taphofacies analysis of late early givetian fossil assemblages of the parnaiba basin state of piaui northeast brazil abstract taphonomic signatures of brachiopod dominated fossil assemblages from the passagem member middle devonian late early givetian are described in the present study this rock unit originally assigned to the cabecas formation but actually related to the underlying pimenteira formation is restricted to the eastern border of the parnaiba basin it consists mostly of fine grained sandstones with sigmoidal clinoform structures bearing asymptotic cross stratification and climbing ripples and interbedded hummocky cross stratified hcs parallel sided graded sandstone lobes three taphofacies identified and characterized in four outcrops in the municipalities of pimenteiras oiti and rio bangue picos br 316 km 305 and sussuapara barreiro branco state of piaui are based on the qualitative and quantitative analysis of the taphonomic signatures of marine macrofossils and land plant debris their origin is associated with shallow water turbidity currents hyperpycnal flows generated by a flood dominated fluvio deltaic system entering shallow marine settings the taphonomic signatures of taphofacies 1 indicate a proximal environment consistent with distal mouth bar deposits this taphofacies dominated by the brachiopod pleurochonetes comstocki rathbun 1874 comprises sandstones with asymptotic cross stratification and climbing ripples these deposits probably originated from the deceleration of medium density essentially unidirectional turbidity currents basinward of taphofacies 1 taphofacies 2 is considered to have accumulated via the deceleration of low density turbidity currents in which the oscillatory component of the flow prevailed this taphofacies is characterized by delta front sandstone lobes with hcs and is rich in terebratulid brachiopods lastly taphofacies 3 was generated by settlement from the upper part of the hyperpycnal flow charged with fine grained sediments plant debris and mica and deposited as laterally extensive silt sand couplets in more distal and marginal areas of the flow

late paleozoic paleomagnetism of south mongolia exploring relationships between siberia mongolia and north china abstract the tectonic evolution of a large region that includes south siberia mongolia and north china is still a matter of fierce debate this is due at least in part to the contentious proposals detailing the kinematics of the major tectonic units in that area one solution to the problem is the acquisition of better defined paleomagnetic data for the various players in the system we carried out a paleomagnetic study of early carboniferous subduction related volcanic rocks of the trans altai zone in south mongolia and successfully isolated a pre folding and presumably primary component from 22 sites a critical analysis of late paleozoic paleomagnetic data from mongolia revealed several problematic data sets while the paleolatitudes derived from more reliable studies agreed well with the expected values for siberia and were consistently different from those for the north china block we also found that late paleozoic declinations from mongolia are rotated counterclockwise through various angles with respect to siberia in addition those rotations are widespread in both inner mongolia and the north china block in this paper we put forward some testable hypotheses and propose a preliminary paleogeographic scheme of the region 1 consistent difference in late paleozoic paleolatitudes between siberia and mongolia on the one hand and the north china block on the other is largely due to strong inclination shallowing in paleomagnetic data for the latter area where most data are from sedimentary rocks 2 widespread counterclockwise rotations in mongolia inner mongolia and north china may be accounted for by a wide zone of sinistral transpression that was active in the early mesozoic 3 in the early mesozoic the mongol okhotsk ocean was much narrower than is usually assumed 4 there was no large scale oroclinal bending between siberia and north china in the permian early mesozoic

alpha and beta diversity of encrusting foraminifera that recruit to long term experiments along a carbonate platform to slope gradient paleoecological and paleoenvironmental implications abstract the spatial and temporal distribution and diversity of sediment dwelling foraminifera are reasonably well known but encrusting hard substrate dwelling foraminifera are little studied encrusting foraminifera are common in the world s oceans attached to floating debris or marine animals in the water column to living on rocks sand grains and organisms in benthic environments from shallow to deep marine regions with projected ocean acidification and warming conditions these important calcifying protists that comprise beaches buffer sediments and contribute to complex food webs are potentially in peril results indicate that calcifying foraminifera were the first to colonize experimental molluscan substrates within the first year in shallow habitats with colonization offshore in subsequent years agglutinated foraminifera become more common after one year species richness diversity remained relatively similar throughout the study but species turnover diversity was greatest within the first year and between the shelf slope break and deeper water following the thermocline and photic zone regions the equivalent of the shannon entropy index provided important information on diversity and community structure paleobathymetric distributions can be resolved after six years into four distinct foraminiferal distributional zones shallow shelf 15 m outer shelf 33 m shelf slope break 73 88 m and slope depths 213 m to 267 m some encrusting foraminifera are invasive settling in high numbers within the first year and increasing their abundance through the duration of the experiment a foraminiferan discorbis bertheloti was discovered to bioerode carbonate and is a potentially excellent paleobathymetric indicator for 15 33 m depths results differ from previously reported pioneer and climax foraminiferal communities documented for caribbean coral reefs because long term experiments reveal the spatial and temporal development and distribution of carbonate producing encrusting foraminifera in these climatically sensitive regions

