paleosol stable isotope evidence for early hominid occupation of east asian temperate environments hominids left africa and occupied mainland asia by 1 8 myr ago about 1 15 myr agohomo erectusand an associatedstegodon ailuropodafauna migrated from subtropical china across the qinling mountains into the temperate loess plateau this migration may be an evolutionary milestone in human adaptability because it may represent the first occupation of a nontropical environment loess paleosol stable isotope ratios from the last interglacial glacial cycle provide comparative data for reconstructing the hominid paleoenvironments the climate during gongwangling hominid occupation about 1 15 myr ago was influenced by both siberian mongolian winter and indian summer monsoon systems characterized as a cold cool dry winter and warm mild semihumid summer and fall the gongwangling hominids preyed mainly on warm climate adapted animals such asstegodon ailuropodafauna suggesting a warm season occupation the stable isotope ratios also indicate that the chenjiawo hominids occupied an environment similar to that of the gongwangling about 650 000 yr ago the associated fauna with a mixture of forest and steppe warm and cold cool climate adapted animal assemblage s suggests a permanent occupation by this time thus the reliable earliest and permanent occupation of temperate environments may have occurred 150 000 yr earlier in eastern asia rather than in europe

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

mapping of serpentinites in the eastern desert of egypt by using landsat thematic mapper data serpentinites in the eastern desert of egypt were mapped from landsat thematic mapper tm data by using procedures that take advantage of the distinctive spectral reflectance of these rocks caused by the abundance of antigorite lizardite clinochrysotile and magnetite the method employs a threshold classifier based on three reflectance ratios 1 band 5 7 for estimating the abundance of hydroxyl bearing phases 2 band 5 1 for magnetite content and 3 the calculated value of reflectance for band 4 based on a linear interpolation between bands 3 and 5 divided by the observed band 4 reflectance the third ratio was used to identify rocks in iron bearing aluminosilicates and thereby to distinguish mafic rocks containing substantial amounts of magnetite and hydroxyl bearing phases from serpentinites the method was first successfully tested over the meatiq dome and wadi ghadir areas where serpentinites and ophiolitic melanges dominated by serpentinites have been mapped during the course of field work a tm based map was then generated the map covered about 60 000 km sup 2 in the eastern desert results demonstrate that tm data can be used with reliability to distinguish serpentinites from surrounding rocks in arid regions and to generate detailed maps over wide regions by using quantitative reproducible mapping criteria more possibilities for locating suture zones over the less well known parts of arid continents are clear less

hydrothermal alteration mapping using aster data in the infiernillo porphyry deposit argentina abstract the infiernillo cu mo porphyry deposit is located in the san rafael massif in southern mendoza province argentina it is hosted by and genetically related to lower permian gondwanan volcanic rocks which developed in a magmatic arc tectonic setting the alteration zone has an oval shape about 3 km 2 km in size with a nne ssw strike it consists of a small central quartz neck with appreciable hematite surrounded by an intense quartz injected zone with local pervasive potassic alteration outwards there is a well developed phyllic halo with intense bleaching which consists of pervasive and vein type silicification sericitization and pyritization cu and mo anomalies are approximately coincident and are located between the silicified zone and the phyllic halo in the outer part of the alteration zone small polymetallic veins with pyrite arsenopyrite galena and minor chalcopyrite sphalerite and electrum in quartz gangue crop out an advanced spaceborne thermal emission and reflection radiometer aster with three visible and near infrared vnir bands six shortwave infrared swir bands and five thermal infrared tir bands was used to characterize the infiernillo porphyry deposit alteration area a circular zoning pattern was clearly observed in the vnir swir band combination spectral analysis of the surface reflectance swir detected 2 20 and 2 26 m absorptions field data and sample spectroscopic analyses obtained using a ger 3700 spectral radiometer and a swir reflectance spectrometer portable infrared mineral analyzer pima showed a good correlation with the aster data the 2 20 m absorptions due to al hydroxyl reveal the presence of clay minerals al illite kaolinite and sericite whereas the 2 26 m absorption due to fe hydroxyl resulted from jarosite the field samples were also analyzed with a tir portable spectrometer micro ftir model 102 the tir was useful for detecting surface silica and potassic alteration through analysis of five band surface emissivity data aster images provided preliminary mineralogic information and geo referenced alteration maps at low cost and with high accuracy in this way aster has been proven to be a powerful tool in the initial steps of ore deposit exploration

