an example of alternative correlation techniques in a low accommodation setting nonmarine hydrocarbon system the lower cretaceous mannville basal quartz succession of southern alberta chemostratigraphy and heavy mineral techniques have been applied to the lower cretaceous basal quartz in the western canada sedimentary basin the aim of the study is to demonstrate that these two techniques can be used to help understand the complex stratigraphy of reservoirs deposited in low accommodation fluvial settings the basal quartz is an ideal unit to demonstrate their applicability in stratigraphic studies of hydrocarbon reservoirs because extensive mapping and petrographic studies have enabled the establishment of a rigorous stratigraphic framework despite its complexity resulting from deposition in a low accommodation fluvial setting the three component units analyzed in the basal quartz horsefly unit bantry alderson taber bat unit and ellerslie unit each have unique geochemical and heavy mineral characteristics chemostratigraphic analysis shows that silty claystones from the horsefly bat and ellerslie units have distinctly different geochemistry from one another with the variations being caused by changes in clay mineralogy and other components such as feldspar apatite and zircon the geochemistry also suggests periodic volcanogenic input influenced the silty claystones of the basal quartz heavy mineral analysis shows that sandstones from the three units can be distinguished on the basis of ratio parameters such as apatite tourmaline rutile zircon and zircon tourmaline which are controlled by differences in provenance and intensity of weathering during transport

chemostratigraphy a method to improve interwell correlation in barren sequences a case study using onshore duckmantian stephanian sequences west midlands u k abstract chemostratigraphy has been applied to onshore duckmantian stephanian successions encountered in outcrop and penetrated by two boreholes from the west midlands u k these successions represent the onshore equivalents of the barren red measures which are important hydrocarbon bearing sequences in the southern north sea much is known about the onshore successions in terms of sedimentology mineralogy and provenance and thus they provide the ideal test for the validity of chemostratigraphy as a stratigraphic tool reliable inorganic geochemical data have been acquired from geochemical analyses of core sidewall core and cuttings samples with 19 elements being determined stratigraphic variations in elemental concentrations are compared with known variations in the mineralogical data the established lithostratigraphic units of the duckmantian stephanian intervals can also be recognized from the geochemical data and by using these data can be subdivided further this results in an independent chemostratigraphic correlation being established for the two boreholes which has been assessed statistically by discriminant function analysis from the geochemical and mineralogical data distinct changes in provenance are identified within the upper carboniferous successions the sediments of the coal measures were derived from a north westerly and westerly source caledonian whereas the etruria formation sediments came from the wales brabant massif the sediments having mixed caledonian and cadomian characteristics eventually these sediments were replaced by sediments from a southern hercynian source halesowen and salop formations