palaeomagnetic constraints on the collision and rotation of north and south china the eastern half of china is dominated by the north china block ncb and south china block scb separated by a complex fold system that trends roughly east west interpretation of the geology of this fold belt has led to a variety of estimates of the age of amalgamation of these two blocks1 7 palaeomagnetic results are few and have also been subject to conflicting interpretations8 11 here we present our own palaeomagnetic results for late permian rocks for both the scb and ncb and summarize other relevant palaeomagnetic data by reinterpreting the polarity given in some previous studies we are able to synthesize the results for the widespread emeishan basalts of the scb and to suggest a new model for the collision and relative rotation of the two blocks

ecology of an encrusting fauna on desquamatia atrypida brachiopoda from cedar valley formation givetian devonian of iowa usa abstract encrusting organisms offer a unique window into fossil ecosystems through direct preservation of in situ interactions between host and encrusters and between neighboring encrusters herein we describe a sclerobiont community collected from the solon limestone cedar valley group of robins quarry iowa the atrypide desquamatia independatrypa is frequently encountered in the off reef carbonates and is commonly encrusted by a moderate diversity of bryozoans hederellids auloporid corals and microconchids comparable to other devonian sclerobiont communities this sclerobiont community represents one of few records regarding the paleoecology of devonian sclerobionts in carbonate settings therefore this study fills a key gap in understanding devonian pre extinction ecosystems given the associated increase in siliciclastic environments during the devonian mass extinction in this study larger desquamatia brachiopods were more likely to be encrusted sclerobionts preferred the convex part of the inflated dorsal valve likely representing a larval preference for substrates elevated above the sediment water interface the life status relationship between host and sclerobiont is unknown with rare evidence for either live or dead interactions interactions between sclerobionts were rare sclerobionts were not space limited resulting in a widely distributed low interaction sclerobiont community our results provide an important insight into sclerobiont communities in carbonate environments allowing comparison with other devonian ecosystems as well as providing a reference for comparisons through time

late paleozoic polar wander path for the tarim platform and its tectonic significance abstract stepwise thermal and a f demagnetizations have been carried out on 518 samples 47 sites from the sishichang section across the akesu area in the tarim basin the results lead to a discussion on some problems concerning the tectonic history of the tarim platform and adjacent blocks during the late paleozoic from the late carboniferous until the early permian the tarim platform collided with the kazakhstan block siberian platform and russian platform no large displacements have occurred between these blocks since the mesozoic however the permian pole position of the tarim platform obviously differs from that for the sino korea platform the difference in paleolatitude between the tarim and sino korea platforms in the permian was about 10 their orientations were also different the paleomagnetic result is in contrast to the geologically accepted idea that the two platforms in question occur as a whole in the late paleozoic

direction and intensity of the geomagnetic field in the middle devonian and lower ordovician southern mugodjary ophiolites urals abstract a considerable quantity of petromagnetic and palaeomagnetic measurements in the field has allowed us to obtain reliable palaeomagnetic results for such difficult and complex objects as ophiolites eifelian baked sediments diabases dyke contacts and gabbros and tremadocian baked sediments were studied continuous thermocleaning conglomerate and fold tests were applied the palaeointensity was investigated by means of several palaeomagnetic methods wilson burakov van zijl shaw and bagina petrova the mean intensities of the geomagnetic fields are 7 and 16 5 t with mean palaeomagnetic pole positions of 9 n 134 e and 6 s 83 e respectively these data demonstrate that southern urals mugodgary was located near the northern margin of the east european plate during ordovician devonian time the allochthonous crustal oceanic plate was thrust upon the edge of the plate and deformed as late as the permian changes in the polarity of the geomagnetic field are recorded in the succession of sheeted dykes a direct corroboration of the vine mathews hypothesis

