fluviokarst and classical karst examples from the dinarics krk island northern adriatic croatia abstract in order to contribute to the debate on the role of fluvial erosion in the shaping of karst two nearby areas with different karstic landscapes were compared areas a and b are located relatively close to each other on the southern side of the krk island adriatic sea croatia both areas are composed of similar limestone with a very high caco 3 content area a is a typical doline or polygonal type classical of karst with numerous dolines up to 57 km 2 covered with terra rossa red soil and mediterranean maquis shrubland dolines are located in zones which correspond to the strike of the main geological structures dry karstic valleys are visible only on gently inclined coastal slopes bordering the karstic plateau in contrast area b is typical of a bare karst landscape with a strong palaeo fluvial imprint the dolines are absent and the bedrock is only sporadically covered with terra rossa palaeogene marls have been observed in a few elongated depressions and in the coastal zone of area b along steep coastal slopes valleys up to 460 m km 2 are cut into the carbonates the traces of episodic surface flows are visible in some of these valleys in contrast to the valleys in area a remnants of a disrupted ancient fluvial network are clearly visible on the elevated karstic plateau in area b differences in the recent morphology are attributed mainly to varying thicknesses of the palaeogene impermeable marly cover and the intensity of tectonics in the two areas

characterization of karst hazards from the perspective of the doline triangle using gpr examples from central ebro basin spain ground penetrating radar gpr is a widespread technique to locate and characterise karst hazards cavities and paleocollapses in this paper we show that the internal structure of sediments obtained from gpr surveys can also be used as an indicator of active karst processes a classification of karst hazard problems by means of gpr in the gpr doline triangle is proposed with three end members cavities evidences of subsidence and paleocollapses these end members show particular signatures in the gpr profiles the field examples shown in this paper indicate that gpr survey is a geophysical technique that offers a very high resolution and provides structural and sedimentological information of the subsoil the use of grid maps elaborated from gpr data is an efficient way to determine anomalous sectors lateral changes of electromagnetic properties different reflectivity and qualitative penetration depth variations or velocity wave propagation changes their relationships with the structural features obtained from gpr profiles on lap geometries zones with depressed reflectors folded reflectors or laterally abrupt structural limits can be used as indicators of karstic processes

polydiapirism of the archean mount edgar batholith pilbara block western australia structural analysis of the mount edgar batholith and the enveloping greenstone belt indicates that the batholith and rocks around its margin were subjected to similar deformation events that involved progressive and stepwise diapiric uplift of the batholith these events may be correlated on the basis of fold style orientation and fabric development early recumbent to reclined structures d1 including thrusts were buckled d2 by rounded upright folds prior to shearing d4 along normal faults parallel with the batholith margin d4 deformation was responsible for uplifting the batholith to its present structural position a deep seated linear deformation zone d3 within the batholith did not affect the supracrustal belt syntectonic granite intrusion amphibolite facies metamorphism and migmatisation were associated with d1 in the batholith whereas greenschist facies metamorphism was associated with d1 in the lowermost unit of the greenstone belt the talga talga subgroup amphibolite facies conditions were maintained within the batholith throughout the structural history but this grade was reached in the supracrustal belt only near the batholith margin progressive deformation d1 d2 and metamorphism occurred in response to early massive granite generation and emplacement producing a first order plutonic dome that reached full maturity during d2 solid state diapirism d4 followed producing a gneiss dome of similar dimension restriction of early recumbent folds and thrusts in the supracrustal belt to areas within or adjacent to the batholith is consistent with the model elsewhere deformation is minor the late stage diapirism brought a gneiss complex within the batholith into juxtaposition with lowermost greenschist facies rocks of the pilbara supergroup this complex represents in part sialic material that existed below the pilbara supergroup before diapirism began the complex closely resembles other archean high grade gneiss terranes which suggests that some of these terranes are deeper crustal exposures of granite greenstone terranes

pitfalls in gpr data interpretation differentiating stratigraphy and buried objects from periodic antenna and target effects periodic events in ground penetrating radar gpr data may result from antenna and target effects rather than reflections from geologic features one of the most common pitfalls in gpr data interpretation is to identify each event on a radar cross section as scattering from a discrete horizon without considering other possible sources of these events soil electrical properties and surface roughness affect ground penetrating radar antenna radiation and waveform characteristics an impedance mismatch occurs over soils with electrical properties different than those for which the antennas were designed to perform optimally over and results in periodic ring down which can be misinterpreted as stratigraphy or multiple reflections in addition target resonance can introduce additional periodic features that can lead to misinterpretation in regards to the number of targets present co pole and cross pole antenna configurations can be combined with polarization dependent scattering characteristics of subsurface objects to recognize and reduce antenna ring down for improved imaging and interpretation

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

the age and origin of younger granitic plutons of the shaw batholith in the archaean pilbara block western australia the whole rock pb pb method has been used to date four of the younger mainly adamellite late tectonic plutonic phases within the ca 3 5 ga shaw batholith of the archaean east pilbara block three suites give ages within error of 2966 ma porphyritic granites at 2948 50 ma leuco adamellites at 2943 46 ma and garden creek adamellite at 3007 48 ma the post tectonic cooglegong adamellite gives an age of 2847 34 ma the sm nd model isotopic systematics of all four suites indicate derivation from crust ranging between ca 3200 and 3600 ma in age the sources for these four younger plutonic phases were heterogeneous and although exhibiting some isotopic characteristics of the older 3 5 3 3 ga calc alkali plutonic suites were more depleted in the lil elements rb u and th in addition the garden creek adamellite and the cooglegong adamellite lack the very fractionated and hree depleted ree patterns characteristic of both the older calc alkali plutonic rocks and the porphyritic granites and leuco adamellites the crust underlying the shaw batholith at ca 2950 ma must have been both markedly heterogeneous and variably depleted a conclusion consistent with the complex tectonic and plutonic evolution of this region