magnetostratigraphy susceptibility of the přidolian lochkovian silurian devonian gssp klonk czech republic and a coeval sequence in anti atlas morocco abstract the magnetosusceptibility event and cyclostratigraphy msec record for the p idolian lochkovian silurian devonian global boundary stratotype section and point gssp klonk prague basin czech republic is described and used to establish a magnetostratigraphy susceptibility profile for the gssp gssp msec data are summarized into three magnetozones msz the tma msz late p idolian with 13 msszs mssz the klonk msz latest p idolian and earliest lochkovian with 17 msszs and the voskop msz early lochkovian with 7 msszs the base of klonk mssz 2 is coincident with the base of lochkovian and the devonian the proposed magnetostratotype for the p idolian lochkovian boundary is supported by ms data from a nearby core through the gssp sequence and into the upper ludlow three additional mszs are recognized for the portion of the core sequence older than the gssp boundary sequence the extension of the mszs and msszs away from the proposed magnetostratotype is tested by comparison with a lochkovian sequence in the western sahara of southeastern morocco mszs are the result of global sea level fluctuations that alter base level and the pattern of erosion and influx of detrital paramagnetic mineral components into the marine environment large scale transgressive and regressive patterns interpreted from the msec data establish that the silurian devonian boundary in the barrandian region falls between a short lived transgressive pulse in the latest p idolian and an equally short lived regressive pulse in the earliest lochkovian msszs identified in the gssp and core sequences are the result of variation in climate cycles and the resulting periodicity can explained by either the 38 9 ka silurian and devonian equivalent of the modern 54 ka obliquity cycle or the eccentricity cycle of 106 ka periodicity use of the obliquity periodicity gives a duration for the barrandian lochkovian of 4 46 ma which agrees with the most recent geochronometric estimate of 4 5 ma for the lochkovian use of the eccentricity periodicity gives a duration for the barrandian lochkovian of 12 16 ma which agrees with the previous geochronometric estimates of 12 2 and 12 5 ma for the lochkovian in any case the cyclic nature of the msec data established by the msszs can be explained by variations in the rate of supply of weathered terrigenous paramagnetic grains to the marine system these variations in supply occurred due to climate changes resulting from the either the obliquity or eccentricity of the earth s orbit knowledge of the periodicity of lochkovian cycles in the barrandian area allows estimation of the rates of sediment accumulation the duration of fossil ranges and the rates of evolution depending on the choice of obliquity or eccentricity to explain the cyclicity in the barrandian lochkovian the estimated rate of sediment accumulation in the gssp outcrop averaged either 51 or 140 ka m the range of the graptoloid monograptus uniformis angustidens wholly contained within the lochkovian sequence at the gssp is also estimated at either 51 or 140 ka

hydrothermal brecciation in the jemez fault zone valles caldera new mexico results from continental scientific drilling program core hole vc 1 an unusual breccia sequence penetrated in the lower 30 m of continental scientific drilling program core hole vc 1 total depth 856 m records a complex hydrothermal history culminating in hydraulic rock rupture and associated alteration at the edge of the quaternary valles caldera the breccias both tectonic and hydrothermal in origin were formed in the jemez fault zone near the intersection of this major regional structure with the caldera s ring fracture margin tectonic breccias in the sequence are contorted crushed and sheared coexisting hydrothermal breccias lack such frictional textures but display matrix flow foliation and prominent clast rounding features characteristic of fluidization these hydrothermal breccias were intensely altered during at least five major stages to quartz illite phengite pyrite aggregates traces of molybdenite occur locally this assemblage indicates interaction with hydrothermal fluid at temperatures in excess of 200 c the extrapolated present maximum temperature of 184 c in the breccia zone therefore represents considerable cooling since these phases were formed fluid inclusions in the breccias also preserve evidence of the prior passage of hotter fluids the inclusions are principally two phase liquid rich secondary in origin and concentrated in hydrothermal quartz older high salinity inclusions unrelated to brecciation homogenize in the temperature range 189 246 c younger inclusions in part of interbreccia origin are low salinity and homogenize in the temperature range 230 283 c locally coexisting liquid and vapor rich inclusions document periodic boiling of the dilute fluids these fluid inclusion data along with the probable age of the hydrothermal breccias 1 5 ma the assumed depth at which they developed about 515 m and the contemporaneous state of stress extensional can be combined to model hydrothermal brecciation at the vc 1 site the minimum fluid pressure pfr required to hydrofracture these rocks was probably about 7 5 mpa 0 0146 mpa m a boiling point versus depth curve based on these pfr values graphically defines the physical conditions prevailing when the breccias were formed when fluid pressure at the assumed depth of brecciation exceeded that curve in response to rapid release of confining pressure possibly augmented by renewed heating flashing hydrothermal fluid fractured the enclosing rock large overpressures most likely induced by sudden seismic cracking of a hydrothermally sealed portion of the jemez fault zone led to local fluidization of the resulting breccias late quartz veining hydrothermal alteration and molybdenite mineralization were probably produced by the fluids responsible for brecciation

