 10 cm above the k t boundary only rare species disappeared their combined relative abundance constitute less than 20 of the total population about 52 of these extinct taxa 8 of the population are large ornate morphologically complex tropical subtropical forms that lived at or below the thermocline no planktic foraminifera from this depth range survived the k t boundary event all survivor taxa were surface dwellers living within the photic zone their relative abundance 80 dominates both cretaceous and early tertiary populations these data indicate that the k t biotic record in the shallow continental shelf section at el kef was significantly influenced by local conditions which combined with the latest maastrichtian sea level regression and subsequent sea level rise resulted in shallowing of the local omz relative to the sea surface shallowing of the local omz lead to the selective disappearance of benthic faunas and may have adversely affected the surviving photic zone dwellers the selective nature of species extinctions however appear to be related partly to long term global oceanographic changes which were accelerated at the k t boundary possibly by a bolide impact

determination of rapid deccan eruptions across the cretaceous tertiary boundary using paleomagnetic secular variation 2 constraints from analysis of eight new sections and synthesis for a 3500 m thick composite section 1 the present paper completes a restudy of the main lava pile in the deccan flood basalt province trap of india chenet et al 2008 reported results from the upper third and this paper reports the lower two thirds of the 3500 m thick composite section the methods employed are the same i e combined use of petrology volcanology chemostratigraphy morphology k ar absolute dating study of sedimentary alteration horizons and as the main correlation tool analysis of detailed paleomagnetic remanence directions the thickness and volume of the flood basalt province studied in this way are therefore tripled a total of 169 sites from eight new sections are reported in this paper together with the results of chenet et al 2008 these data represent in total 70 of the 3500 m combined section of the main deccan traps province this lava pile was erupted in some 30 major eruptive periods or single eruptive events see each with volumes ranging from 1000 to 20 000 km3 and 41 individual lava units with a typical volume of 1300 km3 paleomagnetic analysis shows that some sees with thicknesses attaining 200 m were emplaced over distances in excess of 100 km both likely underestimates due to outcrop conditions and up to 800 km the total time of emission of all combined sees could have been much less than 10 ka with most of the time recorded in a very small number of intervening alteration levels marking periods of volcanic quiescence so called big red boles the number of boles thickness of the pulses and morphology of the traps suggest that eruptive fluxes and volumes were larger in the older formations and slowed down with more and longer quiescence periods in the end on the basis of geochronologic results published by chenet et al 2007 and paleontological results from keller et al 2008 we propose that volcanism occurred in three rather short discrete phases or megapulses an early one at 67 5 1 ma near the c30r c30n transition and the two largest around 65 1 ma one entirely within c29r just before the k t boundary the other shortly afterward spanning the c29r c29n reversal we next estimate sulfur dioxide likely a major agent of environmental stress amounts and fluxes released by sees they would have ranged from 5 to 100 gt and 0 1 to 1 gt a respectively over durations possibly as short as 100 years for each see the chemical input of the chicxulub impact would have been on the same order as that of a very large single pulse the impact therefore appears as important but incremental neither the sole nor main cause of the cretaceous tertiary mass extinctions

the global stratigraphy of the cretaceous tertiary boundary impact ejecta the chicxulub crater ejecta stratigraphy is reviewed in the context of the stratigraphy of underlying and overlying rock sequences the ejecta sequence is regionally grouped in a thick polymict and monomict breccia sequences inside the crater and within 300 km from the rim of the crater known from drill holes in and close to the breater and exposures near the border of yucatan and belize b gulf of mexico region 2500 m from the crater with up to 9 m thick complex tsunami wave influenced tektite bearing sequences in shallow marine 500 m deep environments and tektite bearing decimeter thick gravity flow deposits in deep water sites c an intermediate region between 2500 and 4000 km from the crater where centimeter thick tektite bearing layers occur and d a global distal region with a millimeter thin ejecta layer the distal ejecta layer is characterized by sub millimeter sized microkrystites often rich in ni rich spinels and altered clinopyroxene wherever present the ejecta layers mark exactly the sudden mass mortality horizon of the k t boundary what exactly caused the mass mortality is still uncertain but it appears the main event leading to the k t mass extinctions

extended cretaceous tertiary boundary extinctions and delayed population change in planktonic foraminifera from brazos river texas high resolution planktonic foraminiferal analysis of three brazos river sections indicates a nearly continuous cretaceous tertiary k t boundary sedimentary record second only to the world s most complete record at el kef tunisia species extinctions occur over an extended period of time and with two major extinction episodes the first extinction episode with 46 of the species extinct occurs at and just below 10 15 cm a short hiatus at the base of a sandy shell hash and clay sand unit which was interpreted by bourgeois et al 1988 to represent a tsunami bed generated by the k t boundary bolide impact the top of this tsunami bed is about 17 20 cm below the k t boundary as defined by the first appearance of tertiary planktonic foraminifera the second extinction phase with 45 of the species extinct occurs 25 cm above the k t boundary zone p0 p1a boundary of the remaining seven surviving cretaceous species six gradually disappear during planktonic foraminiferal subzones p1a and basal p1b no species extinctions or major faunal assemblage changes are directly associated with the k t boundary iridium distribution is ambiguous with one peak in the upper part of the tsunami bed and a second peak at the micropaleontologically defined k t boundary relative abundances of dominant species are stable through the late maastrichtian and only minor abundance changes coincide with the first extinction episode or the k t boundary the first major faunal change in the dominant species group coincides with the second extinction episode and leads to decline and eventual extinction of this group in subzone p1a species disappearing at the two extinction episodes 46 and 45 constitute only a small percentage 8 and 5 of the individuals of the total planktonic foraminiferal population this suggests that weakened species with low numbers of individuals and sensitive to relatively minor environmental changes were primarily affected by these extinction episodes magnetostratigraphy indicates that the first extinction phase began about 310 000 years before the k t boundary and the second extinction phase occurred 50 000 years after the k t boundary this stepped pattern of species extinctions suggests a progressively stressed ecosystem in continental shelf settings which may be related to an observed sea level regression and global cooling the hypothesis of a global catastrophic mass extinction at the k t boundary caused by a large extraterrestrial impact is not supported by the brazos river planktonic foraminiferal data

chemostratigraphic evidence of deccan volcanism from the marine osmium isotope record continental flood basalt cfb volcanism is hypothesized to have played a causative role in global climate change and mass extinctions uncertainties associated with radiometric dating preclude a clear chronological assessment of the environmental consequences of cfb volcanism our results document a 25 decline in the marine 187 os 188 os record that predates the cretaceous tertiary boundary ktb and coincides with late maastrichtian warming we argue that this decline provides a chemostratigraphic marker of deccan volcanism and thus constitutes compelling evidence that the main environmental consequence of deccan volcanism was a transient global warming event of 3 to 5 c that is fully resolved from the ktb mass extinction

spherule deposits in cretaceous tertiary boundary sediments in belize and guatemala large spheroid deposits at albion island and armenia in northern and central belize and the spherule deposits of southern belize and eastern guatemala have the same glass origin based on the presence of almost pure cheto smectite derived from alteration of impact glass from the chicxulub impact on yucatan mexico the same origin has also been determined for altered glass spherules in mexico haiti and the caribbean however the spherule layers have variable ages as a result of erosion and redeposition with an early danian parvularugoglobigerina eugubina zone pla 1 age in southern belize guatemala haiti southern mexico and the caribbean and a pre k t plummerita hantkeninoides zone cf1 age of 65 27 0 03 ma in ne mexico a pre k t age for the chicxulub impact has now also been determined from the new yaxcopoil 1 core drilled in the impact crater these data show that chicxulub was not the k t impact that caused the end cretaceous mass extinction but an earlier impact event a multiple impact hypothesis volcanism and climate change appears the likely scenario for the end cretaceous mass extinction

chicxulub impact predates k t boundary new evidence from brazos texas abstract multidisciplinary studies including stratigraphy sedimentology mineralogy and geochemistry of the new core mullinax 1 and outcrops along the brazos river and cottonmouth creek falls county texas reveal the complex history of the chicxulub impact the event deposit and the k t boundary event the k t boundary as identified by the negative 13c shift first occurrence of danian planktic foraminifera and palynomorphs occurs 80 cm above the event deposit in core mullinax 1 the underlying 80 cm interval was deposited in a shallow low oxygen environment during the latest maastrichtian as indicated by high stress microfossil assemblages small shells and burrows infilled with framboidal pyrite the underlying event deposit commonly interpreted as k t impact tsunami consists of a basal conglomerate with clasts containing chicxulub impact spherules repeated upward fining units of spherule rich sands followed by hummocky cross bedded and laminated sands which are burrowed by thalassinoides planolites and ophiomorpha and truncated by erosion this suggests a series of temporally separated storm events with re colonization of the ocean floor by invertebrates between storms rather than a series of waning tsunami generated waves the lithified clasts with impact spherules at the base of the event deposit provide strong evidence that the chicxulub impact ejecta layer predates the event deposit but was eroded and re deposited during the latest maastrichtian sea level lowstand the original chicxulub ejecta layer was discovered in a 3 cm thick yellow clay layer interbedded in undisturbed late maastrichtian clay and mudstones 40 cm below the base of the event deposit and near the base of planktic foraminiferal zone cf1 which spans the last 300 kyr of the maastrichtian the yellow clay consists of cheto smectite derived from alteration of impact glass as indicated by rare altered glass spherules with similar chemical compositions as reworked spherules from the event deposit and chicxulub impact spherules from ne mexico and haiti the brazos sections thus provide strong evidence that the chicxulub impact predates the k t boundary by about 300 kyr consistent with earlier observations in ne mexico and the chicxulub crater core yaxcopoil 1

a laboratory evaluation of the laser in situ scattering and transmissometery instrument using natural sediments abstract the lisst laser in situ scattering and transmissometery instrument was designed by sequoia scientific to measure the particle size distributions and concentrations of sediment suspensions in the field environment to understand the lisst s performance with natural sediments from a variety of marine sources several experiments were performed to compare the lisst s results to traditional sieving filtering and weighing techniques the lisst was able to correctly locate the peak of a unimodal particle size distribution and resolve the two peaks of a bimodal distribution if they are separated by at least 1 for sediment sizes of 5 to 250 m unlike a single frequency scattering sensor for sediment concentration which require sediment size specific calibration constants the lisst is able to accurately measure sediment concentration with a single calibration constant for varying size distributions within the size range of 5 to 250 m the lisst was also found to adequately represent the particle volumetric size distribution for two different samples from marine environments

