in situ la icp ms trace elements analysis of scheelites from the giant beiya gold polymetallic deposit in yunnan province southwest china and its metallogenic implications abstract the beiya gold polymetallic deposit located in the middle of the jinshajiang ailaoshan alkaline porphyry metallogenic belt is the largest skarn gold deposit in china scheelite is a typical hydrothermal mineral which can serve as mineralization process tracer and is significant for the hydrothermal deposit study in this paper we present in situ la icp ms scheelite geochemical data from the different parts of the skarn mineralization in the beiya deposit the data indicate that the beiya scheelite has high mo average 38 943 ppm and high lree hree average 29 6 resembling typical skarn type scheelite the mechanism of ree substitution of ca in the beiya scheelite was probably 3ca 2 2ree 3 ca which implies that the scheelite inherited its ree composition from magma derived ore forming fluids the scheelite from near the marble shows negative eu anomaly average eu 0 45 indicating an oxidizing condition whereas that from near the porphyry shows positive eu anomaly average eu 3 58 indicating a reducing environment scheelite from the sandstone hosted stratiform orebody shows slight and variable eu anomalies eu 0 66 1 47 indicating possible fluctuating physicochemical conditions our data demonstrate an increasing oxygen fugacity f o 2 trend from the ore related intrusion to the surrounding carbonates at beiya the rb sr nb ta and zr hf ratios of the beiya scheelite suggest an addition of mantle derived components to the ore forming materials of the beiya deposit

late miocene to pleistocene sequences at the new jersey outer continental shelf odp leg 174a sites 1071 and 1072 abstract 2 d seismic wireline log and core data at odp leg 174a sites 1071 and 1072 on the outer continental shelf of new jersey reveal two major depositional sequences of late miocene pliocene and pleistocene age the late miocene pliocene sequence is a thick 100 m deepening upward succession landward of the clinoform rollover and a shoaling upward succession seaward of the clinoform rollover the pleistocene sequence deepens abruptly near its base shoals upward and then deepens again before it is truncated by its overlying unconformity there is no onlap onto clinoforms no lowstand wedge in either sequence sequence stratigraphic analysis and a geometric depositional model are used to interpret that the unusually thick transgressive component of the late miocene pliocene sequence was formed by high frequency eustatic cycles 1 2 m y superimposed on a longer term eustatic rise 5 m y this conclusion is supported by independent evidence of eustasy the sequences of this study are correlated to sequences in the north atlantic coastal plain and in the great bahama bank these sequences have very different architectures than underlying middle miocene sequences which contain thick lowstand wedge deposits and are interpreted to have formed by high frequency eustatic cycles superimposed on longer term eustatic fall

rates and possible causes of neotectonic vertical crustal movements of the emerged southeastern united states atlantic coastal plain emerged pliocene and pleistocene shorelines and associated marine deposits were used to determine the magnitude and rate of vertical crustal movement during the past 3 m y in the united states atlantic coastal plain of south and north carolina on the basis of a new regional ostracode assemblage zonation planktic biostratigraphic data and radiometric data emerged marine deposits were determined to be primarily interglacial and can tentatively be correlated with hemispheric warm intervals in evidence from deep sea data the paleontologic evidence indicates a primary glacio eustatic component to the local sea level record and a secondary tectonic component net vertical uplift rates averaging 1 to 3 cm 1 000 yr but perhaps as high as 5 to 10 cm 1 000 yr are in evidence for the emerged coastal plain although details of the timing of regional rheological events remain obscure the trend of net uplift contrasts with general subsidence rates of about 2 to 4 cm 1 000 yr since the cretaceous in submerged parts of the continental margin near subsiding sedimentary troughs hydro isostatic crustal response to multiple deglaciation events may have periodically uplifted the coast but long term lithospheric flexural upwarping in response to sediment loading offshore is a more plausible mechanism to explain the present positions of shorelines above present mean sea level a eustatic sea level model is proposed for interglacial high stands of the past 3 0 m y

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

geochronology of the giant beiya gold polymetallic deposit in yunnan province southwest china and its relationship with the petrogenesis of alkaline porphyry abstract the beiya gold polymetallic deposit located at the junction of the sanjiang tethys himalaya orogenic belt and the yangtze craton in southwestern china is the largest gold deposit in the region mineralization mainly occurs in skarn which formed along the contacts between porphyry intrusions and limestone host rocks the ore formation process is suggested to be closely related to the himalayan age alkaline porphyries u pb dating of magmatic zircons from the beiya quartz syenite porphyry yields a weighted average 206 pb 238 u ages of 36 07 0 43 ma n 25 mswd 1 17 calculated isochron age of five molybdenite samples from beiya is 34 7 1 6 ma mswd 0 99 initial 187 os of 0 21 0 16 ppb which indicates that mineralization is coeval with the intrusion of the beiya alkaline porphyry this age is also in agreement with the results of apatite fission track analysis in the porphyry magmatic zircon e hf t values range from 7 4 to 0 1 which correspond to the two stage hf model with ages between 1112 ma and 1588 ma this finding suggests that the main source of porphyry was probably melting of thickened mesoproterozoic lower crust triggered by partial melting of the lithospheric mantle zircon ce iv ce iii ratios of ore related porphyry are high given that all eu n eu n ratios are above 0 4 which demonstrates that the magma source of the porphyry was highly oxidized which was favorable for cu au mineralization the medium re concentrations in molybdenite re 2 08 20 54 ppm suggest that the ore forming materials were characterized by mixed crustal mantle sources mineralization in the beiya deposit was one of the many metallogenic events related to the india eurasia collision that was responsible for the fertile deep sourced magmatism

cenozoic ice volume history development of a composite oxygen isotope record to view cenozoic ice volume and ocean temperature history a composite 18 o time series was constructed for tropical shallow dwelling planktonic foraminifers and for deep water benthic foraminifers we conclude that cenozoic benthic 18 o primarily reflect considerable deep ocean temperature variation and that tropical planktonic 18 o afford the best record of cenozoic ice volume the planktonic composite indicates the presence of a significant ice budget for the past 40 m y the difference between the benthic and planktonic 18 o composites suggests that low latitude production of warm saline bottom water dominated tertiary thermohaline circulation

