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The rock weathering literature contains the hypothesis that case hardening exemplifies equifinality, where the same end state can be reached by many potential processes in an open system. We present analytical data from six different sites in the western USA to assess the hypothesis of equifinality. Case hardening can be produced on: (1) sandstone in Petrified Forest National Park, Arizona, from the addition of silica glaze, rock varnish and heavy-metal skins; (2) sandstone in Whoopup Canyon, Wyoming, from silica glaze that formed originally inside subsurface joints combined with externally applied iron film, silica glaze, and rock varnish; (3) welded tuff in Death Valley, California, from the accumulation of rock varnish and heavy metal skins of Mn and Fe; (4) sandstone in Sedona, Arizona, from the protective effects of rock varnish accretion and heavy metal skins of Mn and Fe; (5) basalt on the Big Island, Hawai'i, from the accumulation of silica glaze inside vesicles; and (6) sandstone at Point Reyes, California, from a lithobiont mat of fungi and lichen. Each developed the general form of a case-hardened shell, protecting the surface from erosion. In accordance with the hypothesis of equifinality, the processes that led to similar appearance differ., Introduction DIFFERENTIAL WEATHERING of rocks leads to varying degrees of resistivity of different rock types to erosion. Such differences in weathering provide a fundamental control on Earth's topography (Ollier 1984, [...]

We report the occurrence and characteristics of diopsidite dykes and veins from the Palghat-Cauvery Suture Zone (PCSZ) marking the boundary between the Archaean Dharwar craton to the north and the Proterozoic Madurai Block to the south, which is considered as a trace of the Cambrian Gondwana suture zone in southern India. The diopsidites are composed predominantly of coarse crystals of diopside [Mg no. (100 Mg/(Mg+[Fe.sup.101])) up to 89] surrounded by retrograde calcic amphibole, plagioclase and phlogopite with accessory titanite and calcite. The major, trace and rare earth element characteristics of the diopside crystals suggest their formation in a subduction zone setting. We correlate the petrogenesis of the diopsidites with the tectonics associated with the subduction and closure of the Neoproterozoic Mozambique Ocean prior to the final collisional assembly of the Gondwana supercontinent in Cambrian. Keywords: diopsidite, subduction, suture zone, southern India, Gondwana. doi: 10.1017/S0016756810000154

The Khanka Massif is a crustal block located along the eastern margin of the Central Asian Orogenic Belt (CAOB) and bordered to the east by Late Jurassic-Early Cretaceous circum- Pacific accretionary complexes of the Eastern Asian continental margin. It consists of graphite-, sillimanite- and cordierite-bearing gneisses, carbonates and felsic paragneisses, in association with various orthogneisses. Metamorphic zircons from a sillimanite gneiss from the Hutou complex yield a weighted mean [sup.Pb]206pb/[238.sup.U] age of 490 [+ or -] 4 Ma, whereas detrital zircons from the same sample give ages from 934-610 Ma. Magmatic zircon cores in two garnet-bearing granite gneiss samples, also collected from the Hutou complex, yield weighted mean [sup.206][pb/.sup.Z38]U ages of 522 [+ or -] 5 Ma and 515 [+ or -] 8 Ma, whereas their metamorphic rims record [sup.206][pb/.sup.23]SU ages of 510 500 Ma. These data indicate that the Hutou complex in the Khanka Massif records early Palaeozoic magmatic and metamorphic events, identical in age to those in the Mashan Complex of the Jiamusi Massif to the west. The older zircon populations in the sillimanite gneiss indicate derivation from Neoproterozoic sources, as do similar rocks in the Jiamusi Massif. These data confirm that the Khanka Massif has a close affinity with other major components of the CAOB to the west of the Dun-Mi Fault. Based on these results and previously published data, the Khanka Massif is therefore confirmed as having formed a single crustal entity with the Jiamusi (and possibly the Bureya) massif since Neoproterozoic time. Keywords: SHRIMP U-Pb dating, Neoproterozoic, Late Pan-African, granulites, Khanka Massif. doi:10.1017/S0016756810000063

An approach to quantify nonuniformity of compacted earth materials using spatially referenced roller-integrated compaction measurements and geostatistical analysis is discussed. Measurements from two detailed case studies are presented in which univariate statistical parameters are discussed and compared to geostatistical semivariogram modeling parameters and analysis. The univariate and geostatistical parameter values calculated from the roller-integrated measurements are also compared to traditional spot test acceptance criteria. Univariate statistical parameter values based on roller-integrated measurement values provide significantly more information than traditional point measurements, while geostatistics can be used to identify regions of noncompliance and prioritize areas for rework. DOI: 10.1061/(ASCE)GT.1943-5606.0000285 CE Database subject headings: Statistics; Soil compaction; Quality control; Earthwork; Measurement. Author keywords: Geostatistics; Semivariogram; Soil compaction; Quality control; Earthwork; Intelligent compaction.