paleozoic brachiopod symbioses testing the limits of modern analogues in paleoecology paleoecologic interpretations involving symbiotic interactions begin with a determination that the partners were simultaneously alive criteria for recognizing live live interactions among benthic suspension feeders include 1 preferred locations of symbionts on encrusting or in boring or embedding the host 2 preferred orientations of elongate symbionts or clustering of symbiont apertures and feeding structures in relation to host induced currents and 3 growth abnormalities and or distortions of the host the symbiont or both interpretations of the nutritional aspects of ancient symbioses involve establishment of feeding locations and methods and the diets of holocene descendants however use of living analogues and hence their value in paleoecology commonly invoke the unwarranted assumption that the host symbiont interaction and the foods available to the partners have not evolved in concert with their skeletons these nutritional uncertainties are compounded further in symbioses involving fossils of unknown biological affinities or taxa that have evolved by different rules analyses of paleozoic brachiopod symbioses spanning the gamut from symbionts of undoubted ancestor descendent relations e g spirorbis to trace fossils e g trypanites exemplify these nutritional uncertainties most of these symbionts suggest that in life spiriferaceans were attached to the substrate by a thick short pedicle and that the hinge line and or umbo of the brachial valve acted as a fulcrum to elevate the commissure into the water column for efficient suspension feeding conversely the same symbionts provide equivocal results when used to infer the circulation pattern of spiriferacean mantle cavity currents these analyses also exemplify the great limitations of uniformitarian concepts in evolving biological systems

palaeomagnetic and structural constraints on 90 anticlockwise rotation in sw mongolia during the permo triassic implications for altaid oroclinal bending preliminary palaeomagnetic results abstract new and published paleomagnetic measurements from trans altai and south gobi zones in south mongolia document large tectonic motions in between late carboniferous and triassic magnetic inclinations confirm equatorial position of south mongolian terranes in late carboniferous permian times the evolution of magnetic declinations indicates 90 anticlockwise rotation in between latest carboniferous and early triassic of all studied tectonic units around the eulerian pole located close to axis of mongolian orocline the anticlockwise rotation continues in triassic being accompanied by a major drift to the north the structural and published geochronological data suggest carboniferous e w shortening of the whole region resulting in n s trend of all continental and oceanic geological units followed by orthogonal n s shortening during late permian to early jurassic both paleomagnetic and geological data converge in a tectonic model of oroclinal bending of mongolian ribbon continent westerly back arc oceanic domain and mongol okhotsk subduction zone to the east the oroclinal bending model is consistent with the coincidence of the eulerian pole of rotation with the structural axis of mongolian orocline in addition the mesozoic collisional tectonics is reflected by late remagnetizations due to formation of wide deformation fronts and hydrothermal activity

ocean quahogs arctica islandica and atlantic surfclams spisula solidissima on the mid atlantic bight continental shelf and georges bank the death assemblage as a recorder of climate change and the reorganization of the continental shelf benthos abstract the degree to which evidence of range shifts in shelf biomass dominants atlantic surfclams and ocean quahogs as a function of climate change is examined by comparing the dissimilarity in distribution of the living community and the record of habitation ensconced in the death assemblage comparison of the distribution of live animals and dead shells reveals for both species that live animals are rarely found where dead shells were not collected but dead shells were collected at a substantively larger number of sites than where live animals were found the geographic footprint resolved by the dead shells was much broader than that of live animals extensive spatially coherent regions exist inshore and offshore of the present day habitat of occupation where evidence of previous occupation exists sites where ocean quahog shells were found without live ocean quahogs included a portion of the continental shelf inshore of the present day habitable range an area only habitable under colder climatic conditions than observed today surfclam shells were found offshore of the present day habitable region in deeper water additional warming of bottom waters offshore would be necessary for surfclams to occupy the region now occupied solely by dead shells the death assemblage shows that these biomass dominants have repositioned themselves across the continental shelf during the past and this repositioning certainly is driven by changes in bottom water temperature moreover the distribution of surfclam shells indicates that the death assemblage may provide a possible window into the future as movement of the present day population is towards these deeper water previously occupied regions overall the death assemblage may provide an important source of information on range shifts sparing the need to carry out extensive and frequent benthic surveys and may permit reconstruction of ongoing shifts in community composition as a product of climate change when adequate survey data are not available