age and correlation of emerged pliocene and pleistocene deposits u s atlantic coastal plain abstract paleontologic and paleomagnetic investigations were conducted on several hundred pliocene and pleistocene marine samples from five regions of the emerged atlantic coastal plain 1 the delmarva peninsula 2 eastern virginia 3 central and northern north carolina 4 southern north carolina and northeastern south carolina and 5 the charleston area south carolina molluscan and ostracode interval and assemblage zonations which are the primary means of regional correlation have been calibrated using planktic biochronologic paleomagnetic radiometric and amino acid recemization data these multiple dating criteria were used to determine the age and where possible the duration of marine transgressive regressive sequences a correlation chart illustrates the age relationships of 27 formations from five regions one important conclusion is some of the yorktown formation of virginia and north carolina including the duplin formation and some of the raysor of south carolina are late pliocene in age the late pliocene chowan river formation of north carolina is older than the early pleistocene waccamaw formation of south carolina which in turn may be older than the james city formation of north carolina during the last 1 0 million years multiple marine transgressions occurred in each region but the age of these middle and late pleistocene formations often may differ from one area to the next a significant result of the study is the evidence for the lack of time equivalence of formations in the five different regions that is the sequence of marine transgressions in one region does not necessarily correspond to that in another this appears to be the result of differing subsidence and uplift histories the patchiness of the depositional record and the limitations of the dating techniques in light of the rapidity and frequency of sea level fluctuations

late cenozoic marine deposition in the united states atlantic coastal plain related to tectonism and global climate abstract major hiatuses in upper cenozoic marine deposits in the united states atlantic coastal plain are recognized on the basis of molluscan faunal changes at erosional unconformities these hiatuses generally coincided with periods of global cooling and ice sheet formation such hiatuses provide information to supplement global climatic data major hiatuses are recognized within the early miocene 23 20 m y ago at the end of the middle miocene 11 10 m y ago at the end of the late miocene 6 5 5 m y ago at the end of the early pliocene 4 0 2 5 m y ago at the end of the late pliocene 1 9 or 1 8 m y ago within the pleistocene 1 1 0 5 m y ago and several times within the last 0 4 m y estimates of the amount of water contained in ice sheets at different times in the pliocene and pleistocene facilitate calculation of probable minimum sea levels on the coastal plain during different high stands of the sea the altitudes of dated shoreline deposits in the atlantic coastal plain show that the amount of uplift in the cape fear area has averaged at least 1 3 cm per 1000 years since the beginning of pliocene time the coastal plain of georgia has apparently experienced relatively little vertical deformation during this same time

cenozoic marine sedimentation and ice volume variation on the east antarctic craton recycled cretaceous and cenozoic marine microfossils have been recovered from samples of the pliocene sinus formation samples were collected from outcrops in the reedy beardmore and ferrar glacier areas of the transantarctic mountains between lat 77 and 86 s the glaciogene sediments contained diatoms foraminifera calcareous nannoplankton silicoflagellates radiolarians sponge spicules palynomorphs and ostracodes of late cretaceous paleocene eocene late oligocene late miocene and pliocene age this suggests the presence of open marine basins on the east antarctic craton during late mesozoic and cenozoic time the apparent absence of early oligocene and early through middle and earliest late miocene assemblages suggests either that marine regression exposed the basin floors or that ice filled the basins during these times the high elevation setting of sirius formation outcrops suggests one of two hypotheses for their origin 1 they are in situ pliocene glaciomarine deposits that were uplifted 1 750 2 500 m with the transantarctic mountains to their present elevation 2 the sirius formation deposits are a mixture of derived sediments stripped from sub ice intracratonic basins and subsequently redeposited by ice flowing up the inland slope of the transantarctic mountains we favor the second hypothesis with transport to sites sometime within the past 3 m y

early pliocene marine sediments coastline and climate of east antarctica we record the first onshore late tertiary fossiliferous marine deposit from the 8000 km long coastline of east antarctica glaciomarine sediments containing abundant diatoms and molluscs were deposited in shallow waters off an open coast during the early pliocene 4 5 3 5 ma and are now exposed less than 15 m above sea level on marine plain in the vestfold hills lat 68 359s long 78 009e marine diatoms suggest early pliocene as the most probable age of the sediments fossil sand wedges show that the deposit was above sea level at least briefly before it was covered with water and subsequently capped with glaciomarine till the coastline at the time of deposition of the marine sediments is inferred to have been close to but farther inland than that of today the ice margin may have been 50 km farther inland considerably reducing the ice volume of antarctica climate at the time of deposition was interglacial and perhaps warmer than the present

cenozoic unconformities and depositional supersequences of north atlantic continental margins testing the vail model integrated outcrop borehole and seismic reflection stratigraphy from the u s and irish margins of the north atlantic basin reveals a framework of cenozoic depositional supersequences and interregional unconformities that resembles the vail depositional model paleo bathymetric and paleoceanographic analyses of associated microfossil assemblages indicate a genetic link between the depositional framework and the relative position of sea level

toward a high resolution chronology for latest miocene paleoceanographic events it is now widely accepted that expansion of continental glaciers is one manifestation of profound paleoenvironmental change in latest miocene time the oxygen isotopic record in deep sea cores is inferred to document brief pulses in glaciation based on covariance of 18o in benthic and planktonic foraminifera which probably lowered latest miocene sea level by a minimum of 60 m additional evidence of glacial activity in the oxygen isotope record is obscured by the small signal amplitude before further details of paleoenvironmental change can be investigated it is essential to have a high resolution stratigraphy and chronology this has not been achieved previously because most studies of the latest miocene have had a sampling interval greater than the duration of events they seek to resolve a high resolution stable isotope record from the north atlantic deep sea drilling project dsdp 552 is correlated with a second record from the southwest pacific dsdp 588 each core has magnetostratigraphy but there are two possible interpretations of magnetic results in the atlantic core by assuming that brief events of 18o enrichment and 13c depletion in each core are synchronous it is possible to assign the most likely age model to the atlantic core results of this exercise indicate that two 18o maxima occurred at 4 8 and 5 2 ma if these events reflect continental glaciation and if sea level was lowered enough to contribute to isolation and desiccation of the mediterranean then the miocene pliocene boundary must be close to 4 8 ma in age because messinian deposits are latest miocene in age this interpretation is consistent with biostratigraphy at dsdp 552 magnetostratigraphy biostratigraphy and isotope stratigraphy at a site commonly referred to because of its proximity to the mediterranean dsdp 397 northwest african continental margin and recent work on land in the mediterranean region