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

constraints on the age of the warrawoona group eastern pilbara block western australia abstract zircons from mafic and felsic volcanic rocks in the type area of the warrawoona group the basal archaean greenstone succession of the eastern pilbara block have been dated precisely using the ion microprobe shrimp the results allow two alternative time frames for the duration of the warrawoona group dependent on how the dated zircons are considered to relate to the volcanic rocks our favoured interpretation requires a hiatus of 135 5 ma between the duffer formation at 3 46 ga and the overlying felsic volcanic rocks of the wyman formation and a hydrothermal or later magmatic origin for zircons of age 3 33 ga within one duffer formation sample and the underlying metabasalts the alternative time frame requires a short time for deposition of the entire group less than 15 ma at 3 33 ga and a xenocrystic origin for the 3 46 ga zircons of the duffer formation outside the type area of the warrawoona group the age of an intrusive granodiorite requires that greenstones be older than 3 43 ga and the group formed over an interval of 120 ma visibly different zircons within one of the duffer formation samples were found to be palaeozoic in age and presumably constitute hydrothermal growth of new zircon within the rock at low temperature similar zircons were found within samples from other rock units but with a spread of proterozoic ages

characterization of the porosity distribution in the upper part of the karst biscayne aquifer using common offset ground penetrating radar everglades national park florida summary the karst biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity and hydraulic conductivity making conceptualization difficult the biscayne aquifer is the primary source of drinking water for millions of people in south florida thus information concerning the distribution of karst features that concentrate the groundwater flow and affect contaminant transport is critical the principal purpose of the study was to investigate the ability of two dimensional ground penetrating radar gpr to rapidly characterize porosity variability in the karst biscayne aquifer in south florida an 800 m long gpr transect of a previously investigated area at the long pine key nature trail in everglades national park collected in fast acquisition common offset mode shows hundreds of diffraction hyperbolae the distribution of diffraction hyperbolae was used to estimate electromagnetic em wave velocity at each diffraction location and to assess both horizontal and vertical changes in velocity within the transect a petrophysical model complex refractive index model or crim was used to estimate total bulk porosity a set of common midpoint surveys at selected locations distributed along the common offset transect also were collected for comparison with the common offsets and were used to constrain one dimensional 1 d distributions of porosity with depth porosity values for the saturated miami limestone ranged between 25 and 41 for common offset gpr surveys and between 23 and 39 for common midpoint gpr surveys laboratory measurements of porosity in five whole core samples from the saturated part of the aquifer in the study area ranged between 7 1 and 41 8 gpr estimates of porosity were found to be valid only under saturated conditions other limitations are related to the vertical resolution of the gpr signal and the volume of the material considered by the measurement methodology overall good correspondence between gpr estimates and the direct porosity values from the whole core samples confirms the ability of gpr common offset surveys to provide rapid characterization of porosity variability in the biscayne aquifer the common offset survey method has several advantages 1 improved time efficiency in comparison to other gpr acquisition modes such as common midpoints and 2 enhanced lateral continuity of porosity estimates particularly when compared to porosity measurements on 1 d samples such as rock cores the results also support the presence of areas of low em wave velocity or high porosity under saturated conditions causing velocity pull down areas and apparent sag features in the reflection record this study shows that gpr can be a useful tool for improving understanding of the petrophysical properties of highly heterogeneous systems such as karst aquifers and thus may assist with the development of more accurate groundwater flow models such as those used for restoration efforts in the everglades

cave detection in limestone using ground penetrating radar ground penetrating radar gpr is becoming a more common component of the standard array of geophysical techniques that are used by archaeologists in this paper we report on the use of gpr to survey an area of archaeologically important karst topography at kitley caves in devon u k we describe the use of gpr to detect voids within a limestone outcrop as an aid to locating cave systems which might contain sediments suitable for excavation the performance of the gpr equipment is analysed and the results compared to those obtained with an electrical resistance survey carried out at the same location in particular the depth of penetration of the gpr is estimated and we report discernible echo signals from a much greater depth than is usually reported in archaeological applications of gpr

a 3500 ma plutonic and volcanic calc alkaline province in the archaean east pilbara block variably foliated predominantly granodioritic plutonic rocks from the northern part of the shaw batholith in the east pilbara archaean craton are dated at 3 499 22 ma 2 errors by a whole rock pb pb isochron these rocks intrude the surrounding greenstone sequence and their age is indistinguishable from that sequence high strain grey gneisses which occupy much of the western and southern shaw batholith are chemically and isotopically similar to the north shaw suite and are inferred to have been derived from this suite by tectonic processes felsic volcanics within the greenstones together with a major portion of the granitic batholiths apparently formed in a calc alkaline volcanic and plutonic province at 3 500 ma this volcanic and plutonic suite is similar to modern calc alkaline suites on the basis of major element rare earh element and most other trace element contents the archaean suite contrasts with modern equivalents only in having lower concentrations of hree and higher concentrations of ni and cr