An efficient method for a structural reliability analysis is proposed under the Bayesian framework, which can deal with the epistemic uncertainty arising from a limited amount of data. Until recently, conventional reliability analyses dealt mostly with the aleatory uncertainty, which is related to the inherent physical randomness and its statistical properties are completely known. In reality, however, epistemic uncertainties are prevalent, which makes the existing methods less useful. In the Bayesian approach, the probability itself is treated as a random variable of a beta distribution conditional on the provided data, which is determined by conducting a double loop of reliability analyses. The Kriging dimension reduction method is employed to promote efficient implementation of the reliability analysis, which can construct the PDF of the limit state function with favorable accuracy using a small number of analyses. Mathematical examples are used to demonstrate the proposed method. An engineering design problem is also addressed, which is to find an optimum design of a pigtail spring in a vehicle suspension, taking material uncertainty due to limited test data into account. [DOI: 10.1115/1.4001377] Keywords: Bayesian approach, reliability analysis, epistemic uncertainty, Kriging dimension reduction method, pigtail spring, side load

Spatial autocorrelation is an intrinsic characteristic in freshwater stream environments where nested watersheds and flow connectivity may produce patterns that are not captured by Euclidean distance. Yet, many common autocovariance functions used in geostatistical models are statistically invalid when Euclidean distance is replaced with hydrologic distance. We use simple worked examples to illustrate a recently developed moving-average approach used to construct two types of valid autocovariance models that are based on hydrologic distances. These models were designed to represent the spatial configuration, longitudinal connectivity, discharge, and flow direction in a stream network. They also exhibit a different covariance structure than Euclidean models and represent a true difference in the way that spatial relationships are represented. Nevertheless, the multi-scale complexities of stream environments may not be fully captured using a model based on one covariance structure. We advocate using a variance component approach, which allows a mixture of autocovariance models (Euclidean and stream models) to be incorporated into a single geostatistical model. As an example, we fit and compare 'mixed models,' based on multiple covariance structures, for a biological indicator. The mixed model proves to be a flexible approach because many sources of information can be incorporated into a single model. Key words: geostatistics; hydrologic distance; moving average; scale; spatial autocorrelation; streams.

The volatile concentrations and thermal characteristics of hydrothermally altered rhyolitic deposits erupted under Icelandic glaciers have been studied by combined differential scanning calorimetry thermogravimetric analysis mass spectrometry (DSC--TGA--MS) and X-ray diffraction (XRD). Samples range from pristine obsidians to strongly perlitized and altered fragmental deposits. Four types of samples are determined to have notable differences in total volatile concentrations: obsidians (0.44-3.04 wt%), perlites (2.15-8.15 wt%), obsidian-breccias (8.49-9.41 wt%) and hyaloclastites (3.23-7.78 wt%). DSC--TGA--MS and textural data indicate that the volatile concentration of the perlitic samples increases as the amount of perlitization increases. XRD data show that the volatile-rich samples are rich in the low-temperature zeolite minerals heulandite and mordenite. The temperature at which volatile exsolution occurs is shown to decrease as the volatile concentration increases, reflecting the speciation of water as well as zeolite mineral growth. Supplementary material: Detailed grain-size fraction analysis data in table and histogram form are available at http://www.geolsoc.org.uk/SUP 18366.

Regression models were developed to estimate the optimum moisture content and maximum dry density of clayey and fine-grained soils using physical and index properties from 30 soil samples collected in Central Italy and 41 soils described in the literature. The liquid limit of the soils analyzed ranged between 18 and 82%, the plasticity index between 1 and 51%, and specific gravity between 2.47 and 3.09. The most significant regression variables were the specific gravity and the Atterberg limits. The developed models are accurate and can be used as a simple tool to approximate the maximum dry density and optimum water content of clayey and fine-grained soils. DOI: 10.1061/(ASCE)GT. 1943-5606.0000022 CE Database subject headings: Soil properties; Mechanic properties; Soil compaction; Geostatistics.

In this paper, a modified approach for noise estimation in optical remotely sensed images is developed under the framework of semivariogram (SV) technique in geostatistics, which is a fundamental and important task for on-ground quantitative application. In comparison with the original method, which involves the extrapolation of modeled SV to the ordinate, in the modified approach, the relationship between two different SVs of true objects at different lags is established. Simulation results show that the latter is more accurate and stable in estimating noise, particularly in the conditions of usual subimage sizes (i.e., 16 x 16 and 32 x 32) as well as in lower noise level. Moreover, the potential negative values in the original method no longer exist in the modified one. Additionally, after the removal of the analog-to-digital conversion noise effects, detection sensitivity evaluations and long-term surveillances for on-orbit optical remotely sensed instrument, for example FY-2 visible infrared spin-scan radiometer, are performed successfully, and the absolute error for noise-equivalent delta temperature estimation is within 0.05 K at 300 K. A common and feasible way for estimating nugget variance of SV in geostatistics is proposed in this paper with the assumption of stationary for both objects and noise process. Index Terms--Noise measurement, optical-image processing, sensitivity.

In West Africa, which is an extremely moisture-limited region, soil water information plays a vital role in hydrologic and meteorologic modeling for improved water resource planning and food security. Recent and upcoming satellite missions, such as SMOS and MetOp, hold promise for the regional observation of soil moisture. The resolution of the satellites is relatively coarse (> 100 [km.sup.2]), which brings with it the need for large-scale soil moisture information for calibration and validation purposes. We put forward a soil moisture sampling protocol based on hydrotopes. Hydrotopes are defined as landscape units that show internally consistent hydrologic behavior. This hydrotope analysis helps in the following ways: 1) by ensuring statistically reliable validation via the reduction of the overall pixel variance and 2) by improving sampling schemes for ground truthing by reducing the chance of sampling bias. As a sample application, we present data from three locations with different moisture regimes within the Volta Basin during both dry and wet periods. Results show that different levels of reduction in the overall pixel variance of soil moisture are obtained, depending on the general moisture status. With respect to the distinction between the different hydrotope units, it is shown that under intermediate moisture conditions, the distinction between the different hydrotope units is highest, whereas extremely dry or wet conditions tend to have a homogenizing effect on the spatial soil moisture distribution. This paper confirms that well-defined hydrotope units yield an improvement at pixel-scale soil moisture averages that can easily be applied. Index Terms--Geostatistics, hydrotopes, MetOP, satellites, scaling, soil moisture, Soil Moisture and Ocean Salinity (SMOS), West Africa.