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

major deglaciation of east antarctica during the early late pliocene not likely from a marine perspective abstract we have conducted an integrated study of ice rafted debris ird and oxygen isotopes measured on cibicides globigerina bulloides and neogloboquadrina pachyderma using identical samples we used samples from the early late pliocene gauss chron from odp site 114 704 on the meteor rise in the subantarctic south atlantic during the early gauss chron the oxygen isotopic ratios are generally up to 0 5 0 6 less than their respective holocene values the lowest values in this record can accommodate a warming of about 2 5 c or a sea level rise of about 50 m but not both and probably result from some warming and a small reduction in global ice volume starting with isotope stage mg2 3 23 ma on the berggren et al 1985 time scale 3 38 on the shackleton et al 1995b time scale oxygen isotopic values generally increase and oscillate about a holocene mean the first significant ird appears at the same time there is a subsequent increase in ird amounts upsection in order to reach the site this material must have been transported by large tabular icebergs derived from antarctic ice shelves or ice tongues similar to occasional large modern icebergs this combined record suggests strongly that the antarctic ice sheet was essentially intact some warming at the drill site is indicated but not a major reduction in ice volume on antarctica

geological history of chesapeake bay usa abstract chesapeake bay began to form as a partially enclosed coastal water body separated from the open ocean in the late pliocene and developed through the pleistocene and into the holocene in response to coastal marine processes and major cycles of sea level rise and fall during times of emergence and low sea level the rivers excavated channels in the broad coastal plain and subaerial processes eroded and modified existing landforms during periods of high sea level the delmarva peninsula lengthened as a major barrier spit progressively enclosing what was to become chesapeake bay and nearshore deposits of sediment accumulated along the western shore enlarging the inter river peninsulas highstands of sea level also resulted in the carving of regional scarps that mark the maximum shorelines as the sea cycled back and forth across the coastal plain and continental shelf a series of thin strata were deposited then modified the bay as it exists today may be at an end stage in the progression as the bay mouth has begun to function as a tidal inlet

quaternary fluvial history of the delaware river new jersey and pennsylvania usa the effects of glaciation glacioisostasy and eustasy on a proglacial river system abstract fluvial glacial and estuarine deposits in the delaware valley record the response of the delaware river to glaciation sea level change and glacioisostasy during the quaternary incision following an early pleistocene glaciation created the present valley which is inset into a pliocene strath and fluvial plain middle and upper pleistocene and holocene deposits were laid down in this inset valley estuarine terraces in the lower valley and bayshore at 20 m probably marine isotope stage mis 11 8 m mis 5e and 3 m mis 5a or c and a fluvial deposit that correlates to offshore mis 3 marine deposits at 20 m are at elevations consistent with glacioisostatic models successive incisions during lowstands in the middle and late pleistocene lengthened deepened and narrowed the channel in the lower valley and shifted the channel westward in delaware bay during mis 2 glaciation from 25 to 18 ka the delaware was diverted to the hudson shelf valley by glacioisostatic tilting most glacial sediment was trapped in fluvial lacustrine valley fills north of the terminal moraine incision of the valley fill was accomplished during the early stage of rebound between 17 and 12 ka drainage to the delaware shelf was restored between 15 and 13 ka as the forebulge collapsed during incision multiple postglacial terraces formed where the valley was perpendicular to rebound contours and so was steepened and elevated northward and a single terrace formed where the valley paralleled the contours and there was no differential elevation or steepening about 65 of the original volume of mis 2 glacial sediment remains in the main valley and most of the eroded volume is in the channel in the lower valley beneath holocene estuarine fill little glacial sediment reached the delaware or hudson shelf overbank deposition on the lower postglacial terrace and modern floodplain spans the holocene the volume of holocene sediment in the estuary and bay yields a basinwide denudation rate of about 20 m my

mid pliocene shorelines of the us atlantic coastal plain an improved elevation database with comparison to earth model predictions abstract for nearly a century the atlantic coastal plain acp of the united states has been the focus of studies investigating pliocene and pleistocene shorelines however the mapping of paleoshorelines was primarily done by using elevation contours on topographic maps here we review published geologic maps and compare them to paleoshoreline locations obtained through geomorphometric classification and satellite data we furthermore present the results of an extensive field campaign that measured the mid pliocene 3 3 2 9 ma shorelines of the atlantic coastal plain using high accuracy gps and digital elevation models we compare our new dataset to positions and elevations extracted from published maps and find that the extracted site information from earlier studies is prone to significant error both in the location and more severely in the elevation of the paleoshoreline we also investigate using geophysical modeling the origin of post depositional displacement of the shoreline from georgia to virginia in particular we correct the elevation of our shoreline for glacial isostatic adjustment gia and then compare the corrected elevation to predictions of mantle flow induced dynamic topography dt while a subset of these models does reconcile the general trends in the observed elevation of the mid pliocene shoreline local discrepancies persist these discrepancies suggests that either i the dt and gia models presented here do not capture the full range of uncertainty in the input parameters and or ii other influences such as sediment loading and unloading or local fault driven tectonics may have contributed to post depositional deformation of the mid pliocene shoreline that are not captured in the above models in this context our field measurements represent an important observational dataset with which to compare future generations of geodynamic models improvements in models for dt gia and other relevant processes together with an expanded geographically distributed set of shoreline records will ultimately be the key to obtaining more accurate estimates of eustatic sea level not only in the mid pliocene but also earlier in the cenozoic

nonlinear response of pliocene climate to orbital forcing evidence from the eastern equatorial pacific a high resolution radiolarian record from the eastern equatorial pacific is used to examine paleoceanographic events during the pliocene from 1 8 to 4 9 ma these data provide a means to evaluate the response of the equatorial pacific to the onset of northern hemisphere glaciation near 2 47 ma and to the closure of the isthmus of panama near 3 2 ma responses are recorded both as long term trends and as variations within the milankovitch band 104 to 105 years radiolarian based sea surface temperature sst estimates indicate a mean cooling from lower to upper pliocene but no significant changes occur near the onset of northern hemisphere glaciation and no abrupt changes are observed before or after the closure of the isthmus spectral and cross spectral analyses of this sst time series indicate concentrations of variance within the precession 23 kyr and obliquity 41 kyr bands in several but not all time intervals variance is commonly concentrated at lower frequencies cross spectral analysis of sst time series and calculated orbital variations indicates that the sst record is not coherent with and therefore not linearly related to orbital variations detailed time series analysis of the sst and 18o time series indicates the absence of a direct linear relationship but rather the presence of a strongly nonlinear relationship between pliocene climatic variables and earth s orbit high coherence is seen between the amplitude of the 23 kyr component of sst and the amplitude modulation of precession the amplitude modulation of the 41 kyr component of the sst record is dissimilar to the amplitude modulation of obliquity but is extremely similar to and coherent with the amplitude of the 23 kyr component of sst the amplitude modulations of sst and 18o at a range of frequency bands have the same features features that roughly follow the modulation of precession this suggests a strongly nonlinear response of equatorial pacific sst and planktonic 18o to orbital forcing in the pliocene such a response extending over a number of frequency bands has not previously been seen in a paleoclimatic data set but may be consistent with proposed models describing paleoclimatic variability although the reasons for this response are still unclear it is evident that strong nonlinearities in climate are present during this time

