organic matter maturity in northern italy some determining agents abstract in previous agip studies concerning the origin of oil in northern italy thematurity evolution of the source rocks beneath a thrust plate and the anomalous depth trends of maturity parameters were exained this paper focuses on the possible effects of different thermal histories and of high pressure on the catagenesis of kerogen the effects of overthrusting on the degree of maturity of source rocks is investigating in two areas of the northern apennines near the cortemaggiore oil and gas field and ponte del olio no 1 well respectively the model by angevine and turcotte is used for reconstructionof the temperature evolution and that by tissot and espitalie to model the hydrocarbon generation in addition it was examined how different thermal histories affect the oil to gas ratio computed according to tissot espitalie the results for sediments beneath thrust plates which are subjected to rapid increases in temperature are compared to those typical of regularly subsiding basin in the po basin intervals of abnormally pressured sediments were drilled in the lombardy area the organic matter appears immature in early jurassic and late triassic sediments at depth even down to 6000 m as recognized by different maturity parameters possible causes for the low maturity levels of the organic matter are examined with particular emphasis on the effects of high pressures

seismic stratigraphy of mcmurdo sound antarctica implications for glacially influenced early cenozoic eustatic change abstract analyses by barrett et al 1989 of the stratigraphic sequences of the ciros 1 drill core provided evidence of late paleogene and early neogene glacial advances and retreats that appear to correlate with the global eustatic curve of haq et al 1987 during leg 2 of the polar duke 90 pd90 cruise in the ross sea approximately 650 km of highresolution seismic data were collected in mcmurdo sound with the main objective of facilitating regional correlation of stratigraphic events observed in the cores of the ciros 1 dvdp 15 and mssts 1 drilling programs and therefore providing an opportunity to test hypotheses on linkages between cenozoic eustatic and antarctic ice volume fluctuations twenty unconformity bound seismic stratigraphic sequences labeled from top a to t were identified in the mcmurdo sound pd90 data base however seismic data from the shallow shelf on which ciros 1 was drilled show erosional surfaces at many levels indicating a condensed section in this area it is difficult to distinguish individual lithological units identified by barrett et al 1989 in the seismic data but seismic units o p and q correspond to the upper oligocene interval where they recognized 3 glacioeustatic events these three sequences totaling around 300 m in thickness can be traced over a distance of almost 100 km however they lack the seismic characteristics of glacial facies identified by anderson and bartek 1992 and thus the significance of waxing and waning events suggested for upper oligocene strata in ciros 1 remains equivocal the younger sequences in the mcmurdo sound data base are largely miocene e n the oldest of these forming the upper 70 m in ciros 1 these sequences can be traced 300 km north into the center of the victoria land basin where they have seismic features characteristic of glacial facies this suggests that ice sheets of continental scale and hence large enough to affect eustasy waxed and waned across the ross sea continental shelf at least 10 times during the miocene the data presented here for the oligocene do not preclude similar ice sheet behavior but are insufficient to test the hypothesis properly

antarctic climate at the eocene oligocene boundary climate model sensitivity to high latitude vegetation type and comparisons with the palaeobotanical record abstract simulated climate for the antarctic continent using the genesis version 2 1 global climate model with 34 ma boundary conditions is shown to be highly sensitive to polar vegetation type six experiments were run using different levels of atmospheric co2 orbital configurations ice sheet geometries and vegetation types to assess model sensitivity to antarctica being covered with either a needle leaf evergreen forest or tundra simulations using 2 pre industrial levels of co2 combined mean annual temperature mat 19 c are about 7 c cooler than minimum estimates from the antarctic cenozoic plant record mat 12 to 15 c however simulations using 3 co2 mat 7 c are in good agreement with our empirical estimates of mean annual temperature with ice sheets and orbits set up to represent early oligocene interglacial conditions the tundra climate is significantly cooler than the evergreen forest climate with local austral summer averages up to 6 c cooler in non glaciated areas and continental averages 2 5 c cooler in the model this is mainly due to higher albedo and decreases in net radiation and sensible and latent heat flux especially during spring and summer feedbacks between coastal and continental cooling marginal sea surface temperatures and sea ice also appear to be significant a review of the late palaeocene to earliest miocene plant fossil record in the antarctic peninsula and ross sea regions shows that the vegetation was in transition 34 ma from a relatively diverse mainly evergreen forest to a tundra vegetation the modelled sensitivity of continental temperatures to a change from forest to tundra suggests vegetation climate feedbacks during the eocene oligocene transition played a significant role in the initial rapid glaciation of the continent

resolving a late oligocene conundrum deep sea warming and antarctic glaciation abstract changes in ice volume and resulting changes in sea level were determined for the late oligocene 26 23 ma astronomical timescale ats by applying 18 o to sea level calibrations to deep sea 18 o records from odp sites 689 690 929 1090 and 1218 our results show that maximum global ice volume occurred during two late oligocene 18 o events oi2c 24 4 ma and mi1 23 0 ma inferred glacioeustatic lowering with volumes up to 25 greater than the present day east antarctic ice sheet eais ice volume during glacial minima was on the order of about 50 of the present day eais this is supported by late oligocene stratigraphic records from antarctica that contain evidence of cold climates and repeated episodes of glaciation at sea level and grounding lines of glacial ice on the antarctic continental shelf in the ross sea and prydz bay in contrast composite deep sea 18 o records show a significant decrease 1 between 26 7 and 23 5 ma which have long been interpreted as bottom water warming combined with deglaciation of antarctica however a close examination of individual 18 o records indicates a clear divergence after 26 8 ma between records from southern ocean locations i e ocean drilling program sites 689 690 744 and those of other ocean basins high 18 o values 2 9 3 3 from these southern ocean 18 o records are consistent with an ice sheet on the east antarctic continent equivalent to present day values and cold bottom water temperatures 2 0 c these differences suggest a reduction in deep water produced near the antarctic continent i e proto antarctic bottom water proto aabw which were quickly entrained and mixed with warmer and presumably more saline bottom water originating from lower latitudes expansion of a warmer deep water mass and the weakening of the proto aabw may explain the large intra basinal isotopic gradients that developed among late oligocene benthic 18 o records these conclusions are also supported by ocean modeling suggesting a reduction of deep water formed in the southern ocean strengthening of deep water from the northern hemisphere and decreasing temperatures in high southern latitudes occurred as the drake passage opened to deep water low 18 o values reported from deep sea locations other than the southern ocean are shown to bias estimates of antarctic ice volume calling for a re evaluation of the notion that antarctic ice volume was significantly reduced during the late oligocene

stratigraphic architecture of the cenozoic succession in the mcmurdo sound region antarctica an archive of polar palaeoenvironmental change in a failed rift setting the victoria land basin forms part of the failed west antarctic rift and preserves a cenozoic succession up to 4 km thick that records the onset of cenozoic glaciation and the history of antarctic glaciation over the past 34 myr this succession is relevant both to investigations of modern climate change and to studies of long term palaeoclimate change in general this study provides a sedimentological and stratigraphic review of the victoria land basin succession based on analysis of several continuous drillcores acquired since the 1970s and supported by seismic stratigraphic analysis of a large array of seismic reflection data an array of fifteen lithofacies is recognized within the victoria land basin cenozoic succession including fossiliferous and diversely bioturbated mudrocks and diatomites texturally mature sandstones and conglomerates mixed mudstones and sandstones with dispersed gravel with restricted bioturbation and diamictites and associated lithologies these facies record a variety of marine glaciomarine proglacial and subglacial environments locally volcanic and volcaniclastic deposits are interbedded in the succession lithofacies are arranged in repetitive vertical stacking patterns depositional sequences that record glacial advance retreat cycles with attendant relative sea level changes seven varieties of depositional sequences stratigraphic motifs are recognized within the succession as a whole and interpreted to record a range of depositional settings from rifts unaffected by glacial ice motif 7 through varying degrees of glacial influence with abundant meltwater contributions motifs 6 to 3 to cold polar glaciated environments such as that of today motifs 2 and 1 overall there is a gradual trend upward through the succession from motif 7 at the base towards motif 1 at the top but the trend is not monotonic a significant conclusion of this work is that a record of dynamic climate and glacial conditions is preserved through the entire 34 myr period of the cenozoic icehouse at least in the victoria land basin intervals characterized by consistent stratigraphic style motifs are recognized throughout the victoria land basin succession these intervals are of 1 to 6 myr duration each containing numerous depositional sequences they are one to two orders of magnitude longer than glacial interglacial cycles and record periods during which environmental conditions varied in an internally consistent manner these intervals are considered to reflect convolutions of orbital parameters that remained stable for periods of 106 a and then switched to alternative configurations such intervals are directly analogous to 1 to 8 myr intervals characterized by glaciogenic strata that are preserved within the late palaeozoic of eastern australia among other areas and may be a recurring stratigraphic response to icehouse climate regimes through geological time