evaluating the structure characteristics of epikarst at a typical peak cluster depression in guizhou plateau area using ground penetrating radar attributes abstract epikarst defined as the skin of karst environment is widely developed in southwest china largely as a result of the subtropical monsoon climate typical sw china karst accommodates a dual hydrogeological structure with surface and subsurface hydrological systems the epikarst ecosystem of karst environments plays a key role in biogeochemical cycling and energy and material storage and transport due to low rates of soil formation derived from carbonate rock weathering the soil layer is shallow and scattered presenting interlocked features within carbonate rock research on epikarst structure is primarily based on section field survey with semi quantitative characterization often lacking a fully quantitative description of soil rock structural characteristics we utilized ground penetrating radar gpr attributes to interpret the structure of epikarst at a peak cluster depression in the guizhou karst plateau two typical types of epikarst slope profiles and one peak cluster depression in maguan town puding county were selected for study we used mala gpr equipment with 500 mhz and 50 mhz antennas to acquire data gpr data was processed conventionally and then average energy attributes average amplitude attributes and coherence attributes were extracted to interpret the structure of the two epikarst profiles and the soil depth of the depression the results show that i energy and coherence attributes can highlight the soil rock structure of the epikarst profiles with relative ease ii compared to the original returned image the energy attributes visualise the soil and rock medium more effectively and iii the coherence attributes can identify the reflection interface between complete bedrock and bedrock containing fissure and grikes epikarst in addition using the 50 mhz antenna we were able to determine the soil depth in depression with coherence attributes indicating a depth of 3 6 m very close to the real depth 3 58 m measured by our auger verification work gpr attributes provide evidence that the epikarst has developed a large number of fissures filled with soil or other materials but that the bedrock under the epikarst has few fractures gpr attributes are therefore helpful for increasing our confidence of studying the structure of slope epikarst structure and depression soil depth

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

reconstructing the internal structure and long term evolution of hazardous sinkholes combining trenching electrical resistivity imaging eri and ground penetrating radar gpr abstract the approaches aimed at characterising specific damaging sinkholes have received limited attention compared with other ground instability phenomena e g landslides moreover the practicality of the trenching technique in combination with numerical dating and retro deformation analysis for sinkhole site investigations has been barely explored this work illustrates the advantages of combining geomorphic mapping electrical resistivity imaging eri ground penetrating radar gpr and trenching for sinkhole characterisation and shows how the trenching technique contributes to fill significant gaps that neither geomorphic nor geophysical methods can address two large sinkholes 200 m long related to the interstratal karstification of evaporites and generated by contrasting subsidence mechanisms sagging collapse were investigated in the fluvia valley ne spain although gpr data may provide high resolution information on subsidence related stratigraphic and structural features at shallow depth the profiles acquired in the investigated sites with 100 mhz shielded and 40 mhz unshielded antennae provided limited insight into the internal geometry of the sinkholes due to reduced signal penetration related to the presence of conductive clayey material the eri sections satisfactorily imaged the general geometry of the sagging and collapse subsidence structures up to depths higher than 100 m and clearly captured the basal contact of the low resistivity sinkhole fill in the sections with adequate layout and resolution the trenches despite their limited depth ca 5 m allowed us to obtain valuable objective information on several key aspects of the subsidence phenomenon 1 mechanisms deformation style and kinematics progressive versus episodic 2 limits of ground deformation 3 temporal evolution expansion versus contraction 4 chronology and timing of most recent deformation phase 5 rates of subsidence and sedimentation and 6 the role played by subsidence in the development of lacustrine environments and the associated sedimentation patterns

evaluation of trenching ground penetrating radar gpr and electrical resistivity tomography ert for sinkhole characterization this paper explores the suitability and advantages of combining the trenching technique with geophysical surveys ground penetrating radar gpr and electrical resistivity tomography ert for sinkhole characterization in a mantled karst area the approach is applied to two active sinkholes concealed by anthropogenic deposits and formed by contrasting subsidence mechanisms collapse and sagging the ert section acquired across the collapse sinkhole images the clayey fill of the depression as an obvious low resistivity area showing the approximate location of the sinkhole edges spatially dense gpr surveys provide information on the position of the boundaries of the concealed subsidence structures and their three dimensional 3d internal geometry revealing the dominant subsidence mechanism we illustrate the impact of several factors on the quality of the gpr data such as sinkhole size nominal frequency of the antennas antenna shielding and the presence of backfilled excavations and above surface objects trenches provided detailed information on the subsurface structure of the sinkhole subsidence magnitude partitioning of the strain and the position of the sinkhole edges especially when they are deep enough and excavated across the central sector and perpendicular to the boundaries the stratigraphic and structural relationships observed in the trench were then used to infer the spatial evolution of the sinkholes e g enlargement their kinematic behavior episodic versus progressive and to differentiate discrete subsidence events and their associated magnitude numerical dates were used to estimate average subsidence rates and the recurrence of subsidence events such integrated data sets may be used as an objective basis to forecast the future behavior of potentially damaging sinkholes and to assess the associated hazard and risk copyright 2013 john wiley sons ltd