diverse sclerozoan assemblages encrusting large bivalve shells from the callovian middle jurassic of southern poland a diverse sclerozoan assemblages consisting of both encrusting and boring biota are described from the large limid bivalves ctenostreon from the callovian hardground setting of zalas in southern poland at least 27 encrusting and seven bioerosion taxa are reported here which makes this assemblage not only one of the most diverse in the middle jurassic but the richest in encrusting taxa from the callovian the encrusters consist of cryptic biota of which sedentary polychaetes and cyclostome bryozoans dominate with respect to both species number and abundance the bioerosion traces are dominated by tiny pits referred to the ichnogenus oichnus probably made by some soft bodied biota in the present case followed by the borings of acrothoracican barnacles rogerella the first colonizers of the bivalve shells probably were borers as they only occur in the host shells the encrusting pioneers presumably were oysters and oyster like bivalves followed by opportunistic serpulid sabellid polychaetes and cyclostome bryozoans the last colonizers were calcisponges and thecideide brachiopods in comparison to the only known late callovian shallow and reef associated tropical sclerozoans of israel the assemblage from the open marine deeper setting of poland is much richer in encrusting taxa such a surprising high encruster diversity in the marine northern paleo latitude may have resulted from the deeper and calmer environment with a both reduced sedimentation rate and algal cover and without any significant salinity changes the factors that are thought to have impacted the tropical and shallow marine sclerozoans from israel

the temporal resolution of epibiont assemblages are they ecological snapshots or overexposures abstract the effects of time averaging on the fossil record of soft substrate marine faunas have been investigated in great detail but the temporal resolution of epibiont assemblages has been inferred only from limited duration deployment experiments individually dated shells provide insight into the temporal resolution of epibiont assemblages and the taphonomic history of their hosts over decades to centuries epibiont abundance and richness were evaluated for 86 dated valves of the rhynchonelliform brachiopod bouchardia rosea collected from the inner shelf maximum abundance occurred on shells less than 400 yr old and maximum diversity was attained within a century taphonomic evidence does not support models of live host colonization net accumulation or erasure of epibionts over time encrustation appears to have occurred during a brief interval between host death and burial with no evidence of significant recolonization of exhumed shells epibiont assemblages of individually dated shells preserv

palaeomagnetism and palaeogeography of mongolia in the cretaceous permian and carboniferous preliminary data abstract the paper reports on the results of palaeomagnetic stability tests of oriented samples of lithologically different types of cretaceous permian and carboniferous rocks from northern and southern mongolia the permian andesites and tuffites from three localities barun buren tel tin gol and chulut tsagan del have yielded interesting results groups of normally and reversely polarized andesite tuffs were found even within a single outcrop by means of thermal field demagnetization and multicomponent analysis of the magnetization with a view to the number of samples 177 suitable for analysis and the number of localities 9 the reported palaeomagnetic data should be considered as preliminary the interpreted results indicate a different palaeogeographic evolution of northern and southern mongolia relative to the siberian platform and north china in the permian and carboniferous on the other hand similar apparent polar wander paths for north china lin et al 1985 and the studied regions of northern and southern mongolia indicate similar palaeogeographic evolution in the permian to carboniferous

taphonomy of holocene cryptic biotas from st croix virgin islands information loss and preservational biases surveys of submarine caves and overhanging ledges from st croix virgin islands provide new insights into the preservational processes active therein and into the taphonomy of ancient counterparts comparisons of preservable skeletonized versus nonpreservable unskeletonized components of these modern cryptic communities indicate that there is significant information loss in areals coverage taxonomic richness and diversity of fossilized examples quantitative estimates of such losses have been made in addition skeletal differences between early and late stage successional groups suggest biased representation of the former in the geologic record nonpreservable later colonizers may further erase the record of skeletonized forms through destructive life processes such forms of taphonomic information loss are probable in ancient counterparts and must be considered in accurate reconstruction of cryptic paleocommunities

