hiatal duration of correlative sequence boundaries from oligocene pliocene mixed carbonate siliciclastic sediments of the south florida platform abstract sequence boundaries defined by regional unconformities in mixed carbonate siliciclastic sediments have a variable duration from the margin to the interior of the florida platform factors controlling the timing and duration of these unconformities include a combination of global eustatic and regional mechanisms sediment supply current intensification integrated chronostratigraphies developed from a transect of continuous cores in the south central interior to the southern margin of the florida platform show an increase in duration of the hiatal gaps along correlative sequence boundaries toward the platform edge two sequence boundaries are correlated across the south florida platform and mark formation contacts the lower sequence boundary sb a marks the suwannee limestone arcadia formation contact and is of significantly less duration in the platform interior southwest peninsular florida 2 0 m y than at the south platform margin middle florida keys 8 1 m y the hiatal gap along the upper sequence boundary sb b marking the arcadia formation overlain by miocene pliocene sediments that vary in age and composition regionally records the same increase from the central part of the platform southwest florida arcadia fm peace river fm 1 6 m y to the south platform edge lower florida keys arcadia fm stock island fm 11 5 m y eustatic fluctuations affected the relative sedimentation rates of the mixed sediments in the platform interior and at the margin most notably the large eustatic fall at the end of the early oligocene terminated carbonate deposition of the suwannee limestone sb a sediment accumulation on the platform interior was more temporally continuous than at the margin because of greater siliciclastic input from the north the strengthening of marine currents beginning in the middle miocene limited sediment accumulation across the southern platform margin sb b and possibly caused erosion of the margin carbonates increasing the duration of the hiatal gap on top of the arcadia formation

segmentation and coalescence of cenozoic carbonate platforms northwestern great bahama bank seismic profiles over the northwestern great bahama bank reveal that it is formed by the coalescence of three smaller platforms and significant lateral progradation this conclusion is contrary to previous models which assumed that the bank is the result of continuous accumulation on one huge buildup in late cretaceous to early tertiary time a north south trending depression the straits of andros separated an eastern platform andros bank from a western platform bimini bank initially the straits of andros had dimensions similar to the modem tongue of the ocean but was progressively filled from east to west in early to middle tertiary time a second depression the bimini embayment formed within bimini bank by folding it had a maximum depth of about 470 m this depression was also filled from east to west in addition prograding systems built the western margin of bimini bank more than 25 km westward into the straits of florida

controls on facies and sequence stratigraphy of an upper miocene carbonate ramp and platform melilla basin ne morocco abstract upwelling of cool seawater paleoceanographic circulation paleoclimate local tectonics and relative sea level change controlled the lithofacies and sequence stratigraphy of a carbonate ramp and overlying platform that are part of a temporally well constrained carbonate complex in the melilla basin northeastern morocco at melilla from oldest to youngest a third order depositional sequence within the carbonate complex contains 1 a retrogradational transgressive warm temperate type rhodalgal ramp 2 an early highstand progradational bioclastic platform composed mainly of a temperate type bivalve rich molechfor facies and 3 late highstand progradational to downstepping subtropical tropical type chlorozoan fringing porites reefs the change from rhodalgal ramp to molechfor platform occurred at 7 0 0 14 ma near the tortonian messinian boundary during a late stage in the development of the bioclastic platform a transition from temperate type molechfor facies to subtropical tropical type chlorozoan facies occurred and is bracketed by chron 3an 2n 6 3 6 6 ma comparison to a well dated carbonate complex in southeastern spain at cabo de gata suggests that upwelling of cool seawater influenced production of temperate type limestone within the ramp and platform at melilla during postulated late tortonian early messinian subtropical tropical paleoclimatic conditions in the western paleo mediterranean region the upwelling of cool seawater across the bioclastic platform at melilla could be related to the beginning of siphoning of deep cold atlantic waters into the paleo mediterranean sea at 7 17 ma the facies change within the bioclastic platform from molechfor to chlorozoan facies may be coincident with a reduction of the siphoning of atlantic waters and the end of upwelling at melilla during chron 3an 2n the ramp contains one retrogradational parasequence and the bioclastic platform three progradational parasequences minor erosional surfaces that bound the upper surface of the ramp and upper surface of the oldest platform parasequence are related to relative falls in sea level induced by local volcanism and associated tectonic uplift these local relative falls had little influence on a broader scale rise to stillstand in relative sea level that controlled development of the transgressive and early highstand systems tracts represented in the ramp and platform respectively