A new modeling framework combining neural-network-based models, passive microwave data, and geostatistics is proposed for snow water equivalent (SWE) retrieval and mapping. Brightness temperature data from the seven-channel Special Sensor Microwave/Imager and the interpolated minimum temperature are the inputs of a multilayer feedforward neural network (MFF). Kriging with an External Drift algorithm is applied to ground-based SWE data to produce gridded SWE data that are used as the target of the neural network. An optimal division of the sample of available pixels is achieved by a self-organizing feature map. Prediction error is used for model selection and is assessed by bootstrap. It is shown that a committee of a network containing neural networks with different architectures can provide consistent SWE retrievals. This modeling framework is applied for SWE retrieval and mapping over La Grande River basin in north eastern Quebec (Canada). The results are very promising for operational purposes particularly for SWE mapping during periods with no ground measurements and operational streamflow forecasting. Index Terms--Bootstrap, Kriging with an External Drift (KED), multilayer perceptrons (MLPs), passive microwave, self-organizing feature map (SOFM), snow water equivalent (SWE), Special Sensor Microwave/Imager (SSM/I).

Linking of the activities in a critical path method schedule with the corresponding elements of a three-dimensional (3D) model makes the project sequence easier to understand. Although some commercial tools allow the planner to build a 4D model and create graphical simulation of the construction process, it still lacks features like generation and manipulation of a 4D model within a single environment. This paper presents a geographic information systems (GIS) based methodology for scheduling as an alternative to the existing 4D computer aided design tools. A methodology to build a 3D model and link it with the construction schedule using several in-house scripts written in GIS environment is discussed. It allows the planner to understand the construction schedule quickly by linking the activities of the schedule with the corresponding 3D components as well as to visualize a buildable schedule on a computer screen. The proposed methodology utilizes the dynamic linkage between the activities in the schedule and corresponding 3D components, thus, making it possible to detect the incompleteness and logical errors in the schedule sequence. The ability of GIS to maintain spatial data (i.e., 3D components corresponding to each activity) in separate themes, which can be superimposed spatially, is utilized. The related nonspatial information (like schedule, material type and quantity, safety and quality control recommendations, etc.) are stored in the attribute tables of corresponding components, which can be extracted from the database maintained within the GIS itself. CE Database subject headings: Geographic information systems; Scheduling; Construction management; Project management; Information systems.

The main aim of this paper is to show the implementation and application of downscaling cokriging for super-resolution image mapping. By super-resolution, we mean increasing the spatial resolution of satellite sensor images where the pixel size to be predicted is smaller than the pixel size of the empirical image with the finest spatial resolution. It is assumed that coregistered images with different spatial and spectral resolutions of the same scene are available. The main advantages of cokriging are that it takes into account the correlation and cross correlation of images, it accounts for the different supports (i.e., pixel sizes), it can explicitly take into account the point spread function of the sensor, and it has the property of prediction coherence. In addition, ancillary images (topographic maps, thematic maps, etc.) as well as sparse experimental data could be included in the process. The main problem is that super-resolution cokriging requires several covariances and cross covariances, some of which are not empirically accessible (i.e., from the pixel values of the images). In the adopted solution, the fundamental concept is that of covariances and cross-covariance models with point support. Once the set of point-support models is estimated using linear systems theory, any pixel-support covariance and cross covariance can be easily obtained by regularization. We show the performance of the method using Landsat Enhanced Thematic Mapper Plus images. Index Terms--Covariance, cross variogram, deconvolution, geostatistics, Landsat Enhanced Thematic Mapper (ETM), point support, remote sensing, subpixel, super-resolution image enhancement, variogram.

Liquefaction triggering assessments are often performed for individual locations, providing little information in regard to the expected spatial extent of liquefaction events. The present paper proposes a method to quantify the potential extent of liquefaction by accounting for spatial dependence of soil properties and potential future earthquake shaking. Random-field theory and geostatistics tools are used to model soil properties and earthquake shaking intensity; this approach facilitates incorporation of measurement results obtained at individual locations within the area of interest. An empirical liquefaction triggering criterion is then used to model liquefaction occurrence as a function of the random-field realizations. The framework components are briefly described and an example analysis is performed to illustrate the details of the approach. The area of liquefied soil under a building in Adapazari, Turkey, is considered in the example, conditional upon soil property measurements obtained from nearby standard penetration tests. DOI: 10.1061/(ASCE)1090-0241(2008)134:1(14) CE Database subject headings: Liquefaction; Statistics; Earthquakes; Soil properties.

Chair: James Starnes, MS Department of Environmental Quality Vice-chair: George Phillips, Dept. of Wildlife, Fisheries, and Parks THURSDAY MORNING Juniper O5.01 9:00 MINING IN STREAMS: POLICY QUESTIONS FOR MISSISSIPPI Michael [...]

The contribution of biblical literalists or earth-historians of the early nineteenth-century Britain to the history of science is discussed. The article shows that the historians combined the assessment of 'scriptural geology' with the study of literatures for a better understanding.