karst geosites at risk of collapse the sinkholes at nociglia apulia se italy this paper focuses on the impacts of contemporary geomorphological processes on fruition activities in a karst area of salento apulia southeastern italy the work illustrates the results of studies in a sinkhole field at nociglia in the lecce province recently recognized as a geosite and where shallow phreatic speleogenesis operates close to the water table level with the formation of karst caves successive roof collapse formation of wide caverns and sinkhole development at the surface all these features threaten the nearby infrastructures including a province road salento has a great number of active sinkholes related to natural and anthropogenic cavities their presence is at the origin of several problems in the built up environment due to increasing population growth and development pressures in such a context the detection of cavities and the assessment of sinkhole hazards present numerous difficulties to assess the potential danger from sinkholes it is important to identify and monitor the main factors contributing to the formation process a multi disciplinary approach comprising geological geomorphological and geophysical analyses is necessary to obtain a comprehensive knowledge of these complex phenomena in karst areas geophysical methods can be of great help to monitor the processes and for identifying and mapping features related to the underground voids by detecting contrasts in physical properties such as density and electrical resistivity with the surrounding sediments at the same time recognition of the presence of sinkholes by geophysical methods has to adapt to the local geological conditions and take advantage of the integration of the several methodologies available the territory of nociglia demonstrates that monitoring is essential for the safe exploitation of these type of geomorphosites

orogenic evolution of the external dinarides in the ne adriatic region a model constrained by tectonostratigraphy of upper cretaceous to paleogene carbonates abstract mesozoic to cenozoic evolution of the central part of the adriatic plate external dinarides and adriatic foreland is still a matter of debate this is expressed by opposing paleogeographic models single carbonate platform adriatic or adriatic dinaridic versus two carbonate platforms adriatic and dinaridic separated by the inter platform budva cukali basin estimates of shortening during adria ne subduction that resulted in the development of the dinaric alps differ substantially the single platform model involves minor shortening achieved by folding and faulting along steep reverse faults the two platform model involves significant shortening achieved mainly by thrust stacking which resulted in almost complete underthrusting of the intervening basinal deposits analysis of upper cretaceous to paleogene stratigraphical data from both outcrops and boreholes allows regional correlation and the interpretation of major lithostratigraphic units as a result a few tectonostratigraphic units are recognized the tectonostratigraphy is used as a basis for a new model on the late mesozoic to cenozoic evolution of the region generally adriatic and dinaridic segments acted as major regional crustal entities of adria the upper portions of the sedimentary cover were differentially affected by progressive southwestward verging thin skinned deformations during the paleocene to eocene miocene the adriatic foreland stayed out of the deformations and is characterized predominantly by wrench and salt tectonics the regional tectonic map shows arcuate thrust fronts of the external dinarides they could be a consequence of both differential propagation of early orogenic thin skinned deformations over crustal fragments separated by transversal faults and or differential isostatic movements of the fragments the collision zone of the adriatic and dinaridic segments is characterized by late orogenic oligocene to miocene thick skinned compressional uplift exhumation related gravity gliding and still active escape tectonics wrenching these processes masked primary thin skinned deformations a significant amount of shortening within and between the thin skinned sedimentary covers is proposed therefore the question of the general paleogeography of the region and the original nw extent of the budva cukali basin ne adriatic trough remains open

stratigraphy and sedimentology of an early archean felsic volcanic sequence eastern pilbara block western australia with special reference to the duffer formation and implications for crustal evolution abstract a sequence of early archean felsic volcanic and volcaniclastic rocks and chert is present in the upper half of the warrawoona group throughout greenstone belts in the eastern pilbara block western australia it includes three formations the duffer formation which makes up the bulk of the sequence consists of up to 5 km of metamorphosed dacitic to rhyolitic volcaniclastic breccia and lava and lesser amounts of tuffaceous rocks and mafic lava it is overlain in several sections by the sandy panorama formation and both are capped by silicified orthochemical and biogenic deposits of the towers formation including both the strelley pool and marble bar cherts these units are identifiable in at least six greenstone belts in the eastern pilbara block the duffer formation is divided into four facies a structureless and graded breccia b complexly organized conglomerate c turbiditic tuff breccia and tuff and d lava these facies represent deposition on predominantly subaqueous volcaniclastic aprons flanking felsic volcanic centers a three stage model of the evolution of these aprons includes 1 an early stage of felsic and mafic eruptions and subaqueous deposition 2 a middle stage during which the bulk of the sequence was deposited involving shallow water to subaerial felsic volcanism and subaqueous deposition and 3 a terminal stage of subaerial felsic eruptions and subaerial deposition post duffer felsic volcanism was marked by explosive pyroclastic activity which resulted in widespread deposition of ash in surrounding shallow water and subaerial systems this phase of activity is represented by the panorama formation after the cessation of volcanism erosion of the emergent vents and regional subsidence led to an interval of orthochemical and biogenic sedimentation represented by the towers formation paleocurrent and facies patterns in the duffer and panorama formations support earlier proposals that the intrusion of granitoid rocks in the eastern pilbara block was coeval with felsic volcanism it seems likely that this volcanism was the surficial expression of plutonism that represented early stages of cratonization in the eastern pilbara the calc alkaline volcanism and depositional styles represented by this sequence are similar to those associated with many phanerozoic arcs the abundance of shallow water facies closely spaced and possibly non linear distribution of felsic centers close association of felsic units with thick sequences of basalt erupted at or near sea level sparse syn volcanic deformation and lack of granitic detritus suggest however that the setting of this archean felsic volcanism was in many details unlike that of most modern arcs