earliest oligocene increase in south atlantic productivity as interpreted from rock magnetics at deep sea drilling project site 522 the magnetic properties of the sediments rock magnetics at dsdp site 522 in the south atlantic exhibit clear differences between the latest eocene and earliest oligocene based on low temperature behavior of saturation remanence and hysteresis loops we attribute the difference to a slightly greater proportion of the finest grained so called superparamagnetic magnetite in the eocene sediments we believe that the lower proportion of very fine grained magnetite in the oligocene sediments is a result of incipient reduction diagenesis caused by increased productivity and hence increased labile organic carbon transport to the sediments due to an early oligocene increase in thermohaline circulation the eocene to oligocene transition at site 522 is also expressed by changes in microfossil assemblages increased carbonate content decreased insoluble residue and decreased foraminiferal shell fragmentation the increase in carbonate is synchronous with and parallels a change in the ratio of two of the rock magnetic parameters a ratio that tracks the decrease in the very fine grained magnetite component also parallel to these is a trend toward heavier 13c values in foraminiferal tests the increase in organic carbon transport to the sediments led to chemical dissolution of the finest grain size fraction of magnetite in the oligocene sediments hence a reduction in the superparamagnetic component and the change in the rock magnetic ratio in this way rock magnetics can be sensitive indicators of environmental changes such as fluctuations in organic carbon transport which may leave little other trace in the sedimentary record

magnetosusceptibility event and cyclostratigraphy method applied to marine rocks detrital input versus carbonate productivity magnetic susceptibility data from marine rocks can be used for global correlation due to synchronous variations in global erosion we show here that the magnetic susceptibility signature found in two forms resides mainly in paramagnetic and other detrital constituents in most marine rocks the first form is a short term low magnitude high frequency cyclic climate signature that is often useful for regional correlation the second form is a longer term higher magnitude low frequency signature resulting from transgressive and regressive events that can be used for global correlation fluctuations in detrital input due to eustatic based erosion are the primary cause of events these fluctuations are driven by large scale processes such as global orogenic cycles however variations in carbonate productivity cannot be ruled out when explaining the low magnitude climate driven cyclicity also observed in magnetic susceptibility data sets

cenomanian turonian and δ13c and δ18o sea level and salinity variations at pueblo colorado stable isotopes of the surface dwelling planktic foraminifera hedbergella planispira its abundance variations and mineralogical analysis of the cenomanian turonian at pueblo co reveal cyclic variations in surface salinity due to changes in precipitation freshwater influx marine incursions and long term sea level fluctuations hedbergella planispira is a proxy for salinity variations as indicated by 2 4 more negative 18o values in intervals of peak abundances as compared to intervals with reduced populations negative 18o values reflect periods of brackish surface waters caused by freshwater influx during wet humid periods accompanied by increased clastic transport more positive 18o values reflect more normal marine salinities as a result of arid periods and or marine incursions and correlate with intervals of increased biogenic carbonate deposition the magnitude of salinity variations during the low sea level of the hartland shale is twice that during the sea level transgression of the bridge creek limestone the rapid positive 13c shift that marks the onset of oceanic anoxic event 2 oae 2 at pueblo occurred over a period of about 100 ky 93 90 94 00 ma and coincided with the major sea level transgression that culminated in the deposition of the basal bridge creek limestone a positive 13c shift also occurred in the rotalipora cushmani zone prior to oae 2 and coincided with a sea level rise and enhanced preservation of terrestrial organic matter the likely cause for oae 2 is depletion of 12c in the water column as a result of high primary productivity whereas an earlier r cushmani zone event was primarily caused by increased input of terrigenous organic matter both 13c events are associated with enhanced organic matter preservation and anoxic or dysoxic bottom waters

the use of chemical element analyses in the study of biostratigraphically barren sequences an example from the triassic of the central north sea ukcs