structural and litho tectonic controls on neoproterozoic base metal sulfide and gold mineralization in north hamisana shear zone south eastern desert egypt the integrated field structural landsat 7 etm and aster data approach abstract the hamisana shear zone hsz is an excellent example of high strain shear belt of the neoproterozoic arabian nubian shield ans situated in a position between three major pan african terranes se desert gabgaba and gebeit terranes the north hamisana shear zone area nhsz cuts across sequences of island arc related metasediment metavolcanic which are structurally overlain by ophiolitic nappes and intruded by a number of granitoids and gabbroic rocks although it is interesting geological tectonic setting for base metal sulfide and gold ores there is a lack of detailed studies on structure geology and mineralization in this area which considered as poorly mapped remote region not only in egypt but also in sudan for these reasons we integrated image transformation methods include principal components analysis pca band ratios br false color composite fcc and filtering on the spectral bands of two distinct datasets etm and aster for detailed mapping of the nhsz area spectral data fusion with structural data analysis and field observations provide a better understand of the temporal and spatial relationships between the litho tectonic units and regional tectonic setting in the course of controls on base metal sulfide and associated gold mineralization merging these different data sources in the study area suggests that the base metal sulfide and associated gold mineralization are restricted to quartzites member of island arc related metasediments and mostly controlled by d3 deformational event main hsz deformational event this event characterized by transpressional stress regime with 1 trending e w and 3 trending n s activated conjugate nnw sinistral and nne ssw dextral strike slip faulting likely during syn tectonic granodiorite emplacement

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

vegetation and seasonality shifts during the late quaternary deduced from 13c 12c ratios of grazers at equus cave south africa abstract season of rainfall can be a major influence on the relative proportions of c3 and c4 grasses in a landscape since their relative distribution is essentially constrained by temperatures during the growing season cool growing seasons favor c3 grasses whereas warm ones favor c4 grasses 13c 12c ratios in tooth enamel carbonate of grazers from the site of equus cave northern cape province south africa were used to determine vegetation and rainfall seasonality shifts during the late quaternary the results show shifts in the relative proportion of c3 and c4 grasses during the latter stages of the pleistocene and domination by c4 grasses in the holocene the data show that the northwestern cape did not fall within a winter rainfall zone during this period as has been postulated in recent climate models instead a more complex situation is suggested in which at least two periods of enhanced winter rainfall occurred within a predominantly summer rainfall regime

circulation changes in the faeroe shetland channel correlating with cold events during the last glacial period 58 10 ka a core from the margin of the faeroe shetland channel covering the last glacial period 58 10 ka reveals a very detailed record of oscillations in benthic and planktic foraminifera oxygen isotopes and ice rafted detritus the oscillations correlate almost exactly with the dansgaard oeschger cycles in the greenland ice cores including similar subdivision of the cycles into warmer interstadial and colder stadial sections the remarkably close agreement between the benthic faunas and their 18 o data and the record of the ice cores provides new empirical evidence for a close relationship between the deep ocean circulation and the abrupt climatic changes of the last glacial period

a new classification of the gold deposits of egypt abstract gold deposits and occurrences located in the nubian shield have been known in egypt since predynastic times despite the fact that these deposits were long under exploitation and investigated many times they are still insufficiently classified in harmony with the crustal evolution models suggested for the evolution of the nubian shield several plate tectonic models were proposed for the development of the nubian shield and the present classification relies heavily on the model that implies collision of arc inferred continent through subduction and obduction of oceanic lithosphere a three fold classification of gold deposits of egypt is offered here in harmony with this evolutionary model these are stratabound deposits and non stratabound deposits hosted in igneous and metamorphic rocks as well as placer gold deposits the stratabound deposits are hosted in island arc volcanic and volcaniclastic rocks of comparable composition formed in ensimatic island arcs they are thought to have formed by exhalative hydrothermal processes during the waning phases of sub marine volcanic activity stratabound deposits are sub divided into three main types gold bearing algoma type banded iron formation gold bearing tuffaceous sediments and gold bearing volcanogenic massive sulphide deposits non stratabound deposits occur in a wide range of igneous and metamorphic rocks they were formed during orogenic and post cratonization periods by mineralizing fluids of different sources non stratabound deposits are divided into vein type mineralization which constituted the main target for gold in egypt since pharaonic times and disseminated type mineralization hosted in hydrothermally altered rocks alteration zones which are taken recently into consideration as a new target for gold in egypt placer gold deposits are divided into modern placers and lithified placers the former are sub divided into alluvial placers and beach placers conglomerates occurring on or near ancient eroded surfaces represent lithified placers