a detrital apatite fission track study of the ciros 2 sedimentary record tracing ice pathways in the ross sea area over the last 5 ma

tectonic and climatic signals from apatite detrital fission track analysis of the cape roberts project core records south victoria land antarctica abstract the cenozoic tectonic reorganization of the west antarctic rift system in the ross sea region occurred concurrently with a major change in the global climate system and a global reorganization of plate motions this region thus provides the opportunity to study in detail a range of geological issues dealing with tectonic and climate feedbacks during the late eocene early oligocene greenhouse icehouse transition at high latitudes with the aim to decipher tectonic vs climatic forcing in the ice sheet drainage evolution a detrital apatite fission track study was carried out throughout the cenozoic drill cored stratigraphic succession of the cape roberts project mcmurdo sound victoria land basin apatite fission track ages of detrital samples with depositional ages between 34 ma and 17 ma were decomposed into statistically significant age populations three age peaks were detected reflecting different bedrock provenance areas i a young peak p1 between 34 ma and 26 ma recording the signal of a source area exhumed with a constant denudation rate but absent in the proximal continental area and ii two peaks older than 40 ma that are instead compatible with thermochronological data available from the onshore bedrock p1 peak testifies a late oligocene early miocene denudation event and traces a southern provenance of a fraction of the sediments filling the cape roberts basin we propose that this denudation event might have been triggered by renewed n s transtensional shearing along the western shoulder of victoria land basin controlling glacial flow pattern and the associated sediment transport

reorganization of pacific deep waters linked to middle miocene antarctic cryosphere expansion a perspective from the south china sea article i nfo article history changes in intermediate and deep ocean circulation likely played a significant role in global carbon cycling and meridional heat moisture transport during the middle miocene climate transition 14 ma high resolution middle miocene 16 13 ma benthic foraminifer stable isotope records from the south china sea reveal a reorganization of regional bottom waters which preceded the globally recognized middle miocene 1 18 o increase 13 8 ma by 100 000 years an observed reversal of the benthic foraminifera 13 c gradient between odp sites 1146 2092 m and 1148 3294 m 13 9 13 5 ma is interpreted to reflect an

oligocene paleoceanographic changes based on an interbasinal comparison of cibicidoides spp δ18o records and a new compilation of data abstract oligocene paleoceanographic changes are useful for assessing future changes in the warming world because the levels of atmospheric pco2 in the oligocene were similar to those expected within the next century however the overall oligocene history is still unclear even though our understanding has been improved by previous studies in this paper we review the preexisting hypotheses for the eocene oligocene and oligocene miocene changes as well as the long term global changes based on newly compiled cibicidoides spp 18o 18ocib records we divide the oligocene paleoceanographic changes into five phases an abrupt increase in 18ocib values during the eocene oligocene transition eot phase 1 a gradual decrease in the early oligocene phase 2 a long term slow increase in the early to middle oligocene phase 3 a gradual decrease in the late oligocene phase 4 and an abrupt increase near the oligocene miocene transition omt phase 5 these recurring sequential changes in the global scale 18ocib profile following the eot are likely not directly connected to the strengthening and stratification of ocean currents during the oligocene as a result of the unidirectional strengthening of the antarctic circumpolar current acc and the northern component water ncw instead we suggest that the strengthened ocean currents contributed significantly to interbasinal differences in 18ocib values for a more robust explanation of oligocene long term 18ocib changes following the eot future studies will require high resolution and more reproducible records of changes in the volume of antarctic ice and atmospheric pco2 as well as information about the tectonic history

magnetobiostratigraphic chronology and palaeoenvironmental history of cenozoic sequences from odp sites 1165 and 1166 prydz bay antarctica a transect of three sites was drilled during leg 188 of the ocean drilling program odp proximal to the east antarctic ice sheet eais across the prydz bay continental shelf site 1166 slope site 1167 and rise site 1165 we present results of a palaeomagnetic and rock magnetic study of sediments recovered at sites 1165 and 1166 magnetostratigraphic interpretations are presented for both holes and are mainly constrained by diatom and radiolarian biostratigraphies interpreted in the light of recent refinements to southern ocean zonal schemes and datum calibrations for these microfossil groups site 1165 records a history of sedimentation on the continental rise extending back to earliest miocene times about 22 ma several long term changes characterise this record including an overall trend of decreasing sedimentation rates from the bottom to the top of the hole there is a progressive decrease in the sedimentation rate above about 308 mbsf meters below sea floor which is marked by a transition from dark grey fissile claystones to greenish grey diatom bearing clays at this transition ice rafted debris sand grains and total clay content also increase the chronology presented here indicates a middle miocene age 14 3 ma for the lithological transition correlation to odp hole 747a from the kerguelen plateau suggests that this lithological transition coincides with the base of the mi 3 3a 18o event which suggests palaeoclimatic control on middle miocene sedimentation changes at site 1165 core recovery was poor at site 1166 consequently the magnetostratigraphic data are of limited value the deepest cores recovered at site 1166 record brief intervals in the early history of the eais for the prydz bay region extending back through the early stage of glaciation to pre glacial times an early cretaceous fluvio lacustrine unit lagoonal deposits and sandy fluvio deltaic units of mid late eocene age contain a sporadic record of the transition from humid and mild conditions to cool temperate conditions

thrust faulting and hydrocarbon generation discussion following the discovery of large volumes of hydrocarbons in the cordilleran thrust belt of southwestern wyoming and northern utah angevine and turcotte 1983 edman and surdam 1984 and furlong and edman 1984 discussed the role of thrust faulting in hydrocarbon generation the authors concluded that overthrusting plays an important or even dominant role in the process of hydrocarbon generation in overthrust terrains these conclusions may be in error because they are based on a mathematical analysis of thermal and geologic models that have little resemblance to actual thrust belt geology in this discussion the authors discuss shortcomings of the thermal model used in the papers referred to above emphasize the differences between their model and the geologic facts as they exist in thrust belts in general and in western wyoming in particular and caution readers about applying the conclusions based on such a model in the search for hydrocarbons they contend that the temperature effects of thrust faulting were rather insignificant in the process of hydrocarbon generation in the wyoming thrust belt

late oligocene climatic changes evidence from calcareous nannofossils at kerguelen plateau site 748 southern ocean abstract palaeoecological changes in nannofossil assemblages in the southern ocean during oligocene times are examined through high resolution quantitative analyses of samples from ocean drilling program odp site 748 kerguelen plateau we quantitatively characterized the palaeoecological preference of groups of species and compared their general trends with those determined at maud rise odp sites 690 and 689 persico d villa g 2004 eocene oligocene calcareous nannofossils from maud rise and kerguelen plateau antarctica palaeoecological and palaeoceanographic implications marine micropaleontology 52 153 179 we then attempt a correlation between the main assemblage variation and sea surface temperature sst changes in the southern ocean at this time relatively stable cool conditions are interpreted to have persisted from earliest to late oligocene times when an increase in abundance of temperate water taxa is recorded both at maud rise and kerguelen plateau before the mi 1 event this reveals a climatic event that probably involved both sites and which is comparable to that indicated by the global oxygen isotope curve miller k g wright j d fairbanks r g 1991 unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion journal of geophysical research 96 6829 6848 zachos j pagani m sloan l thomas e billups k 2001 trends rhythms and aberrations in global climate 65 ma to present science 292 686 693 in the uppermost oligocene at site 689 the temperate water taxa index temperate temperate cool 100 increases from 25 2 ma similarly at site 748 the temperate water taxa index indicates an increase in sst in the late oligocene from about 26 5 ma at the base of chron c8n 2n which is offset by about 1 m y between the two areas the reason for this time difference can probably be found in the location of site 748 with respect to site 689 and in the palaeoceanographic setting taking into account that site 748 lies north of a deep water passage that separates kerguelen plateau from antarctica and north of the present day front of the antarctic circumpolar current the presence of warm water taxa exclusively at site 748 corroborates this hypothesis