belemnite taphonomy upper jurassic western tethys part i biostratinomy abstract a detailed taphonomic analysis was performed on 188 belemnites and 56 thin sections from the pozo canada section external prebetic as well as 101 belemnites and 31 thin sections from the rio segura internal prebetic both from the upper oxfordian lower kimmeridgian this manuscript is focused on biostratinomic features and a second part is focused on fossildiagenetic aspects the belemnites correspond to hibolithes and less commonly belemnopsis biostratinomic features including size fragmentation corrasion microboring and encrustation were analysed in each specimen using petrographic conventional cathodoluminescence epifluorescence and scanning electron microscopy techniques fragmentation affects the phragmocone and the rostrum cavum and is usually transversal and rarely longitudinal through the apical line isolated fragments of epirostrum are common corrasion produces irregular surfaces microborings are very common represented by a fungal hyphae b fascichnus dactilus like and scolecia filosa like borings cyanobacteria c entobia sponges d large microborings with y shaped branching diameter 100 500 m subparallel to rostrum surface e large cylindrical to ellipsoidal borings related to cirripeds and f palaeconchocelis starmachii rhodophyte microbes and sessile foraminifera vinelloidea bullopora tolypammina thurammina placopsilina and subdelloidina are the main encrusters microbial films are composed of dense micrite or clotted peloidal microfabrics the biostratinomic features analysed in the belemnite rostra are clearly influenced by the lithofacies and shelf setting the intensity of corrasion microborings and encrustation by indicating time exposure help establish which lithofacies shows the highest sedimentation rate the belemnites from internal prebetic lithofacies that is the outer shelf deposits lumpy limestone and lumpy oncolitic limestone present high values of corrasion microboring and encrustation thereby indicating long time exposure in sharp contrast belemnites from the lithofacies of the external prebetic represent deposition in mid shelf environments spongiolithic limestone spongiolithic marl peloidal limestone and marl limestone rhythmite featuring higher clay content

gradients and patterns of sclerobionts on experimentally deployed bivalve shells synopsis of bathymetric and temporal trends on a decadal time scale bivalve shells deployed experimentally in a variety of environments of deposition eods and over a wide range of depths from 15 to 570 m in the bahamas and gulf of mexico were assessed for encrusting and endolithic bionts sclerobionts sensu taylor and wilson 2002 that accumulated over 1 2 8 and 12 13 year intervals data include percent coverage and when possible identification to generic or species level taxonomic categories data were binned into two further categories based on guilds and whether or not sclerobionts were judged to be preservable each study site shows substantial variability in both percent coverage and species richness composition which we attribute to partial burial of different individuals or parts of arrays average values of taxonomic richness guild number and percent coverage for a given eod represent a combination of exposed and buried shells as would be typical of a time averaged fossil assemblage maximally covered shells give the potential coverage for each site in both study areas there are characteristic patterns in terms of overall percentage of shells covered by sclerobionts numbers and extent of coverage by different guilds as well as by different taxa for most eods there is a progressive though non linear increase in both species richness and areal coverage through the twelve years exceptions are in the 30 m site in the bahamas and parker bank and flower garden sites in the gulf of mexico which show a significant decline in areal coverage though not in richness this effect may result from differences in sediment cover over time these sites showed a tendency to have many or all experimental bags completely sediment covered in the later sampling cluster analysis and non metric multidimensional scaling nmds of various shell substrate species at all eods from the bahamas and gulf of mexico reveal discrete groupings that are related to both depth light gradient and other factors such as variations in sedimentation and salinity similar numbers of guilds are found at various eods although the specific guild types represented differ in general highest average richness values are recorded for carbonate 70 90 m wall and deep reef sites 69 to 70 taxa and lowest are for the efg brine pool no sclerobionts other than bacterial films after 12 13 years and deeper dysphotic to subphotic sites max values 25 taxa surprisingly shallow water sites 30 m yield only moderate diversities of 40 50 taxa this results in part from the fact that certain encrusters especially the foraminifer gypsina and coralline algae tend to overgrow others and dominate space in addition to burial effects certain taxa notably the serpulid pseudovermilia are ubiquitous while other taxa e g larger foraminifera vermetid gastropods and many bryozoans are largely restricted to shallower depths a combination of species richness average coverage and key taxa permits discrimination of groups of eods and potentially in tandem with other evidence of depth gradients