the cretaceous palaeogene boundary succession at stevns klint denmark foraminifers and stable isotope stratigraphy the cretaceous palaeogene boundary exposed at stevns klint denmark provides an important location for the investigation of the end cretaceous event in this work we have used a number of sections across the boundary including the little described expanded stratigraphic sequence at kulstirenden which is located 7 km north of hojerup where most published work is derived using stratigraphical micropalaeontological and stable isotope 18o and 13c data we have shown that there is clear evidence of shallowing in the latest maastrichtian prior to and across the cretaceous palaeogene boundary there are significant changes in sea water temperature including an important cooling event in the very latest maastrichtian the 13c record in the expanded boundary clay fish clay sequence at kulstirenden indicates a number of significant excursions of decreasing magnitude up section the evidence from the distribution of the foraminifers has been incorporated with previous work to develop a sequence stratigraphical interpretation for the succession that can be compared to other cretaceous palaeogene boundary successions in europe

sulfur and chlorine in late cretaceous deccan magmas and eruptive gas release large volume p hoehoe lava flows erupted 67 to 65 million years ago forming the deccan traps india the impact of these flood basalt eruptions on the global atmosphere and the coeval end cretaceous mass extinction has been uncertain to assess the potential gas release from this volcanism we measured sulfur and chlorine concentrations in rare glass inclusions inside crystals and on glassy selvages preserved within lavas concentrations range from 1400 parts per million of s and 900 parts per million of cl in inclusions down to a few hundred parts per million in the lava these data indicate that eruptions of deccan lavas could have released at most 0 103 weight of s yielding up to 5 4 teragrams of so2 per cubic kilometer of lava a more conservative estimate is 0 07 weight of s and 0 04 weight of cl yielding 3 5 teragrams of so2 and 1 teragram of hcl for every cubic kilometer of lava erupted the flows were very large in volume and these results imply that huge amounts of s and cl gases were released the environmental impact from even individual eruptions during past flood basalt activity was probably severe

age and paleoenvironment of the maastrichtian to paleocene of the mahajanga basin madagascar a multidisciplinary approach abstract lithology geochemistry stable isotopes and integrated high resolution biostratigraphy of the berivotra and amboanio sections provide new insights into the age faunal turnovers climate sea level and environmental changes of the maastrichtian to early paleocene of the mahajanga basin of madagascar in the berivotra type area the dinosaur rich fluvial lowland sediments of the anembalemba member prevailed into the earliest maastrichtian these are overlain by marginal marine and near shore clastics that deepen upwards to hemipelagic middle neritic marls by 69 6 ma accompanied by arid to seasonally cool temperate climates through the early and late maastrichtian an unconformity between the berivotra formation and betsiboka limestone marks the k t boundary and juxtaposes early danian zone plc or pld and latest maastrichtian zones cf2 cf1 micula prinsii sediments seasonally humid warm climates began near the end of the maastrichtian and prevailed into the early danian accompanied by increased volcanic activity during the late danian zones p1d p2 a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths

laboratory evaluation of the lisst in a stratified fluid a laboratory study to evaluate the performance of a laser in situ scattering and transmissometry lisst in a stratified environment is presented light passing through a stratified turbulent fluid is scattered due to changes in the index of refraction in natural water bodies density stratification due to surface heating and fresh water salt water mixing is widespread therefore in situ instruments designed to measure particle size based on the principle of laser diffraction such as the lisst are likely to encounter operational limits under stratified conditions results from a laboratory study show that salinity fluctuations cause small angle forward scattering patterns that are indistinguishable from particle scattering for a type c lisst which measures particles in the 2 5 to 500 m range the scattering is confined primarily to the inner 9 rings under salinity stratification ranging from 2 to 10 ppt experiments conducted with stratification and particles reveal that the type c lisst can distinguish particle size distributions so long as the median particle size is smaller than about 128 m

is the transition impact to post impact rock complete some remarks based on xrf scanning electron microprobe and thin section analyses of the yaxcopoil 1 core in the chicxulub crater the transition from impact to post impact rocks in the yaxcopoil 1 core is marked by a 2 cm thick clay layer characterized by dissolution features the clay overlies a 9 cm thick hardground overlying a 66 cm thick crossbedded unit consisting of dolomite sandstone alternating with thin micro conglomerate layers with litho and bioclasts and the altered remains of impact glass now smectite the micro conglomerates mark erosion surfaces microprobe and backscatter sem analysis of the dolomite rhombs show an early diagenetic complex zoned idiomorphic overgrowth with mn rich zones possibly formed by hot fluids related to cooling melt sheet in the crater the pore spaces are filled with several generations of coelestite barite k feldpar and sparry calcite xrf core scanning analysis detected high mn values in the crossbedded sediments but no anomalous enrichment of the siderophile elements cr co fe and ni in the clay layer shocked quartz occurs in the crossbedded unit but is absent in the clay layer the basal paleocene marls are strongly dissolved and do not contain a basal paleocene fauna the presence of a hardground the lack of siderophile elements shocked quartz or ni rich spinels in the clay layer and the absence of basal paleocene biozones p0 and pa all suggest that the top of the ejecta sequence and a significant part of the lower paleocene is missing due to the high energy sedimentation infill a hiatus at the top of the impactite is not unexpected but there is nothing in the biostratigraphy geochemistry and petrology of the yaxcopoil 1 core that can be used to argue against the synchroneity of the end cretaceous mass extinctions and the chicxulub crater

characterization of late campanian and maastrichtian planktonic foraminiferal depth habitats and vital activities based on stable isotopes abstract depth habitats of 56 late cretaceous planktonic foraminiferal species from cool and warm climate modes were determined based on stable isotope analyses of deep sea samples from the equatorial pacific dsdp sites 577a and 463 and south atlantic dsdp site 525a the following conclusions can be reached planoglobulina multicamerata de klasz and heterohelix rajagopalani govindan occupied the deepest plankton habitats followed by abathomphalus mayaroensis bolli globotruncanella havanensis voorwijk gublerina cuvillieri kikoine and laeviheterohelix glabrans cushman also at subthermocline depth most keeled globotruncanids and possibly globigerinelliodes and racemiguembelina species lived at or within the thermocline layer heterohelix globulosa ehrenberg and rugoglobigerina pseudotextularia and planoglobulina occupied the subsurface depth of the mixed layer and pseudoguembelina species inhabited the surface mixed layer however depth ranking of some species varied depending on warm or cool climate modes and late campanian or maastrichtian age for example most keeled globotruncanids occupied similar shallow subsurface habitats as rugoglobigerina during the warm late campanian but occupied the deeper thermocline layer during cool climatic intervals two distinct types of vital effect mechanisms reflecting photosymbiosis and respiration effects can be recognized by the exceptional 13c signals of some species 1 photosymbiosis is implied by the repetitive pattern of relatively enriched 13c values of racemiguembelina strongest planoglobulina rosita and rugoglobigerina species pseudoguembelina excolata weakest 2 enriched respiration 12c products are recognized in a mayaroensis gublerina acuta de klasz and heterohelix planata cushman isotopic trends between samples suggest that photosymbiotic activities varied between localities or during different climate modes and may have ceased under certain environmental conditions the appearance of most photosymbiotic species in the late maastrichtian suggests oligotrophic conditions associated with increased water mass stratification

biotic effects of the chicxulub impact k t catastrophe and sea level change in texas abstract biotic effects of the chicxulub impact the k t event and sea level change upon planktic foraminifera were evaluated in a new core and outcrops along the brazos river texas about 1000 km from the chicxulub impact crater on yucatan mexico sediment deposition occurred in a middle neritic environment that shallowed to inner neritic depths near the end of the maastrichtian the sea level fall scoured submarine channels which were infilled by a sandstone complex with reworked chicxulub impact spherules and clasts with spherules near the base the original chicxulub impact ejecta layer was discovered 45 60 cm below the sandstone complex and predates the k t mass extinction by about 300 000 years results show that the chicxulub impact caused no species extinctions or any other significant biotic effects the subsequent sea level fall to inner neritic depth resulted in the disappearance of all larger 150 m deeper dwelling species creating a pseudo mass extinction and a survivor assemblage of small surface dwellers and low oxygen tolerant taxa the k t boundary and mass extinction was identified 40 80 cm above the sandstone complex where all but some heterohelicids hedbergellids and the disaster opportunistic guembelitrids went extinct coincident with the evolution of first danian species and the global 13c shift these data reveal that sea level changes profoundly influenced marine assemblages in near shore environments that the chicxulub impact and k t mass extinction are two separate and unrelated events and that the biotic effects of this impact have been vastly overestimated

a laboratory evaluation of optical backscatterance suspended solids sensors exposed to sand mud mixtures abstract optical suspended solids sensors were studied in the laboratory in order to obtain calibration factors and evaluate the general behavior of the instrument when exposed to suspensions of mud and sand the sensors were found to be capable of measuring the time averaged concentration of either suspended sand or suspended mud but the relative sensitivity of the sensor to these two different types of sediment varied by approximately an order of magnitude in mixtures with a constant or known mud concentration the instrument response to the mud may be treated as an offset and gains appropriate to sand may be used to estimate the suspended sand concentrations semi quantitative observations of the effects of flow direction relative to sensor orientation indicate that significant concern is warranted

impact and extinction in remarkably complete cretaceous tertiary boundary sections from demerara rise tropical western north atlantic ocean drilling program odp leg 207 on the demerara rise in the western tropical north atlantic recovered multiple cretaceous paleogene boundary sections containing an ejecta layer sedimentological geochemical and paleontological changes across the boundary closely match patterns expected for a mass extinction caused by a single impact a normally graded 2 cmthick bed of spherules that is interpreted as a primary air fall deposit of impact ejecta occurs between sediments of the highest cretaceous plummerita hantkeninoides foraminiferal zone and the lowest paleogene p0 foraminiferal zone there are no other spherule layers in the section in addition to extinction of cretaceous taxa foraminiferal abundance drops from abundant to rare across the boundary ir concentrations reach a maximum of 1 5 ppb at the top of the spherule bed and the ir anomaly is associated with enrichment in other siderophile elements we attribute the unusually well preserved and relatively simple stratigraphy to the fact that demerara rise was close enough 4500 km to the chicxulub impact site to receive 2 cm of ejecta yet was far enough away and perhaps sheltered by the curve of northern south america to have been relatively unaffected by impact induced waves