a pan african age for the hp ht granulite gneisses of zabargad island implications for the early stages of the red sea rifting abstract up to now the age of granulite gneisses intruded by the zabargad mantle diapir has been an unsolved problem these gneisses may represent either a part of the adjacent continental crust primarily differentiated during the pan african orogeny or new crust composed of miocene clastic sediments deposited in a developing rift crosscut by a diabase dike swarm and gabbroic intrusions and finally metamorphosed and deformed by the mantle diapir previous geochronological results obtained on zabargad island and al lith and tihama asir complexes saudi arabia suggest an early miocene age of emplacement for the zabargad mantle diapir during the early opening of the red sea rift in contrast sm nd and rb sr internal isochrons yield pan african dates for felsic and basic granulites collected 500 600 m from the contact zone with the peridotites devoid of evidence for retrograde metamorphic minerals from a felsic granulite provide well defined rb sr and sm nd dates of 655 8 and 699 34 ma for the hp ht metamorphic event 10 kbar 850 c the thermal event related to the diapir emplacement is not recorded in the sm nd and rb sr systems of the studied gneisses in contrast the development of a retrograde amphibolite metamorphic paragenesis strongly disturbed the rb sr isotopic system of the mafic granulite the initial 143 nd 144 nd ratio of the felsic granulite is higher than the contemporaneous value for chur and is in agreement with other nd isotopic data for samples of upper crust from the arabian shield this result suggests that source rocks of the felsic granulite were derived at 1 0 to 1 2 ga from either an average morb type mantle or a local 2 2 ga lree depleted mantle zabargad gneisses represent a part of the disrupted lower continental crust of the pan african afro arabian shield during early stages of the red sea rifting in the miocene these precambrian granulites were intruded and dragged upwards by a rising peridotite diapir

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

late proterozoic evolution of the northern part of the hamisana zone northeast sudan constraints on pan african accretionary tectonics new structural data from the red sea hills northeast sudan add constraints to accretionary tectonic processes that acted in the arabian nubian shield during the late proterozoic geometric constraints provided by field data are used together with landsat thematic mapper imagery to interpret the regional distribution and structural relations of spectrally and lithologically distinctive rock assemblages in contrast to interpretations reported elsewhere these studies indicate that the hamisana zone a prominent structural feature in the northern red sea hills post dated terrane accretion it is characterized by east west crustal shortening and by steep folds and thrust faults calc alkaline magmatism was contemporaneous with and outlasted main phase deformation thus deformation occurred in an intra arc setting thrust faults were reactivated after east west contraction compromising their usefulness in delineating 9sutures9 or as piercing points across older faults pan african accretionary processes may have been analogous to phanerozoic ophiolite and island arc accretion in the western north american cordillera where penetrative deformation occurred in response to periodic intra plate shortening events rather than an ultimate collision of unrelated crustal fragments such an analogy implies a mechanism for crustal thickening by structural as well as igneous processes during evolution of an accretionary belt in a long lived convergent margin setting consistent with the long standing observation that pan african magmatism became more evolved with time this view emphasizes that an interplay of deformation and magmatism resulted in protracted accretion and crustal thickening in contrast to models where crustal shortening results directly from collision of a volcanic arc microcontinent or other buoyant features

orientation of late precambrian sutures in the arabian nubian shield recent tectonic models have resulted in conflicting descriptions of how the late precambrian sutures of the arabian nubian shield extend into northeast africa the hamisana shear zone in northeastern sudan is critical to this discussion because it truncates and disrupts two sutures the allagi heiani and the onib sol harried analysis of field structural data thematic mapper imagery and rb sr and u pb geochronology suggests that the allagi heiani suture is the western extension of the onib sol harried suture and that both make up the exposed parts of a far traveled polydeformed ophiolitic nappe complex subsequent deformation localized in the hamisana shear zone disrupted this nappe and displaced the suture between 660 and 550 ma during regional deformation associated with the najd fault system these results indicate that at least one suture extends westward into the interior of northern africa

geological control of massive sulfide mineralization in the neoproterozoic wadi bidah shear zone southwestern saudi arabia inferences from orbital remote sensing and field studies abstract this study combines new field and orbital remote sensing data to determine geologic controls on sulfide mineralization in the wadi bidah mineral district wbmd located in the neoproterozoic 900 550 ma arabian shield of southwestern saudi arabia the brittle and ductile deformation of these massive sulfide deposits and host rock reflect tectonic events occurring in the arabian shield during the neoproterozoic 900 550 ma remote sensing data were used in conjunction with gis software arcview to map lithologic units and mineral deposits analyze and define regional structural trends and establish geologic controls on sulfide mineralization orbital remote sensing data sets include scenes from landsat 7 and aster the sulfide deposits of the wbmd are found within a group of felsic volcaniclastics a marble unit within the felsic volcaniclastic group is used as a marker horizon based on the distribution of the sulfide deposits relative to the marble unit all sulfide deposits appear to be stratabound deposits have been folded and faulted into their present positions structural control of mineralization appears to be limited to post mineralization folding and shearing