dead delta s former productivity two trillion shells at the mouth of the colorado river the diversion of the colorado river by dams and irrigation projects started in the 1930s triggered the collapse of the colorado delta ecosystem paleontological ecological geochronological stable isotope field and satellite image data provide estimates of the delta s benthic productivity during the 1 k y directly preceding the artificial shutdown of the river at least 2 1012 shells of bivalve mollusks make up the current beaches and islands of the delta the 125 individual valves dated using 14c calibrated amino acid racemization indicate that these shells range in age from a d 950 to 1950 seasonal intrashell cycles in 180 values indicate that average sized bivalves lived at least 3 yr the most conservative calculation based on these numbers indicates that during the time of natural river flow an average standing population of 6 109 bivalve mollusks population density 50 m2 thrived on the delta in contrast the present abundance of shelly benthic macroinvertebrates is 94 lower 3 m2 in 1999 2000 the dramatic decrease in abundance testifies to the severe loss of benthic productivity resulting from diversion of the river s flow and the inadequacy of its partial resumption 1981 to present an integration of paleontological records with geomorphological geochemical and geochronological data can provide quantitative insights into human impact on coastal ecosystems

new paleomagnetic results from northern china collision and suturing with siberia and kazakhstan abstract we report new results from our paleomagnetic studies of the inner mongolia autonomous region in northeastern china and the xinjiang autonomous region in northwestern china primary magnetizations are isolated in tertiary cretaceous late jurassic and late permian rocks and secondary components of magnetization of late jurassic and recent ages are seen in strata of inner mongolia western junggar basin and part of the tarim block suffered widespread complete tectono thermal remagnetization at about 280 ma permian the paleomagnetic evidence suggests that the sampled areas in inner mongolia have been part of the north china block at least since late permian time and the junggar block collided with the tarim block by late permian time our own paleomagnetic results together with available data from other parts of eastern eurasia suggest a tectonic model in which kazakhstan europe and siberia collided with each other and formed the europe siberia kazakhstan plate eur sib kaz in late permian time to the east mongolia outer mongolia inner mongolia and the north china block were also wedged together forming the mongolia north china plate mon nc by this time these two composite continental plates were not a stable unit in the late permian the geometrical relationship of the paleomagnetic poles for these two plates suggests that collision initially occurred in the late permian near the western end 50 n 75 e of the southern siberian fold belt and progressed eastward as the mon nc plate rotated and clockwise about 117 relative to the eur sib kaz plate during the early mesozoic suturing and rotation were probably complete by the late jurassic significant relative motion between the tarim and siberia blocks continued from early triassic to late jurassic as tarim moved northeastward 1400 km relative to siberia

an apparent polar wander path from the tarim block china abstract the apparent polar wander apw path from the tarim block consists of devonian 16 n 165 e a95 4 late carboniferous 41 n 160 e a95 4 permian 61 n 177 e a95 9 early triassic 69 n 183 e a95 11 and jurassic cretaceous 65 n 214 e a95 6 poles on the basis of this apw path we conclude that tarim rode on a plate subducting under the kazakhstan plate between devonian and permian times by the end of the permian subduction had almost finished early triassic poles from tarim siberia north china and south china are discordant indicating post early triassic relative motions among them cretaceous paleomagnetic poles from tarim north china and south china however are consistent suggesting that china has been a coherent tectonic unit since cretaceous time the shape of the apw path from tarim is similar to that of siberia except that tarim s apw path is systematically displaced to the east a 26 clockwise rotation of tarim s apw path about the euler pole 60 n and 14 e reconciles these two apw paths tarim has moved northeastward some 2000 km relative to a fixed siberia since the cretaceous this northeastward motion of tarim with respect to siberia agrees well with the overall cenozoic tectonic style of asia most of southern china has been pushed eastward to give way to the penetrating indian continent east west and northeast trending left lateral strike slip faults north of the tarim block have been documented however the exact amounts of displacement along these faults are not well known using paleomagnetic data from tarim we will also discuss the tectonic evolution of terranes in central asia and the amount of continental shortening in the tibetan plateau

towards defining a baseline status of scarce groundwater resources in anticipation of hydraulic fracturing in the eastern cape karoo south africa salinity aquifer yields and groundwater levels