Overpressures in sedimentary basins are commonly assumed to be the result of two distinct and separate mechanisms: disequilibrium compaction and fluid expansion. However, the potential for overpressures to be redistributed or transferred to other pressure compartments over time has been seldom considered and rarely demonstrated. Pore-pressure data and velocity-effective stress plots from 61 fields across the Baram Delta province of Brunei (northwest Borneo) reveal that two different types of overpressure occur in stratigraphically defined sections: the basal pro-delta shales contain overpressures generated by disequilibrium compaction, whereas the overlying sand/shale deltaic sequence contains overpressures that appear to be generated by fluid expansion. However, the geology of the deltaic sequences and high magnitude of the pore pressures precludes the overpressures in the deltaic sequences being generated by any conventional fluid expansion mechanism, such as kerogen-to-gas maturation or clay diagenesis. The fluid expansion overpressures are located in fields that were inverted during the Pliocene, an event that resulted in large-scale fluid migration from the pro-delta shales into the deltaic sequences, including charging of the numerous oil fields in the inner shelf. Hence, we propose that the overpressures in Brunei provide the first evidence for a new overpressuring mechanism whereby overpressured fluids have been 'vertically transferred' from the pro-delta shales into the deltaic sequences during basin inversion. Furthermore, vertical transfer may be a mechanism for explaining overpressures observed in basins that have been recently uplifted or inverted. Keywords: Overpressure, Brunei, vertical transfer, Baram Delta. doi: 10.1130/G23906A.1

The Subbetic units consist of a deformed wedge of sedimentary rocks deriving from the South Iberian palaeomargin, in the westernmost segment of the Alpine-Mediterranean orogenic belt. In the central Betics, shortening produced folding, thrusting and nappe-stacking. The structural trend is NE-SW to ENE-WSW, and the internal structure of the thrust sheets, which shows no preferred vergence, is strongly controlled by the rheology of the decollement level, a viscous layer of Triassic evaporites, and of the overlying carbonate rock sequence. The relationships of piggyback basin Miocene sediments with the main structures show that the latter developed during the Aquitanian-Burdigalian transition. Superimposed folding is described for the first time in the study area. The origin of the interference cannot be determined at present, but may be related to initially oblique structures refolded during progressive deformation. A revision of previously published palaeomagnetic data in the light of the data presented in this paper, in conjunction with a model of the structural evolution of the Subbetic units of the western Betics, permits us to establish milestones of the tectonic evolution of the external zones in the northern branch of the Gibraltar Arc.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.07.015 Byline: E.R. Stofan (a), J.I. Lunine (b)(c), R. Lopes (d), F. Paganelli (d), R.D. Lorenz (c), C.A. Wood (e), R. Kirk (f), S. Wall (d), C. Elachi (d), L.A. Soderblom (f), S. Ostro (d), M. Janssen (d), J. Radebaugh (c), L. Wye (g), H. Zebker (g), Y. Anderson (d), M. Allison (h), R. Boehmer (d), P. Callahan (d), P. Encrenaz (i), E. Flamini (j), G. Francescetti (k), Y. Gim (d), G. Hamilton (d), S. Hensley (d), W.T.K. Johnson (d), K. Kelleher (d), D. Muhleman (l), G. Picardi (m), F. Posa (n), L. Roth (d), R. Seu (m), S. Shaffer (d), B. Stiles (d), S. Vetrella (k), R. West (d) Keywords: Titan; Geological processes; Saturn; satellites; Satellites; surfaces Abstract: The first two swaths collected by Cassini's Titan Radar Mapper were obtained in October of 2004 (Ta) and February of 2005 (T3). The Ta swath provides evidence for cryovolcanic processes, the possible occurrence of fluvial channels and lakes, and some tectonic activity. The T3 swath has extensive areas of dunes and two large impact craters. We interpret the brightness variations in much of the swaths to result from roughness variations caused by fracturing and erosion of Titan's icy surface, with additional contributions from a combination of volume scattering and compositional variations. Despite the small amount of Titan mapped to date, the significant differences between the terrains of the two swaths suggest that Titan is geologically complex. The overall scarcity of impact craters provides evidence that the surface imaged to date is relatively young, with resurfacing by cryovolcanism, fluvial erosion, aeolian erosion, and likely atmospheric deposition of materials. Future radar swaths will help to further define the nature of and extent to which internal and external processes have shaped Titan's surface. Author Affiliation: (a) Proxemy Research, P.O. Box 338, Rectortown, VA 20140, USA (b) Istituto di Fisica dello Spazio Interplanetario, Via del Fosso del Cavaliere, 00133 Rome, Italy (c) Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA (d) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA (e) Planetary Science Institute, 1700 E. Ft. Lowell, Suite 106, Tucson, AZ 85719-2395, USA (f) U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001, USA (g) Department of Geophysics, Stanford University, 360 Mitchell, Stanford, CA 94305, USA (h) NASA/Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA (i) L'Observatoire de Paris, DEMIRM 61, avenue de l'Observatoire, 75014 Paris, France (j) Agenzia Spaziale Italiana, Viale Liegi 26, 00198 Rome, Italy (k) Department of Electronic Engineering, University of Napoli, Via Claudio 21, 80125 Napoli, Italy (l) California Institute of Technology, Geological and Planetary Sciences, Pasadena, CA 91125, USA (m) Radar and Remote Sensing, Info-Com Department, University of Rome, La Sapienza, Via Eudossiana 18, 00184 Rome, Italy (n) INFM and Dipartimento Interateneo di Fisica, Politecnico di Bari, 70126 Bari, Italy Article History: Received 25 April 2006; Revised 18 July 2006

Two distinct Neoproterozoic glacial episodes are known for the Dalradian Supergroup in the British-Irish Caledonides, the Port Askaig Formation and the Inishowen-Loch na Cille ice-rafted debris (IRD) beds. Here we describe a third, intermediate between those two, the Stralinchy-Reelan formations, composed of diamictite and IRD. Developed directly above these rocks is the Cranford Limestone, which consists of a basal, 1-6-m-thick, tan-gray dolostone overlain by a variably developed, but as much as 340-m-thick, sequence of thin-bedded limestone and dolostone. This unit exhibits a C isotopic trend that begins negative in the basal dolostone, reaches a nadir of -7[per thousand], and then rises to 0[per thousand]-2[per thousand]. These characteristics match strikingly those of Marinoan-style cap carbonates. Consequently, we interpret the Port Askaig Formation, the Stralinchy-Reelan units, and the Inishowan-Loch na Cille beds as equivalents of the ca. 700 Ma Sturtian, the 635 Ma Marinoan, and the ca. 580 Ma Gaskiers glacials, respectively. Two additional observations are noteworthy. Carbonate rocks below the Port Askaig Formation record a [[delta].sup.13]C decline to -6[per thousand] that implies that such downturns may occur in both pre-Sturtian and pre-Marinoan strata. In addition, the Bonahaven Dolomite is not a cap carbonate to the Port Askaig Formation, but exhibits a [[delta].sup.13]C rise to 12[per thousand], which we correlate with the inferred global Keele peak. These data further document the utility of Neoproterozoic glacial-cap carbonate sequences in global correlations and denote the base of the Cranford Linestone as the Cryogenian-Ediacaran boundary. Keywords: Dalradian, Neoproterozoic, cap carbonate, glacial, Caledonides.