the tethys sea and the alpine himalayan orogenic belt mega elements in a new global tectonic system abstract analysis of meso cainozoic palaeomagnetic data for africa india and eurasia has led to the development of a new mobilistic alpine plate tectonic model characterized by a hierarchical system of plates in relative rotation the new model which discounts seafloor spreading implies that there have been no significant palaeogeographic changes in the overall distribution of continental and oceanic regions the mid oceanic ridges are interpreted as transpressive tectonic features caused by rotation of megaplates containing both continental and oceanic crust the isostatic uplift due to crustal lithospheric thickening giving rise to the general ridge topography as well as to the ridge parallel structural grain the new plate tectonic theory gains strong support from a variety of geophysical geological and palaeoclimatological evidence and several observations that have remained enigmatic or awkward within the context of the orthodox model can be readily accounted for in the new tectonic framework the model maintains the tethys as a relatively narrow epicontinental sea which during its maximum extent stretched latitudinally from the caribbean across the central atlantic to se asia the alpine himalayan orogenic belt developed along the boundary of two megaplates in relative rotation which provided a transpressive tectonic regime the location of the plate boundary to the north of the mediterranean has important implications for discussion of mediterranean microplates for example it now seems that italy has been subjected to 10 15 of clockwise microplate rotation previous conclusions in favour of 30 40 of anticlockwise rotation are regarded as artefacts which arise from incorrectly linking the mediterranean region to the european palaeomagnetic frame instead of to the african one the model suggests further that the indo pakistani plate was closely tied to eurasia this challenges the conventional view that the peninsula was part of an alleged gondwanaland the new pre drift configuration implies that the indo pakistani plate rotated 135 clockwise at around the cretaceous tertiary boundary before redocking with asia in approximately its present relative orientation

δ13c variations of loess organic matter as a record of the vegetation response to climatic changes during the weichselian this paper presents high resolution records of 13 c 12 c ratios of organic matter from two loess sequences in northwestern europe our analysis is the first attempt to use organic matter 13 c as a record of the response of vegetation to climatic variations in an area where climatic changes were not strong enough to induce a radical change in vegetation cover over the last climatic cycle the vegetation of the rhine valley showed a strong predominance of c3 plants thus the small 13 c variations with an amplitude of only 1 5 to 3 are interpreted as corresponding to fluctuations in water supply and atmospheric co 2 concentration variations rather than to the ratio of c4 to c3 vegetation furthermore loess sequences accumulated at high rates and allow high correlation with climatic proxy data like the greenland ice sheet project 2 gisp2 18 o and the variations in co 2 concentration recorded in the vostok ice core the 13 c constitutes a reliable and complementary proxy to study small climatic stresses endured by vegetation during the weichselian in northwestern europe moreover by using absolute age control and correlations between global vostok co 2 or semi global gisp2 18 o climate effects 13 c values of organic matter in loess sequences offer a new tool to establish a refined chronology in continental sequences

remote sensing for porphyry copper deposits in southern arizona landsat multispectral scanners landsat 4 thematic mapper three porphyry copper deposits used as test sites landsat data useful for delineating areas of iron oxide on the surface limited spatial resolution of mss hampered mapping of some critical geologic relationships synoptic view well suited for examining regional tectonic patterns landsat 4 thematic mapper is an improved mapping tool compared to the previous landsat scanners modified journal abstract

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

a 150 000 year climatic record from antarctic ice during much of the quaternary the earth s climate has undergone drastic changes most notably successive glacial and interglacial episodes the past 150 kyr includes such a climatic cycle the last interglacial the last glacial and the present holocene interglacial a new climatic time series for this period has been obtained using 18 o data from an antarctic ice core

a carbon isotope record of the upper chinese loess sequence estimates of plant types during stadials and interstadials the upper three couplets of paleosol loess in the luochuan section of northern china were analyzed for carbon isotopes these units date back to about 205 ka and have been correlated with the marine oxygen isotope stages 1 6 calcite is present as nodules concretions and interstitial cement analyses were performed on bulk samples of slightly cemented soil and loess material an ashing study indicates the presence of organic matter in the samples and it is possible that analyzed gases included a contribution from this source the measured 13c values and the estimates of co2 content in the atmosphere over this time derived from studies of the vostok ice core and from the 13c values of planktic benthic foraminifera are used following the method of cerling 1984 1991 to calculate the proportions of c3 vs c4 plants which contributed co2 to the formation of calcite in the paleosols and the loess c3 plants were dominant at all times paleosols 70 80 loess 55 60 c3 and both loess and paleosols show a decrease toward the present these relationships suggest a progressive drying of the environments due either to climate change or to changes in the local drainage network