magnetotelluric image linked to surface geology across the cape fold belt south africa terra nova 24 207 212 2012 abstract the subsurface structure of the cape fold belt cfb that traverses southern africa remains largely unknown because it lacks deep penetrating high resolution geophysics this hampers studies from local scale exploration for important resources such as water to continental scale modelling such as gondwana reconstructions our magnetotelluric mt soundings across the cfb provide a high resolution crustal scale electrical conductivity image inversion models of these data correlate well with surface geology and resolve deep resistive roots of the cfb s regional palaeozoic quartzite ridges swartberg and outeniqua mountains and thin tectonic wedges of proterozoic rocks of higher resistivity kango and kaaimans inliers separated by 2 3 km of cretaceous sediments in asymmetric intermontaine basins one of these basins the oudtshoorn basin is flanked by a listric normal fault rooted in an upper crustal detachment zone and is underlain by a massive conductivity anomaly that is likely to be a major saline water reservoir

preliminary phanerozoic polar wander paths for the north and south china blocks polar wander paths for the north and south china blocks suggest that 1 both were parts of gondwana in the palaeozoic 2 the north china block accreted to siberia in the late permian and 3 the south china block accreted to the north china block in the middle triassic to the early jurassic comparison of the polar wander path for the south china block with that for northern eurasia suggests that relative motion of over 4 000 km has occurred between them

magnetism of south mongolian middle paleozoic ophiolites abstract this paper presents new paleomagnetic data from south mongolia middle paleozoic rocks were studied from three different tectonic zones within the south mongolian fold belt from north to south these are the gobi altai zone in terms of paleotectonic position the north shelf of the paleobasin the trans altai zone ophiolite complexes and the south gobia zone the south shelf several paleomagnetic field tests including conglomerate baked contact and fold tests were carried out to determine magnetic stability in addition principal component analysis of the stepwise thermal demagnetization data was used the ophiolites are characterized by three ancient components one magnetic component is pre folding and directed to the south with a very gentle inclination declination d 180 210 inclination i 6 2 k 120 two post folding magnetic components were observed also the first post folding magnetic component has d 282 4 i 36 4 k 30 3 and the second has d 318 6 i 33 0 k 60 5 the final magnetic component is very close to the permian paleomagnetic direction expected from the north china platform the first post folding component of magnetization may have been acquired during the variscan accretion in early carboniferous time when the basin was closed the south mongolian paleo ocean was located in equatorial latitudes near the tarim block the south china platform and probably the north china platform in the devonian

late paleozoic early mesozoic geodynamics of central asia abstract correlation and synthesis of published and new structural paleomagnetic and geochronological data from central asia show the important role of strike slip faulting in their evolution the pattern of major strike slip faults outlines a terrane collage produced by a late devonian early carboniferous collision of the gondwana derived altai mongolia tuva composite microcontinent with siberia and a late carboniferous permian collision of east europe and kazakhstan with siberia the accreted continental margins were cut by strike slip faults and conjugate thrusts into numerous terranes which mixed with one another and disturbed the previous structural and facies framework those complex and multi stage deformations resulted from the late devonian early carboniferous collision of gondwana derived terranes the deformations reached their peak in the late carboniferous permian due to the collision of the kazakhstan east european baltica and siberian continents a system of sinistral strike slip faults formed a mosaic block structure of central asia along the margin of the siberian continent as a result of the late carboniferous permian collision this resulted in the formation of the northern eurasia continent early mesozoic strike slip faulting and conjugate thrusting resulted from the rotation of the siberian and east european cratons

paleomagnetism of the upper proterozoic and devonian rocks from the klodzko metamorphic complex in the west sudetes sw poland tectonic implications for the variscan belt of central europe abstract the klodzko metamorphic complex kmc consists of upper proterozoic metaigneous and metasedimentary rocks forming a stack pile thrusted over the givetian and overlain by frasnian fammenian sediments magnetomineralogical experiments show that the magnetic minerals are secondary the paleomagnetic experiments identified three components of the natural remanent magnetization labeled a1 a2 and m the mean pole positions calculated in situ correspond with the baltica upper devonian a1 plats 18 plonge 317 permo carboniferous a2 plats 39 plonge 2 and triassic jurassic m plats 60 c plonge 308 segments of the apparent polar wander path apwp for baltica this indicates that the region studied was situated close to the baltica plate at least since the upper devonian and was not folded after this period