restricted shallow water sedimentation of early archean stromatolitic and evaporitic strata of the strelley pool chert pilbara block western australia abstract the 3 4 ga old strelley pool chert is a 25 m thick sedimentary unit near the top of the predominantly volcanic warrawoona group in greenstone belts of the eastern pilbara block western australia it is here subdivided into 5 members containing 13 lithofacies the basal member i is composed of quartzose sandstone deposited in a high energy wave or tide dominated shallow water system overlying this are members ii and iii which make up the bulk of the formation and were deposited in a low energy partially restricted hypersaline basin they record a predominantly regressive succesion of deposits including subaqueous laminite stromatolite and evaporite stromatolite carbonaceous laminite black and white banded chert evaporite and intraformational detrital units deposited under intermittently to predominantly exposed conditions and subaerially deposited windblown sand evaporite and evaporite solution layers members iv and v record the progradation of a volcaniclastic alluvial fringe the strelley pool chert represents an association of sedimentary environments directly comparable to that observed in modern low energy shallow marine carbonate evaporite systems such as along the trucial coast of the persian gulf and abundantly developed in phanerozoic carbonate platform deposits there is no evidence however that uniquely identifies the environment as having been marine deposition may have taken place in either a large hypersaline lake or a restricted marine basin evidence of predominantly low energy depositional conditions and a paucity of terrigenous detritus indicate that sedimentation was dominated by orthochemical and biological processes silicified evaporites including coarsely crystalline layers resembling messinian selenite are widespread and similar to younger evaporite deposits they clearly indicate that evaporites were common within shallow water archean sequences the presence of an assemblage of biogenic deposits including organic laminite stromatolites encrusting carbonaceous mats carbonaceous granules and oncolites deposited under conditions ranging from fully subaqueous to nearly subaerial and locally evaporitic points to the existence of an ecologically and probably biologically diverse microbial community 3 4 ga ago

the sm nd age of kambalda volcanics is 500 ma too old although sm nd isotopic analyses of volcanics from kambalda western australia form a 3 2 ga linear array pb pb analyses of the same suite give an isochron age of 2 73 0 03 ga and a 2 7 ga model age for the associated sulphides we suggest that the 3 2 ga age is incorrect and that the sm nd array results from mixing between depleted mantle and either older continental crust or enriched mantle

sinkhole structure imaging in covered karst terrain 1 ground penetrating radar gpr and resistivity techniques have been widely used to map the locations of sinkholes in covered karst terrain to determine whether a sinkhole is a likely preferential conduit for groundwater flow however requires higher resolution imaging than that used in conventional sinkhole mapping surveys field observations combined with simulated surveys for a 15 m diameter 3 m deep sinkhole in west central florida are used to assess the resolution of gpr and resistivity surveys targeting the semiconfining unit that floors the sinkhole depression 2d resistivity surveys clearly show the central depression as well as resistivity contrasts between the cover sediments within and outside of the sinkhole but are inadequate for resolving breaches in the semiconfining unit or underlying conduits a 3d gpr survey resolves vertical structure on the order of tens of centimeters within the semiconfining unit as well as indicators of conduits that extend several meters beneath the central depression 3d gpr thus holds promise for imaging hydrologically significant features of sinkholes

assessing the risk of subsidence of a sinkhole collapse using ground penetrating radar and electrical resistivity tomography abstract in segovia province spain there are numerous carbonate rock outcrops that are affected by karstification processes in which there are numerous galleries caves and sinkholes this is the case of the sima de madrona a sinkhole collapse caused by the sinking of dolostone the objective of this study was to ascertain the existence and the characteristics of cavities and galleries as well as to evaluate the risk of subsidence in the area by applying shallow and non invasive geophysical techniques ground penetrating radar and electrical resistivity tomography the joint combination of these two independent shallow geophysical techniques has provided the best combination of investigation depth up to 8 m and resolution needed to image small to medium 1 to 4 m size cavities the associated risks are evident because the cavities found herein affect various anthropic structures a highway and crop fields

structural geological and karst feature investigations of the limestone flysch thrust fault contact using low frequency ground penetrating radar adria dinarides thrust zone sw slovenia the karstic thrust edge a pronounced geomorphologic step which is a result of the tectonostratigraphic evolution of the active adria dinarides thrust zone represents a major obstacle for the planned new railway route divaca koper thus the geotechnical and structural properties as well as the geometry of the thrust fault planes in this area are of great importance since geological mapping cannot give insight into the subsurface to reveal a complex 3d structure and the numerous boreholes needed to investigate the area would be too expensive and time consuming the application of a geophysical method such as ground penetrating radar gpr is needed to test the method for determining near surface features and detecting low angle inclined thrusts a low frequency gpr system with 50 mhz rough terrain antenna was used to record 13 gpr profiles along all three floors of the crnotice quarry where the spatial position of the socerb thrust fault that separates limestones above and flysch layers below is relatively well documented the profiles were positioned across selected existing boreholes the gpr results were correlated with borehole data as well as geological mapping results the gpr provided not only precise information on the geometry of the socerb thrust fault but was also very useful for establishing the position of some known as well as several potential cavities both air and sediment filled in areas further from the thrust fault zone where the limestone is less tectonically damaged it was also possible to determine apparent dip angles of the strata which after reconstruction matched the true dips gathered from geological mapping

three dimensional characterization of complex mantled karst structures decision making and engineering solutions applied to a road overlying evaporite rocks in the ebro basin spain abstract at mantle cover evaporite karst settings evidences of surficial subsidence are usually strongly dependent on geomechanical properties and spatial inhomogeneities within the cover series in infrastructure assets affected by karst processes the evaluation of mitigation or engineering solutions requires a 3d reconstruction of the underground karst affected materials analysis and surveillance are also required to avoid deterioration of natural conditions and the migration or the increase in rate of karst features in the central ebro basin fluvial deposits cover soluble salts mainly gypsum located below the regional water table variations of geomechanical parameters of the cover mainly related to carbonate crusts and the contemporaneous sedimentation of fluvial deposits during karst activity can complicate the characterization of affected volumes in this work an integrated analysis including the available information 3d characterization by means of gpr and three boreholes in a peri urban road was carried out to finally define the geometry and evolution of karst phenomena an evaluation of metastable situations is also considered in order to define the zoning for hazard mitigation this evaluation shows that the volumetric affection to the cover series is in the range of tens of thousands of cubic meters a proposed list of factors related to social aspects infrastructure relevance and budget is analyzed