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

stability of the astronomical frequencies over the earth s history for paleoclimate studies the expected changes over the past 500 million years in the principal astronomical frequencies influencing the earth s climate may be strong enough to be detectable in the geological records and such effects have been inferred in several cases calculations suggest that the shortening of the earth moon distance and of the length of the day back in time induced a shortening of the fundamental periods for the obliquity and climatic precession from 54 to 35 41 to 29 23 to 19 and 19 to 16 thousand years over the last half billion years at the same time the precessional constant increased from 50 to 61 arc seconds per year the changes in the frequencies of the planetary system due to its chaotic motion are much smaller their influence on the changes of the periods of climatic precession obliquity and eccentricity of the earth s orbit around the sun can be neglected eccentricity periods used for quaternary climate studies may therefore be considered to have been more or less constant for pre quaternary times

magnetostratigraphy susceptibility of the frasnian famennian boundary magnetosusceptibility event and cyclostratigraphy msec is used to establish a non polarity based magnetostratigraphy susceptibility mss between the stratotype region for the frasnian famennian f f boundary sequence in the montagne noire of southern france the eastern rheinisches schiefergebirge of germany belgium the eastern anti atlas of morocco and the arbuckle mountains of southern oklahoma usa despite differences of depositional environment the mss is remarkably consistent and can be described in the context of a hierarchy of magnetozones that allow the extension of correlation away from the montagne noire reference section the nature of the controls on the influx of iron into the marine system produces a natural hierarchy of at least seven orders or magnetozones designated msz1 msz2 msz3 msz4 msz5 msz6 and msz7 these are characterized in terms of the magnitude of their duration the mss reference section of choice for the f f boundary is the well known trench c at la serre lsc in the northeastern montagne noire of southern france the f f boundary is located at the lower boundary of magnetozone la serre i 3b at la serre as well as in all other sections studied msz4 and msz5 magnetozones are used to establish intra and inter regional correlation between the reference sequence and the other regions the base of the upper kellwasser event is as variable within the mss zonation as it is within the biostratigraphic zonation as is the position of the lower kellwasser event

magnetostratigraphy susceptibility of the upper ordovician kope formation northern kentucky abstract as a test of the utility of magnetic susceptibility ms measurements for correlation among lithified marine sequences samples were collected from well studied shale and limestone outcrops of the upper ordovician kope formation northern kentucky the bulk initial low field ms of these samples is compared among two litho and biostratigraphically correlated sections containing the same beds the results of this comparison demonstrated an excellent correlation among equivalent beds thermomagnetic susceptibility analysis supports previous xrd work indicating that illite is primary and is the main paramagnetic mineral responsible for the ms variations observed in this study a composite of ms results for a sequence of 31 named shale limestone couplets is used to build a composite section of kope sequences for the area these ms variations permit division of the various sections into a set of 28 ms cycles within the kope formation covering 50 m of section these cycles suggest a systematic control by climate on the influx of detrital material that formed these sedimentary sequences and support other work indicating kope climate cyclicity

paleoceanographic significance of high resolution carbon isotope records across the cenomanian turonian boundary in the western interior and new jersey coastal plain usa carbon isotope measurements have been made on bulk carbonate and organic matter in three sections across the cenomanian turonian boundary the stratigraphy records the positive carbon isotopic excursion that is associated with the major oceanic anoxic event oae2 comparison of toc and isotopic data in sections from a range of different environments suggests that the positive excursion is a response to increased burial of organic matter in the deep ocean the lack of coupled negative shifts in 13corg and 13ccarb records at the onset of oae2 does not support a causal role for volcanism or methane hydrate dissociation