eustatic implications of late miocene depositional sequences in the melilla basin northeastern morocco abstract the age 5 78 ma or lower chron c3r of the major drawdown of the paleo mediterranean sea during the messinian salinity crisis has been established by combining results from stratigraphy paleontology magnetostratigraphy and argon dating for a late miocene sedimentary succession in the melilla basin ne morocco this event is inferred from a marine to continental series of carbonate and siliciclastic rocks that record the end of messinian marine deposition in the melilla basin and presumably marks the final isolation of the paleo mediterranean sea the evidence from the melilla basin is approximately coeval with an increase in benthic foraminiferal 18 o values from a deep marine section in the bou regreg valley nw morocco hodell et al 1994 this increase suggests that a glacio eustatic lowering of sea level at least contributed to the final closure of the mediterranean during the messinian salinity crisis the marine to continental succession onlaps a carbonate complex that contains evidence for multiple relative sea level changes leading up to the main drawdown from bottom to top the carbonate complex is composed of 1 an onlapping ramp 2 a prograding bioclastic platform 3 a prograding and locally downstepping porites reef complex and 4 a topography draping sequence composed of grainstones porites reefs and stromatolites terminal carbonate complex of esteban 1979 the transgressive ramp correlates to relatively low values of benthic foraminiferal 18 o values from a tortonian to lower messinian section at bou regreg hodell et al 1994 this correlation indicates at least in part a link between rising sea level and a reduction in global ice volume during deposition of the ramp a major fall in relative sea level 60 m occurred near the demise of the reef complex during chron c3n 1n at 5 95 0 10 ma this signals the initiation of drawdown and changing environmental conditions in the melilla basin a marginal basin and perhaps the entire paleo mediterranean sea a megabreccia interpreted as forming by solution collapse of evaporites on the basin margin of the reef complex occurs at the base of the terminal carbonate complex updip a major subaerial unconformity separates the reef complex and terminal carbonate complex evaporite deposition likely occurred during this exposure event and has been dated at 5 82 0 02 ma near the base of chron c3r we contend that these evaporites restricted to the shallow melilla basin are related to the continuation of the initial stage of the major drawdown of the paleo mediterranean sea

new tertiary stratigraphy for the florida keys and southern peninsula of florida seven lithologic formations ranging in age from oligocene to pleistocene were recently penetrated by core holes in southernmost florida from bottom to top they are the early oligocene suwannee limestone late early oligocene to miocene arcadia formation basal hawthorn group late miocene peace river formation upper hawthorn group newly proposed late miocene to pliocene long key and stock island formations and pleistocene key largo and miami limestones the rocks of the suwannee limestone form a third order sequence although the entire thickness was not penetrated 96 m of suwannee core from one well contains at least 50 vertically stacked exposure capped limestone cycles presumably related to rapid eustatic fluctuations while experiencing tropical to subtropical conditions the arcadia formation is a composite sequence containing four high frequency sequences composed of multiple vertically stacked carbonate cycles most cycles do not show evidence of subaerial exposure and were deposited under more temperate conditions relative to the suwannee limestone the arcadia formation in southernmost florida is bounded by regional unconformities representing third order sequence boundaries post arcadia transgression produced a major backstepping of sediment accumulation above the upper sequence boundary of the arcadia formation the peace river formation composed of diatomaceous mudstones has been identified only beneath the florida peninsula and is not present beneath the florida keys deposition occurred during marine transgressive to high stand conditions and a local phosphatization event recorded in northeast florida the transgression is possibly related to a global rise in sea level which resulted in upwelling of relatively cooler relatively nutrient rich water masses onto the florida platform it is proposed that the absence of peace river sediments beneath the keys is due to sediment bypass of the upper surface of the arcadia a result of sediment sweeping by an ancestral florida current during late miocene to pliocene time in the florida keys siliciclastics of the long key formation and fine grained carbonates of the stock island formation prograded toward the southern edge of the florida platform and downlapped onto the regional unconformity at the top of the arcadia shallow marine pleistocene limestones key largo and miami limestones deposited during tropical to subtropical conditions drape over accretionary successions of the long key and stock island formations