palynological foraminiferal and aminostratigraphic studies of quaternary sediments from the u s middle atlantic upper continental slope continental shelf and coastal plain abstract a pollen climate index curve provides the basic stratigraphic subdivision of the 305 m cored quaternary section of amcor 6021c located on the upper continental slope off new jersey u s a cold and warm intervals from top to bottom were assigned to marine oxygen isotope stages 1 through 13 at a sub bottom depth of about 220 m foraminiferal data indicate a possible hiatus and if so sediments below this may be as old as isotope stage 16 or older aminostratigraphic studies yielded results that are consistent with either interpretation benthic foraminifers are dominated by elphidium excavatum and islandiella norcrossi the planktic foraminiferal record provided no independent means of subdividing the section the stratigraphic distribution in 6021c of six species of quercus oak and aminozone determinations were applied to dating in terms of presumed oxygen isotope stages of other offshore core hole samples and some onshore quaternary deposits of delaware stratigraphic information from amcor sites 6021 and 6009 correlated to seismic reflection profiles that cross the shelf slope break indicate that the thickest accumulations of terrigenous quaternary sediments are located along the outer continental shelf upper continental slope offshore the northeastern united states

middle pliocene sea surface temperatures a global reconstruction identification and analyses of pliocene marine microfossils from 64 globally distributed stratigraphic sequences have been used to produce a middle pliocene sea surface temperature reconstruction of the earth this reconstruction shows little or no change from current conditions in low latitude regions and significant warming of the ocean surface at mid and higher latitudes of both hemispheres this pattern of warming is consistent with terrestrial records and suggests a combination of enhanced meridional ocean heat transport and enhanced greenhouse effect were responsible for the middle pliocene warmth

nature of the antarctic peninsula ice sheet during the pliocene geological evidence and modelling results compared abstract in this paper we examine the nature of the pliocene antarctic peninsula ice sheet by comparing the terrestrial and marine geological records of the antarctic peninsula and surrounding sea floor with estimated net snow accumulation in the region derived from numerical palaeoclimate model experiments pliocene geological data and our new modelling results are consistent and mutually supportive in suggesting that an ice sheet was present even during the warmest episodes of the pliocene the combined results suggest that the ice sheet in the antarctic peninsula is more robust to globally warmer conditions than is generally assumed at least up to the climatic limits examined in our study

neogene stratigraphy of the submerged u s atlantic margin abstract thirty boreholes and several hundred sea floor samples provide a detailed but incomplete record of neogene strata and depositional environments along the submerged part of the united states atlantic margin three major sedimentary basins the blake plateau basin the baltimore canyon trough and the georges bank basin contain neogene sedimentary prisms as thick as 1200 m comprising bathyal marine to nonmarine strata middle miocene rocks compose the most widely represented and thickest unit 600 m in the baltimore canyon trough calcareous microfossils provide excellent biostratigraphic and paleoenvironmental indicators except in some sparsely fossilferous shallow water intervals and where shallow water diatomaceous assemblages predominate however in outer sublittoral assemblages of the blake plateau basin and baltimore canyon trough the co occurrence of abundant diatoms radiolarians and planktic foraminifera provide an excellent opportunity for intercalibration of biozones preliminary correlations between chronostratigraphic and paleoenvironmental interpretations indicate a close association of depositional sequences with sea level fluctuations but some local exception persist

middle pliocene sea surface temperature variability 1 estimates of sea surface temperature sst based upon foraminifer diatom and ostracod assemblages from ocean cores reveal a warm phase of the pliocene between about 3 3 and 3 0 ma pollen records and plant megafossils although not as well dated show evidence for a warmer climate at about the same time increased greenhouse forcing and altered ocean heat transport are the leading candidates for the underlying cause of pliocene global warmth despite being a period of global warmth this interval encompasses considerable variability two new sst reconstructions are presented that are designed to provide a climatological error bar for warm peak phases of the pliocene and to document the spatial distribution and magnitude of sst variability within the mid pliocene warm period these data suggest long term stability of low latitude sst and document greater variability in regions of maximum warming

the record of pliocene sea level change at enewetak atoll abstract detailed seismic stratigraphy lithostratigraphy and chemostratigraphy indicate that atoll wide subaerial exposure surfaces major disconformities developed during major sea level lowstands form prominent seismic reflectors and are coincident with biostratigraphic breaks in the plio pleistocene on enewetak atoll sea level models based on the stratigraphic position and age of major disconformities suggest a maximum sea level highstand elevation of 36 m above present sea level and a maximum sea level lowstand elevation of 63 m below present sea level for the pliocene

anthropogenic co2 in southern ocean surface waters evidence from stable organic carbon isotopes we present an approach for tracing the fate of anthropogenic co2 compiling a large data set of stable organic carbon isotope ratios from surface sediments plankton and sinking matter in the atlantic ocean the 13c values of sinking matter are generally lower by 0 5 4 6 compared to the surface sediments this difference increases with increasing latitude which is explained by a stronger modern increase in surface water co2 aq in the southern ocean relative to the tropical subtropical ocean preindustrial dissolved co2 concentrations in atlantic surface waters estimated from the 13corg of surface sediments are compared to recently measured surface water co2 aq values taken from literature we obtain only a slight increase in co2 aq at lower latitudes but a significant change of about 7 2 m in high latitudinal surface waters which we attribute to anthropogenic perturbation our results suggest that co2 released by human activities has been stored in southern ocean surface waters

isotopic evidence of cool winter conditions in the mid piacenzian pliocene of the southern north sea basin oxygen isotope thermometry of aequipecten opercularis and atrina fragilis bivalves which demonstrate all year growth provides quantitative evidence of cool temperate winter conditions below 10 c during deposition of the mid piacenzian oorderen sands and time equivalent strata in the southern north sea basin snsb isotopic summer temperatures seafloor are within or only marginally above the cool temperate range upper limit 20 c the occurrence of warm temperate dinoflagellate cysts alongside and presumably contemporaneous with the bivalves indicates the development of a correspondingly warm surface layer in summer encystment allowing the dinoflagellates to survive cool winter conditions this evidence of greater surface seasonality than now is consistent with greater global warmth and a reduction in the vigour of the gulf stream north atlantic drift gs nad leading to a reduced supply of winter heat this reduction in gs nad strength may be linked to breaching of the emerging isthmus of panama