high resolution magnetic susceptibility and geochemistry for the cenomanian turonian boundary gssp with correlation to time equivalent core abstract the upper cretaceous cenomanian turonian c t boundary represents the most significant thermal climatic event in the mesozoic and it has been well studied here we present a relatively new approach for providing both independent climate based cyclostratigraphic analysis and correlation among c t sections we have collected samples for bulk initial low field magnetic susceptibility ms measurement and high resolution inorganic geochemical analyses from two c t sequences 1 the well defined c t global boundary stratotype section and point gssp located at lake pueblo colorado and deposited in the upper cretaceous western interior seaway of north america and 2 the well studied marlstone and limestone usgs 1 portland core drilled at portland colorado 40 km to the west of the c t gssp comparing the lithostratigraphy chemostratigraphy and magnetostratigraphic susceptibility developed from magnetic susceptibility ms data indicates that the usgs 1 portland core closely compares with the c t gssp sequence using any of the three measures demonstrating that intervals collected and sampled from these two sequences are highly correlated a preliminary magnetostratigraphic susceptibility zonation for the c t boundary is presented to which other ms work can be compared fourier transform ft analysis of the ms data from the gssp when compared with previous ft work using geochemical analysis of portland core samples shows close similarities to the gssp with milankovitch eccentricity obliquity and precession bands well defined in both data sets using this result we assign relative ages to the intervals sampled and evaluate changes in absolute sediment accumulation rates through the c t boundary interval we show that while sediment accumulation rate is relatively high in the upper cenomanian a change toward lower accumulation rates in the gssp section at the c t boundary is due to reduced productivity following the c t extinction events that resulted from global warming associated with oceanic anoxic event 2 oae2 that began in the uppermost cenomanian

gulf of mexico sediment sources and sediment transport trends from magnetic susceptibility measurements of surface samples abstract the magnetic properties from 200 trigger core top and van veen grab sediment samples recovered from throughout the gulf of mexico have been analyzed and used to characterize sediment source and flow pattern distributions magnetic parameters included are anhysteretic remanent magnetism arm and magnetic susceptibility ms measurements results from these measurements are compared to previously determined calcium carbonate percentages and clay and hematite influx trajectories into the gulf of mexico for the same samples reported by balsam and beeson balsam w l and beeson j p 2003 sea floor sediment distribution in the gulf of mexico deep sea res i 50 1421 1444 the arm results give an estimate of magnetic grain size distributions and by analogy grain size distributions in general whereas ms patterns show high detrital sediment accumulation zones within the gulf the dominant influx of modern high susceptibility sediment into the gulf of mexico appears to originate from the red river flow into atchafalaya river basin and out into the gulf from atchafalaya bay with significant additional contributions from the mississippi river through the southwest pass of the mississippi river delta this material then moves across the continental shelf and down through the mississippi canyon into the deep gulf where it is redistributed at depths 3600 m the eastern shelf margins in the gulf offshore from alabama and florida are accumulating calcite or quartz rich medium to fine grained sediment that has a very low or diamagnetic ms signature from the louisiana to texas gulf coast margins ms is moderate to high suggesting a river influx of magnetic constituents from the volcanic fields in new mexico and from igneous and metamorphic sources in the mississippi basin offshore from western mexico the ms is high to moderate but the yucatan shelf margin is characterized by low to diamagnetic ms values due to sediment dominated by calcite sands and oozes a trend that continues to the east onto the west florida shelf additional measurements of samples collected in association with sites characterized by hydrocarbon seepage exhibit anomalously low ms values the samples from the lower shelf and slope areas are typified by iron reduction by bacterial organisms in these samples these results produce anomalous localized lows in the ms trends observed