evidence for a heavily glaciated antarctica during the late oligocene warming 27 8 24 5 ma stable isotope records from odp site 690 high 18o values 3 0 from a 9 kyr resolution benthic foraminiferal stable isotope record from the ocean drilling program odp site 690b located on the maud rise antarctica indicate a heavily glaciated antarctic continent during late oligocene 27 8 24 5 ma values ranging 2 5 3 0 during interglacial periods and 3 0 3 6 during glacial intervals are consistent with an ice sheet near or larger than modern size in addition this record does not exhibit the long term late oligocene warming trend seen in records from low latitude drill sites oxygen isotope values from 26 0 24 5 ma are comparable ranging between 2 5 and 3 3 to values that preceded the 18o event oi2b at 26 7 ma indicating no significant glacial collapse occurred during the late oligocene a gradient between ocean basins during the oligocene has already been linked to the development of a modern multi layered ocean and worked to bathe the low to mid latitude deep sea records with a warmer water mass we suggest this masked the significant antarctic glaciation in low latitude paleoceanographic records additionally we propose a resolution for conflicting lines of evidence from some antarctic proximal records suggesting significant glaciation and others suggesting reduced glaciation during the late oligocene by allowing a modern sized ice sheet to grow on an antarctic continent as more land surface area existed above sea level during this time this could allow at least some portions of the antarctic coastline to remain ice free during glacial minima while still maintaining modern or near modern ice volume

a quantitative analysis of calcareous nannofossils across a late oligocene paleolatitudinal transect of the north atlantic ocean abstract samples from six ocean drilling sites were analyzed quantitatively across a paleolatitude transect of the north atlantic ocean to determine the paleolatitudinal distribution of calcareous nannofossils in the late oligocene and the effects of that distribution on biostratigraphic resolution quantitative methodology utilized a detrended correspondence analysis dca nannofossil temperature index nti and shannon index h to examine the paleoenvironmental gradients which exerted the most control over the distribution of species and their abundances the dca produced two axes which explain 82 of the data matrix the dca1 explaining 57 of the variance significantly correlates with the nti suggesting that thermal controls were the most important factor in the paleoceanographic distribution of nannofossils the dca2 explained 25 of the variance and significantly correlates with the percent abundance of the taxon reticulofenestra minuta as well as the shannon index suggesting that surface water productivity was an important secondary control the characteristics of the nannofossil assemblage distributions indicate the existence of a well developed latitudinal diversity gradient in the late oligocene of the north atlantic based on the loss of biostratigraphic index taxa in higher paleolatitudes the primary limiter on biostratigraphic resolution for the late oligocene north atlantic is sea surface temperature particularly cold water regimes

organic matter type origin and thermal maturity of paleozoic mesozoic and cenozoic successions of the new siberian islands eastern russian arctic abstract geological investigations in the offshore area of eastern russian arctic attracted an increased interest in the recent years data concerning organic and coal petrology is scarce for the shelf and offshore area of the eastern russian arctic consequently thermal maturity and depositional environments of sedimentary facies remain less described and examined a detailed characterisation of organic matter type and origin as well as determination of thermal maturity have been carried out on siliciclastic and carbonate sedimentary samples from paleozoic mesozoic and cenozoic outcrops of the new siberian islands eastern russian arctic the acquired organic and coal petrological data contribute to the overall assessment of petroleum potential of the studied offshore area and the neighboring shelf area the investigated organic matter of silurian and middle devonian mudstones and siltstones contain distinct multi staged solid bitumen dead oil preserved either as fracture fissure and vein fillings indicating activation of migrations pathways for re occurring crude oil bearing fluids or in form of streaks the examined dispersed organic matter of triassic deposits is predominantly composed of terrestrially derived macerals followed by alginite macerals tasmanite and leiosphaeridia prasinophytes the analysed cretaceous and tertiary deposits reveal i aptian albian inertinite rich sub bituminous coal and lignites formed in fresh water lakes and swamps to brackish near shore depositional environments with phases of wildfires as well as ii cenomanian turonian lignites with pollen grains and carbonised debris pyrofusinite indicating stages of forest moor paleofires the iii paleocene and eocene deposits bear mineral rich and xylite rich lignites characterised by the lowest coal rank stage containing different fossil conifer species the thermal maturity of organic matter in silurian to tertiary deposits obtained from random vitrinite and bitumen reflectance measurements is an important parameter in determining the petroleum generation stage at the studied localities the calculated thermal maturities of silurian to middle devonian deposits acquired from random reflectance measurements of bitumen indicate condensate wet gas to early dry gas generation window the thermal maturities of sedimentary organic matter in samples collected from tertiary to triassic successions ranges from immature to main phase of oil generation the composition of the organic matter and thermal maturity of the analysed triassic siliciclastic deposits suggesting mature stage for oil generation can be used among others to evaluate their hydrocarbon potential the cretaceous and tertiary deposits can be described as thermally immature in two localities where the thermal maturity is anomalously high the examined organic matter has been thermally altered beyond the dry gas preservation limit

coal rank and petrography of upper carboniferous seams in the amasra coalfield turkey abstract the amasra coalfield is a part of the upper carboniferous zonguldak coal basin of turkey within the istanbul zone a hercynian deformed unit forming the eastern continuation of the moesian platform in se europe which was later deformed by alpine tectogenesis the mainly westphalian aged coals were sampled from an underground mine and from cores from nine exploration wells and petrographic maceral and microlithotype analysis and mean maximum vitrinite telocollinite reflectance r max in oil were determined the coals were characterised by low ash and low total sulphur contents abundant vitrinite group macerals and relatively abundant vitrite clarite and duroclarite microlithotypes vitrinite reflectance was in the range 0 58 1 04 r max indicating ranks from high volatile c bituminous to high volatile a bituminous coal the r max generally increases with increasing depth in the exploration wells with gradients ranging from 0 21 to 0 40 r max km and an average of 0 30 r max km the highest value occurs in the south of the coalfield in a region of hercynian folding and thrusting the relationship between vitrinite reflectance and thrusts in the wells suggests that coal rank was developed mainly pre thrusting but that some wells arguably show evidence for post thrust coalification peak coalification probably occurred during late mesozoic early tertiary rifting so that the thrusts which developed after coalification are likely to be alpine in age whereas the thrusts that pre date coalification may have been hercynian structures

graphic approach to determination of hydrocarbon maturation in overthrust terrains with the current exploration efforts in areas of overthrust tectonics it is important to evaluate efficiently and effectively the effects of thrust related thermal perturbations on hydrocarbon maturation a simple graphic technique which combines lopatin diagrams with theoretical models of temperatures in overthrust regimes allows one to develop relatively detailed models for the timing of hydrocarbon maturation in overthrust terrains these models provide the critical combination between rigorous consideration of thermal perturbations and simplification necessary for routine application the approach described here is applicable not only in cases of simple overthrusting at the surface but can also be modified to include the effects of multiple thrusting events she ts thrust in the subsurface and post thrusting erosion all of these models provide critical constraints on the timing of maturation and migration as well as information on the maturity of potential source rocks

organic maturity in the western canada sedimentary basin abstract organic maturity of strata in the western canada sedimentary basin has been investigated in numerous studies using petrological chemical and physical methods compilation of these data has facilitated a regional analysis of the maturity patterns and maturation history variation in maturity patterns can be divided into three levels basin wide 1st order regional 2nd order and local 3rd order first order variations are manifested by an overall increase in maturity of strata of the same age from east to west from the plains to the rocky mountain foothills and front ranges in response to progressively deeper burial and higher paleo geothermal gradients superimposed on this first order basinal scale variation in maturity are second and third order variations which reflect local differences in depth of burial conductive and advective heat transport or effects of thrust faulting maturity gradients in the axis of the basin are low averaging 0 10 log r omax km whereas in the front ranges and foothills the gradients are substantially greater average 0 25 log r omax km variations in maturity gradients reflect lower paleo geothermal gradients resulting from rapid sediment loading and subsequent unloading in the plains and higher conductive heat transport in the deformed belt the main component of maturity of most phanerozoic strata occurred during deep burial under upper cretaceous and or paleogene molasse in foredeeps developed in response to crustal loading during the easterly migration of the foreland fold and thrust belt as a result of the west to east propagation of deformation during the laramide orogeny deep burial maturation hydrocarbon generation and uplift occurred earlier in the foreland belt late cretaceous than in the plains to the east where the main component of maturity and hydrocarbon generation occurred as late as eocene in the plains because of the low maturity gradients a thick succession of strata currently is within the oil window in the deformed belt however higher maturity gradients have resulted in a thinner succession of strata within the oil window in response to higher paleo geothermal gradients strata in the deformed belt matured more quickly leading to more rapid hydrocarbon generation and migration than areas to the east in the southern part of the cordillera a significant component of maturation post dates structural deformation of the strata whereas in northeastern british columbia and adjacent parts of alberta maturity primarily pre dates structural deformation data from some deep bore holes and surface samples in the southern part of the cordillera provide evidence for maturity post dating or accompanying emplacement of major overthrust sheets tectonic burial in most areas however there is no clear evidence for the timing of maturity relative to faulting or evidence of frictional heating the maturity gradients and levels of maturity of surface and near surface strata in the western plains and rocky mountain foothills indicate that a succession several kilometres of paleogene strata were deposited in these regions foredeep and subsequently eroded in response to post laramide uplift