suspended particulate matter dynamics and aggregate sizes in a high turbidity area measurements of aggregate size suspended particulate matter spm concentration and current velocity have been carried out in the belgian coastal zone southern north sea two stations were situated in the coastal turbidity maximum zone another station was located more offshore at the edge of this turbidity maximum the data have been collected using a lisst 100 obs sensors water samples and a bottom mounted adcp turbulence kolmogorov microscale has been modelled for the same period using a 3d numerical model the results show that the size of the aggregates is significantly smaller in the coastal turbidity maximum area the processes responsible for the occurrence of smaller aggregate size in the coastal zone compared with the more offshore location are the higher turbulence the smaller time available for the aggregates to grow up to an equilibrium size the higher deposition of mud resulting in a break up of the floes and the lower availability of organic matter which may limit the size of the floes c 2006 elsevier b v all rights reserved

the chicxulub impact event and its environmental consequences at the cretaceous tertiary boundary abstract an impact mass extinction hypothesis for the cretaceous tertiary k t boundary transition has been confirmed with multiple lines of evidence beginning with the discovery of impact derived ir in k t boundary sediments and culminating in the discovery of the chicxulub impact crater likewise a link between the chicxulub impact crater and k t boundary sediments has been confirmed with multiple lines of evidence including stratigraphic petrological geochemical and isotopic data the environmental effects of the chicxulub impact event were global in their extent largely because of the interaction of ejected impact debris with the atmosphere the environmental consequences of the chicxulub impact event and their association with the k t boundary mass extinction event indicate that impact cratering processes can affect both the geologic and biologic evolution of our planet

laboratory evaluation of two lisst 25x using river sediments abstract there are different methods to determine particle size most of them are only applicable in the laboratory in order to describe the suspended fine sediment sizes where flocs may be part of the suspension in situ measurements are essential this work shows the results of sediment size measurements done in the laboratory using two lisst 25x diffractometers developed for in situ measurements and a malvern mastersizer 2000 diffractometer for laboratory use the two lisst 25x models characterize the sample size through the sauter mean diameter smd besides the smd the malvern diffractometer determines the granulometric distributions of the samples the tested samples are from different fluvial and estuarine environments parana salado and the amazon rivers and their sizes smd range from 4 to 300 m the relationship between smd obtained with the two lisst 25x and the malvern diffractometers gave a determination coefficient of r2 0 98 compared to the malvern instrument used as a reference it was observed that the lisst instruments tend to overestimate the measured smd for diameters lower than 20 m and to underestimate the values of samples with larger diameters 20 m aiming to obtain other characteristic diameters of the granulometric distribution from smd measurements obtained with lisst 25x diffractometers correlations between smd and d10 d50 and d90 were established the dependency of the measurement of sediment mass concentration obtained with lisst instruments with the particle size is also addressed

main deccan volcanism phase ends near the k t boundary evidence from the krishna godavari basin se india abstract recent studies indicate that the bulk 80 of the deccan trap eruptions occurred over less than 0 8 m y in magnetic polarity c29r spanning the cretaceous tertiary k t boundary determining where within this major eruptive phase the k t mass extinction occurred has remained problematic for this reason models estimating the biotic and environmental consequences have generally underestimated the rate and quantity of deccan gas emissions by orders of magnitude leading to conclusions that volcanism could not have been one of the major causes for the k t mass extinction in this study we report that the most massive deccan trap eruption occurred near the k t mass extinction these results are based on sedimentologic microfacies and biostratigraphic data of 4 9 m thick intertrappean sediments in four quarry outcrops in the rajahmundry area of the krishna godavari basin of southeastern india in this area two deccan basalt flows known as the rajahmundry traps mark the longest lava flows extending 1500 km across the indian continent and into the bay of bengal the sediments directly overlying the lower rajahmundry trap contain early danian planktic foraminiferal assemblages of zone p1a which mark the evolution in the aftermath of the k t mass extinction the upper rajahmundry trap was deposited in magnetic polarity c29n preceding full biotic recovery these results suggest that volcanism may have played critical roles in both the k t mass extinction and the delayed biotic recovery

the acoustic properties of in situ measured suspended sediments and their implications on concurrent adcp response case studies of the portuguese inner shelf abstract in this work we explore the possibility of extracting indicative suspended sediment information in terms of estimates of concentration and particle size from adcp single frequency monitoring datasets in order to accomplish this task four datasets of lisst field measurements collected in similar low concentration near shore transitional environments in the portuguese continental shelf were used to evaluate the suspended sediments acoustic properties backscatter and sound attenuation and evaluate their impact on concurrently measured adcp acoustic backscatter in a second step the adcp s acoustic signal was used in an attempt to estimate suspended sediment concentration and grain size and the inverted results were compared with lisst data results show that the chosen acoustic models to estimate backscatter and sound attenuation do not fully explain the adcp s backscatter temporal variation nevertheless the established relations between the ensemble form function which describes the scattering properties of the suspension and the mean particle size the temporal variation of the instrumental factor c with the adcp s acoustic intensity and the fact that sound attenuation due to the suspended particles is negligible under these deployment conditions allowed for the inversion of the adcp data yielding estimates of sediment concentration and mean grain size with errors within one order of magnitude when compared with lisst data

mineralogy and phase chemistry of an ir enriched pre k t layer from the lattengebirge bavarian alps and significance for the ktb problem abstract three distinct iridium anomalies are exposed in the cretaceous tertiary boundary ktb section of the lattengebirge bavarian alps comprising a pelagic calcareous sequence from below a continental slope multiple ir anomalies are in contrast to most reported k t sections which are characterized by a single ir peak two of these ir spikes are contained in the 20 cm thick actual ktb termed clayey interval with the main peak of 4 4 ppb precisely at the boundary and the second peak of 2 8 ppb 10 cm above a third peak of 3 6 ppb was detected at 16 cm below the ktb in a thin turbiditic and coal bearing sandstone layer of upper maastrichtian age the distribution of ir anomalies provides evidence of episodic ir delivering events over an extended period of time whereas the worldwide distributed single spiked ktb layers are composed entirely of diagenetically altered materials various phases are discernible in the well preserved ir bearing pre k t layer 1 sandstone clastic minerals in a carbonate matrix 2 coal which is partly burned 3 sulfides chalcopyrite included in coal and 4 silicate melt glasses the glasses represent the first ones reported from a k t section and were formed by combustion metamorphism from sedimentary parent rocks of the coal as indicated by their major element chemistry and ree patterns phase chemistry of the layer components reveals ir concentrations of up to 110 ppb indicating that ir and chalcophile trace elements tre are primarily contained in the sulfides this carrier phase points to ir enrichment by processes unrelated to impact and its stratigraphic position demonstrates availability of ir for incorporation into sediments before the ktb the uptake of ir and chalcophile tre into the coal and subsequent combustion metamorphism occurred on the continent during a time interval of 14 000 9000 yr prior to the ktb as constrained by radiometric age determinations stratigraphy and sedimentation rates in the lattengebirge k t sediments no indications of shock are found the results suggest a volcanic origin for the multiple ir bearing horizons like the worldwide ktb layers they are concomitantly enriched in ir and chalcophile tre and hence have a common source the lattengebirge k t profile is largely continuous and was recently reexamined by micropaleontological methods contribution by d herm and k f weidich the preservation of multiple ir anomalies is attributed to high sedimentation rates of 1 75 cm kyr and the absence of carbonate dissolution and condensation of sediments usually encountered in the worldwide ktb layers

new instrumentation for the investigation of sediment suspension processes in the shallow marine environment abstract an instrumentation system has been developed that continuously measures flow velocity water depth and suspended sediment concentration profiles in the nearshore zone the system consists of four components 1 an array of electronic sensors including an electromagnetic current meter a surface piercing resistance wave gauge and a five element array of optical back scatterance sensors 2 a signal processing electronics unit 3 a guyed mast support structure and 4 a data acquisition system the small size of the sensors and their response characteristics make the array suitable for monitoring sediment transport to within a few centimeters of the bed under moderately large breaking waves 2 m results from an experiment on an exposed ocean beach on the coast of washington u s a indicate that sand suspension events of long duration 15 40 sec relative to the period of incident waves contribute a significant quantity of sand to the total littoral drift work is now in progress to modify the system for self contained operation on the continental shelf field investigations with the modified system will focus on the acquisition of a data set to test the validity of the suspended sediment distribution equation

40k 40ar dating of the main deccan large igneous province further evidence of ktb age and short duration most mass extinctions coincide in time with outpourings of continental flood basalts cfb some 20 years ago it was shown courtillot v besse j vandamme d montigny r jaeger j j cappetta h 1986 deccan flood basalts at the cretaceous tertiary boundary earth planet sci lett 80 361 374 courtillot v feraud g maluski h vandamme d moreau m g besse j 1988 deccan flood basalts and the cretaceous tertiary boundary nature 333 843 846 duncan r a pyle d g 1988 rapid eruption of the deccan flood basalts at the cretaceous tertiary boundary nature 333 841 843 that the age of the deccan traps was close to the cretaceous tertiary kt boundary and its duration under 1 myr we have undertaken a new geochronological study using the unconventional 40k 40ar cassignol gillot technique which is particularly well suited to the potassium poor deccan lavas the mean of 4 determinations from the topmost ambenali and mahabaleshwar formations is 64 5 0 6 ma they straddle the c29r c29n reversal boundary for which they provide a new constraint the mean age of 3 determinations from the oldest jawhar formation is 64 8 0 6 ma the difference in age between top and bottom of a 3500 m composite section probably comprising 80 of the total deccan volume is statistically insignificant with the overall mean age being 64 7 0 6 ma n 7 our results are consistent with the most recent 40ar 39ar determinations knight k b renne p r halkett a white n 2003 40ar 39ar dating of the rajahmundry traps eastern india and their relationship to the deccan traps earth planet sci lett 208 85 99 knight k b renne p r baker j waight t white n 2005 reply to 40ar 39ar dating of the rajahmundry traps eastern india and their relationship to the deccan traps discussion by a k baksi earth planet sci lett 239 374 382 confirming that there should be no systematic difference between the two methods when they are used in an optimal way an earlier smaller but significant pulse of volcanism between 68 and 67 ma extending over at least 500 km in latitude in the northern part of the deccan cfb has also been identified after 2 to 3 ma of quiescence the second major phase of volcanism occurred near 65 ma expanding over most of the area covered by the first pulse and another 500 km to the south consistent with drift of india by 300 to 450 km at not vert similar 150 mm yr during the quiescence period new paleontological data from the remote rajahmundry section keller g adatte t gardin s bartolini a bajpai s humler e in prep the cretaceous tertiary boundary in deccan traps of the krishna godavari basin of southeastern india epsl to be submitted suggest that this second pulse can itself be divided into two major pulses one starting in c29r and ending at the kt boundary the second starting in the upper part of c29r and ending within c29n