midlatitude shelf seas in the cenomanian turonian greenhouse world temperature evolution and north atlantic circulation 1 an 8 million year record of subtropical and midlatitude shelf sea temperatures derived from oxygen isotopes of well preserved brachiopods from a variety of european sections demonstrates a long term cenomanian temperature rise 16 20 c midlatitudes that reached its maximum early in the late turonian 23 c midlatitudes superimposed on the long term trend shelf sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations in the mid cenomanian and the late turonian two minor shelf sea cooling events 2 3 c coincide with carbon cycle perturbations and times of high amplitude sea level falls although this evidence supports the hypothesis of potential glacioeustatic effects on cretaceous sea level the occurrence of minimum shelf sea temperatures within transgressive beds argues for regional changes in shelf sea circulation as the most plausible mechanism the major carbon cycle event in the latest cenomanian oceanic anoxic event 2 is accompanied by a substantial increase in shelf sea temperatures 4 5 c that occurred 150 kyr after the commencement of the 13c excursion and is related to the spread of oceanic conditions in western european shelf sea basins our oxygen isotope record and published 18o data of pristinely preserved foraminifera allow the consideration of north atlantic surface water properties in the cenomanian along a transect from the tropics to the midlatitudes on the basis of fossil derived 18o estimated w ranges and modeled salinities temperature salinity density ranges were estimated for tropical subtropical and midlatitude surface waters accordingly the cenomanian temperate shelf seas waters have potentially the highest surface water density and could have contributed to north atlantic intermediate to deep waters in the preopening stage of the equatorial atlantic gateway

stratigraphy of the middle devonian boundary formal definition of the susceptibility magnetostratotype in germany with comparisons to sections in the czech republic morocco and spain abstract one major difficulty in geology is high resolution correlation among widely separated sections especially in the paleozoic where magnetostratigraphy polarity is not well established because rocks are often remagnetized where critical biostratigraphic zonation may be poor or lacking or where structural complexities make correlations very difficult to address this problem we have been using magnetostratigraphy susceptibility measurements here we report our work from the middle devonian in europe and north africa the middle devonian emsian eifelian global boundary stratotype section and point gssp located in the eifel hills western germany was ratified by the international subcommission on stratigraphy in 1985 after careful evaluation of the biostratigraphy for this and many other sections the boundary interval has been characterized using biostratigraphy and the beginning of the eifelian stage has been specifically defined by the first occurrence of the conodont polygnathus costatus partitus we have collected the eifel hills section for magnetic susceptibility ms measurement and here we establish it as the magnetostratotype for the emsian eifelian stage boundary by formally defining the magnetostratigraphy susceptibility for the section we then collected measured and compared the magnetostratotype to four other sections for which conodont biostratigraphy has been studied and where p costatus partitus is present two emsian eifelian sections in morocco and two sections in the czech republic including the emsian eifelian parastratotype finally we have measured the ms for the el puerto creek section in the cantabrian mountains of spain and identified the location of the emsian eifelian boundary within the section based on ms comparison to the gssp in conjunction with excellent biostratigraphic indicators primarily brachiopods while the conodont zonation in the el puerto creek section is poorly defined we believe that the correspondence between the ms and biostratigraphy in the section allows the identification of the emsian eifelian boundary these results indicate that this method can be successfully applied to marine sequences where ambiguities in correlation exist

the importance of slab pull and a global asthenosphere to plate motions 1 earth s subducting plates move 3 4 times faster than its overriding plates but it remains unclear whether these contrasting plate speeds are caused by additional pull from subducting slabs or by increased viscous drag on the lithosphere asthenosphere boundary beneath deeply protruding continental roots to investigate the relative importance of plausible controls we predicted global patterns of plate motions using numerical models that incorporate the influence of subducting slabs convective mantle flow and continental roots from the mantle convection models we computed a set of dynamically consistent plate velocities by balancing forces that drive and resist the motion of each plate when deep continental roots anchor to the sub asthenospheric upper mantle the calculated patterns of plate motions are close to the observations if only 20 of excess upper mantle slab weight contributes to the slab pull force however this small contribution causes plates to move too slowly on average unless mantle viscosity is a factor of 2 lower than expected from post glacial rebound in contrast we show that predicted and observed plate motions are more easily reconciled if even the deepest continental roots are underlain by a low viscosity layer and at least half of excess upper mantle slab weight contributes to the slab pull force this preferred scenario agrees with recent seismological evidence for a global asthenosphere and previously proposed mechanisms for partial decoupling of slabs from surface plates