metallogenic setting and ore genetic model for the beiya porphyry skarn polymetallic au orefield western yunnan china abstract the beiya in western yunnan china is a world class porphyry skarn polymetallic au orefield that is currently being explored and constitutes the topic of this paper the beiya orefield is a composite mineral system with a distinct zoning surrounding the causative intrusions for instance the wandongshan the largest deposit in the beiya orefield exhibits a zoning with 1 porphyry au fe cu orebodies in the cupolas to the intrusions 2 au fe cu skarn orebodies along contact zones between the alkaline porphyritic intrusions and triassic limestone country rocks and 3 distal stratiform pb zn ag au epithermal orebodies subsequent au and cu bearing quartz ankerite veins and barren calcite veins overprint the earlier magmatic hydrothermal zoned ore system the hypogene orebodies were weathered to form supergene au ores at shallow levels which were historically termed laterite gold deposits the 2000 km nwn striking jinshajiang ailaoshan metallogenic province located in the three river region of western yunnan western sichuan and eastern tibet hosts numerous world class porphyry and skarn cu mo au ores associated with alkaline porphyry emplacement the beiya polymetallic au orefield a representative example of these ore types is located close to the triassic ailaoshan songma suture to the east and formed during eocene oligocene intraplate extension the distal stratiform pb zn ag au orebodies are hosted by bedding or detachment faults based on exploration data and previous research and combined with our detailed field investigation and further studies in the beiya area we propose a new and comprehensive porphyry skarn epithermal deposit model the model explains the geological setting ore characteristics metallogenic zoning and ore forming processes of the deposits in the beiya area it provides useful insights for further mineral exploration in the jinshajiang ailaoshan province for porphyry and skarn cu mo au ore systems associated with alkaline magmatism and may also be applied to other metallogenic provinces within similar continental arc settings

zoning of mineralization in hypogene porphyry copper deposits insight from comb microfractures within quartz chalcopyrite veins in the hongshan porphyry cu deposit western yunnan sw china abstract the origin of zonal mineralization in porphyry copper deposit is important for understanding the mineralization processes we propose a new modified orthomagmatic genetic model for mineralization zoning in hypogene porphyry copper deposits this new model is based on the features and formation mechanism of comb microfractures in quartz chalcopyrite veins within pyrite vein from the hongshan porphyry copper deposit in zhongdian county western yunnan province sw china the main evidence for this model is volume expansion related to crystallization of chalcopyrite magnetite and k metasomatism in the deposit comb microfractures are well developed in quartz chalcopyrite veins and are present as comb quartz veinlets consisting of a zone of central longitudinal quartz overprinted by laterally grown quartz combs chalcopyrite fragments lie perpendicular to the central quartz veinlet and were dismembered by the quartz combs the combed microfractures are typical tensional hydrofractures the formation of the comb microfractures is related to volume expansion that was induced by crystallization of chalcopyrite from a chalcopyrite melt that resulted in the subsequent increase of volumetric pressure in the confined residual silica melt the formation mechanism of the comb microfractures including volume expansion induced by crystallization increases volumetric pressure hydrofracturing and fluid expulsion and was the most likely process for zoning of minerals in hypogene porphyry copper deposits fabrics in the veins and veinlets are consistent with overpressuring and injection and are common structures that are directly related to volumetric pressure and crystallization of chalcopyrite and magnetite and k metasomatism in hypogene porphyry copper deposits the volume expansion ratio of chalcopyrite mineral to melt and that of magnetite mineral to melt are approximately 19 vol and 20 vol respectively the volume expansion rate of a monomolecular lattice is 8 vol for orthoclase replacing plagioclase we suggest that zoning of mineralization in hypogene porphyry copper deposits is mainly related to hydrofracturing migration and distribution of ore forming fluids including 1 the enclosure and formation of a mush core 2 concentration of ore forming fluids in the orthoclase shell 3 k metasomatism and pressure building 4 hydrofracturing and migration of ore forming fluids and 5 prior crystallization of magnetite and chalcopyrite that will expel residual fluids upwards and outwards due to the change in volumetric pressure

post miocene diagenetic and eustatic history of enewetak atoll model and data comparison the post miocene diagenetic and eustatic history of enewetak atoll was investigated using a one dimensional forward model comparison of model and data suggests that the post miocene history of enewetak atoll was dominated by multiple episodes of meteoric phreatic diagenesis attendant with high frequency 10 sup 4 to 10 sup 5 yr fluctuations in sea level and a subsidence rate of 39 0 m m y sensitivity testing indicates that subaerial erosion results in the preservation of additional subaerial unconformities because stratigraphic shortening permits a succeeding sea level rise to flood the exposure surface and deposit sediment whereas without subaerial erosion this sea level rise would be recorded as a paleophreatic lens model results indicate that less then 10 of lapsed time is recorded by sediment deposition during periods of high frequency changes in sea level incompleteness of the stratigraphic record suggest that magnetostratigraphy may give erroneous ages for shallow marine carbonate sequences deposited during times of high frequency changes in sea level and frequent magnetic polarity reversals

palynology of the bryn mawr formation miocene insights on the age and genesis of middle atlantic margin fluvial deposits abstract the ages of fluvial deposits at the head of chesapeake bay thought to be the updip chronostratigraphic equivalents of a well dated late oligocene to quaternary marine sequence in the salisbury embayment are poorly known we present data regarding a new occurrence of a palynoflora recovered from the bryn mawr formation in cecil county maryland the floral assemblage for the bryn mawr formation includes at least 40 taxa at the generic level where quercus cupuliferae ilex carya taxodium and pinus are important elements most of the taxa identified from the bryn mawr formation palynoflora are extant and occur within the modern middle atlantic coastal plain however several important taxa such as alangium engelhardia sciadopitys tricolporopollenites sp and cupuliferoidaepollenites sp are at present either extinct or exotic to the middle atlantic coastal plain comparison of the bryn mawr formation palynoflora to well dated marine deposits of the salisbury embayment suggests a late middle to early late miocene age late serravallian early tortonian for bryn mawr formation phase 2 deposition supporting previously proposed genetic links to the marine deposits of the choptank formation in the subsurface of the delmarva peninsula relative abundances of common extant taxa such as quercus carya pinus and nap the total non arboreal pollen vary considerably throughout late cenozoic deposits of the middle atlantic coastal plain we present data for common extant taxa in a ternary diagram to define discrete palynofacies that discriminate among middle miocene late miocene pliocene and pleistocene palynofloras these results show that relative abunances of common easily identifiable extant pollen may be as diagnostic as exotic taxa in assigning ages to middle atlantic coastal plain deposits the bryn mawr formation palynoflora like other middle to late miocene palynofloras of the middle atlantic coastal plain suggests terrestrial climatic cooling in the larger temporal scale of climate change throughout the cenozoic this change in miocene climate is one of three major events that may have had a significant impact on the rate of sediment yield from the appalachians as recorded in the volume of offshore basin sediments

micropaleontological evidence for increased meridional heat transport in the north atlantic ocean during the pliocene the middle pliocene approximately 3 million years ago has been identified as the last time the earth was significantly warmer than it was during the last interglacial and holocene a quantitative micropaleontological paleotemperature transect from equator to high latitudes in the north atlantic indicates that middle pliocene warmth involved increased meridional oceanic heat transport