origin signature and palaeoclimatic influence of the antarctic circumpolar current the antarctic circumpolar current acc is today the strongest current in the world s ocean with a significant influence on global climate its assumed history and influence on palaeoclimate while almost certainly equally profound are here called into question in this paper we review 30 years of accumulated data interpretation and speculation about the acc deriving mainly from dsdp and odp drilling in the southern ocean for most of this time a conventional view of acc development signature and influence has held sway among palaeoceanographers and marine geologists in this view the acc began at about 34 ma close to the eocene oligocene boundary the time of onset of significant antarctic glaciation and the time of creation of a deep water gap tasmanian seaway between australia and antarctica as the south tasman rise separated from north victoria land this is the smoking gun of synchroneity the southern ocean sediment record shows a latest eocene development and subsequent geographic expansion of a siliceous biofacies its northern limit taken to indicate the palaeoposition of the acc axis in addition the acc was considered to have caused antarctic glaciation by isolating the continent within a cold water annulus reducing north south heat transport a different and later date for antarctic south american opening drake passage was proposed but the timing of acc onset there was disputed and the simple story survived recent developments however call it into question modern physical oceanography shows that all or most of present day acc transport is confined to narrow jets within deep reaching circumpolar fronts and numerical modelling has suggested that a steady reduction in greenhouse gas concentration through the cenozoic could cause antarctic glaciation with or without a contribution from ocean circulation change the rapidity of antarctic glacial onset at the eocene oligocene boundary and coeval creation of a deep water gap south of tasmania both survive but in light of the new information the presence of a siliceous biofacies cannot be claimed as evidence of the existence of a continuous deep reaching oceanic front and therefore of an acc and the possibility arises that cool and cold sea surface temperatures were effects of antarctic glaciation rather than evidence of a major contributor to its cause in considering future work we emphasise the importance of additional information from ancillary fields better definition of the necessary and sufficient properties of oceanic fronts additional determinations of cenozoic atmospheric pco2 and further developments in models of antarctic glaciation but also suggest the way forward in marine geology our knowledge of the development and palaeoclimatic significance of the acc will be best served by grainsize studies of bottom current strength at selected locations and geochemical or mineralogical studies of clays and ird as a way of examining provenance and therefore surface and bottom current directions and the existence of interocean connections

new magnetobiostratigraphic chronology and paleoceanographic changes across the oligocene miocene boundary at dsdp site 516 rio grande rise sw atlantic new magnetobiostratigraphic data for the late oligocene through early miocene at deep sea drilling project dsdp hole 516f provide a significantly revised age model which permits reevaluation of developments that led to the mi 1 glacial event at the oligocene miocene boundary our new high resolution paleomagnetic study which is supported by quantitative calcareous nannofossil and planktonic foraminiferal analyses significantly refines previous age models for oligocene miocene sediments from dsdp hole 516f with ages that are systematically younger than those previously determined in some parts of the oligocene the discrepancy with previous studies exceeds 450 kyr based on this new age model we infer a progressive increase in sedimentation rate and paleoproductivity between circa 23 9 ma and circa 22 9 ma with the highest rate coinciding with the mi 1 glacial event at the oligocene miocene boundary this productivity increase would have resulted in higher rates of carbon burial and in turn a drawdown of atmospheric co2 immediately afterward an abrupt decrease in sedimentation rate and paleoproductivity suggests that the mi 1 deglaciation was associated with decreased carbon input into the ocean elevated sedimentation rates are also documented at 24 5 ma coincident with the oi2d glacioeustatic event the presence of volcanic material within the sediments during these glacial events is interpreted to have resulted from redeposition of sediment scoured from nearby sites on the rio grande rise due to transient variations in bottom water flow patterns

late oligocene to early miocene geochronology and paleoceanography from the subantarctic south atlantic mi2 as well as several other distinctive isotope events our data suggest that the d 18 o maximum commonly associated with the oligocene miocene o m boundary falls within c6cn 2r 23 86 ma the d 13 c maximum coincides within the temporal resolution of our record with c6cn 2n r boundary and hence to the o m boundary comparison of the stable isotope record from site 1090 to the orbitally tuned stable isotope record from odp site 929 across the o m boundary shows that variability in the two records is very similar and can be correlated at and below the o m boundary site 1090 stable isotope records also provide the first deep southern ocean end member for reconstructions of circulation patterns and late oligocene to early miocene climate change comparison to previously published records suggests that basin to basin carbon isotope gradients were small or nonexistent and are inconclusive with respect to the direction of deep water flow oxygen isotope gradients between sites suggest that the deep southern ocean was cold in comparison to the north atlantic indian and the pacific oceans dominance of cold southern component deep water at site 1090 at least until 17 ma suggests that relatively cold circumpolar climatic conditions prevailed during the late oligocene and early miocene we believe that a relatively cold southern ocean reflects unrestricted circumpolar flow through the drake passage in agreement with bathymetric reconstructions index terms 4267 oceanography general paleoceanography 1035 geochemistry geochronology 4870 oceanography biological and chemical stable isotopes keywords paleoceanography 1035 geochronology stable isotopes

glaciation across the oligocene miocene boundary in southern mcmurdo sound antarctica new chronology from the ciros 1 drill hole few palaeogene and neogene sediment cores from the antarctic continental margin have been dated with sufficient precision to enable establishment of direct linkages between glacial events on the antarctic continent and marked events in deep sea delta 18o records as a result much of our knowledge of the gradual but stepwise shift from greenhouse climates of the cretaceous to the ice house climates of the quaternary is inferred from well dated and more continuously deposited deep sea sediments in this study we present new magnetostratigraphic results from the ciros 1 drill core from mcmurdo sound antarctica along with a reinterpretation of a published diatom biostratigraphic zonation that is constrained by correlation to a high precision age model from the nearby crp 2 2a drill core our results suggest that most of the upper 350 m of the ciros 1 drill core represents rapid sediment accumulation during a short time interval spanning the oligocene miocene boundary chronostratigraphic control is precise enough to enable correlation of this interval of glacimarine sedimentation with the mi 1 deep sea delta 18o event which confirms that the mi 1 event was related to a major expansion of antarctic ice a major unconformity at 366 m in the ciros 1 drill core which is widely observed in regional seismic reflection studies represents 9 myr of missing time this unconformity can be traced offshore into the ross sea using seismic stratigraphy and is interpreted to indicate significant east antarctic ice sheet development during the mi 1 glaciation the stratigraphic expression of this 400 kyr glacial event is evidently multiphase and complex in the victoria land basin probably because it was punctuated by higher frequency orbitally induced glacial oscillations the presence of nothofagidites pollen throughout the ciros 1 drill core and the presence of a nothofagus southern beech leaf within the early miocene portion of the core indicate that antarctic mean summer temperatures did not decrease below 5 deg c throughout the mi 1 glaciation these temperatures are significantly warmer than present day mean summer temperatures at sea level in mcmurdo sound the persistence of a nothofagus forest in coastal southern victoria land throughout this time interval suggests that the present state of deep refrigeration was not reached until some time after the mi 1 glaciation

heating during thrust faulting in the rocky mountains friction or fiction abstract measurement of the levels of organic maturation below and within shear zones of thrust faults in the rocky mountains has revealed no general thermal metamorphism that can be attributed to faulting with the exception of very localized areas with few exceptions the vitrinite reflectance values obtained are in the range expected if the maximum level of organic maturation was produced as a result of increasing temperature during progressive burial accompanying sedimentation only at marias pass evidence has been found to suggest additional maturation as a result of post orogenic burial below the thrust sheets anomalously high vitrinite reflectances obtained from the lewis thrust mcconnell thrust coleman thrust and two unnamed thrusts are restricted to very narrow films immediatly adjacent to or within the shear zone which considering any reasonable thermal conductivity indicates elevated temperatures were very short lived the anomalously high vitrinite reflectances within these films when compared to laboratory heated coals suggest temperatures in the order of 350 650 c were locally generated during faulting such high temperatures are considered to have been generated during stick slip faulting at macro asperities or at ramps on the fault plane where local and possibly transient high frictional stresses existed the absence of evidence for extensive frictional heating supports previous arguments that stable sliding and or low frictional stress must exist during thrusting