Baltica is a progeny of Rodinia, born from the breakup of the supercontinent in the Neoproterozoic. Within Rodinia, Baltica is generally placed adjacent to NE Laurentia but in a variety of configurations, which vary by up to 3000 km along the strike of the Laurentian margin and include both right-way-up and upside-down orientations (current coordinates). Geological and palaeomagnetic data show that the only viable reconstruction juxtaposes the western Scandinavian margin of Baltica, in its right-way-up orientation, against the Rockall--Scotland--SE Greenland segment of Laurentia.

By comparing Silurian through end Permian [approximately equal to] 250 million years (Myr)] charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long-term variations in fire occurrence and fire system diversification are related to fluctuations in Late Paleozoic atmospheric oxygen concentration. Charcoal, a proxy for fire, occurs in the fossil record from the Late Silurian ([approximately equal to] 420 Myr) to the present. Its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13% to 35% (the 'fire window'). Herein, we observe that, as predicted, atmospheric oxygen levels rise from [approximately equal to] 13% in the Late Devonian to [approximately equal to]30% in the Late Permian so, too, fires progressively occur in an increasing diversity of ecosystems. Sequentially, data of note include: the occurrence of charcoal in the Late Silurian/Early Devonian, indicating the burning of a diminutive, dominantly rhyniophytoid vegetation; an apparent paucity of charcoal in the Middle to Late Devonian that coincides with a predicted atmospheric oxygen low; and the subsequent diversification of fire systems throughout the remainder of the Late Paleozoic. First, fires become widespread during the Early Mississippian, they then become commonplace in mire systems in the Middle Mississippian; in the Pennsylvanian they are first recorded in upland settings and finally, based on coal petrology, become extremely important in many Permian mire settings. These trends conform well to changes in atmospheric oxygen concentration, as predicted by modeling, and indicate oxygen levels are a significant control on long-term fire occurrence. Earth system processes | global change | coal | charcoal | inertinite

Recent data indicating that the Piaxtla Suite (Acatlan Complex, southern Mexico) underwent eclogite-facies metamorphism and exhumation during the Devono-Carboniferous suggest an origin within the Rheic Ocean rather than the Iapetus Ocean. The Asis Lithodeme (Piaxtla Suite) consists of polydeformed metasediments and eclogitic amphibolites that are intruded by megacrystic granitoid rocks. U--Pb (zircon) data indicate that the metasediments were deposited after c. 700 Ma and before intrusion of c. 470-420 Ma quartz-augen granite. The metasedimentary rocks contain abundant Mesoproterozoic detrital zircons (c. 1050-1250 Ma) and a few zircons in the range of c. 900-992 and c. 1330-1662 Ma. Their geochemical and Sm-Nd isotopic signature is typical of rift-related, passive margin sediments derived from an ancient cratonic source, which is interpreted to be the adjacent Mesoproterozoic Oaxacan Complex. Megacrystic granites were derived by partial melting of a c. 1 Ga crustal source, similar to the Oaxacan Complex. Amphibolitic layers exhibit a continental tholeiitic geochemistry, with a c. 0.8-1.1 Ga source (ToM age), and are inferred to have originated in a rift-related environment by melting of lithospheric mantle in the Ordovician. This rifting may be related to the Early Ordovician drift of peri-Gondwanan terranes (e.g. Avalonia) from Gondwana and the origin of the Rheic Ocean.

Sensitive high-resolution ion microprobe (SHRIMP) U--Pb ages for detrital zircons from the Caspian region reveal the age ranges of basement terrains that supplied the sediment. One sample from the modern Volga river has groupings at c. 340-370 Ma, c. 900-1300 Ma and c. 1450-1800 Ma, with a small number of older zircons. This is consistent with derivation from the Precambrian basement of the East European Craton, and Palaeozoic arcs in the Urals. Mid- and Late Proterozoic components may be derived from beyond the present Volga drainage basin, such as the Sveconorwegian orogen. A Bajocian sandstone from the Greater Caucasus has 73% zircons that post-date 350 Ma. Ages cluster at c. 165-185 Ma, c. 220-260 Ma, c. 280-360 Ma and c. 440-460 Ma. This pattern suggests derivation from Palaeozoic basement of the Greater Caucasus itself and/or the Scythian Platform, and igneous rocks generated at a Jurassic arc in the Lesser Caucasus. Four samples from the Lower Pliocene Productive Series of the South Caspian Basin have common Phanerozoic grains, and groups between c. 900-1300 Ma and 1500-2000 Ma. Each sample contains zircons dated to c. 2700 Ma. The overall age patterns in the Productive Series samples suggest a combination of East European Craton and Greater Caucasus source components.

Detailed studies of morphological, micromorphological and geochemical characteristics of silcretes in the deep bleached and weathered regolith across a large area of inland Australia have provided a new interpretation of the history of the regolith and its climatic and morphological evolution during the Tertiary. Pedogenic silcretes have distinctive morphological and mineralogical features caused by a succession of phases of silica dissolution and recrystallization resulting from multiple episodes of water infiltration and percolation under alternately wet and dry climates. These are the oldest of the regolith features. Deep, bleached profiles formed over a wide area in a variety of substrates ranging from Precambrian granites to Palaeozoic sandstones, Cretaceous sediments and Tertiary deposits, and represent the second major stage in regolith development. These profiles, in which kaolinite coexists with gypsum, alunite and opal, formed by reaction of the substrates with saline groundwaters, the water-table levels of which progressively fell over the region. Extensive networks of termite burrows constructed to great depth in the bleached regolith followed the water tables down. The climate was warm and dry with a high water deficit. Groundwater silcretes formed near-horizontal lenses and pods of porcellanite and jasper in the bleached regolith. They preserve the primary fabric of the host rock. Groundwater silcretes post-date the construction of termite burrows and were formed during a rise in groundwater tables across the landscape, in places to near-surface environments in broad landscape depressions. The climate was more humid but the presence of gypsum during silicification demonstrates that the groundwaters were still saline. Red--brown hardpans are the youngest silicification features and represent periods of successive infiltration and percolation, and waterlogging, during high rainfall or flood events. They are confined to low regions in the landscape. Mineralogical and geochemical analysis of the bleached profiles, together with geochemical modelling, suggests that ferrolysis is the most likely cause of acidity in groundwater leading to the development of the bleach profiles and/or alunite. Present-day groundwater tables are both at low levels and sulphate-rich. It is possible that acidic alteration leading to bleaching is still active around the extensive playa landscapes in the region.

The type area of the Bahia lnglesa Formation (north--central Chile) is structurally complex as a result of active margin subduction at the Peru--Chile Trench. Inliers of subaerially exposed Mesozoic igneous basement are unconformably overlain by a mid-Miocene to late Pliocene marine siliciclastic sequence, which has become known for its abundance of fossil vertebrates found concentrated in a phosphatite on an omission surface. Mega-boulders derived from one of the largest inliers occur exclusively within this bonebed, which appears to have formed after major localized uplift caused removal of a significant thickness of unconsolidated sediment. The mega-boulders were probably dislodged by a high-magnitude earthquake event that accompanied tilting of the sea floor, and their emplacement was an integral part of the processes involved in genesis of the bonebed.

The sea-cliffs of Ogmore-by-Sea in Glamorgan, South Wales, expose a succession of Early Jurassic nearshore carbonates that drape rocky palaeoplatforms. A sequence-stratigraphic interpretation allows the recognition of four retrogradationally stacked parasequences, the internal facies architecture of each of which is controlled by the bathymetry and geometry of the underlying shore platforms. Preserved facies are interpreted as representative of foreshore, shoreface and offshore environments. Supratidal facies are absent, but representative storm-terrace clast assemblages are preserved in all lithofacies as a result of the cannibalization of the backshore during periods of shoreline retreat driven by sea-level rise. Biostratigraphical calibration allows the reconstruction of sea-level history and the correlation of regionally important flooding surfaces in the Rhaetian--Sinemurian of Southern Britain with the position of the contemporary shoreline. This suggests that platform incision in South Wales occurred several million years before the onset of major deposition; superseding deposits above ancient rock shore platforms may therefore not be representative of the environment in which coastal incision took place. As one of the best examples of its kind, the rockshore at Ogmore acts as a deposystem model for ancient rocky shores worldwide.

This paper deals with the origin and structural relationships of the leucocratic dykes that intruded the Ronda peridotites. Plagiogranites are frequent in ophiolitic sequences, but similar Si-rich melts are scarce in orogenic lherzolites. The Ronda peridotites could be an excellent target in which to look for Si-rich melts of mantle origin, as they form the largest mass of orogenic lherzolites in the world and contain many granite dykes. However, petrographic and geochemical data provide evidence that the dykes come from felsic magmas originated from partial melting of the continental crust. Structural studies of the deformed and undeformed dykes reveal that they are non-Andersonian dykes that exploited pre-existing fractures. Undeformed dykes display N15[degrees]E strike, whereas the deformed ones show N[degrees]E or N100[degrees]E trends and sinistral and dextral shear senses, respectively. These structural data point to reactivation of pre-existing fractures either as tensional cracks (undeformed dykes) or transtensional shear zones (deformed dykes) during the ENE-directed thrusting of the Ronda peridotites. Consequently, the dominant N15[degrees]E trend of the undeformed dykes can be used to infer an ENE-thrusting direction for the buried basal shear zone of the Ronda peridotites.

The Chachil depocentre is one of a number of early Mesozoic extensional basins that form the early depocentres of the southern Neuquen Basin in Argentina. The synrift volcanic fill is composed of andesites, rhyolites and volcaniclastic deposits. Coarse-grained, non-marine facies dominate the sedimentary fill, mainly in the form of sediment gravity flow deposits. Stream flow deposits and minor non-marine carbonates are also locally present. The evolution of the graben border system was mainly controlled by subsidence along the main boundary fault (the Chihuido Bayo fault system) and recurrent volcanic activity. Marked changes in the thickness of the synrift megasequence indicate that episodic normal faulting in the hanging wall was also important. The integration of structural, magmatic and sedimentary data from the study area has led to the definition of three stages in the evolution of the synrift succession. The early rift stage is defined by the interplay between bimodal volcanism and gravity-driven sedimentation. The mid-tiff stage is marked by the transition to acidic magmatism (rhyolitic and pyroclastic flows), also associated with coarsegrained non-marine deposition. The late-rift stage is dominated by fine-grained turbidites and pyroclastic falls related to the first marine sedimentation in the Neuquen Basin.

The Karoo large igneous province, formed at c. 183 Ma, is characterized by the presence of voluminous basaltic intrusive complexes within the Karoo Basin, extrusive lava sequences and hydrothermal vent complexes. These last are pipe-like structures, up to several hundred metres in diameter, piercing the horizontally stratified sediments of the basin. Detailed mapping of two sediment-dominated hydrothermal vent complexes shows that they are composed of sediment breccias and sandstone. The breccias cut and intrude tilted host rocks, and are composed of mudstone and sandstone fragments with rare dolerite boulders. Sandstone clasts in the breccias are locally cemented by zeolite, which represents the only hydrothermal mineral in the vent complexes. Our data document that the hydrothermal vent complexes were formed by one or a few phreatic events, leading to the collapse of the surrounding sedimentary strata. We propose a model in which hydrothermal vent complexes originate in contact metamorphic aureoles around sill intrusions. Heating and expansion of host rock pore fluids resulted in rapid pore pressure build-up and phreatic eruptions. The hydrothermal vent complexes represent conduits for gases and fluids produced in contact metamorphic aureoles, slightly predating the onset of the main phase of flood volcanism.

The distribution of primary minerals in a peat profile was investigated in a dated core ([sup.21]Pb, [sup.14]C) taken from the upper part of an ombrotrophic bog. Using XRD, the most abundant minerals present in the peat were those of the local granite, suggesting that the dust entering the bog is mainly of local origin. Apatite and calcite are restricted to the top 8 cm of the profile, which suggests rapid dissolution. The release of P by apatite dissolution is possibly the main source of plant-available P to the oligotrophic waters. In contrast, quartz and feldspars appear to be preserved for thousands of years despite the low pH and abundance of organic acids. This study suggests that ombrotrophic peat bogs could be valuable archives of aluminosilicate deposition since the Late Glacial.

The Dariv Basin is an actively evolving intracontinental transpressional basin located on the eastern flank of the Mongolian Altai. The basin occupies a complex tectonic position between a restraining bend, a thrusted basement block, and two major conjugate strike-slip fault systems. Structures and sedimentary strata exposed within the Dariv Basin suggest a Mesozoic and Cenozoic two-stage evolution. Jurassic--Cretaceous strata fine upward and record alluvial fan, fluvial and lacustrine depositional environments. The distribution of Mesozoic sedimentary rocks and the presence of a suspected Jurassic normal fault array suggest that the Dariv Basin initially formed as an extensional basin. Following Palaeogene tectonic quiescence, Oligocene--Recent basin fill is dominated by alluvial fan sediments derived from basin-flanking ranges. The modern basin is deforming by thrusting, normal fault inversion and folding along discrete belts expressed as intrabasinal ridges and domes. These belts define a rhomboid of active deformation that compartmentalizes the basin. Sediments derived from these discrete deforming belts and from basin flanking ranges continue to accumulate in the basin centre. Thus, modern fans contain reworked older basin fill and competing processes of sedimentation, deformation, erosion and resedimentation can be observed. The Dariv Basin is an excellent example of a transpressional piggyback basin in the early stages of basin inversion and destruction.

The magnetic fabrics and microstructures of the Variscan granite pluton of Bodmin (Cornwall) have been studied. Its low susceptibility magnitude, consistent with its lack of magnetite, comes from biotite and tourmaline. As the magneto-crystalline behaviour of tourmaline is 'inverse' compared with that of the phyllosilicates, the magnetic fabric was remeasured after heating the specimens to enhance the biotite magnetic signal by the growth of mimetic magnetite. The roughly similar magnetic fabrics before and after heating demonstrate that the effect of tourmaline is not important as long as the tourmaline content does not exceed that of the phyllosilicates. Regionally, this study reveals a well-defined NNW trend of the magnetic lineations with opposite plunges on each side of a separation line crossing the pluton centre. This pattern, very similar to that documented in the nearby Carnmenellis pluton, is ascribed to unroofing during emplacement. It agrees with the late to post-magmatic NW stretch that characterizes the Devonian to Carboniferous formations located to the north of this region, the thrust-and-fold structure of which is attributed to southward compression. We conclude that syntectonic emplacement may have characterized the whole Cornubian batholith at the very end of the Variscan orogeny in Cornwall.

The tectonic evolution of the Campania margin during the late Pliocene--Pleistocene is characterized by extensional deformation coeval with the opening of the Marsili oceanic basin. The initial stages of stretching are represented in the analysed area by the development of low-angle normal faults that extended the belt in the same direction as the direction of spreading recognized for the oceanic basin. Detachment faulting was accompanied by the onset of magmatic activity and by major uplifts that resulted in the accumulation of thick conglomerate successions in the half-grabens that developed in the upper plate of the extensional detachment. Deformation continued during the Mid-Pleistocene with the formation of strikeslip and normal faults trending almost parallel to the spreading direction of the Marsili basin. These faults dissected the extensional detachment and promoted counter-clockwise block rotations about vertical axes, which accommodated the ESE-directed stretching of the Marsili basin and the consequent sinistral shear imposed on the southern Apennine chain. The development of a regional detachment fault along the Tyrrhenian margin of Campania explains the complex patterns of subsidence and uplift that characterize this area during the Pleistocene and fits well within the regional geodynamic framework of the southern Tyrrhenian Sea.

New stratigraphically controlled pollen data from the late Early Cretaceous of Portugal allow a recalibration of the classical continental succession of the Potomac Group (USA), which has long been used to demonstrate the gradual morphological changes of angiosperm leaves and pollen. The Portuguese record represents the best dated succession of angiosperm pollen assemblages of the interval between the late Barremian and the mid-Albian. Comparison of the angiosperm pollen record of the Potomac Group with the pollen assemblages from Portugal and with other independently dated records indicates that the distinct differences in the angiosperm pollen assemblages between the three formations of this group (the Patuxent Formation, Arundel Clay Formation and Patapsco Formation) are related to discontinuities. Our revised age model for the Potomac Group implies a major discontinuity between the Arundel Clay (of early Albian age), and the Patapsco Formation (of mid-Albian--early Cenomanian age). The Portuguese record reveals a so far undocumented radiation phase of angiosperms within the early Aptian to mid-Albian in which monocolpate angiosperm pollen of monocot and/or maguoliid affinity appear as a highly diversified group. These new findings imply that the onset of the radiation of monocots--magnoliids preceded the radiation of eudicots by at least 10 Ma.

This study tested the potential for high-resolution quantitative biostratigraphic methods to distinguish tectonic from supposedly eustatic sequences. The study employed automated multidimensional graphic correlation using constrained optimization (program CONOP). Our analysis was based on 15 onshore sections in eastern New Zealand spanning the Coniacian to Maastrichtian stages (Upper Cretaceous), and 398 well-constrained lowest- or highest-occurrence records derived from 245 dinoflagellate species. The age of the resulting composite section was calibrated using six dated bioevents; two of these events were tied to geochemical or paleomagnetic datums. Following calibration, the composite section had an average relative temporal resolution of less than 130 k.y. through the study interval, although the succession of events was not dated to this level of precision in an absolute sense. Although the CONOP composite will not resolve unconformities or condensed intervals that occur across all studied sections, such 'global' unconformities can be identified using clusters of events that are placed at a single composite level. Fifteen major event clusters were identified, 10 of which coincided closely with sequence boundaries identified in the Northern Hemisphere; the probability of this coincidence arising by chance alone is ~8%. Although these results must be regarded as provisional, they suggest that high-resolution quantitative stratigraphy can provide a potent tool for the identification and correlation of stratigraphic sequences. Furthermore, our findings add significant support for recent studies that have argued for the presence of Late Cretaceous eustasy. Keywords: biostratigraphy, correlation, eustasy, Late Cretaceous, New Zealand, quantitative analysis, sequence stratigraphy, unconformities.

The Dorrel Rock intrusive complex in Marie Byrd Land, West Antarctica, consists of a coarse-grained gabbro cut by fine-grained benmoreite and trachyte dikes, all exposed in a single nunatak. It is the only exposed plutonic body related to late Cenozoic volcanism in this part of the West Antarctic rift system. Our [sup.40]Ar-[sup.39]Ar age determinations indicate emplacement of the gabbro took place ca. 34 Ma, followed by dike injection at ca. 33.5 Ma. Marie Byrd Land volcanoes are all younger than ca. 27-29 Ma, and lie on a low-relief Late Cretaceous erosion surface that has been disrupted by block faulting and dome uplitt since late Oligocene time. The erosion surface and overlying volcanoes are well preserved, but in contrast, we estimate that at least 3 km of overburden has been eroded away to expose the gabbro. This anomaly is most easily explained if most of the exhumation took place during a period of rapid erosion between ca. 34 Ma and 27-29 Ma and was followed by a pronounced decrease in erosion rate in the late Oligocene. Temporal anomalies in the degree of dissection of volcanic edifices, together with evidence from hydrovolcanic deposits, suggest there was an ice cap in Marie Byrd Land in the late Oligocene and that inland (200+ km) volcanoes were being actively eroded by glaciers until ca. 15 Ma. This is consistent with seismic and stratigraphic work in the Ross Sea, which documents at least two expansions of the West Antarctic Ice Sheet in the early mid-Miocene. We find that rates of glacial erosion in Marie Byrd Land increase significantly with nearness to the coast, and in nonresistant rock. Thus, the observation that inland volcanoes younger than ca. 15Ma show no effects of glacial erosion, except for one with a basal section of weak tuffs, suggests that a transition from warm-based to cold-based glaciers took place around 15 Ma. These findings are similar to many of those reported from well-studied McMurdo Sound and Ross Sea localities, so they provide a wider regional picture of middle to late Cenozoic climatic and surficial geologic events in Antarctica. Keywords: erosion anomalies, erosion rate, glacial erosion, volcanic morphology, West Antarctic Ice Sheet.

During detachment folding, the relationship between differential uplift and shortening depends on the mechanism of fold growth, such as limb rotation or hinge migration, and may vary over the lifetime of a fold. Thus, neither long-term shortening rates nor the present fold geometry unambiguously constrain the kinematics of fold growth. Where rivers cut through growing anticlines, flights of abandoned fluvial terraces act as passive kinematic markers. As shortening progresses, the terraces become deformed and thereby preserve critical information about the kinematics and evolution of active fold growth. To constrain recent fold growth across three detachment folds in the Kashi-Atushi fold system in the SW Tian Shan, China, we surveyed flights of deformed terraces and compared them with geometric models of successively emplaced horizontal unconformities (terraces) across pregrowth strata deformed by hinge migration, limb rotation, and a combination of the two. Migration of angular hinges and curved hinge zones were also compared. Each kinematic model predicts both a distinct geometry for the deformed terraces and contrasting angular relationships between the terraces and the pregrowth strata. Notably, limb rotation and migration of curved hinge zones result in progressively rotated terraces that cut across pregrowth strata, whereas all limb-lengthening models result in parallelism between pregrowth strata and terrace straths across much of the fold. The Kashi-Atushi terraces show clear evidence of abandoned axial surfaces, concentrated deformation near the core of the folds, and progressive tilting with age. When compared to the model predictions, the folds are likely growing by a combination of limb rotation in the tight cores of the folds and hinge-zone migration of pregrowth strata across the flanks of the folds. Keywords: strath terrace, active folding, intracontinental mountains, fault-related fold, landform evolution.