late miocene early pliocene stratigraphy and paleoceanography of the south atlantic and southwest pacific oceans a synthesis the stratigraphy and paleoceanography of the late miocene and early pliocene have been examined at six sites in the south atlantic and southwest pacific oceans deep sea drilling project dsdp sites 284 516a 519 588 and 590 and two piston cores from chain cruise 115 a consistent stratigraphy was developed among sites using graphic correlation which resulted in age models for all sites that are tied to the revised paleomagnetic time scale of berggren et al 1985 applying these chronologies we assessed latitudinal and interocean contrasts in the stratigraphic ranges of late miocene early pliocene planktonic foraminiferal and nanno fossil datums salient stratigraphic results include 1 the last appearance datum lad of globoquadrina dehiscens is a late miocene 6 4 ma event in the subtropics and is not useful for the placement of the miocene pliocene m p boundary in this biogeographic province 2 the first appearance datum fad of globorotalia crassaformis occurred at 5 1 ma in the south atlantic near the m p boundary suggesting that gr crassaformis may have first evolved in the south atlantic and later migrated to other regions 3 in the southwest pacific the fads of gr margaritae 5 97 ma gr puncticulata 5 09 ma and gr crassaformis 4 87 ma are significantly time transgressive between temperate and warm subtropical regions time lags of 1 0 m y were required for these species to adapt to physical and or biotic conditions peripheral to their endemic biogeographic provinces 4 between the subtropics of the south atlantic and southwest pacific many planktonic foraminiferal datums fad of dentogloboquadrina altispira gr cibaoensis gr conomiozea gr margaritae and gq dehiscens and lad of gr cibaoensis markedly depart from the correlation suggested by magnetostratigraphy indicating that these datum levels are unreliable for correlation between these ocean basins 5 in contrast available calcareous nannofossil datum levels fall on or near the paleomagnetic correlation line indicating synchroneity of events within the subtropics 6 biostratigraphic magnetic and 87sr 86sr correlation between sites 588 and 519 and the m p neostratotype at capo rossello sicily suggests that the base of the zanclean stratotype occurs at 5 1 5 0 ma in the lower reversed subchron of the gilbert about 2 3 105 years above the gilbert chron 5 boundary oxygen isotopic results from dsdp sites 284 519 and ch115 piston cores confirm a prolonged benthic 18o increase in the latest miocene between 5 6 and 5 0 ma as originally proposed by shackleton and kennett 1975 at dsdp site 588 the benthic 18o record in the latest miocene is marked by high frequency fluctuations with amplitude variations of 0 5 and a long period wavelength component of 400 000 years maximum 18o values however occurred during the late miocene kapitean stage between 5 5 and 5 1 ma the late miocene 18o changes resulted from mid and high latitude cooling and pulses of ice sheet expansion and contraction glacial events were most intense during the latest miocene kapitean stage and occurred at 5 50 5 35 ma and at 5 10 ma glacial events are estimated to have lowered sea level by 40 to 60 m and contributed to the isolation and desiccation of the mediterranean basin during the late messinian interglacial conditions prevailed at 5 2 ma and between 5 0 and 4 1 ma ihe early pliocene the beginning of the pliocene was marked by changes in many proxy climatic indicators at all sites suggesting a prolonged interval of warm interglacial conditions between 5 0 and 4 1 ma during the earliest pliocene supplementary tables are available with entire article onmicrofiche order from american geophysical union 2000florida avenue n w washington dc 20009 documentp86 001 2 50 payment must accompany order

the role of co2 decline for the onset of northern hemisphere glaciation the pliocene pleistocene transition ppt from around 3 2 to 2 5 million years ago ma represented a major shift in the climate system and was characterized by a gradual cooling trend and the appearance of large continental ice sheets over northern eurasia and north america paleo evidence indicates that the ppt was accompanied and possibly caused by a decrease in atmospheric co2 but the temporal resolution of co2 reconstructions is low for this period of time and uncertainties remain large therefore instead of applying existent co2 reconstructions we solved an inverse problem by finding a schematic co2 concentration scenario that allows us to simulate the temporal evolution of key climate characteristics in agreement with paleoclimate records to this end we performed an ensemble of transient simulations with an earth system model of intermediate complexity from which we derived a best guess transient co2 scenario for the interval from 3 2 to 2 4 ma that gives the best fit between the simulated and reconstructed benthic 18o and global sea surface temperature evolution our data constrained co2 scenarios are consistent with recent co2 reconstructions and suggest a gradual co2 decline from 375 425 to 275 300 ppm between 3 2 and 2 4 ma in addition to a gradual decline the best fit to paleoclimate data requires the existence of pronounced co2 variability coherent with the 41 kyr 1 kyr 1000 years obliquity cycle in our simulations the long term co2 decline is accompanied by a relatively abrupt intensification of northern hemisphere glaciation at around 2 7 ma this is the result of a threshold behaviour of the ice sheets response to gradual co2 decrease and orbital forcing the simulated northern hemisphere ice sheets during the early pleistocene glacial cycles reach a maximum volume equivalent to a sea level drop of about 40 m both ice volume and benthic 18o are dominated by 41 kyr cyclicity our simulations suggest that before 2 7 ma greenland was ice free during summer insolation maxima and only partly ice covered during periods of minimum summer insolation a fully glaciated greenland comparable to its present day ice volume is modelled only during glacial maxima after 2 7 ma and more continuously after 2 5 ma

rates and patterns of late cenozoic denudation in the northernmost atlantic coastal plain and piedmont topography of a 2800 km 2 section of the u s atlantic coastal plain and piedmont is reconstructed at five times from the late miocene to the holocene the reconstructions are based on mapping of fluvial colluvial and marginal marine deposits that are dated by radiocarbon palynostratigraphy and correlation to adjacent glacial and marine units denudation rates and patterns are calculated by subtracting successive topographies with 60 m horizontal resolution and 6 m vertical resolution the overall late miocene to holocene denudation rate of 10 m m y is similar to other estimates of long term denudation in the region the overall rate resolves spatially into a wide range of local rates varying from a minimum of 0 2 m m y on residual uplands to as high as 600 m m y in glacially rerouted stream channels the distribution of local rates shows that denudation is accomplished by stream incision in response to long term glacio eustatic decline followed by slope retreat into residual uplands from the incised channels slope retreat replaces the uplands with pediments and straths pediment landforms and sediments and observation of modern scarps and valley heads indicate that groundwater seepage from the base of residual uplands is an important mechanism of slope retreat this process is self limiting because as the volume of residual upland is reduced seepage diminishes and slope retreat slows until small residuals undergo little or no further reduction thus relict topography is preserved even as most of the landscape actively erodes

covariance patterns of foraminiferal dgr18o an evaluation of pliocene ice volume changes near 3 2 million years ago oxygen isotope data for a pliocene interval from 3 6 to 2 8 million years ago show a mean increase 0 5 per mil of benthic delta 18 o at about 3 2 million years ago whereas planktic delta 18 o does not increase this lack of covariance indicates that the event at 3 2 million years did not result in a permanent increase in the ice budget of either the northern or the southern hemisphere