geothermal gradients in the hinton area of west central alberta temperature data from petroleum exploration well logs of 3360 wells in a region of west central alberta are used to estimate thermal gradients a relatively high geothermal gradient 36 c km of oblong shape located near hinton is observed the axis of the anomaly strikes approximately southwest northeast and passes through the miette hot springs area it appears that water is heated at depth in the rocky mountain disturbed region and travels eastward and toward the surface along fault planes

regional coalification pattern of lower cretaceous coal bearing strata rocky mountain foothills and foreland canada implications for future exploration abstract the regional coalification pattern of lower cretaceous strata in parts of the canadian foothills belt and adjacent foreland has been determined by vitrinite reflectance measurements the present study focusses on two coal bearing sequences bluesky gething and gates formation both of which contain coal resources of economic interest the vitrinite reflectances r max in the bluesky gething formation range from 0 76 high volatile a bituminous to 2 55 semianthracite rank changes from top to the base of bluesky gething formation follow 1st order regression lines factors influencing the rate of increase of r max per depth interval coalification gradient include paleogeothermal gradients the rank level under investigation conductivities of host rocks and thicknesses of coal seams time depth burial curves for the lower cretaceous bluesky gething formation suggest that the regional coalification pattern for the top of the formation results largerly from variations in the depth and or duration of burial beneath maastrichtian tertiary foredeep deposits coalification largerly predates deformation the coalification pattern is more complicated for the base of the bluesky gething formation because thickness changes in the lower cretaceous bluesky gething interval locally have a greater effect on the rank than does the regional change in the thickness of maastrichtian tertiary sedimentary wedge detailed rank studies on laterally continuous coal seams of the gates formation showed that coalification levels were largerly established before folding and thrusting started isoreflectance lines of the beds run parallel to the bedding of the folded strata seams collected from various thrust sheets exposed at surface do not in general show significant changes in vitrinite reflectances from one thrust sheet to another many of the coals of the gates formation were found to have biaxial negative reflectance in dicatrices orientation of r max is in all cases parallel of subparallel to the mactroscopic fold axes indicating preferential orientation of the aromatic lamellae in the coals in the direction of minimum compressive stress it is suggested that the occurrence of biaxial negative coals is related to a tectonic stress field that existed during the later stages of burial and subsequent deformation

paleotemperatures and ice volume of the past 27 myr revisited with paired mg ca and 18o 16o measurements on benthic foraminifera 1 we explore the applicability of paired mg ca and 18o 16o measurements on benthic foraminifera from southern ocean site 747 to paleoceanographic reconstructions on pre pleistocene timescales we focus on the late oligocene through pleistocene 27 0 ma history of paleotemperatures and the evolution of the 18o values of seawater 18osw at a temporal resolution of 100 200 kyr absolute paleotemperature estimates depend on assumptions of how mg ca ratios of seawater have changed over the past 27 myr but relative changes that occur on geologically brief timescales are robust results indicate that at the oligocene to miocene boundary 23 8 ma temperatures lag the increase in global ice volume deduced from benthic foraminiferal 18o values but the smaller scale miocene glaciations are accompanied by ocean cooling of 1 c during the mid miocene phase of antarctic ice sheet growth 15 13 ma water temperatures cool by 3 c unlike the benthic foraminiferal 18o values which remain relatively constant thereafter temperatures vary by 3 c and reach maxima at 12 and 8 5 ma the onset of significant northern hemisphere glaciation during the late pliocene is synchronous with an 4 c cooling at site 747 a comparison of our 18osw curve to the haq et al 1987 sea level curve yields excellent agreement between sequence boundaries and times of increasing seawater 18o 16o ratios at 12 11 ma in particular when benthic foraminiferal 18o values do not support a further increase in ice volume the 18osw curve comes to a maximum that corresponds to a major mid miocene sea level regression the agreement between the character of our mg ca based 18osw curve and sequence stratigraphy demonstrates that benthic foramaniferal mg ca ratios can be used to trace the 18osw on pre pleistocene timescales despite a number of uncertainties related to poorly constrained temperature calibrations and paleoseawater mg ca ratios the mg ca record also highlights that deep ocean temperatures can vary independently and unexpectedly from ice volume changes which can lead to misinterpretations of the 18o record

environmental magnetic record of antarctic palaeoclimate from eocene oligocene glaciomarine sediments victoria land basin summary the onset of continent wide glaciation in antarctica is still poorly understood despite being one of the most important palaeoclimatic events in the cenozoic the eocene oligocene boundary interval has recently been recognized as a critical time for antarctic climatic evolution and it may mark the preglacial glacial transition magnetic susceptibility intensity of natural and artificial remanences hysteresis parameters and magnetic anisotropy of the lower half late eocene early oligocene of the ciros 1 core from mcmurdo sound antarctica reveal alternating intervals of high and low magnetic mineral concentrations that do not correspond to lithostratigraphic units in the core pseudo single domain magnetite is the main magnetic mineral throughout the sequence and sharp changes in magnetite concentration match changes in clay mineralogy beneath and at the eocene oligocene boundary the detrital magnetite originated from weathering of the ferrar group which comprises basic extrusive and intrusive igneous rocks weathering processes and input of magnetite to the victoria land basin were intense during periods when the antarctic climate was warmer than today but during intervals when the climate was relatively cool chemical weathering of the ferrar group was suppressed and input of detrital magnetite to the victoria land basin decreased our results also indicate that a cold and dry climate was not established in antarctica until the eocene oligocene boundary with major ice sheet growth occurring at the early late oligocene boundary some earlier cold intervals are identified which indicate that climate had begun to deteriorate by the middle late eocene boundary

searching for single domain magnetite in the pseudo single domain sedimentary haystack implications of biogenic magnetite preservation for sediment magnetism and relative paleointensity determinations 1 magnetic hysteresis measurements of sediments have resulted in widespread reporting of pseudo single domain like magnetic properties in contrast the ideal single domain sd properties that would be expected to be responsible for high quality paleomagnetic records are rare determining whether sd particles are rare or common in sediments requires application of techniques that enable discrimination among different magnetic components in a sediment we apply a range of such techniques and find that sd particles are much more common than has been reported in the literature and that magnetite magnetofossils the inorganic remains of magnetotactic bacteria are widely preserved at depth in a range of sediment types including biogenic pelagic carbonates lacustrine and marine clays and possibly even in glaci marine sediments thus instead of being rarely preserved in the geological record we find that magnetofossils are widespread this observation has important implications for our understanding of how sediments become magnetized and highlights the need to develop a more robust basis for understanding how biogenic magnetite contributes to the magnetization of sediments magnetofossils also have grain sizes that are substantially smaller than the 1 15 m size range for which there is reasonable empirical support for relative paleointensity studies the different magnetic response of coexisting fine biogenic and coarser lithogenic particles is likely to complicate relative paleointensity studies this issue needs much closer attention despite the fact that sediments have been subjected to paleomagnetic investigation for over 60 years much remains to be understood about how they become magnetized

magnetobiostratigraphic chronology of the eocene oligocene transition in the ciros 1 core victoria land margin antarctica implications for antarctic glacial history in 1986 cores were obtained to a depth of 702 m with 98 recovery from the ciros 1 drill hole beneath the ross sea on the victoria land margin glaciogene sediments identified near the base of the hole mark the earliest known record of antarctic glaciation initial biostratigraphic analysis indicated that the lower 336 m of the core is early oligocene in age and that the upper 366 m is of late oligocene early miocene age recently the chronology of the ciros 1 core has been questioned we developed a magnetostratigraphy for the lower 400 m of the ciros 1 core to clarify the chronology our magnetobiostratigraphic results indicate that the base of the ciros 1 core is early late eocene in age corresponding to chron c16r ca 36 5 ma we identify the eocene oligocene boundary at about 410 420 m within a 20 m thick poorly stratified bioturbated sandy mudstone this makes the ciros 1 core the highest latitude site 77 1 s from which this datum event has been recognized at 366 m a 4 m y hiatus which lies immediately beneath fluvial sediments accounts for most of chrons c11 and c12 we recognize three major climatic episodes in the ciros 1 core 1 the late eocene 34 5 36 5 ma 430 702 m when relatively warm conditions dominated and there were high sedimentation rates and some glacial activity 2 the late eocene early oligocene boundary interval 28 5 34 5 ma 340 430 m which was a transition from relatively warm to cooler conditions that coincided with glacial intensification sea level fall and subaerial erosion of the shelf and 3 the late oligocene early miocene 22 28 5 ma 50 340 m when large scale glaciation dominated the region and glaciers grounded across the continental shelf from correlation with global oxygen isotope and sea level records we infer that the antarctic climate and surrounding oceans cooled after separation of australia and antarctica and development of deep water circulation between them this marked the onset of the eocene oligocene transition at ca 34 5 ma a major east antarctic ice sheet did not develop until the early late oligocene boundary toward the end of the eocene oligocene transition ca 28 5 ma outlet glaciers did not breach the transantarctic mountains and ground across the ross sea shelf until 0 5 m y later ca 28 ma