conceptualization and characterization of a coastal multi layered aquifer system in the taranto gulf southern italy in some mediterranean karst areas groundwater is often the only available supply for fresh water besides the contamination induced by human activities coastal aquifers often suffer from the saltwater intrusion phenomenon which can be enhanced by both extensive withdrawals and climatic changes establishing an effective set of regulatory and management measures to ensure the sustainability of coastal aquifers requires a deep knowledge about natural and anthropic stresses involved in groundwater dynamics in this regard a prior conceptualization of aquifer systems and a deeper characterization of balance terms through mathematical modeling are of paramount importance in this paper previous works on the three dimensional hydrostratigraphic characterization and two dimensional groundwater flow modeling at the regional scale for the salento peninsula southeastern italy are shown to provide a fundamental basis for an overall conceptualization of the multi layered aquifer system of the taranto gulf northwestern salento this is done by identifying source terms and providing a preliminary estimate of different balance terms based on available data and information then a further characterization will be provided using three dimensional groundwater flow models and calibration techniques based on the solution of an inverse problem as a result the hydraulic features of the deep karst aquifer can be mapped the stresses due to human water demanding activities and the occurrence of the saltwater intrusion phenomenon were analyzed and possible weaknesses of the conceptual and of the preliminary numerical model pointed out

tectonic constraints on the late pleistocene holocene relative sea level change along the north eastern adriatic coast croatia abstract in spite of very favourable coastal features late pleistocene holocene relative sea level changes along the eastern adriatic coast are still not completely resolved mostly due to the intensive and complicated regional and local neotectonics we gathered current knowledge that generally presents the north adriatic area as subsiding one and proposed a reconstruction in new light of possible very slow local uplift average rate of 0 1 0 25 mm a for last 80 ka which is supported by well dated submerged speleothems and tectonic reconstruction in addition such a scenario supports also the formation of tidal notches that are common in the north adriatic region but not yet entirely understood however according to the latest mediterranean data on sea level during the marine isotope stage mis 5 1 being at 1 m 80 ka ago we do not dismiss the possibility of subsidence which would have been 0 18 0 23 mm a on average for the last 80 ka but notch formation under such condition would not have been realistic apparently the position of the north eastern adriatic coast on a convergence area requires extensive palaeoenvironmental studies including structural lithostratigraphical palaeontological archaeological and radiometric data and application of isostatic modelling

evolution of the adriatic carbonate platform palaeogeography main events and depositional dynamics abstract the adriatic carbonate platform adcp is one of the largest mesozoic carbonate platforms of the perimediterranean region its deposits comprise a major part of the entire carbonate succession of the croatian karst external or outer dinarides which is very thick in places more than 8000 m and ranges in age from the middle permian or even upper carboniferous to the eocene however only deposits ranging from the top of the lower jurassic toarcian to the top of the cretaceous can be attributed to the adcp defined as an isolated palaeogeographical entity although the entire carbonate succession of the karst dinarides was deposited within carbonate platform environments there were different types of carbonate platforms located in different palaeogeographical settings carboniferous to middle triassic mixed siliciclastic carbonate deposits were accumulated along the gondwanian margin on a spacious epeiric carbonate platform after tectonic activity culminating by regional middle triassic volcanism recorded throughout adria the african promontory a huge isolated carbonate southern tethyan megaplatform abbreviated as stm was formed with the area of the future adcp located in its inner part tectonic disintegration of the megaplatform during the middle to late early jurassic resulted in the establishment of several carbonate platforms including the adriatic apenninic and apulian separated by newly drowned deeper marine areas including the adriatic basin as a connection between the ionian and belluno basins lagonero basin and the area of the slovenian and bosnian troughs the adcp was characterised by predominantly shallow marine deposition although short or long periods of emergence were numerous as a consequence of the interaction of synsedimentary tectonics and eustatic changes also several events of temporary platform drowning were recorded especially in the late cretaceous when synsedimentary tectonics became stronger leading up to the final disintegration of the adcp the thickness of deposits formed during the 125 my of the adcp s existence is variable between 3500 and 5000 m the end of adcp deposition was marked by regional emergence between the cretaceous and the palaeogene deposition during the palaeogene was mainly controlled by intense synsedimentary tectonic deformation of the former platform area some carbonates mostly eocene in age were deposited on irregular ramp type carbonate platforms surrounding newly formed flysch basins and the final uplift of the dinarides reached its maximum in the oligocene miocene the adriatic carbonate platform represents a part although a relatively large and well preserved one of the broader shallow water carbonate platform that extended from ne italy to turkey although its continuity is somewhat debatable in the area near albanian greece boundary this large carbonate body which was deformed mostly in the cenozoic including a significant reduction of its width needs a specific name and the central mediterranean carbonate platform is proposed abbreviated to cmcp although the local names such as adcp for its nw part should be kept to enable easier communication and to facilitate description of local differences in platform evolution