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

quaternary climates and sea levels of the u s atlantic coastal plain uranium series dating of corals from marine deposits of the u s atlantic coastal plain coupled with paleoclimatic reconstructions based on ostracode marine and pollen continent data document at least five relatively warm intervals during the last 500 000 years on the basis of multiple paleoenvironmental criteria we determined relative sea level positions during the warm intervals relative to present mean sea level were 7 5 meters at 188 000 years ago 7 5 1 5 meters at 120 000 years ago 6 5 3 5 meters at 94 000 years ago and 7 3 meters at 72 000 years ago the composite sea level chronology for the atlantic coastal plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200 000 years hydroisostatic adjustment from glacial interglacial sea level fluctuations lithospheric flexure and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies alternatively current eustatic sea level estimates for the middle and late quaternary may require revision

neogene mass extinction of western atlantic molluscs there have been many hypotheses for the global mass extinctions that occurred during the phanerozoic history of the earth and although we cannot study the course of such a mass extinction in progress it is possible to evaluate major pulses of extinction that have taken place recently in geological time explanations of the unusually high rates of extinction within late cenozoic marine faunas of the tropical western atlantic have focused on possible blocking of nutrient laden waters by the origin of the isthmus of panama1 2 and on pleistocene cooling2 3 5 6 or regression2 4 5 of seas here we report that major episodes of molluscan extinction occurred at least as far north as virginia and we conclude that these episodes were caused primarily by refrigeration associated with the late pliocene and pleistocene growth of continental glaciers

cenozoic glaciation in the southern hemisphere with the end of glaciation in gondwana in early permian time a prolonged interval began when the earth was without ice sheets though not necessarily free of mountain glaciers not until sometime during the tertiary era did ice sheets build up once more first in antarctica and later in the northern hemisphere the fundamental cause of the cooling that led to the formation of the antarctic ice sheet and eventually to major glaciation in lower latitudes is generally held to have been the increasing thermal isolation of antarctica as australia and later south america separated from it allowing zonal oceanic circulation to develop rifting between australia and antarctica began between 1 10 and 90 m y ago cande mutter 1982 but not until much later probably sometime between 30 and 25 m y ago had it progressed far enough for deep circulation to begin as the south tasman rise cleared north victoria land kennett et a1 1974 kennett 1977 weissel et ai 1977 however antarctica did not reach its present high level of thermal isolation until south america had separated from it enabling the antarctic circumpolar current to become established savin et ai 1975 according to barker burrell 1977 1982 coherent spreading between the antarctic peninsula and tierra del fuego started about 29 m y ago and deep circulation began 23 5 2 5 m y ago thereafter increasing in volume the initial ice fields and ice caps that later expanded to become the

comparison of amino acid racemization geochronometry with lithostratigraphy biostratigraphy uranium series coral dating and magnetostratigraphy in the atlantic coastal plain of the southeastern united states the results of an integrated study comprising litho and biostratigraphic investigations uranium series coral dating amino acid racemization in molluscs and paleomagnetic measurements are compared to ascertain relative and absolute ages of pleistocene deposits of the atlantic coastal plain in north and south carolina four depositional events are inferred for south carolina and two for north carolina by all methods the data suggest that there are four pleistocene units containing corals that have been dated at about 100 000 yr 200 000 yr 450 000 yr and over 1 000 000 yr some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between charleston and myrtle beach lack of good uranium series dates for the younger material at myrtle beach makes the correlation with the deposits at charleston more difficult

genetic types and framework model of beiya gold ore district in western yunnan the beiya ore district as a part of the cenozoic alkali rich porphyry belt in the eastern tibet western yunnan southeastern yunnan area possesses three types of alkaline porphyries formed at three stages and has experienced repeated mineralization there are three genetic types of mineral deposits in the beiya ore district cu au polymetallic deposits related to alkaline porphyries comprising porphyritic cu au deposits and polymetallic skarn deposits related to quartz albite porphyry and quartz k feldspar porphyry fe au deposits related to gabbro or basalt magma consisting of magmatic fe au deposits and sedimentary polymetallic deposits formed in caves and lakes and palaeo placers formed at the weathering surface in lakes and in karsts complex and superimposed magmatism and hydrothermal processes resulted in the formation of a superlarge gold and polymetallic ore district in the beiya area

pacific ocean intermediate and deep water circulation during the pliocene abstract new benthic foraminiferal stable isotopic records of northeast pacific intermediate water odp site 1014 1177 m and mid depth water odp site 1018 2476 m were compared to isotopic records of deep water in the tropical pacific odp site 849 3851 m for the reconstruction of vertical profiles of nutrient and physical properties from the early pliocene to the early pleistocene approx 5 1 4 ma our data indicate that for the entire interval there was enhanced north pacific intermediate water ventilation relative to today and a similar to modern circulation pattern with northward flowing pacific bottom water pbw beneath its southward flowing return flow however the core of maximally aged return flow resided as deep as 2500 m as compared to 1500 m today probably due to the strengthened intermediate water flow less apparent aging of deep water along its path before 2 7 ma indicates that thermohaline overturning may have been more rapid in the warm period of the early pliocene in addition prior to 2 7 ma foraminiferal oxygen isotopic values at mid depth sites are higher than at deep sites a reversed vertical gradient relative to today in both the atlantic and pacific oceans we suggest that nadw was warmer and more saline than today and that it influenced mid depth waters throughout the atlantic and pacific oceans enhanced pliocene formation of warmer saltier intermediate water in the north pacific and deep water in the north atlantic may have been a result of higher than modern high mid latitude sea surface temperatures evaporation and salinity

a chronology of pliocene sea level fluctuations the u s middle atlantic coastal plain record abstract the sequence of marine and marginal marine silts and sands of the u s middle atlantic coastal plain preserves a relatively complete record of pliocene sea level highstands a general chronology for the deposition of these units has been developed previously from studies of the microfossil biostratigraphy complemented by a limited number of paleomagnetic and radiometric dates within this broad temporal framework it is currently difficult to assign ages to individual transgressive events with a resolution much better than 0 5 ma the age model proposed here attempts to refine the depositional history of the atlantic coastal plain by correlation with the more continuous deep ocean record the model assigns probable ages to the pliocene transgressions onto the atlantic coastal plain based on evidence for sea level highstands inferred from high resolution deep ocean 18 o records at least five major transgressive regressive events can be correlated with presumed eustatic fluctuations the temporal resolution for the timing of the transgressive events is greatly improved over that of the biostratigraphy alone many aspects of the proposed chronology require verification by more detailed field study but it is offered as a testable working hypothesis