orbital time scale and new c isotope record for cenomanian turonian boundary stratotype previous time scales for the cenomanian turonian boundary ctb interval containing oceanic anoxic event ii oae ii vary by a factor of three in this paper we present a new orbital time scale for the ctb stratotype established independently of radiometric biostratigraphic or geochemical data sets update revisions of ctb biostratigraphic zonation and provide a new detailed carbon isotopic record for the ctb study interval the orbital time scale allows an independent assessment of basal biozone ages relative to the new ctb date of 93 55 ma gts04 the d 13 corg data document the abrupt onset of oae ii significant variability in d 13 corg values and values enriched to almost 222 these new data underscore the difficulty in defining oae ii termination using the new isotope curve and time scale estimates of oae ii duration can be determined and exported to other sites based on integration of well established chemostratigraphic and biostratigraphic datums the new data will allow more accurate calculations of biogeochemical and paleobiologic rates across the ctb

a 164 ka record of environmental change in the american southwest from a carlsbad cavern speleothem abstract a horizontal core 2 8 m in length drilled from the georgia giant column in carlsbad cavern provides climate information for the last 164 ka forty six alpha spectrometric u series ages determined at intervals of 7 6 cm along the core indicate five periods of deposition and five hiatuses the longest from 136 to 110 ka variations in growth rate 0 to 70 mm ka in the abundance of aragonite chalcedony and fe bearing phases and in 13c indicate that glacial intervals of the last 164 ka ois 6 4 and 2 were much wetter than today as were the colder substages 5d and 5b of ois 5 by contrast during the two warmest periods of the past 164 ka namely ois 5e and 1 there was no deposition on either side of the speleothem suggesting conditions as dry or drier than today the record from carlsbad parallels data from many other sites in the southwestern usa and northern mexico and data from marine sediments and ice cores demonstrating the extent to which ice sheet fluctuations influenced conditions in southern new mexico detailed correlation of 13c values in the georgia giant which range from 6 6 to 0 9 relative to pdb with distant speleothem records and with data from ice cores further documents the linkage of southwestern climate with global scale extent of glaciation values of 18o in the georgia giant core range from 9 7 to 4 7 relative to pdb and average 6 6 18o depleted carbonate in the georgia giant during ois 6 at a time when the world s oceans were enriched in 18o suggests that precipitation during cold intervals was brought largely by pacific air masses in fall winter and spring as a result of the southward displacement of the polar jet stream by the growth of the laurentide ice sheet termination ii marking the end of the penultimate glaciation is well defined in the core s 18o data analytical uncertainties in the radiometric ages do not preclude a start of termination ii as late as 128 ka as suggested by specmap data however data from the georgia giant core are more compatible with an earlier start like that obtained from devils hole and vostok data raising the possibility that early warming was widespread in the u s southwest region by 145 ka

the magneto susceptibility event and cyclostratigraphy msec method used in geological correlation of devonian rocks from anti atlas morocco magneto susceptibility event and cyclostratigraphy msec is used here as a means of establishing sensitive chronostratigraphic markers and chronohorizons useful for high resolution correlation msec is a composite of the magnetic susceptibility ms record of marine strata and the coeval biostratigraphic record and similar to chronozones zones based on msec data have boundaries that are isochronous ms a measure of the concentration of magnetic grains in sediments proxies for the ratio of lithogenic to biogenic components controls on the detrital input of lithogenic material include eustasy and climate however induced and sea floor basin subsidence the development of an initial msec composite reference curve for the middle upper devonian of the anti atlas region of southern morocco is presented and discussed in the context of global sea level transgressive and regressive cycles msec trends composed of increasing ms magnitudes correlate well with episodes of regression whereas trends of decreasing ms magnitudes correlate with episodes of transgression