accumulation rates from well dated late neogene carbonate platforms and margins abstract margins of large carbonate platforms isolated platforms and atolls are dynamic settings that both generate and accumulate sediments with the exceptions of modern platforms the rates of accumulation are often poorly constrained due to inadequate or unreliable subsurface age data a compilation is here presented of well dated late neogene ice house platform and margin accumulation for the interval from 7 to 2 ma the rates are grouped according to platform type and setting sea level effects and subsidence bathymetry control are the significant influences the six settings are 1 slow aggraded platform 2 partially drowned platform 3 fast aggraded platform 4 atolls 5 prograded margin and 6 periplatform mean rates are 10 to 20 m my for slow aggraded and partially drowned platforms 20 40 m my for atolls and a fast aggraded platform 40 m my for a current dominated prograded margin and 40 110 m my for most prograded and periplatform systems the maximum rates measured from the age depth plot are generally two to three times as high the mean accumulation rates and maximum rates are primarily related to the influence of sea level and to a lesser extent regional subsidence the shallow platforms and atolls are directly sea level controlled whereas the deeper margins are sea level influenced the platform top deposits have the lowest rates of accumulation 10 26 m my due to subaerial exposure and only intermittent flooding the deeper platform margins below lowstand base level are influenced by events on the shallow platform mainly to sediment production and offbank transport slope erosion and redeposition are also important prograded margins and periplatforms accept large volumes of allochthonous sediment and can have periods of extremely high 200 m my vertical accumulation separated by intervals of non deposition erosion or sediment bypass these data despite limitations provide some basic values for ice house carbonate accumulation and the relevant extrinsic controls the late neogene rates can help constrain the sediment dynamics of the carbonate platform and flank system data especially important for calibration of computer models and for the resultant reservoir attributes

tertiary oxygen isotope synthesis sea level history and continental margin erosion tertiary benthic and planktonic foraminiferal oxygen isotope records are correlated to a standard geomagnetic polarity time scale making use of improved chronostratigraphic control and additional oligocene isotope data synchronous changes in both benthic and planktonic 18o values which occurred in the oligocene to miocene 36 5 2 ma are interpreted in part to represent ice growth and decay the inferred ice growth events correlate with erosion on passive continental margins as interpreted from seismic and chronostratigraphic records this association is consistent with a link between oligocene to miocene erosional events and rapid 15 m m y glacioeustatic lowerings of about 50 m high benthic foraminiferal 18o values suggest the presence of continental ice sheets during much of the oligocene to recent 36 0 ma substantially ice free conditions probably existed throughout the paleocene and eocene 66 36 ma the mechanisms and rates of sea level change apparently were different between the early and late tertiary with glacioeustatic changes restricted to the past 36 m y pre oligocene erosion on passive continental margins was caused by eustatic lowerings resulting from global spreading rate changes we apply a model which suggests that large areas of the continental shelves were subaerially exposed during such tectonoeustatic lowstands stimulating slope failure and submarine erosion the different mechanisms and rates of eustatic change may have caused contrasting erosional patterns between the early and late tertiary on passive continental margins this speculation needs to be confirmed by examination of data from several passive margins

magnetostratigraphic dating of the uplifted atoll of mare geodynamics of the loyalty ridge sw pacific the loyalty islands sw pacific are uplifted as they are progressively affected by the lithospheric flexure of the australian plate before its subduction under the new hebrides arc these geodynamic changes are constrained by magnetostratigraphically dating two sections from mare island where mineral extractions coupled with rock magnetic experiments suggest that the magnetic remanence is mostly carried by a mixture of single domain to multidomain magnetite maghemite with the help of faunal determinations and radiometric dating the sequences of polarity reversals correlated to the geomagnetic polarity timescale range from the top of chron c4n late miocene to the top of the gauss chron late pliocene this new chronostratigraphy refines the timing of two distinctive carbonate units rhodolith platform coral reefs separated by a hardground whose transition is known to coincide approximately with a regional event around the miocene pliocene boundary the magnetostratigraphic dating indicates that the hardground represents about a 1 9 m y hiatus and suggests variable sedimentation rates ranging from 4 7 to 65 4 m m y during the atoll construction the lithospheric bulge seems to have influenced the evolution of mare island some 3 1 m y ago leading to a diachronous emersion of the northeast and southwest rim of the atoll with a mean uplift rate of the order of 4 cm kyr