palynology of the peace creek site polk county florida the peace creek site in the central florida peninsula is a sinkhole completely filled with sediment the basal 50 m of an 70m long core contains well preserved pollen the regular occurrence of pterocarya and other regionally extinct taxa indicates a late neogene age geological data place the age in the pliocene and high sea levels during the middle pliocene argue for a late pliocene age the most probable time of formation and infilling is in the late pliocene after 2 8 ma corresponding with the onset of significant eurasian and north american glaciation and lower sea levels in addition to pterocarya and sciadopitys wellknown indicators of late neogene pollen assemblages from the atlantic coastal region we identify cf ginkgo and cf dacrydium for the first time from neogene sediments in eastern north america cf here indicates a type that is similar in morphology to an extant family genus or species however these regionally extinct types are rare and the overall pollen assemblage is quantitatively similar to late holocene assemblages from florida and quite distinct from late pleistocene glacial stage assemblages a rich and diverse aquatic pollen assemblage indicates that a shallow freshwater wetland occupied the sinkhole throughout the time of deposition three cycles having a long pinus phase and a short quercus phase characterize the upland pollen assemblage

pliocene palaeotemperature reconstruction for the southern north sea based on ostracoda abstract the development of a large northeastern atlantic shelf ostracod database has confirmed that an intrinsic relationship exists between watermass temperature and the spatial latitudinal distribution of benthonic shelf ostracoda a second pliocene ostracod database using assemblages from four boreholes in the netherlands and a number of localities from the east anglian neogene succession has also been constructed a quantitative method of modern analogues and the squared chord distance dissimilarity coefficient has been employed as a means of calculating the level of similarity between recent and neogene assemblages and therefore to aid in the reconstruction of palaeotemperatures in the southern north sea basin during the pliocene the results in the form of contoured dissimilarity values indicate the presence of at least seven palaeoceanographical climatic phases between ca 5 2 and 1 6 ma bp an early pliocene cooling phase ecozone a in which the fauna is dominated by the cryophilic species palmenella limicola norman elofsonella concinna jones robertsonites tuberculatus sars neomonoceratina tsurugasakensis tabuki and acanthocythereis dunelmensis norman supervenes a period of stable subtropical conditions in the miocene a mid pliocene warming phase ecozone b which has been documented throughout the north atlantic can be recognized in the faunal composition of the sublittoral ostracod assemblages of both the netherlands and east anglia a hiatus between the coralline and waltonian crags is thought to be associated with a deterioration in climatic conditions recent analogues to the netherlands faunas of ecozone c first phase late pliocene cooling ca 2 9 ma bp indicate a decrease of approximately 5 6 c in mean summer surface temperatures a return to elevated temperatures of a mauritanian aspect can be seen in the fauna of the fa2 zone and waltonian crag this amelioration of climate occurred prior to the praetiglian cold phase second phase late pliocene cooling ca 2 4 ma bp which again saw the reintroduction of cryophilic species including baffinicythere howei hazel fimarchinella logani brady crosskey and robertson and hemicythere emarginata sars into the southern north sea during the newbournian and butleyan stages the final phase of the latest pliocene third phase late pliocene cooling is only documented in the ostracod fauna of the norwich crag evidence in the covariance of loxoconchidae and norwegian provincial cryophilic species indicates that the polar front may have been as much as 2000 km further south during the deposition of the chillesford sand member norwich crag fm ca 2 0 1 6 ma bp

in situ la icp ms u pb geochronology and trace elements analysis of polygenetic titanite from the giant beiya gold polymetallic deposit in yunnan province southwest china abstract the beiya gold polymetallic deposit located in the middle of the jinshajiang ailaoshan alkaline porphyry metallogenic belt is one of the largest gold deposits in china the mineralization mainly occurs in skarn along the intrusive contacts between the alkaline porphyries and middle triassic limestone in this paper we present u pb age as well as major and trace element geochemistry of titanite from the beiya deposit and distinguish the titanite into a magmatic and a hydrothermal suite our study indicates that the titanite from the ore related porphyry and from the mineralized skarn is texturally and geochemically very different the euhedral envelope shaped titanite from the ore related porphyry has lower feo f hfses nb ta and lu hf together with higher tio2 and th u than the subhedral titanite from the mineralized skarn the titanite from the porphyry also displays higher lree hree and more subtle negative eu anomaly than its mineralized skarn counterpart this suggests a magmatic and a hydrothermal origin for respectively the titanite from the ore related porphyry and from the mineralized skarn in situ magmatic titanite u pb dating has yielded an eocene age of 36 0 5 9 ma consistent with the porphyry zircon u pb age 36 07 0 43 ma obtained in previous studies hydrothermal titanite has yielded a weighted average 206pb 238u age of 33 1 1 0 ma mswd 2 0 which represents the age of the retrograde skarn alteration and the maximum age for the gold mineralization together with the previous molybdenite re os age we have further constrained the beiya gold polymetallic metallogeny to 33 1 34 1 ma the mineralization age is slightly younger than the porphyry emplacement indicating that the beiya metallogeny was likely to be a post magmatic hydrothermal product of the himalayan orogenic event the ree characteristics of hydrothermal titanite also reveal that the ore forming fluids may have been derived from a highly oxidized magma

a new chronology for the age of appalachian erosional surfaces determined by cosmogenic nuclides in cave sediments the relative chronology of landscape evolution across the unglaciated appalachian plateaus of kentucky and tennessee is well documented for more than a century geomorphologists have carefully mapped and correlated upland erosional surfaces inset by wide valley straths and smaller terraces constraining the timing of river incision into the appalachian uplands was difficult in the past due to unsuitable dating methods and poorly preserved surface materials today burial dating using the differential decay of cosmogenic 26al and 10be in clastic cave sediments reveals more than five million years of landscape evolution preserved underground multilevel caves linked hydrologically to the incision history of the cumberland river contain in situ sediments equivalent to fluvial deposits found scattered across the eastern highland rim erosional surface cave sediments correlate with 1 thick lafayette type gravels on the eastern highland rim deposited between c 5 7 and c 3 5 ma 2 initial incision of the cumberland river into the eastern highland rim after c 3 5 ma 3 formation of the parker strath between c 3 5 ma and c 2 0 ma 4 incision into the parker strath at c 2 ma 5 formation of a major terrace between c 2 0 ma and c 1 5 ma 6 shorter cycles of accelerated incision and base level stability beginning at c 1 5 ma and 7 regional aggradation at c 0 85 ma initial incision into the appalachian uplands is interpreted as a response to eustasy at 3 2 3 1 ma incision of the parker strath is interpreted as a response to eustasy at 2 5 2 4 ma a third incision event at c 1 5 ma corresponds with glacial reorganization of the ohio river basin widespread aggradation of cave passages at c 0 85 ma is interpreted as the beginning of intense glacial interglacial cycling associated with global climate change copyright 2006 john wiley sons ltd