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

ground penetrating radar and structural geological mapping investigation of karst and tectonic features in flyschoid rocks as geological hazard for exploitation abstract we evaluated the use of ground penetrating radar gpr in detecting karst cavities and discontinuities that could form potential landslide surfaces in flyschoid rocks of the rode open pit mine in anhovo w slovenia we recorded 21 gpr profiles in three consecutive benches with the unshielded 50 mhz rough terrain antenna rta system and correlated them with the results of detailed structural and lithological mapping of the area we located several karst cavities and confirmed the presence of discontinuities with the interpretation of gpr profiles alone however their correlation with geological and structural data gave a more precise insight into the structural setting of the studied area the different discontinuity families specified in the rode open pit mine are mainly the result of the strike slip tectonics and gradual anisotropic lithology the complexity of the intersections of structural discontinuities and the mechanical properties of rocks contribute to the formation of sliding surfaces and the developing of karst features cavities and phreatic channels develop in the vadose zone in calcarenites and result from complex structural deformation and karstification factors at the open joints or larger structural fractures

use of ground penetrating radar for assessment of potential sinkhole conditions an example from ghor al haditha area jordan sinkholes are near surface indicators of active karst features at depth such as cavities conduits and solutionally enlarged fractures this study tests the usefulness of ground penetrating radar gpr to identify and locate buried sinkholes as a means of interpreting the existence of these subsurface hydraulically active karst features gpr survey was made at the ghor al haditha area west of the jordan dstf in the jordan valley escarpment at the eastern dead sea shoreline gpr profiles 100 mhz made along the eastern dead sea shoreline showed a trough like pattern of radar reflections outlining a series of possible filled sinkholes this feature is about 38 m wide and about 12 m deep its width is consistent with the width of the feature obtained from the topographic map of the area the gpr survey suggests that this feature has been filled with relatively dense and resistive materials this structure lies almost directly above a major water bearing zone

origin of the 3500 3300 ma calc alkaline rocks in the pilbara archaean isotopic and geochemical constraints from the shaw batholith abstract calc alkaline plutonic rocks intruded at 3450ma comprise a major component of the shaw batholith in the archaean east pilbara block western australia new whole rock pb isotopic geochronology confirms the extent of these rocks but a minor plutonic phase is dated at 3338 52 ma and represents a second plutonic event of the same age as much of the nearby mt edgar batholith the sm nd isotopic systematics of the 3450ma rocks imply their derivation from a heterogeneous source which probably included a slightly older crustal component as well as a depleted mantle component the 3338 52 ma pluton includes components derived from crustal sources older than 3600 ma the geochemistry and sm nd isotopic systematics of these rocks are consistent with crustal growth in the early archaean from upper mantle sources as depleted as the modern upper mantle the shaw batholith calc alkaline suites exhibit very similar chemical trends on variation diagrams to modern calc alkaline plutonic rocks which can be modelled by a combination of mixing and fractionation a suite collected from outcrops displaying prominent igneous layering shows distinct geochemical trends which can be modelled by differentiation into a component enriched in ferromagnesian minerals principally hornblende and possibly sphene magnetite and epidote and into a leucocratic component containing quartz plagioclase and k feld par these archaean calc alkaline plutonic rocks in common with rocks from many other archaean calc alkaline provinces exhibit very fractionated ree patterns with depleted hree contents a feature considered to result from equilibrium with garnet at depth in lower crustal regions the geochemistry of the pilbara archaean calc alkaline rocks is identical to the subset of modern continental margin calc alkaline plutonic rocks with fractionated ree patterns such as those from the central and eastern peninsular ranges batholith western usa the tectonic setting in which the archaean calc alkaline rocks formed is still not known this reflects both uncertainty associated with the petrogenesis and environments of modern calc alkaline rocks as well as the limited knowledge of the precise timing and relationships of plutonic depositional and tectonic events in the pilbara archaean

combined microgravity electrical resistivity tomography and induced polarization to detect deeply buried caves algaidilla cave southern spain abstract the suitability of the combined microgravity and electrical tomography to detect and characterize caves deeply buried in limestones is tested we have selected the buried algaidilla cave in the estepa range western betic cordillera which is partially submerged below the water table and which was intersected between 26 and 66 m in depth by two boreholes at that location microgravity electrical resistivity tomography ert and induced polarization ip data was collected along four profiles algaidilla cave is associated with a 0 5 mgal residual gravity anomaly minimum microgravity models reveal an approximately horizontal n s elongated shape with a maximum length of 150 m and a width of 40 m resistivity variations provide information on the cave sectors remaining above as well as below the water table forward modeling and depth of investigation doi support the suitability of ert to constrain the cave geometry the cave is identified as having an intermediate to low resistivity feature which approximately matches the 250 m contour line along its ceiling in addition induced polarization models show high chargeability anomalies probably associated with decalcification clays the location and approximately geometry of algaidilla cave estimated from geophysical modeling suggests that nearby overburden may develop cave ins and collapse sinkholes microgravity is proved as a powerful tool to detect caves at this depth but this method alone fails to estimate the geometry ert results delineate the cavity both above and below the water table although the deepest sectors of the models should be interpreted with caution since they are less constrained by the data below the water table the cavity shows great resistivity contrast with regard to the background carbonate in addition this study points out the usefulness of the ip method for detecting decalcification clays often present at the base of karstic caves