latest miocene benthic δ 18 o changes global ice volume sea level and the messinian salinity crisis oxygen isotope evidence indicates high but variable 18o values in benthic foraminiferal calcite during the latest miocene and earliest pliocene these high values may represent increases in global ice volume and associated sea level fall the 18o record resembles glacial interglacial cycles but with only one third the amplitude of the late pleistocene signal this variability may reflect instability in the antarctic ice sheet and palaeomagnetic correlation points to an isotopic event coinciding with the isolation and desiccation of the mediterranean basin during the latest messinian

magnetostratigraphy of the uplifted former atoll of niue south pacific implications for accretion history and carbonate diagenesis abstract cenozoic carbonate platforms are a potential rich source of information concerning eustasy but their prerequisite dating is fraught with difficulties paleomagnetism has long been established as a highly successful tool for dating deep sea sediments but its applicability to shallow water reef carbonates has only recently been explored here we derive a detailed magnetostratigraphy of the carbonate platform at niue on the basis of cores drilled into lagoonal facies to a maximum depth of 303 m below surface the carbonates consist of limestone which has been partially dolomitized and contain 16 zones of meteoric diagenesis caused by a succession of sea level falls the paleomagnetic record spanning chron c4r tortonian to chron c2n late piacenzian and covering about 7 1 m y of deposition and erosion was tied to the geomagnetic polarity time scale gpts using verified control points coincidence of high accretion rates up to 62 1 m m y and high sea levels caused the tortonian early messinian section to mirror the contemporaneous gpts polarity reversal intervals in contrast decelerated subsidence coupled with frequent eustatic fluctuations yielded compressed and truncated polarity intervals in the younger section during late messinian the accretion rate was anomalously high 114 1 m m y probably due to a short lived endogenic heating event isothermal remanent magnetization data suggest that magnetite is the dominant magnetic carrier in the niue carbonates nrm intensities of limestones mean 0 126 0 95 ma m for n 76 and dolomites mean 0 121 0 097 ma m for n 73 are indistinguishable and their nrm sirm ratios are similar close to 10 2 suggesting they underwent the same process of remanence acquisition the nrm at niue are comparable in their intensities to those reported from san salvador and mururoa but much weaker than those of deep sea sediments in general meteoric diagenesis and dolomitization did not overprint the primary magnetization record at niue one exceptional case of magnetic resetting depicted within a well developed meteoric diagenesis zone suggests that magnetic overprinting cannot be ruled out in carbonate platforms possessing weak primary magnetizations and therefore their polarity records must be evaluated on a case by case basis

atoll magnetostratigraphy calibration of their eustatic records results of palaeomagnetic measurements of a core from mururoa atoll french polynesia led us to document for the first time the atoll s magnetostratigraphy periods of slow aggradation correlated with sea level low stands show that atolls are accurate recorders of sea level fluctuations the timing and amplitude of sea level fluctuations may be reconstructed on the basis of precise dating of atolls and shallow water platforms magnetostratigraphy is therefore a first step towards a quantitative calibration of the eustatic records of coral atolls

sedimentary patterns and geometries of the bahamian outer carbonate ramp miocene lower pliocene great bahama bank core logging and high resolution seismic data from odp leg 166 were used to analyse deposits of the neogene miocene lower pliocene bahamian outer carbonate ramp ramp sediments are cyclic alternations of light and dark grey wackestones packstones with interbedded calciturbidite packages and minor slumps cyclicity was driven by high frequency sea level changes light grey layers containing shallow water bioclasts were formed when the ramp exported material whereas the dark grey layers are dominantly pelagic calciturbidites are arranged into mounded lobes with feeder channels internal bedding of the lobes shows a north directed shingling as a result of the asymmetrical growth of these bodies calciturbidite packages occur below and above sequence boundaries indicating that turbidite shedding occurred during third order sea level highstands and lowstands highstand turbidites contain shallow water components such as green algal debris and epiphytic foraminifera whereas lowstand turbidites are dominated by abraded bioclastic detritus gravity flow depocentres shifted from an outer ramp position during the early miocene to a basin floor setting during the late miocene to early pliocene this change was triggered by an intensification of the strength of bottom currents during the tortonian which was also responsible for shaping the convex morphology of the outer ramp the miocene and lower pliocene of the leeward flank of great bahama bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps the contrast between its sedimentary patterns and the well known upper pliocene quaternary slope facies associations of the flat topped great bahama bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base of slope successions

temporal changes in ventilation and the carbonate system in the atlantic sector of the southern ocean the southern ocean is the most important area of anthropogenic carbon cant uptake in the world ocean only rivalled in importance by the north atlantic ocean significant variability on decadal time scales in the uptake of cant in the southern ocean has been observed and modelled likely with consequences for the interior ocean storage of cant in the region and implications for the global carbon budget here we use eight cruises between 1973 and 2012 to assess decadal variability in cant storage rates in the southeast atlantic sector of the southern ocean for this we employed the extended multiple linear regression emlr method we relate variability in dic dissolved inorganic carbon storage which is assumed to equal anthropogenic carbon storage to changes in ventilation as observed from repeat measurements of transient tracers within the antarctic intermediate water aaiw layer which is the dominant transport conduit for cant into the interior ocean moderate cant storage rates were found without any clear temporal trend in subantarctic mode water samw a less dense water mass found north of the subantarctic front and above aaiw high storage rates of cant were observed up to about 2005 but lower rates in more recent times the transient tracer data suggest a significant speed up of ventilation in the summer warmed upper part of aaiw between 1998 and 2012 which is consistent with the high storage rate of cant a shift of more northern cant storage to more southern storage in near surface waters was detected in the early 2000s beneath the aaiw the emlr method as applied here did not detect significant storage of cant however the presence of the transient tracer cfc 12 all through the water column suggests that some cant should be present but at concentrations not reliably quantifiable the observed temporal variability in the interior ocean seems at a first glance to be out of phase with observed surface ocean cant fluxes but this can be explained by the time delay for the surface ocean signal to manifest itself in the interior of the ocean

high eustatic sea level during the middle pliocene evidence from the southeastern u s atlantic coastal plain the middle pliocene approximately 3 5 2 5 ma was a period of global warmth preceding the growth of major northern hemisphere ice sheets the authors report on eustatic sea level for the middle pliocene based on microspaleontologic study of marine deposits of the duplin formation of south carolina and north carolina the duplin was deposited during a middle pliocene marine transgression that formed the orangeburg scarp a prominent wave cut geomorphic paleoshoreline of the southeastern u s atlantic coastal plain they concluded that 1 the scarp in south carolina was formed mostly during the middle pliocene 3 5 3 0 ma 2 eustatic sea level was about 35 plus minus 18 m higher than modern sea level the scarp has been uplifted about 50 65 m since the middle pliocene and 3 ocean water temperatures along eastern north america were warmer when the scarp was formed that they are at present

magnetostratigraphic dating of shallow water carbonates from san salvador bahamas magnetostratigraphic results are reported here from a sequence of late neogene quaternary shallow water carbonate sediments from a continuous core drilled on the island of san salvador bahamas on the basis of the remanent magnetism of 136 samples from a 91 m measured section of core the polarity sequence can be correlated with the magnetic polarity time scale from the gilbert chron early pliocene through the late brunhes chron late pleistocene holocene magnetic polarities were determined on the basis of relative up down direction in the unoriented core extraction studies of the magnetic particles reveal the presence of single domain crystals of magnetite resembling those produced by the magnetotactic bacteria and algae the sequence of reversals provides a minimum of six new major chronostratigraphic markers for the pliocene pleistocene of the bahamas it confirms and refines the local timing of both the lithologic change from skeletal to nonskeletal sediments and the disappearance of coral and molluscan species from the bahamas as upper late pliocene between 2 6 and 2 7 ma that the primary magnetic remanence is preserved in shallow water carbonates including replacement dolomites suggests that this technique could be used to date similar tertiary and possibly even older carbonate sequences the establishment of a reliable magnetostratigraphy provides refined dating of shallow water carbonates and regional faunal appearances or disappearances sediment accumulation rates subsidence and depositional events

anatomy of a modern open ocean carbonate slope northern little bahama bank the open ocean carbonate slope north of little bahama bank consists of a relatively steep 4 upper slope between water depths of 200 and 900 m and a more gentle 1 2 lower slope between depths of 900 and 1300 m the upper slope is dissected by numerous small submarine canyons 50 150 m in relief that act as a line source for the downslope transport of coarse grained carbonate debris the lower slope is devoid of any well defined canyons but does contain numerous small 1 5 m hummocks of uncertain origin and numerous larger 5 40 m patchily distributed ahermatypic coral mounds sediments along the upper slope have prograded seaward during the cenozoic as a slope front fill seismic facies of fine grained peri platform ooze surface sediments show lateral gradation of both grain size and carbonate mineralogy with the fine fraction derived largely from the adjacent shallow water platform near surface sedimentary facies along the upper slope display a gradual downslope decrease in the degree of submarine cementation from well lithified hardgrounds to patchily cemented nodular ooze to unlithified peri platform ooze controlled by lateral variations in diagenetic potential and or winnowing by bottom currents submarine cementation stabilizes the upper part of the slope allowing upbuilding of the platform margin and controls the distribution of submarine slides as well as the headward extent of submarine canyons where unlithified sediments are heavily bioturbated and are locally undergoing dolomitization upper slope sediments are also conditioned eustatically resulting in vertical cyclic sequences of diagenetically unstable aragonite and magnesian calcite rich and stable calcite rich carbonates that may explain the well bedded nature of ancient peri platform ooze sequences lower slope sediments have prograded seaward during the cenozoic as a chaotic fill seismic facies of coarse grained carbonate turbidites and debris flow deposits with subordinate amounts of peri platform ooze coarse clasts are internally derived from fine grained upper slope sediments via incipient cementation submarine sliding and the generation of sediment gravity flows gravity flows bypass the upper slope via a multitude of canyons and are deposited along the lower slope as a wedge shaped apron of debris parallel to the adjacent shelf edge consisting of a complex spatial arrangement of localized turbidites and debris flow deposits a proximal apron facies of thick mud supported debris flow deposits plus thick coarse grained ta turbidites grades seaward into a distal apron facies of thinner grain supported debris flow deposits and thinner finer grained ta b turbidites with increasing proportions of peri platform ooze both the geomorphology and sedimentary facies relationships of the carbonate apron north of little bahama bank differ significantly from the classic submarine fan model as such a carbonate apron model offers an alternative to the fan model for palaeoenvironmental analysis of ancient open ocean carbonate slope sequences

redeposition of late cretaceous pelagic sediments controlled by sea level fluctuations northwest and middle european upper cretaceous pelagic carbonates contain abundant gravity transported sediments in short lived stratigraphic intervals of 100 500 ka redeposition terminates synchronously in different basins at horizons that are always overlain by deeper water sediments these horizons can be correlated with defined sequence boundaries that are believed to be caused by eustatic sea level falls the change of hydrostatic pressure in the water column during sea level fluctuations was not in equilibrium with pore water pressures in the fine grained sediments about 10 of the hydrostatic pressure at times of sea level highstands was preserved in the sediment as pore water overpressure during sea level falls this may have caused sediment failure theoretical considerations agree with the observed degree of redeposition

tracing organic compounds in aerobically altered methane derived carbonate pipes gulf of cadiz sw iberia abstract the primary geochemical process at methane seeps is anaerobic oxidation of methane aom performed by methanotrophic archaea and sulfate reducing bacteria srb the molecular fingerprints biomarkers of these chemosynthetic microorganisms can be preserved in carbonates formed through aom however thermal maturity and aerobic degradation can change the original preserved compounds making it difficult to establish the relation between aom and carbonate precipitation here we report a study of amino acid and lipid abundances in carbonate matrices of aerobically altered pipes recovered from the seafloor of the gulf of cadiz sw iberian peninsula this area is characterized by a complex tectonic regime that supports numerous cold seeps studies so far have not determined whether the precipitation of carbonate pipes in the gulf of cadiz is a purely chemical process or whether microbial communities are involved samples from this site show signs of exposure to oxygenated waters and of aerobic alteration such as oxidation of authigenic iron sulfides in addition the degradation index calculated from the relative abundance of preserved amino acids indicates aerobic degradation of organic matter although crocetane was the only lipid identified from methanotrophic archaea the organic compounds detected n alkanes regular isoprenoids and alcohols are compatible with an origin from aom coupled with bacterial sulfate reduction bsr and subsequent aerobic degradation we establish a relation among aom bsr and pipe formation in the gulf of cadiz through three types of analysis 1 stable carbon and oxygen isotopic composition of carbonate minerals 2 carbonate microfabrics and 3 mineralogical composition our results suggest that carbonate pipes may form through a process similar to the precipitation of vast amounts of carbonate pavements often found at cold seeps our approach suggests that some organic compound patterns in combination with additional evidence of aom and bsr may help indicate the source of altered methane derived carbonates commonly occurring in ancient and modern deposits

quantifying stratigraphic completeness a probabilistic approach using paleomagnetic data although sedimentary hiati of variable magnitude are abundant in most stratigraphic sections quantification of the degree of completeness for individual sections has proven difficult a new method of estimating stratigraphic completeness is developed for sections that preserve a detrital remanent magnetic reversal history because the timing of geomagnetic reversals is independent of sedimentation events the distribution of reversals in a stratigraphic section can be used to evaluate completeness the most direct method in which sections are sampled at the top and base of each stratigraphic unit evaluates the frequency of reversals within units versus at unit contacts the more complete a section the greater the probability that reversals occurred during depositional events and are recorded as within unit reversals the less complete a section the greater the probability that reversals occurred during depositional hiati and are recorded as unit contact reversals monte carlo simulations suggest that

from the great bahama bank into the straits of florida a margin architecture controlled by sea level fluctuations and ocean currents high resolution multichannel seismic data collected across the great bahama bank margin and the adjacent straits of florida indicate that the deposition of neogene quaternary strata in this transect are controlled by two sedimentation mechanisms 1 west dipping layers of the platform margin which are a product of sea level controlled platform derived downslope sedimentation and 2 east or north dipping drift deposits in the basinal areas which are deposited by ocean currents these two sediment systems are active simultaneously and interfinger at the toe of slope the prograding system consists of sigmoidal clinoforms that advanced the margin some 25 km into the straits of florida the foresets of the clinoforms are approximately 600 m high with variable slope angles that steepen significantly in the pleistocene section the seismic facies of the prograding clinoforms on the slope is characterized by dominant partly chaotic cut and fill geometries caused by submarine canyons that are oriented downslope in the basin axis seismic geometries and facies document deposition from and by currents most impressive is an 800 m thick drift deposit at the confluence of the santaren channel and the straits of florida this santaren drift is slightly asymmetric thinning to the north the drift displays a highly coherent seismic facies characterized by a continuous succession of reflections indicating very regular sedimentation leg 166 of the ocean drilling program odp drilled a transect of five deep holes between 2 and 30 km from the modern platform margin and retrieved the sediments from both the slope and basin systems the neogene slope sediments consist of peri platform oozes intercalated with turbidites whereas the basinal drift deposits consist of more homogeneous fine grained carbonates that were deposited without major hiatuses by the florida current starting at approximately 12 4 ma sea level fluctuations which controlled the carbonate production on great bahama bank by repeated exposure of the platform top controlled lithologic alternations and hiatuses in sedimentation across the transect both sedimentary systems are contained in 17 seismic sequences that were identified in the neogene quaternary section seismic sequence boundaries were identified based on geometric unconformities beneath the great bahama bank all the sequence boundaries could be traced across the entire transect into the straits of florida biostratigraphic age determinations of seismic reflections indicate that the seismic reflections of sequence boundaries have chronostratigraphic significance across both depositional environments