mechanisms of coal metamorphism case studies from paleozoic coalfields controls on coal metamorphism can be complex in this paper we examine four paleozoic coalfields the western kentucky portion of the illinois basin the pennsylvania anthracite fields the south wales coalfield and the bowen basin an increase in temperature with depth of burial is certainly a factor in coal metamorphism in many coalfields however including the coalfields reviewed here it has become apparent that such a simple mechanism does not explain the coal rank patterns observed the flow of hydrothermal fluids through the coals has been proposed as a cause of coal metamorphism evidence includes inverted rank gradients elevated cfl as an indicator of brine fluids isotopic evidence for hydrothermal fluids and vein and cleat mineral assemblages in any case multiple hypotheses must often be evaluated in the examination of any coalfield since the simple paradigm of coal rank increases with a simple increase in temperature with increasing depth does not fit the evidence observed in many cases

implications of late eocene to early miocene clay mineral assemblages in mcmurdo sound ross sea antarctica on paleoclimate and ice dynamics abstract the clay mineral assemblages of upper eocene to lower miocene sediments recovered at the ciros 1 and mssts 1 drill sites on the mcmurdo sound shelf antarctica were analyzed in order to reconstruct the cenozoic antarctic paleoclimate and ice dynamics the assemblages are dominated by smectite and illite with minor amounts of chlorite and kaolinite the highest smectite amounts and best smectite crystallinities occur in the upper eocene part of ciros 1 below 425 445 mbsf they indicate that during their deposition chemical weathering conditions prevailed on the nearby continent large parts of east antarctica were probably ice free at that time but some glaciers reached the sea and contributed to the glaciomarine sedimentation in contrast only minor total amounts of smectite are present in oligocene and younger sediments due to the shift to mainly physical weathering on an ice covered antarctic continent however relative smectite percentages rise to more than 60 during two late oligocene intervals ca 27 5 26 2 and 25 0 24 5 ma and during one early miocene interval starting at ca 23 3 ma these intervals are characterized by ice masses coming probably from the south where volcanic rocks acted as a source as also indicated by the composition of the sand and gravel fractions during the other intervals the ice came from the west where the physical erosion of basement rocks and sedimentary rocks of the beacon supergroup in the transantarctic mountains provided high illite concentrations because the two drill sites are only 4 km apart their clay mineral records can be correlated this led to a new interpretation of the oligocene paleomagnetic data of the mssts 1 site and to a more detailed lithostratigraphic correlation of the miocene parts of the cores

evidence for late oligocene establishment of the antarctic circumpolar current removal of the last impediment to circum antarctic flow opening of the drake passage between antarctica and south america is essential to establishment of the acc and has been placed in both the earliest oligocene and earliest miocene on the basis of paleomagnetic reconstructions the tasman gateway between antarctica and tasmania notably deepened following 33 5 ma completion of the acc circuit has been seen as the key to major growth of the east antarctic ice sheet by thermal isolation of the continent an alternative argument attributes ice sheet growth to changes in atmospheric pco2 we present evidence on current strength and water mass properties suggesting a clear increase in flow speed and homogeneity of southern ocean water masses in the latest oligocene after about 23 95 ma marking establishment of the acc attributable to deep opening of drake passage the mi 1 glaciation may be a consequence establishment of a permanent low altitude ice sheet does not appear to take place prior to mid miocene cooling

coal deposits in the front ranges and foothills of the canadian rocky mountains southern canadian cordillera abstract canada has the fifth largest inventory of coal resources in the world more than one third of canada s resources currently favourable for exploitation occur in the southern canadian rocky mountains with major deposits in the front ranges inner foothills and outer foothills physiographic provinces in the front ranges major deposits of metallurgical and thermal high volatile bituminous to semi anthracite coal occur in the late jurassic early cretaceous mist mountain formation in the inner foothills of northeastern british columbia and west central alberta significant resources of metallurgical and thermal medium and low volatile bituminous coal occur in early cretaceous strata of the gething aptian and gates albian formations in the outer foothills resources of thermal high volatile bituminous coal occur in late cretaceous and paleocene strata of the belly river campanian coalspur maastrichtian paleocene and paskapoo paleocene formations the major coal deposits of the front ranges and inner foothills accumulated within the coastal plains of the fernie and moosebar clearwater seas respectively shorelines prograded to the north and northeast into a foreland basin that evolved in advance of and in response to the evolving columbian orogen in the outer foothills coal deposits of the belly river formation originated within prograding coastal plains during the withdrawal of the pakowki sea the major coal deposits of the coalspur and paskapoo formations accumulated in the alluvial plain environments of the foreland basin during the laramide orogeny coal measures of the southern canadian rocky mountains were variably folded and faulted during the laramide orogeny late cretaceous eocene structural deformation has significantly affected the mineability and quality of the coals many of the coal seams are sheared structurally thickened or thinned and repeated by thrust faults or truncated by normal faults shearing of the seams in adjacent hanging and footwall strata has led locally to pronounced oxidation resulting in weak coal pillars and roofs in underground mines faulting and folding has partitioned many coal deposits into discrete structural domains of varying style and complexity each of which can present a unique challenge in designing optimum coal extraction methods the variation in coal rank in the southern canadian rocky mountains mainly reflects the preorogenic pre laramide depth of burial in some areas however there is evidence for syn and post orogenic coalification resulting from the emplacement of thick overthrust sheets and or deposition of thick tertiary molasse most of which has been subsequently eroded with few exceptions coals of the southern canadian rocky mountains are characterized by low sulphur contents

timing of organic maturation coalification relative to thrust faulting in the southeastern canadian cordillera abstract in order to access the effects if any of overthrusting tectonic burial on levels of organic maturation coalification detailed vitrinite reflectance profiles were constructed for 11 deep boreholes that penetrated stacked thrust sheets of mesozoic and paleozoic strata in the southeastern canadian cordillera recognition of the timing and degree of maturation resulting from emplacement of thrust sheets is largely dependent on the accuracy with which the preorogenic level of maturation of the strata is known the vitrinite reflectance profiles of several boreholes suggest that a significant component of organic maturation coalification postdates emplacement of overthrust sheets and have resulted from tectonic burial for other boreholes however the maturation profiles are ambiguous and suggest that postorogenic maturation if any was insufficient to overprint preorogenic levels of maturity maturity levels and reflectance gradients of mesozoic strata in general are lower in the southern part of the southeastern cordillera than in the northern part which imply higher paleoheat flow in the north

geothermal gradients hydrodynamics and hydrocarbon occurrences alberta canada using coal rank data and the demonstrated genetic link between the present hydrodynamic regime and geothermal gradient pattern it is possible to reconstruct the geothermal history of alberta over the past 60 m y palinspastic adjustment for tectonic compression caused by the major laramide thrusting shows that the predeformation isoreflectance lines increased logarithmically with depth in the late paleocene the geothermal gradient was about 23 c km 1 25 f 100 ft in the eastern alberta plains compared to about 30 c km 1 65 f 100 ft in the western alberta plains a regional trend opposite to the post laramide trends reconstruction of the early eocene surface indicates western uplands with geothermal gradients as low as 21 c km 1 15 f 00 ft and eastern lowlands with geothermal gradients of 27 c km 1 5 f 100 ft compared to the present situation this represents an enhanced topographic surface and a subdued geothermal gradient pattern the genetic relations of topography water table elevation hydrodynamic regime and geothermal gradient pattern in both the early eocene and the present conform to a model developed for any compacted sedimentary basin with subaerial relief in this model on a regional scale high topographic areas have high water table elevations with correspondingly high potentiometric surfaces these areas control the regional recharge of cold meteoric water and hence have low geothermal gradients areas of medium elevation exhibit regional lateral flow and intermediate geothermal gradients regional topographic lows correspond with low potentiometric surfaces and the regional discharge of warm formation waters from deep in the basin results in high geothermal gradients local topographic featur s cause perturbations in this picture study of both the regional pattern and fine detail of the early eocene and present topographic surfaces and geothermal gradient patterns shows the validity of the model the result of the second laramide orogenic pulse was therefore to reverse the geothermal gradient pattern resulting mainly from compaction flow and to impose a topographically controlled hydrodynamic regime with flow in the same direction but with a 9 c km 0 5 f 100 ft decreased geothermal gradient in western alberta and a 4 c km 0 2 f 100 ft increased geothermal gradient in eastern alberta as erosion proceeded during the tertiary the entire alberta basin warmed up until the present temperature regime was attained study of some major hydrocarbon occurrences shows a genetic link between the hydrocarbon occurrence and the present fluid regime which itself is controlled by the present topography for at least the significant upper cretaceous shallow gas reserves in southeastern alberta however their position may already have been determined as early as the beginning of the eocene by the topographic surface at that time therefore the extent to which the present topographic surface is responsible for hydrocarbon accumulation through gravity induced cross formational flow remains unknown because this process was operative as long ago as the early eocene what does not ap ear to be in doubt is the fact that gravity induced cross formational flow does control the hydrodynamic regime which in turn influences the geothermal gradient pattern and the accumulation of hydrocarbons

the mendel formation evidence for late miocene climatic cyclicity at the northern tip of the antarctic peninsula abstract a detailed description of the newly defined mendel formation is presented this late miocene 5 9 5 4 ma sedimentary sequence with an overall thickness of more than 80 m comprises cyclic deposition in terrestrial glacigenic glaciomarine and marine environments subglacial till was deposited by a thick grounded antarctic peninsula ice stream advancing eastwards through the prince gustav channel crossing the northernmost part of present day james ross island with most of the material carried actively at the base of the warm based glacier the form of the prince gustav channel originated before the late miocene and its present glacial over deepening resulted in multiple grounded glacier advances during the neogene and quaternary the sea prograded from the east and the glacier margin became buoyant building a small ice shelf below and in front of which glaciomarine and marine sediments were deposited these sedimentary deposits are composed of material that was transported mostly by small glaciers and subsequently by the floating ice shelf and by calving icebergs towards the open sea these environmental and glaciological conditions differ strongly from the present cold based local glaciers of james ross island and the antarctic peninsula these changes were triggered by the global sea level fluctuation connected with climatic changes due to antarctic ice sheet build up and decay this reveals late miocene obliquity driven cyclicity with a 41 ka period the mendel formation sedimentary sequence is comprised of at least two glacial periods and one interglacial period sea level rise at the northern tip of the antarctic peninsula between glacial lowstand and interglacial highstand was more than 50 m during the late miocene and was followed by a subsequent sea level fall of at least the same magnitude the presence of well preserved articulated pectinid bivalves support interglacial open sea conditions the re deposition of palaeontological material was shown to be important for the mendel formation reworked pectinid shells revealed an open marine interglacial condition in this part of the antarctic peninsula during the early to mid miocene 20 5 17 5 ma unfortunately relevant sedimentary deposits have not been found on land

eocene oligocene calcareous nannofossils from maud rise and kerguelen plateau antarctica paleoecological and paleoceanographic implications abstract the evolution of the southern ocean climate during the late eocene late oligocene interval is examined through high resolution quantitative calcareous nannofossil analyses on samples from the southern ocean sections on maud rise and kerguelen plateau we determined the abundance patterns of the counted species to clarify the biostratigraphy which we correlated with high resolution magnetostratigraphy roberts a p bicknell s j byatt j bohaty s m florindo f harwood d m 2003a magnetostratigraphic calibration of southern ocean diatom datums from the eocene oligocene of kerguelen plateau ocean drilling program sites 744 and 748 in florindo f cooper a k o brien p a eds antarctic cenozoic palaeoenvironments geologic record and models palaeogeogr palaeoclimatol palaeoecol 198 145 168 florindo f roberts a p in press eocene oligocene magnetobiochronology of odp sites 689 and 690 maud rise weddell sea antarctica geol soc am bull and used this data to interpret paleoceanographic changes through the late eocene to late oligocene percentage plots of the individual species compared with r mode principal component and cluster analysis results allowed us to divide the assemblages into three groups temperate water taxa cool water taxa and no temperature affinity taxa we attempt correlations between these paleoecological groups and the major sea surface temperature sst variations with tectonic and paleoceanographic changes in the southern ocean during the late eocene the nannofossil assemblage data reveal that there were several minor sst decreases coolings from 36 to 34 ma before the eocene oligocene e o boundary a sharp cooling event dated at 33 54 ma earliest oligocene occurred about 160 kyr after the e o boundary which is dated at 33 7 ma relatively stable cool conditions are interpreted to persist until the latest oligocene when an increase in abundance of temperate water taxa which corresponds to an antithetical decrease in abundance of cool water indicators is recorded on the basis of our dating the opening of the drake passage allowing shallow water circulation began by 33 54 ma at the latest while the establishment of deep water connections through the tasmanian gateway occurred at 33 ma as suggested by exon et al proc odp init rep 189 2001 1

the association between tectonic deformation inorganic composition and coal rank in the bituminous coals from the south wales coalfield united kingdom analysis of vertical distribution of coal rank in three collieries and one opencast mine in the se of the south wales coalfield has revealed deviations from hilt s law in both proximate analyses and in vitrinite reflectance the variations in rank parameters studied are closely correlated with variations in the intensity of tectonic deformation measured using a numerical deformation index ndi three seams in the sequence were also analysed for major and trace element geochemistry and rock eval pyrolysis variations in these parameters are related to thrust inclusion of floor and or roof mudrocks into the seams a detailed conceptual model of a major thrust and associated in seam thrust detachments and lag faults is developed to explain the vertical rank profile by post coalification faulting it is concluded that although the model can explain the vertical pattern of rank the complexity of the required faults render the model improbable the alternative mechanisms for enhancement of the rank parameters associated with tectonic deformation including shear stress control frictional heating and localised fluid flow are discussed and are thought more likely to be responsible for the deviations from hilt s law in the vertical rank profile rank suppression shown by three seams two of which are overlain by marine bands is thought to be related to biochemical activity in the peat environment resulting from the influx of saline waters

climate response to orbital forcing across the oligocene miocene boundary spectral analyses of an uninterrupted 5 5 million year my long chronology of late oligocene early miocene climate and ocean carbon chemistry from two deep sea cores recovered in the western equatorial atlantic reveal variance concentrated at all milankovitch frequencies exceptional spectral power in climate is recorded at the 406 thousand year ky period eccentricity band over a 3 4 million year period 20 to 23 4 my ago ma as well as in the 125 and 95 ky bands over a 1 3 million year period 21 7 to 23 0 ma of suspected low greenhouse gas levels moreover a major transient glaciation at the epoch boundary approximately 23 ma mi 1 corresponds with a rare orbital congruence involving obliquity and eccentricity the anomaly which consists of low amplitude variance in obliquity a node and a minimum in eccentricity results in an extended period approximately 200 ky of low seasonality orbits favorable to ice sheet expansion on antarctica

environmental magnetic record of paleoclimate unroofing of the transantarctic mountains and volcanism in late eocene to early miocene glaci marine sediments from the victoria land basin ross sea antarctica 1 we synthesize environmental magnetic results for sediments from the victoria land basin vlb which span a total stratigraphic thickness of 2 6 km and a 17 myr age range we assess how magnetic properties record paleoclimatic tectonic and provenance variations or mixtures of signals resulting from these processes the magnetic properties are dominated by large scale magnetite concentration variations in the late eocene and early oligocene magnetite concentration variations coincide with detrital smectite concentration and crystallinity variations which reflect paleoclimatic control on magnetic properties through influence on weathering regime high magnetite and smectite concentrations indicate warmer and wetter climates and vice versa during the early oligocene accelerated uplift of the transantarctic mountains gave rise to magnetic signatures that reflect progressive erosion of the precambrian mesozoic metamorphic intrusive and sedimentary stratigraphic cover succession associated with unroofing of the adjacent transantarctic mountains from the early oligocene to the early miocene a consistent fining upward of magnetite particles through the recovered composite record likely reflects increased physical weathering with glacial grinding contributing to progressively finer grained ferrar dolerite sourced magnetite after 24 ma the magnetic properties of vlb sediments are primarily controlled by the weathering and erosion of mcmurdo volcanic group rocks increased volcanic glass contents contribute to the fining upward of magnetite grain size overall long term magnetic property variations record the first order geological processes that controlled sedimentation in the vlb including paleoclimatic tectonic provenance and volcanic influences

preseismic and coseismic deformation associated with the coyote lake california earthquake supplement is available with entire article on microfiche orderfrom american geophysical union 2000 florida avenue n w washington d c 20006 document j79 008 01 00 payment mustaccompany order the coyote lake earthquake ml 5 9 august 6 1979 epicenter about 100 km southeast of san francisco occurred on the calaveras fault within a geodetic network that had been surveyed annually since 1972 to monitor strain accumulation the rupture surface as defined by aftershocks is a vertical rectangle 20 km in length extending from a depth of 4 km to about 12 km the observed deformation of the geodetic network constrains the average slip to be about 0 33 0 05 m right lateral although the geodetic data furnished an exceptionally detailed picture of the preearthquake deformation no significant premonitory anomaly associated with the coyote lake earthquake can be identified

resolving apparent conflicts between oceanographic and antarctic climate records and evidence for a decrease in pco2 during the oligocene through early miocene 34 16 ma abstract an apparent mismatch between published oxygen isotopic data and other paleoclimate proxies for the span from 26 16 ma is resolved by calibration against global sea level estimates obtained from backstripping continental margin stratigraphy ice volume estimates from calibrated oxygen isotope data compare favorably with stratigraphic and palynological data from antarctica and with estimates of atmospheric pco2 throughout the oligocene to early miocene 34 16 ma isotopic evidence for an east antarctic ice sheet eais as much as 30 larger than its present day volume at glacial maxima during that span is consistent with seismic reflection and stratigraphic evidence for an ice sheet covering much of the antarctic continental shelf at the same glacial maxima palynological data suggest long term cooling during the oligocene with cold near tundra environments developing along the coast at glacial minima no later than the late oligocene a possible mechanism for this long term cooling is a decrease in atmospheric pco2 from the middle eocene to oligocene reaching near pre industrial levels by the latest oligocene and remaining at those depressed levels throughout the miocene

unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on antarctica since the earliest oligocene circa 35 ma the growth and decay of ice sheets during the oligocene to modern ice house world caused glacioeustatic sea level changes the early eocene was an ice free greenhouse world but it is not clear if ice sheets existed during the middle to late eocene doubt house world benthic foraminiferal 18o records place limits on the history of glaciation suggesting the presence of ice sheets at least intermittently since the earliest oligocene the best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic 18o records although planktonic isotope records from the western equatorial regions are limited subtropical planktonic foraminifera may also record such ice volume changes it is difficult to apply these established principles to the cenozoic 18o record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events we improved oligocene to miocene correlations of 18o records and erected eight oxygen isotope zones oi1 oi2 mi1 mi6 benthic foraminiferal 18o increases which are associated with the bases of zones oil circa 35 8 ma oi2 circa 32 5 ma and mil circa 23 5 ma can be linked with 18o increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near antarctica our new correlations of middle miocene benthic and western equatorial planktonic 18o records show remarkable agreement in timing and amplitude we interpret benthic planktonic covariance to reflect substantial ice volume increases near the bases of zones mi2 circa 16 1 ma mi3 circa 13 6 ma and possibly mi5 circa 11 3 ma possible glacioeustatic lowerings are associated with the 18o increases which culminated with the bases of zone mi4 circa 12 6 ma and mi6 circa 9 6 ma although low latitude planktonic 18o records are required to test this these inferred glacioeustatic lowerings can be linked to seismic and rock disconformities for example we link 12 oligocene early late miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries inferred eustatic lowerings of haq et al 1987

geomechanical properties and permeability of coals from the foothills and mountain regions of western canada abstract static and dynamic geomechanical properties and hydraulic permeability were determined for six large blocks of bituminous coal sampled from active mines in the foothills and mountain regions of western canada testing showed a nonlinear shear strength envelope and brittle failure during triaxial loading the dominant failure mode was along distinct shear planes effective compressive strengths increased from 8 6 mpa to 80 8 mpa with increasing confining pressure the mohr coulomb failure criterion showed that the coals had friction angle of 29 8 to 39 8 and cohesion ranging between 3 4 mpa and 8 0 mpa with increasing confining stress the non linear hoek brown failure envelope was also fit to the data which provided a better estimation of the strength values for static young s modulus ranged from 1119 mpa to 5070 mpa and poisson s ratio ranged from 0 26 to 0 48 also varying with the confining stress concurrent ultrasonic measurements indicate that the values for dynamic moduli are consistently higher than those obtained from quasi static measurements permeability of the coals tested at simulated in situ stress conditions and parallel to bedding surfaces was highly variable ranging from 2 09 md in seam 3 greenhills mine to less than 0 001 md in seam 10 elkview mine this variation may be rationalized based on variations in maceral composition stress history degree of shearing and the mode of deformation brittle or ductile of the coal seams in these tectonically complex regions

oil generation in overthrust belts the burial of immature sediments beneath a thrust sheet may result in sufficient heating to generate hydrocarbons we present a model for the thermally activated generation of oil from kerogen and the subsequent destruction of the oil through cracking using this oil generation model in conjunction with a model applicable to the thermal evolution of overthrust belts we have studied the evolution of oil in sediments beneath a thrust sheet composed of sedimentary rocks oil generation may begin soon after emplacement of the thrust sheet beneath thick thrust sheets 8 km all oil in the sedimentary section may be destroyed less than 5 m y after thrusting we apply our results to the timing of oil generation in the sedimentary section beneath the absaroka thrust plate in the fossil syncline of western wyoming our calculations indicate that the paleozoic and a part of the mesozoic section were thermally mature prior to emplacement of the absaroka plate the remaining part of mesozoic sediments matured only after thrusting our results are in agreement with warner s 1980 observations that oil being produced from reservoirs in the absaroka plate was generated in the underthrust mesozoic section

before the ice biogeography of antarctic paleogene molluscan faunas abstract new identifications are listed of antarctic paleogene molluscan faunas lopez de bertodano and sobral formations seymour island paleocene la meseta formation seymour island eocene mcmurdo sound erratics eocene and king george island oligocene early miocene these show that both cosmopolitan and antarctic subantarctic genera increased regularly as percentages of faunas with time 15 of paleocene genera 30 of eocene genera and 59 of oligocene early miocene genera still live in the antarctic subantarctic region the present major antarctic families of larger molluscs have remained the most diverse ones since middle eocene time and the antarctic fauna was well established by then however mytilidae and veneridae have decreased markedly in diversity mactridae and oysters have disappeared from the antarctic and antarctic trochidae volutidae and conoidea are now distinct guilds of more offshore taxa this reflects the present antarctic ice cover shallow water taxa that are no longer able physically to live in antarctica provide an index of antarctic glaciation glaciation was not extensive on the antarctic peninsula by late eocene time and a few genera of shoreface molluscs still inhabited the king george island area during oligocene early miocene time subduction has left only sparse localities around the margins of the pacific and indian australian plates containing shallow water early paleogene macrofossils almost none are known from the central regions of these plates few data points are available so apparent indications of taxa originating in antarctica are not interpretable new names are provided for two junior homonyms gaimardia zinsmeisteri replacing gaimardia flemingi zinsmeister 1984 prosipho stilwelli replacing aeneator huttoni stilwell and zinsmeister 1992

orbitally induced climate and geochemical variability across the oligocene miocene boundary to assess the influence of orbital scale variations on late oligocene to early miocene climate and ocean chemistry high resolution 5 kyr benthic foraminiferal carbon and oxygen isotope and percent coarse fraction time series were constructed for ocean drilling program site 929 on ceara rise in the western equatorial atlantic these time series exhibit pervasive low to high frequency variability across a 5 myr interval 20 5 25 4 ma the records also reveal several large scale secular variations including two positive 1 6 oxygen isotope excursions at 22 95 and 21 1 ma suggestive of large but brief glacial maxima mi 1 and mi 1a events of miller et al 1991 and a long term cyclical increase in the carbon isotopic composition of seawater shift of 1 52 that reaches a maximum coincident with peak 18o values at 22 95 ma lower resolution 25 kyr records constructed from benthic and planktonic foraminifera as well as bulk carbonate at a shallower site on ceara rise site 926 for the period 21 7 24 9 ma covary with site 929 18o values reflecting changes in antarctic ice volume likewise covariance among carbon isotopic records of bulk sediment benthic and planktonic foraminifera suggest that the low frequency cycles 400 kyr and long term increase in 13c values represent changes in the mean carbon composition of seawater co2 the time series presented here constitute the longest most continuous and highest resolution records of pre pliocene climate and oceanography to date the site 929 carbon and oxygen isotope power spectra show significant concentrations of variance at 400 100 and 41 kyr demonstrating that orbitally induced oscillations have been a normal characteristic of the global climate system since at least the oligocene including periods of equable climate and times with no apparent northern component water production