ejecta layer at the cretaceous tertiary boundary bass river new jersey ocean drilling program leg 174ax a continuously cored borehole drilled at bass river new jersey recovered a cretaceous tertiary k t succession with a 6 cm thick spherule layer immediately above the boundary below the spherule layer the cretaceous glauconitic clay is extensively burrowed and contains the uppermost maastrichtian micula prinsii calcareous nannofossil zone spherical impressions of spherules at the top of the cretaceous indicate nearly instantaneous deposition of ejecta from the chicxulub impact the thickest ejecta layer shows clearly that a single impact occurred precisely at k t boundary time above the spherule layer the glauconitic clay contains the planktonic foraminiferal p0 and p alpha zones indicating 1 a complete k t succession and 2 continuous deposition interrupted only by fallout of the ejecta layer clay clasts within a 6 cm interval above the spherule layer contain cretaceous microfossils and may be rip up clasts from a tsunami or possibly a megastorm event extinction of the cretaceous planktonic foraminifers and burrowing organisms occurs abruptly at the k t boundary thus the bass river k t succession unequivocally links the chicxulub bolide impact to the mass extinctions at the end of the mesozoic

mass failure of the north atlantic margin triggered by the cretaceous paleogene bolide impact the 65 ma chicxulub impact is known to have triggered large submarine slope failures near the crater in the gulf of mexico and caribbean here we show that the impact also precipitated massive submarine failure of the continental margin around the western north atlantic we have identified mass flow deposits containing impact ejecta of cretaceous paleogene boundary age in two deep sea cores more than 700 km from the continental margin the mass flows must have originated from the continental margin because they contain microfossils typical of shallow water environments and sedimentary features indicative of deposition by gravity currents geophysical data suggest that the mass wasting deposits may be present over the entire western north atlantic from puerto rico to the grand banks of canada and that much of the eastern margin of north america catastrophically failed during the cretaceous paleogene impact

slumping and a sandbar deposit at the cretaceous tertiary boundary in the el tecolote section northeastern mexico an impact induced sediment gravity flow slumps affecting uppermost mendez formation marls as well as the spherulitic layer and basal part of the sandy deposits of the cretaceous tertiary k t boundary clastic unit are described at the new k t el tecolote section northeastern mexico these k t clastic deposits represent sedimentation at middle bathyal water depths in channel and nonchannel or levee areas of reworked materials coming from environments ranging from outer shelf to shallower slope via a unidirectional high to low density turbidite flow we emphasize the development and accretion of a lateral bar in a channel area from a surging low density turbidity current and under a high flow regime the slumps discovered on land and the sedimentary processes of the k t clastic unit reflect destabilization and collapse of the continental margin support the mechanism of gravity flows in the deep sea and represent important and extensive evidence for the impact effects in the gulf of mexico triggered by the chicxulub event

maastrichtian climate productivity and faunal turnovers in planktic foraminifera in south atlantic dsdp sites 525a and 21 abstract stratigraphic faunal and isotopic analyses of the maastrichtian at dsdp sites 525a and 21 in the south atlantic reveal a planktic foraminiferal fauna characterized by two major events an early late maastrichtian diversification and end maastrichtian mass extinction both events are accompanied by major changes in climate and productivity the diversification event which occurred in two steps between 70 5 and 69 1 ma increased species richness by a total of 43 and coincided with the onset of major cooling in surface and bottom waters and increased surface productivity the onset of the terminal decline in maastrichtian species richness began at 67 5 ma and the first significant decline in surface productivity occurred at 66 2 ma coincident maximum cooling to 13 c in surface waters and the reduction of the surface to deep temperature gradient to less than 5 c major climatic and moderate productivity changes mark the mass extinction and the last 500 kyr of the maastrichtian between 200 and 400 kyr before the k t boundary surface and deep waters warmed rapidly by 3 4 c and cooled again during the last 100 kyr of the maastrichtian surface productivity decreased only moderately across the k t boundary species richness began to decline during the late maastrichtian cooling and by k t boundary time the mass extinction had claimed 66 of the species viewed within the context of maastrichtian climate and productivity changes the k t mass extinction could have resulted from extreme environmental stress even without the addition of an extraterrestrial impact

laboratory and field evaluations of the lisst 100 instrument for suspended particle size determinations abstract advances in technology have resulted in a new instrument that is designed for in situ determination of particle size spectra such an instrument that can measure undisturbed particle size distributions is much needed for sediment transport studies the lisst 100 laser in situ scattering and transmissometry uses the principle of laser diffraction to obtain the size distribution and volume concentration of suspended material in 32 size classes logarithmically spaced between 1 25 and 250 m this paper describes a laboratory evaluation of the ability of lisst 100 to determine particle sizes using suspensions of single size artificial particles findings show the instrument is able to determine particle size to within about 10 with increasing error as particle size increases the instrument determines volume or mass concentration using a volume conversion factor cv this volume conversion factor is theoretically a constant in the laboratory evaluation cv is found to vary by a factor of about three over the particle size range between 5 and 200 m results from field studies in south san francisco bay show that values of mass concentration of suspended marine sediments estimated by lisst 100 agree favorably with estimates from optical backscatterance sensors if an appropriate value of cv according to mean size is used and the assumed average particle aggregate density is carefully chosen analyses of size distribution of suspended materials in south san francisco bay over multiple tide cycles suggest the likelihood of different sources of sediment because of different size characteristics during flood and ebb cycles

variability in late cretaceous climate and deep waters evidence from stable isotopes abstract strong climatic and temperature fluctuations mark the late campanian and maastrichtian as indicated by stable isotope records from the equatorial pacific site 463 and middle and high latitude south atlantic sites 525 689 and 690 the first major global cooling decreased intermediate water temperatures iwt by 5 6 c between 73 70 ma at the same time sea surface temperature sst decreased by 4 5 c in middle and high latitudes intermediate waters iw temporarily warmed by 2 c in low and middle latitudes between 70 68 5 ma global cooling resumed between 68 5 65 5 ma when iwt decreased by 3 4 c and sst by 5 c in middle latitudes about 450 ka before the cretaceous tertiary boundary rapid global warming increased iwt and sst by 3 4 c though sst in the tropics changed little during the last 200 ka of the maastrichtian climate cooled rapidly with iwt and sst decreasing by 2 3 c during the global cooling at 71 70 ma and possibly at 67 65 5 ma the sources of cold intermediate waters in the equatorial pacific indo pacific and south atlantic were derived from the high latitude north pacific in contrast during the global climate warming between 65 2 65 4 ma the middle latitude south atlantic was closest to the source of iw production and implies that the low latitude tethys played a major role in global climate change climate changes sea level fluctuations and associated restricted seaways appear to be the most likely mechanisms for the alternating sources of iw production

the cretaceous paleogene k p boundary at brazos texas sequence stratigraphy depositional events and the chicxulub impact abstract two cores from brazos texas spanning the cretaceous paleogene k p boundary are investigated by a multidisciplinary approach aiming at unraveling environmental changes and sequence stratigraphic setting in addition the sedimentology of the k p event deposit and its correlation with the k p boundary is studied foraminifera and nannofossil stratigraphy indicates that both cores include a latest maastrichtian zone cf1 cf2 and earliest danian p0 p and p1a shale sequence with a sandy and chicxulub ejecta bearing event deposit at the k p boundary a hiatus of unknown duration may be present by the unconformable base of the event deposit planktic foraminifera as well as calcareous nannofossil abundance and diversity both decline abruptly above the event deposit k p mass extinction whereas benthic foraminifera show a pronounced faunal change but no mass extinction mineralogical and geochemical proxies suggest that except for the sandwiched k p event deposit no facies change took place across the k p boundary and no evidence for adverse an or dysoxic sedimentary conditions following the chicxulub impact was observed therefore the interval bracketing the k p event deposit is considered as highstand systems tract increased coarse detritus input and low planktic benthic p b foraminifera ratios during the earliest paleocene p0 and p both suggest an increased coastal proximity or relative sea level lowering although the k p mass extinction of planktic foraminifera might have influenced the p b ratios as well consequently the sandy shales of the early paleocene are considered as late regressive highstand or as lowstand deposit during p1a shales assigned as transgressive systems tract overlie a pyrite and glauconite rich bioturbated transgressive surface or type 2 sequence boundary the smectite dominated clay assemblage with minor illite kaolinite and chlorite indicates semiarid humid climates with no obvious shifts across the k p boundary the magnetic susceptibility signature during the maastrichtian reveals a subtle cyclic or rhythmic pattern whereas a high amplitude cyclic pattern is present during the early danian the k p event deposit shows a succession of high energetic debris flows and turbidites derived from multiple source areas followed by a period of decreasing current energy deposition was likely triggered by multiple tsunami or tempestites followed by a prolonged period of reworking and settling the chicxulub ejecta at the base of the k p event deposit consists of mg rich smectite as well as fe mg rich chlorite spherules their mineralogical composition points to target rocks of mafic to intermediate composition presumably situated in the northwestern sector of the chicxulub impact structure besides these silicic phases the most prominent ejecta components are limestone clasts accretionary carbonate clasts and microspar suggesting that the texas area received ejecta also from shallow carbonate rich lithologies at the impact site on the yucatan carbonate platform the excellent correlation of chicxulub ejecta at brazos with ejecta found in the k p boundary layer worldwide along with the associated mass extinction provides no evidence that chicxulub predated the k p boundary and allows for unequivocal positioning of the k p boundary at the event deposit

a statistical approach to estimate the 3d size distribution of spheres from 2d size distributions size distribution of rigidly embedded spheres in a groundmass is usually determined from measurements of the radii of the two dimensional 2d circular cross sections of the spheres in random flat planes of a sample such as in thin sections or polished slabs several methods have been devised to find a simple factor to convert the mean of such 2d size distributions to the actual 3d mean size of the spheres without a consensus we derive an entirely theoretical solution based on well established probability laws and not constrained by limitations of absolute size which indicates that the ratio of the means of measured 2d and estimated 3d grain size distribution should be 4 785 actual 2d size distribution of the radii of submicron sized pure fe 0 globules in lunar agglutinitic glass determined from backscattered electron images is tested to fit the gamma size distribution model better than the log normal model numerical analysis of 2d size distributions of fe 0 globules in 9 lunar soils shows that the average mean of 2d 3d ratio is 0 84 which is very close to the theoretical value these results converge with the ratio 0 8 that hughes 1978 determined for millimeter sized chondrules from empirical measurements we recommend that a factor of 1 273 reciprocal of 0 785 be used to convert the determined 2d mean size radius or diameter of a population of spheres to estimate their actual 3d size

stable isotope and foraminiferal changes across the cretaceous tertiary boundary at stevns klint denmark arguments for long term oceanic instability before and after bolide impact event abstract stable isotope and planktic and benthic foraminiferal analyses of the k t boundary transition at stevens klint denmark indicate a 100 500 kyr long period of instability in oceanic bottom water temperature and sea level during the latest maastrichtian from 2 7 m below and up to the k t boundary bottom water temperatures gradually cooled about 1 5 c as surface water temperatures remained constant at the k t boundary bottom water temperatures decreased additionally 3 c and then returned to pre boundary values just above the boundary interval coincident with the onset of the first temperature decrease there was a prominent sea level fall estimated between 50 100 m as observed in benthic and planktic foraminiferal assemblages as well as in a decreasing surface to bottom 13 c gradient about 40 cm below the iridium rich k t boundary clay sea level began to rise poor preservation of foraminifera above the k t boundary allows only tentative interpretation of danian events at stevns klint however sea level generally continued to rise interrupted by short sea level falls associated with the observed sea level changes are three important hiatuses at the contact between the white chalk and overlying grey white bryozoan chalk about 2 7 m below the k t boundary at or near the top of the fish clay zone pla parvularugoglobigerina eugubina missing and at the contact of the cerithium limestone and overlying bryozoan limestone about 60 cm above the k t boundary part of zone plc missing these unconformities are coeval with hiatuses observed in many continental shelf sections and indicate a global eustatic rather than regional isostatic response notable is that at stevns klint the episode of oceanic instability is registered over approximately the same stratigraphic interval in which supposed extraterrestrial amino acids occur a circumstance that may indicate a connection a gradual positive shift in 13 c is registered in both benthic and planktic foraminiferal assemblages in the upper maastrichtian at stevns klint the positive shift is followed by a prominent negative 13 c shift 1 3 at the k t boundary an upper maastrichtian positive 13 c excursion followed by a negative 13 c anomaly at or near the k t boundary has previously been observed in deep sea cores from the pacific ocean and the weddell sea antarctica implying a global event previous suggestions of a relation between the uppermost maastrichtian positive 13 c excursion and sea level variation are not supported by the data for stevns klint

investigation of flocculation dynamics under changing hydrodynamic forcing on an intertidal mudflat abstract in situ floc size and turbulent shear stress were measured together with suspended sediment concentration to investigate the floc properties under changing hydrodynamic forcing over the intertidal mudflat a tripod system was established in the field for a period of approximately one month including 6 days of stormy conditions in the middle of the investigation period mean floc size exhibited strong temporal variations within a tidal cycle and inverse relationship was found between mean floc size and shear stress suspended sediment concentration ssc can modulate the flocculation dynamics when shear stress decreases down to enhancing flocculation asymmetrical behaviors of floc sizes between flood and ebb phases were identified with overall larger floc sizes in flood than in ebb tide under the same shear stresses floc structure showed different properties under calm and stormy conditions and the variable fractal dimension and variable primary particle size were more convincing in simulating the variation of floc effective density with mean floc size during the storm period which was inferred to be related to the resuspension of bed sediment as well as organic matter a total of 110 mm bed erosion was measured during the storm and erosion events occurred only around low water due to the high current wave combined bed shear stress and off shore current after the storm 40 of the erosion recovered within one week and the fast settling of large flocs around high water plays significant role in the deposition process leading to 60 of the recovery

thermal histories and hydrocarbon generation example from utah wyoming thrust belt the thermal history of the utah wyoming thrust belt in the vicinity of the pineview oil and gas field is studied with a detailed thermal model the model incorporates a heterogeneous thermal conductivity structure radioactive heat generation in the crust sediment compaction variable basal heat flow through time and thermal effects of sedimentation erosion and thrust faulting the analysis is constrained by 206 corrected bottom hole temperatures 660 thermal conductivity measurements and 10 new vitrinite reflectance measurements present surface heat flow in this part of the utah wyoming thrust belt is estimated to be 60 8 mw m2 surface heat flow in the late cretaceous about 70 ma is inferred to have been 38 8 mw m2 from an lysis of vitrinite reflectance data about half of the apparent difference between ancient and present surface heat flow may be attributed to transient thermal effects of sedimentation erosion and thrusting the hypothesis of a constant background thermal state in this part of the thrust belt for the last 70 m y may not be ruled out however thermal history simulations in which the background thermal state changes through time better match constraints imposed by estimated present surface heat flow and vitrinite reflectance data application of the thermal history analysis to hydrocarbon generation is illustrated with a kinetic model of organic maturation oil and gas at the pineview field may have been generated in two stages first stage just before and during thrusting and the second stage during cenozoic warming

measurements of high concentration suspended sediments using the optical backscatterance sensor abstract an optical backscatterance sensor obs was used to measure extremely high concentration suspended sediments on the amazon continental shelf as part of the amasseds project a multidisciplinary amazon shelf sediment study using a pumping system for obtaining water samples to calibrate the sensor in situ the obs output was observed to increase approximately linearly for concentrations 36 g l the obs response was nearly continuous from 0 to 320 g l making it possible to obtain continuous suspended sediment concentration profiles through fluid muds

calcareous nannofossil biostratigraphy and paleoecology of the cretaceous tertiary transition in the central eastern desert of egypt abstract the gebel qreiya and nearby wadi hamama sections of the central eastern desert are among the most complete k t boundary sequences known from egypt the two sections were analyzed spanning an interval from l 83 myr below to about 3 myr above the k t boundary a 1 cm thick red clay layer at the k t boundary at gebel qreiya contains an ir anomaly of 5 4 ppb the high resolution study and well preserved nannoflora provide good age control and the first quantitative records of calcareous nannofossil assemblages for paleoecological interpretations across the k t transition in egypt four zones micula murus micula prinsii np1 and np2 were distinguished and correlated with other nannofossil and planktonic foraminiferal zonations that are broadly applicable for the eastern tethys region latest maastrichtian assemblages are abundant and diverse though cretaceous species richness progressively decreased across the k t boundary dominant species include arkhangelskiella cymbiformis micula decussata and watznaueria barnesae with high abundance of dissolution resistant m decussata reflecting periods of high environmental stress thoracosphaera blooms mark the k t boundary and are followed by an acme of the opportunistic survivor braarudosphaera bigelowii the first appearance of the new tertiary species cruciplacolithus primus and an acme of coccolithus cavus pelagicus these successive abundance peaks provide the basis for subdivision of the early danian zones np1 and np2 into five subzones correlation of selected nannofossil taxa from the egyptian sections with those from various onshore marine and deep sea sections provides insights into their paleoenvironmental and paleoecological affinities

yucatan subsurface stratigraphy implications and constraints for the chicxulub impact much of the discussion about the effects of an end of cretaceous impact by a large extraterrestrial body in northwestern yucatan has been done in the context of limited and partly erroneous published data on the mesozoic stratigraphy of that area reexamination of cores and geophysical logs taken in several pemex wells has produced improved lithologic and biostratigraphic correlation of the jurassic to maastrichtian section across the northern yucatan peninsula these data suggest that major disturbance of strata by an impact would have been confined to within about 100 km of the proposed impact center near chicxulub the only unusual lithologic unit is polymict breccia which apparently was penetrated at or near the top of the cretaceous section in all the deep wells of northern yucatan this breccia in pemex wells yucatan 1 2 4 5a and 6 is composed predominantly of detrital dolomite limestone and anhydrite clasts set in dolomitized carbonate mud matrix which contains upper maastrichtian foraminifers these constituents mixed with fragments of altered glass or melt rock shocked quartz and feldspar and basement rock suggest an impact as the most likely origin for the breccia the timing of brecciation is poorly constrained by biostratigraphic data there is some evidence however that the breccia unit is overlain by about 18 m of uppermost maastrichtian marls suggesting an impact before the cretaceous tertiary boundary in addition there may have been more than one episode of breccia deposition

characteristics of suspended particles at an 11 hour anchor station in san francisco bay california hourly measurements of suspended sediment in situ floc size distributions constituent grain size distributions total concentrations and average particle densities are presented for five depths from an 11 hour anchor station in san francisco bay the flocs formed well sorted distributions with modal sizes between 100 and 500 m whereas the disaggregated sediment was poorly sorted with about the same volume of material in all size classes and relatively little material coarser than 100 m for both types of size spectra concentrations at the coarse end of the size distribution fall off rapidly at a size range which varied with bottom shear stress the settling rates corresponding to the modal floc diameters were generally related to the maximum disaggregated diameters by a square relationship but turbulence appeared to limit floc size in the coarsest samples both the floc and disaggregated grain size vary with total concentration suggesting that flocs are relatively stable entities which do not change during alternating settling and resuspension

laboratory apparatus for calibrating optical suspended solids sensors abstract an apparatus for testing and calibrating miniature to medium sized optical suspended solids sensors is described stable suspensions of sedimentary particles ranging in size from 10 6 to 4 10 3 m can be produced in water with concentrations exceeding 100 g 1 1 flow velocities in the test volume can be varied continuously from 0 1 to 1 5 m s 1 and samples of suspensions can be withdrawn directly with a peristaltic pump for gravimetric and particle size analyses the apparatus has been used to evaluate the effects of particle size flow speed and air bubbles on the performance of optical backscatterance sensors and transmissometers

decline of the maastrichtian pelagic ecosystem based on planktic foraminifera assemblage change implication for the terminal cretaceous faunal crisis an outer shelf upper slope tropical tethyan pelagic environment existed over southern israel during maastrichtian time planktic foraminifera in the 63 and 149 m size fractions from four sections in this area were studied quantitatively for a high resolution ecostratigraphic analysis of the pre cretaceous tertiary k t paleoenvironment during the maastrichtian 41 of the planktic foraminifera species became extinct mostly keeled globotruncanidae which also became quantitatively reduced near the end of the maastrichtian from as much as 35 to only 5 of the planktic foraminifera population evolutionary replacement of extinct species by new forms nearly ceased in that interval two major opportunistic blooms of guembelitria took place associated with reduced abundances of keeled forms and the dominant species heterohelix globulosa the first bloom occurred within the upper gansserina gansseri to lower abathomphalus mayaroensis zones and the second within the plummerita hantkeninoides zone the extinctions concomitant changes in faunal dominance and opportunist blooms indicate that the pelagic ecosystem in the negev area experienced multiple stresses during the maastrichtian the planktic foraminiferal assemblages were taxonomically impoverished and in decline prior to the k t boundary crisis

fe rich and k rich mafic spherules from slumped and channelized chicxulub ejecta deposits in the northern la sierrita area ne mexico spherule deposits commonly interpreted as ejecta from the chicxulub impact at yucatan mexico are present in many k t cretaceous tertiary sections geological mapping of the northern la sierrita area ne mexico revealed the presence of 1 multiple spherule deposits embedded in late maastrichtian marls which are folded or disaggregated breccia like they are up to 6 m thick locally present in two outcrop areas and show limited lateral continuity these deposits consist of mm cm sized spherical to drop shaped vesiculated spherules angular to filamentous ejecta fragments and abundant carbonate they are interpreted as primary ejecta fallout deposits that have been affected by subsequent local slumps slides liquefaction and debris flows welded components suggest an initial ground surge like ejecta dispersion mode 2 a spherule deposit 10 60 cm thick that constitutes the base of a channelized sand siltstone deposit at or close to the k t boundary and is characterized by wide lateral continuity it is of similar petrologic composition to deposit 1 though slightly enriched in terrigeneous detritus thus reflecting influx from proximal shelf areas it is interpreted to result from debris flows and turbidite currents though no size sorting and abrasion of ejecta has been observed petrological mineralogical and geochemical criteria suggest that ejecta components from both types of spherule deposits are similar and originated from the chicxulub impact with multiple deposits produced by subsequent remolding reworking and redeposition spherules and fragments have an fe 25 30 wt al mg rich and si poor 25 wt sio2 composition and are altered to chlorite and iron oxides though rare k rich mafic glass 50 wt sio2 5 8 wt k is also present they contain ti fe k rich schlieren fe mg rich globules and rare m sized metallic and sulfidic ni co rich inclusions carbonate as clasts and within spherules and fragments shows textures indicative of quenching and or liquid immiscibility although potential ejecta fractionation and alteration make accurate evaluation difficult this composition suggests an ejecta origin mainly from mafic lithologies and carbonaceous sediments in addition to a contribution from intermediate felsic rocks and the possibility of meteoritic contamination

sediment dynamics in a submarine canyon a case of river sea interaction this paper presents findings from a 1 month field experiment conducted during the flood season of 2000 on the southern coast of taiwan to examine the delivery of lithogenic siliciclastic sediment to kao ping submarine canyon from the nearby kao ping river and shelf sources and the transport of suspended lithogenic and nonlithogenic particles near the canyon floor collected time series data included simultaneous measurements of coastal winds salinity temperature flow field suspended sediment concentration ssc and size composition of suspended particles at the river mouth and inside the submarine canyon as well as results from seawater and sediment trap data other collected data included river discharge and sediment load and hydrographic measurements along and across the axis of the canyon during the experiment two significant episodic river sediment discharge events occurred relating to a typhoon and extreme precipitation conditions the findings show that theoretically the time difference between sand and clay siliciclastic grains to settle from the sea surface to the canyon floor is on the order of hours to months analogous to a sorting process river plume dynamics and the coastal wind field largely control the delivery of terrigenous fine grained sediment to the canyon inside the canyon the behavior of suspended lithogenic and nonlithogenic particles of different sizes can be differentiated into a coarse grained group sand which forms the drop in population and a fine grained group mud which forms the standing population each group has distinct spectral characteristics the coarse grained group is delivered directly to the canyon by the river effluent and by wave resuspension of the shelf substrate during the study period the net transport of suspended particles near the canyon floor was landward mostly by tidal currents whose direction was also modulated by spring neap tide both lithogenic and nonlithogenic particles contribute to high mass fluxes exceeding 700 g m 2 day 1 in the lower part of the canyon this river sea system represents a type of systems that consist of three geographically separated dynamic entities the river plume the shelf and the canyon under fair weather conditions the river plume and shelf processes are coupled through the tide and wind field the river and canyon form a direct source to sink link via coarse grained siliciclastic sediment during the flood season in both continuous and pulsed fashion in the typhoon season the shelf becomes a pulsed source region for coarse grained sediment

synchroneity of the k t oceanic mass extinction and meteorite impact blake nose western north atlantic a 10 cm thick layer of green spherules occurs precisely at the biostratigraphic boundary between the cretaceous and paleogene k t boundary at ocean drilling program site 1049 lat 30 08 n long 76 06 w the spherulitic layer contains abundant rock fragments chalk limestone dolomite chert mica books and schist as well as shocked quartz abundant large cretaceous planktic foraminifera and rounded clasts of clay as long as 4 mm interpreted as altered tektite glass probably derived from the chicxulub impact structure most of the cretaceous foraminifera present above the spherule layer are not survivors since small specimens are conspicuously rare compared to large individuals instead the cretaceous taxa in paleocene sediments are thought to be reworked the first paleocene planktic foraminifera and calcareous nannofossil species are recorded immediately above the spherule bed the upper part of which contains an iridium anomaly hence deposition of the impact ejecta exactly coincided with the biostratigraphic k t boundary and demonstrates that the impact event was synchronous with the evolutionary turnover in the oceans these results are consistent with a reanalysis of the biostratigraphy of the k t boundary stratotype which argues that shallow marine k t boundary sections are not biostratigraphically more complete than deep sea k t boundary sites

extended period of extinctions across the cretaceous tertiary boundary in planktonic foraminifera of continental shelf sections implications for impact and volcanism theories discussion and reply

terminal cretaceous warming event in the mid latitude south atlantic ocean evidence from poleward migration of contusotruncana contusa planktonic foraminifera morphotypes abstract spatial and temporal patterns in test size and shape test conicity and spiral roundness and absolute abundance accumulation rate of the planktonic foraminifer contusotruncana contusa were studied in the south atlantic ocean dsdp sites 356 516 525 and 527 during an interval corresponding to the last 800 kyr of the cretaceous the variation in absolute abundance of c contusa was characterised by alternating periods of high and low abundance some of these periods were traceable across the entire mid latitude south atlantic ocean while the mean spiral roundness did not show any interpretable patterns a sudden increase of the mean test size and mean test conicity occurred between 65 3 and 65 2 ma based on linear interpolation within the cretaceous part of subchron c29r at all sites studied indicating a poleward migration followed by rapid withdrawal of the low latitude c contusa morphotypes from the mid latitude south atlantic ocean we suggest that this event was caused by a short period of surface water warming in the southern mid latitudes corresponding to the brief high latitude warming event and associated faunal migrations in the boreal and austral realms

tektite bearing deep water clastic unit at the cretaceous tertiary boundary in northeastern mexico the hypothesis of cretaceous tertiary k t boundary impact on yucatan mexico predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves an outcrop along the arroyo el mimbral in northeastern mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic marl sequence deposited at more than 400 m water depth the marls were found to be unsuitable for determining magnetostratigraphy but foraminiferal biostratigraphy places the clastic unit precisely at the k t boundary we interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact the elastic unit comprises three main subunits 1 the basal spherule bed contains glass in the form of tektites and microtektites glass spherules replaced by chlorite smectite and calcite and quartz grains showing probable shock features this bed is interpreted as a channelized deposit of proximal ejects 2 a set of lenticular massive graded laminated beds contains intraclasts and abundant plant debris and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water 3 at the top several thin ripple beds composed of fine sand are separated by clay drapes they are interpreted as deposits of oscillating currents perhaps a seiche an iridium anomaly 921 23 pg g is observed at the top of the ripple beds our observations at the mimbral locality support the hypothesis of a k t impact on nearby yucatan

geochemical markers of the cretaceous tertiary boundary event at brazos river texas usa the cretaceous tertiary boundary sites around the gulf of mexico are close to the chixculub impact site and are relatively well studied yet much remains to be learned about them therefore the first integrated study of carbon soot and fullerenes in a cretaceous tertiary boundary section was undertaken at the brazos 1 site on the brazos river in texas at the most complete section of end cretaceous and basal paleocene deposits on the texas segment of the gulf coast area up to 409 ppm of native sulfur so were serendipitously discovered in a spherule bearing unit of the br 1 section and lesser amounts were found in spherule bearing units of nearby brazos riverbed sections in a section on darting minnow creek the isotopic composition 33s 12 97 34s 24 89 and 36s 46 4 implies that this so cannot have come to earth by the impactor that formed the chicxulub crater but most likely was produced by sulfate reducing bacteria during a local transient bacterial bloom for which the sulfate was provided by caso4 bearing spherules carbon and soot were determined in twelve samples representing all units of br 1 from the cretaceous corsicana kemp formation to the tertiary kincaid formation a significant increase of c and soot contents up to 2 2 104 ppm and 1 4 104 ppm respectively occurs in a sandy bed at the top of the kt complex fullerenes were determined in fifty four samples from all units of the same br 1 section less than 1 ppb was reliably detected at the same sandy bed where the strongest ir anomaly of the section is known to occur it is suggested here that the chicxulub impact 65 ma ago ignited local wildfires that produced c soot and fullerene which settled onshore or near shore whence they were transported to the brazos site by coastal flooding and associated sediment laden water plumes moving offshore

lilliput effect in late maastrichtian planktic foraminifera response to environmental stress the lilliput effect marks morphologic and intraspecies size reductions in response to environmental stresses commonly associated with the aftermath of mass extinctions this study shows that the lilliput effect is a universal biotic response associated with greenhouse warming mesotrophic or restricted basins shallow marginal settings and volcanically active regions during the late maastrichtian sedimentary sequences analyzed from tunisia egypt texas argentina the south atlantic and indian ocean reveal that the biotic stress response appears uniform regardless of the cause varying only with the degree of biotic stress overall late maastrichtian environments span a continuum from optimum conditions to the catastrophic mass extinctions with a predictable set of biotic responses relative to the degree of stress induced by oxygen salinity temperature and nutrient variations as a result of climate and sea level changes and volcanism early stages of biotic stress result in diversity reduction and the elimination of large specialized species k strategists leading to morphologic size reduction via selective extinction disappearances and intraspecies dwarfing of survivors later stages of biotic stress result in the complete disappearance of k strategists intraspecies dwarfing of r strategists and dominance by low oxygen tolerant small heterohelicids at the extreme end of the biotic response are volcanically influenced environments which cause the same detrimental biotic effects as observed in the aftermath of the k t mass extinction including the disappearance of most species and blooms of the disaster opportunist guembelitria

volcanism impact and mass extinctions incredible or credible coincidences massive continental volcanism and or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years the end permian end cretaceous and end triassic extinctions however reevaluation of the frequency of bolide impacts and plume related flood basalt provinces indicates that both types of event occur much more frequently than mass extinctions and so in isolation may not be responsible for the largest extinctions furthermore the kill mechanisms associated with either flood basalts or impacts do not appear to be sufficiently powerful to cause worldwide collapse of ecosystems leading to the largest mass extinctions contemporaneous flood basalts and bolide impact may be prerequisites for the largest mass extinctions we present a statistical analysis of the probability of coincidence between volcanism and impact and show that three random coincidences of these events in the last 300 m y are likely no causal relationship between impact and volcanism is necessary the lesser mass extinctions on the other hand may not require juxtaposition of two such catastrophic events such coincidences occurring on more than three occasions during the last 300 m y become increasingly unlikely d 2004 elsevier b v all rights reserved

wave breaking patterns control rip current flow regimes and surfzone retention recent research into rip currents has revealed the existence of multiple circulation patterns meaning that no single escape strategy is appropriate in all situations rip circulation is influenced by surfzone morphology which can be inferred from wave breaking patterns in video imagery wave breaking often occurs over the bars adjacent to the rip channel with little breaking over the seaward end of the rip however under varying wave and tide conditions breaking can also occur at the seaward extent of rip channels here we use this difference as a novel wave dissipation parameter to classify a rip channel as either open or closed in terms of rip head wave breaking a 4 day field study provided lagrangian rip current data at a macrotidal dissipative beach monitored by a coastal imaging system using this new parameter rip channels that were identified as closed exhibited a 31 increase in current speeds and 43 increase in horizontal vorticity compared to open channels the transition between open and closed channels occurred over a single tidal cycle which altered surfzone retention rates closed channels promoted surfzone retention with 25 of drifters exiting the surfzone in comparison open channels were more conducive to exchange with exit rates up to 91 analysis of the royal national lifeboat institution lifeguard rip incident database showed that open rips were disproportionately represented in the occurrence of rescue events and calculated here to be twice as dangerous as closed rips the use of this new open closed parameter could be used by surf lifesaving organisations and may have implications for the cross shore exchange of sediment and pollutants

extinction survivorship and evolution of planktic foraminifera across the cretaceous tertiary boundary at el kef tunisia an expanded sediment record at el kef shows that the k t boundary extinctions of planktic foraminifera extend over an interval from 25 cm below the geochemical boundary ir anomaly to 7 cm above species extinctions appear sequential with complex large ornate forms disappearing first and smaller less ornate forms surviving longer the 14 species extinctions below the boundary appear unrelated to an impact event cretaceous species survivorship is greater than previously assumed about 10 species survive 22 into subzone p1a globigerina eugubina all cretaceous survivors are small primitive forms which are generally smaller than their ancestors in cretaceous sediments species evolution after the k t event occurs in two pulses the first new paleocene species evolve in the basal black clay zone po immediately after the major cretaceous extinctions evolving species are small and primitive similar to cretaceous survivors the second pulse in species evolution occurs in the lower part of subzone p1b with the appearance of larger more diverse species the first major increase in carbonate sedimentation and productivity occurs at this time and signals the recoveyr of the ecosystem nearly 300 000 years after the k t event the species extinctions prior to the generally assumed impact event implied by the ir anomaly and the long recovery period of the ecosystem thereafter cannot be explained by a single impact but suggest that multiple causes may be responsible such as climatic changes volcanism a sea level drop production of warm saline bottom water and the chemical consequences associated with increased salinity

the cretaceous tertiary biotic transition mass extinctions are recognized through the study of fossil groups across event horizons and from analyses of long term trends in taxonomic richness and diversity both approaches have inherent flaws and data that once seemed reliable can be readily superseded by the discovery of new fossils and or the application of new analytical techniques herein the current state of the cretaceous tertiary k t biostratigraphical record is reviewed for most major fossil clades including calcareous nannoplankton dinoflagellates diatoms radiolaria foraminifera ostracodes scleractinian corals bryozoans brachio pods molluscs echinoderms fish amphibians reptiles and terrestrial plants macrofossils and palynomorphs these reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the k t biotic crisis available results suggest that many faunal and floral groups ostracodes bryozoa ammonite cephalopods bivalves archosaurs were in decline throughout the latest maastrichtian while others diatoms radiolaria benthic foraminifera brachiopods gastropods fish amphibians lepidosaurs terrestrial plants passed through the k t event horizon with only minor taxonomic richness and or diversity changes a few microfossil groups calcareous nannoplankton dinoflagellates planktonic foraminifera did experience a turnover of varying magnitudes in the latest maastrichtian earliest danian however many of these turnovers along with changes in ecological dominance patterns among benthic foraminifera began in the latest maastrichtian improved taxonomic estimates of the overall pattern and magnitude of the k t extinction event must await the development of more reliable systematic and phylogenetic data for all upper cretaceous clades

iridium and other platinum group elements as geochemical markers in sedimentary environments iridium anomalies are commonly used as indicators of extraterrestrial processes which caused global extinctions however platinum group element pge anomalies may result from several different processes both syn and postdepositional acting separately or jointly the sources and processes of enrichment involved are extraterrestrial asteroid comet cosmic dust impact ejecta volcanogenic pge rich condensates precipitation from seawater low sedimentation rate anoxic conditions microbial concentration dissolution reprecipitation exhalative hydrothermal leaching transport and precipitation at a redox boundary geochemical characteristics of pge and accompanying elements in sediments can be used to identify the contributions of some specific sources and processes 1 extraterrestrial chondritic ru ir and os ir ratios low 187os 186os ratio high ir compared to pt pd and au 2 volcanogenic high iridium and se as sb and in contents 3 exhalative hydrothermal high au pd and pt relatively low ir contents 4 precipitation from seawater high pt and low pd contents also high cd and ag contents under anoxic conditions and 5 reduction from intermediate and low temperature solutions high pge and cu or mo u ni contents

estimating suspended solids concentrations from backscatter intensity measured by acoustic doppler current profiler in san francisco bay california abstract the estimation of mass concentration of suspended solids is one of the properties needed to understand the characteristics of sediment transport in bays and estuaries however useful measurements or estimates of this property are often problematic when employing the usual methods of determination from collected water samples or optical sensors analysis of water samples tends to undersample the highly variable character of suspended solids and optical sensors often become useless from biological fouling in highly productive regions acoustic sensors such as acoustic doppler current profilers that are now routinely used to measure water velocity have been shown to hold promise as a means of quantitatively estimating suspended solids from acoustic backscatter intensity a parameter used in velocity measurement to further evaluate application of this technique using commercially available instruments profiles of suspended solids concentrations are estimated from acoustic backscatter intensity recorded by 1200 and 2400 khz broadband acoustic doppler current profilers located at two sites in san francisco bay california adcp backscatter intensity is calibrated using optical backscatterance data from an instrument located at a depth close to the adcp transducers in addition to losses from spherical spreading and water absorption calculations of acoustic transmission losses account for attenuation from suspended sediment and correction for nonspherical spreading in the near field of the acoustic transducer acoustic estimates of suspended solids consisting of cohesive and noncohesive sediments are found to agree within about 8 10 of the total range of concentration to those values estimated by a second optical backscatterance sensor located at a depth further from the adcp transducers the success of this approach using commercially available doppler profilers provides promise that this technique might be appropriate and useful under certain conditions in spite of some theoretical limitations of the method

suspended sediment transport in an estuarine tidal channel within san francisco bay california abstract a recently developed instrumentation system has been used to monitor simultaneously flow conditions and suspended sediment distribution in the bottom boundary layer of a tidal channel within san francisco bay california measurements were made every 15 min over six successive flood and ebb tidal cycles they included mean velocity profiles from four electromagnetic current meters within 1 m of the seabed mean suspended sediment concentration profiles from seven miniature nephelometers placed within 1 m of the seabed near bottom pressure fluctuations vertical temperature gradient and bottom photographs additionally suspended sediment was sampled from four levels within 1 m of the seabed three times during the tidal cycle the instrument system was retrieved during each slack water period to exchange suspended sediment sample bags while the instrument was deployed std nephelometer measurements were made thoughout the water column and water samples were collected each 1 h and bottom sediment was sampled at the deployment site size distributions of the suspended sediment samples estimates of particle settling velocity s friction velocity u and reference concentration c a at z 20 cm were used in the suspended sediment distribution equations to evaluate their ability to predict the observed suspended sediment profiles three suspended sediment particle conditions were evaluated 1 individual particle sizes in the 4 11 62 5 0 5 m size range with the reference concentration c a at z 20 cm c 2 individual particle sizes in the 4 6 size range flocs representing the 7 11 size range with the reference concentration c a at z 20 cm c f and 3 individual particle sizes in the 4 6 size range flocs representing the 7 11 size range with the reference concentration predicted as a function of the bed sediment size distribution and the square of the excess shear stress an analysis was also carried out on the sensitivity of the suspended sediment distribution equation to deviations in the primary variables s u and c a in addition computations of mass flux were made in order to show vertical variations in mass flux for varying flow conditions

north atlantic warming during global cooling at the end of the cretaceous differences in regional responses to climate fluctuations are well documented on short time scales e g el nino southern oscillation but with the exception of latitudinal temperature gradients regional patterns are seldom considered in discussions of ancient greenhouse climates contrary to the expectation of global warming or global cooling implicit in most treatments of climate evolution over millions of years this paper shows that the north atlantic warmed by as much as 6 c 1 5 decrease in 18o values of planktic foraminifera during the maastrichtian global cooling interval we suggest that warming was the result of the importation of heat from the south atlantic decreasing north atlantic 18o values are also associated with increasing gradients in planktic 13c values suggesting increasing surface water stratification and a correlated strengthening of the north atlantic polar front if correct this conclusion predicts arctic cooling during the late maastrichtian beyond implications for the maastrichtian these data demonstrate that climate does not behave as if there is a simple global thermostat even on geologic time scales

gradual mass extinction species survivorship and long term environmental changes across the cretaceous tertiary boundary in high latitudes stable isotope and planktic foraminiferal analyses across the cretaceous tertiary k t boundary transition at nye klov indicate longterm oceanic instability associated with global sea level fluctuations a gradual mass extinction and decreased magnitude of the 13 c shift in high latitudes oceanic instability which began at least 100 kyr before the k t boundary and continued for about 300 kyr into the tertiary was accompanied by a gradual faunal turnover the maximum sea level lowstand during latest maastrichtian is recorded about 75 cm below the k t boundary a sea level rise first in evidence at 20 cm to 40 cm below the boundary continued into zone p0 boundary clay this sea level rise was accompanied by 2 c of cooling in surface and bottom waters prior to the k t boundary 13 c values remained relatively stable up to 10 cm below the k t boundary a negative shift of 0 5 to 1 0 per mil occurred in the boundary clay in both planktic and benthic foraminifera the surface to deep 13 c gradient remained nearly unchanged in contrast to low latitudes where this gradient is virtually eliminated no sudden mass extinction occurred in this cosmopolitan high latitude fauna and nearly all cretaceous taxa thrived well into the tertiary when they gradually disappeared shallow seas dominated by cretaceous survivor taxa and a well developed oxygen minimum zone prevailed during the earliest tertiary short term sea level lowstands are marked by hiatuses at the top of zones p0 and p1a about 50 kyr and 230 kyr after the k t boundary respectively rising sea level reestablished normal marine conditions about 300 kyr to 350 kyr after the k t boundary coincident with the first post k t boundary recovery of the tertiary fauna and extinction of cretaceous survivors during this time high latitude regions temporarily acted as centers of origin and dispersal for planktic foraminifera long term oceanic instability gradual faunal turnover absence of a sudden mass extinction and greatly diminished 13 c shift in high latitudes suggest that a k t boundary bolide impact was not the primary cause for the k t boundary faunal transition moreover these data strongly imply that the destructive effects of the bolide impact would have been greatest in low latitudes and negligible in high latitudes

paleoecology of the cretaceous tertiary mass extinction in planktonic foraminifera abstract paleobiogeographic patterns of the cretaceous tertiary k t mass extinction in planktonic foraminifera in tunisia spanning environments from open marine upper bathyal to shelf and shallow marginal settings indicate a surprisingly selective and environmentally mediated mass extinction this selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction including species richness ecological generalists ecological specialists surface and subsurface dwellers whether based on the number of species or the relative percent abundances of species the following conclusions can be reached for shallow to deep environments about three quarters of the species disappeared at or near the k t boundary and only ecological generalists able to tolerate wide variations in temperature nutrients salinity and oxygen survived among the ecological generalists heterohelicids guembelitrids hedbergellids and globigerinellids only surface dwellers survived ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively biserials thrived during the latest maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early danian triserials thrived only in shallow marginal marine environments or similarly stressed ecosystems during the latest maastrichtian but dominated both open marine and restricted marginal settings in the early danian this highly selective mass extinction pattern reflects dramatic changes in temperature salinity oxygen and nutrients across the k t boundary in the low latitude tethys ocean which appear to be the result of both long term environmental changes e g climate sea level volcanism and short term effects bolide impact

flocculation a key process in the sediment flux of a large glacier fed lake this study investigates the consequences of flocculation for sediment flux in glacier fed lillooet lake british columbia based on density fractal dimension in situ profiles of sediment concentration and size distribution and settling velocity equations presented in the literature sediment flux attributed to macroflocs during the late spring and summer accounts for a significant portion of sediment flux in the lake equivalent to at least one quarter of the average annual sediment flux fine sediment is reaching the lake floor faster in flocs than occurs if settling as individual grains this flux varies both spatially and temporally over the observation period suggesting a link between deposition via flocculation and the properties of bottom sediments macrofloc flux increased through june reached a peak during july and then declined into august macrofloc flux was greatest in the distal end of the first basin approximately 10 km from the point of inflow relatively high excess densities 0 1 g cm 3 at 500 m for flocs in situ are consistent with a composition dominated by inorganic primary particles microlaminations within lillooet lake varves have been linked by earlier workers to discharge events and the action of turbidity currents emanating from the lillooet river while turbidity currents undoubtedly occur in lillooet lake these results demonstrate flocculation as an adjunct process linking discharge lake level macrofloc flux bulk density and microlaminations in situ measurements of sediment settling velocity in glacier fed lakes are required to better constrain flux rates and permit comparison between flocculation in lacustrine environments with existing studies of estuarine marine and fluvial flocculation copyright 2009 john wiley sons ltd

high resolution planktonic foraminiferal analysis from the cretaceous tertiary boundary at ain settara tunisia evidence of an extended mass extinction the ain settara section located in the kalaat senan area of north central tunisia spans the cretaceous tertiary k t boundary which is characterized by a red layer and a thin non bioturbated boundary clay sediment accumulation across the k t boundary at ain settara was probably interrupted by three short hiatuses and or condensed sedimentation the first hiatus occurs at the top of the cf1 zone the second hiatus condensation occurred just below the boundary clay and the third hiatus at the p0 p1a boundary in the earliest danian these hiatuses are marked by weak unconformities bioturbation and sudden disappearances appearances of species which are known to disappear evolve sequentially in continuous sections quantitative high resolution planktonic foraminiferal analysis across zones cf1 upper p0 and p1a 1 reveals an extended and selective mass extinction all 41 of the species which disappeared at or below the k t boundary are rare to very rare and primarily ecologically specialized keeled deeper dwelling tropical subtropical forms globotruncana globotruncanita gublerina planoglobulina rosita contusotruncana racemiguembelina their combined relative abundance varies between 10 and 15 of the total population at the end of the maastrichtian the k t crisis thus appears more catastrophic when viewed in tropical subtropical assemblages and based on analysis of larger species 200 m which preferentially includes the more specialized forms though in fact the k t mass extinction actually involved a relatively small part of the foraminiferal population in terms of relative abundance the pattern of extinction and changes in dominant population at ain settara appear to be very similar to the planktonic foraminiferal turnover of the other north central tunisian sections el kef elles the selective mass extinction pattern suggests that the catastrophic effects of the bolide impact superimposed those related to long term environmental changes such as variations in temperature sea level and associated water mass changes

disaster opportunists guembelitrinidae index for environmental catastrophes blooms of the disaster opportunist guembelitria species are proxies for environmental catastrophes whether impact or volcanism leading to severe biotic stress crises that may range from temporary exclusion of ecological specialists and generalists to mass extinctions during the late maastrichtian and early danian zones p0 and pla guembelitria blooms show global distributions but with the largest blooms 40 80 guembelitria in low and middle latitudes and only minor blooms 10 20 in high latitudes late maastrichtian guembelitria blooms are so far known from the indian ocean and eastern tethys the most intense guembelitria blooms 60 guembelitria occurred in shallow continental shelf areas slope shelf margins and volcanic provinces of the indian ocean what these environments have in common is high nutrient influx eutrophication either from continental runoff upwelling along continental margins or volcanic input at times of biotic crises guembelitria blooms may have spread rapidly to the exclusion of most or all other species much like today s red tides but with near global distributions a simple model can explain the ecological succession and recovery phases that follow major biotic perturbations caused by impacts or volcanism that lead to exclusion of specialist and most generalist species within such highly stressed environments guembelitria is the only genus to thrive and without competition rapidly reproduce and exponentially increase their populations when nutrients are depleted populations rapidly decrease leading to ecologic niches for other generalists and ecosystem recovery small low o2 tolerant heterohelicid populations mark this second stage followed by small trochospiral and planispiral species with further environmental recovery increasing competition niche development and restoration of a well stratified water mass oligotrophic conditions are restored opening habitats for the highly specialized and diverse species and a return to normal diverse assemblages this ecological succession is observed in association with mantle plume volcanism in the indian ocean and eastern tethys during the late maastrichtian and in association with the k t impact and volcanism during the early tertiary d 2004 elsevier b v all rights reserved

reply to chicxulub impact predates k t boundary new evidence from brazos texas comment by schulte et al we appreciate this opportunity for further discussion of the brazos texas k t boundary sequences and their timing with respect to the chicxulub impact keller et al 2007 used a multidisciplinary approach to document the stratigraphy paleontology mineralogy and geochemistry of the newly drilled mullinax 1 core and a new outcrop sequence based on this multi proxy dataset very strong evidence was presented that reveals that the chicxulub impact predates the k t mass extinction keller et al 2007 schulte et al take issue with this approach and our findings largely because they believe that the chicxulub impact caused the k t mass extinction and therefore the k t boundary must be placed at the impact spherule layer schulte et al this volume schulte et al 2006 smit et al 1996 we welcome this opportunity to clarify misunderstandings misconceptions and misinterpretations of the k t record in texas and elsewhere at the heart of our disagreements is the decades old controversy about the cause of the end cretaceous mass extinction schulte and collaborators have long argued that the sandstone complex or event deposit with impact spherules at the base in ne mexico and texas mark chicxulub impact generated

the maastrichtian record from shatsky rise northwest pacific a tropical perspective on global ecological and oceanographic changes we present new isotopic and micropaleontological data from a depth transect on shatsky rise that record the response of the tropical pacific to global biotic and oceanographic shifts during the mid maastrichtian results reveal a coupling between the upper ocean characterized by a weak thermocline and low to intermediate productivity and intermediate waters during the earliest maastrichtian oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the north pacific isotopic shifts through the early maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the southern ocean although the cooler water mass remained dominant through the remainder of the maastrichtian it was displaced intermittently at shallow intermediate depths by north pacific intermediate water the globally recognized mid maastrichtian event similar to 69 ma manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of shatsky rise is characterized by an abrupt increase similar to 2degrees 3degrees c in sea surface temperatures a greater flux of organic matter out of the surface ocean and warmer similar to 4degrees c intermediate waters results implicate simultaneous changes in surface waters and the sources distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid maastrichtian time

sediment connectivity a framework for analyzing coastal sediment transport pathways connectivity provides a framework for analyzing coastal sediment transport pathways building on conceptual advances in graph theory from other scientific disciplines connectivity schematizes sedi