sequence stratigraphy of the archaean supracrustal belts of the pilbara block western australia abstract the stratigraphic succession of the 3580 2770 m y old granite greenstone terrain of the pilbara block is re assessed by the first and second order sequence stratigraphic techniques that are the standard for phanerozic terrains with the view to testing the conformity of stratigraphic cause and response a holistic tectonostratigraphic framework is presented that pairs the supracrustal and crustal rock records the resulting sequence scheme is tested against the cause of first order sequence cycles viz global sea level responses to supercontinent breakup and assembly three first order inter regional unconformities divide the stratigraphic succession of the supracrustal belts into four units of first order megasequence status in order of decreasing age these are named the warrawoona gorge creek roebourne and mount negri megasequences a total of 17 second order supersequences are also named although some may represent supersequence sets the megasequences and or their genetic crustal equivalents represent the preserved rock record of four megacycles of forearc arc and or back arc geotectonic evolution associated with the convergent margins of a pilbara continent individual supersequences are the rock record of separate second order basins or basin phases and reflect the different geotectonic components of each megasequence the four megacycles had respective longevities from oldest to youngest of 150 m y 230 m y 160 m y and 180 m y they are identical in their stratigraphic successions and predicted first order sea level cycles to phanerozoic first order tectono eustatic cycles and are interpreted as the same response to global tectonic change the warrawoona and gorge creek megacycles and the roebourne and mount negri megacycles are tectonogenetic pairs of the east pilbara and the west pilbara megacycle sets respectively the east pilbara megacycle set evolved over a period of 380 m y from 3490 ma to 3110 ma whereas the west pilbara megacycle set evolved over a period of 340 m y from 3110 ma to 2770 ma the two megacycle sets are identical in their longevity geotectonic components and predicted sea level cycles to convergent margin wilson and supercontinent cycles and are thereby interpreted individually as the oldest established records of the supercontinent cycle the implication of this interpretation is that a steady state global tectonic regime has been in operation from early in earth s history which has important consequences for theoretical modelling of the earth s early tectonic style and secular changes in its geochemical regime

characterization of a coalesced collapsed paleocave reservoir analog using gpr and well core data the three dimensional architecture spatial complexity and pore type distribution are mapped in a near surface analog of a coalesced collapsed paleocave system in the lower ordovician ellenburger group near the city of marble falls in central texas the surface area of the site has dimensions of about 350 1000 m the data collected include about 12 km of 50 mhz ground penetrating radar gpr data arranged in a grid of orthogonal lines 29 cores of about 15 m length and detailed facies maps of an adjacent quarry face electrical property measurements along with detailed core descriptions were the basis of integrated interpretation of the gpr data three main gpr facies are defined on the basis of degree of brecciation in the corresponding cores undisturbed host rock disturbed host rock and paleocave breccia this gpr facies division defined the major paleocave trends and the distribution of porosity types which correlate with reservoir quality highly brecciated zones are separated by disturbed an

detecting and characterizing unroofed caves by ground penetrating radar abstract the bare karst surface in the southeastern part of krk island croatia is characterized by different surface karst features such as valley like shallow linear depressions and partially or fully sediment filled depressions of various shapes and sizes they were noticed due to locally increased thickness of sediment and enhanced vegetation but had not yet been systematically studied and defined considering only the geometry of the investigated surface features and the rare traces of cave environments detected by field surveys it was unclear which processes surface karstification and or speleogenesis contributed most to their formation the low frequency ground penetrating radar gpr method using a special 50 mhz rta antenna was applied to study and describe these karst features three study sites were chosen and 5 km of gpr profiles were positioned to include various surface features the results obtained from the gpr investigation lead to the following conclusions 1 an increased thickness of sediment was detected in all the investigated depressions indicating their considerable depth 2 areas between different depressions expressed as attenuated zones in gpr images reveal their interconnection 3 transitions between surface and underground features are characterized by a collapsed passage visible in the gpr data and 4 an underground continuation of surface valley like depressions was detected proving the speleogenetic origin of such features subsurface information obtained using gpr indicates that the valley like depressions irregular depressions completely or partially filled with sediment and some dolines are associated with a nearly 4 km long unroofed cave and developed as a result of karst denudation in the regional context these results suggest long lasting karstification processes in the area in contrast to the pre karstic fluvial phase previously assumed to have occurred here this research is the first application of the gpr method to survey unroofed caves worldwide and the first detailed study of such karst features in croatia the low frequency gpr proved to be an efficient method not only for detecting underground continuations but also for distinguishing and identifying surface features and transition zones between surface and subsurface segments of unroofed caves and can therefore be used for recognizing similar geomorphological features

assessment of doline geometry using geophysics on the quercy plateau karst south france in the protection of karstic aquifers the role played by dolines is of interest as these shallow structures can be preferential infiltration pathways for groundwater recharge in this study three depressions in south france orniac lot were identified and characterized using combined geophysical methods apparent conductivity mapping allows precise definition of dolines corresponding to topographic depressions it also reveals other dolines that are hidden by soil cover electrical resistivity and seismic refraction tomography provide detailed cross sections even though the dolines studied are close one to another they exhibit great variability in shape and content moreover time lapse data show that the most saturated regions are on the edges of the first doline such information helps to evaluate human impacts and forecast potential groundwater contamination

detection of underground cavities by combining gravity magnetic and ground penetrating radar surveys a case study from the zaragoza area ne spain a geophysical survey routine is proposed to detect underground cavities and dolines it is based on the sequential application of magnetic low frequency ground penetrating radar gpr and microgravity techniques a case study near zaragoza ebro valley spain demonstrates the applicability of these methods the strong contrast of magnetic and electromagnetic properties and to a lesser scale of density between the doline filling and the surrounding stratified tertiary and quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods