Meters In Thickness Research Articles

Detachment-controlled triangle zones in extension and inversion tectonics

“Triangle zone” geometry is well established in thrust tectonics, where the leading edge of a frontal thrust branches backward onto a hinterland-directed roof thrust, and the triangle zone thus formed defines the thrust system’s leading edge. Similar geometries occur in extension and inversion settings, where a triangle zone can form between a deep-seated master fault and a roof fault or backthrust located in a hanging-wall detachment. In basement-controlled extension, triangle zone development can occur when the shear strength of the master fault plane in the zone above a hanging-wall detachment cutoff exceeds that of a new or reactivated antithetic fault detaching on the hanging-wall dip slope. This structural style is characterized by pronounced hanging-wall synclines linked to detached extensional faults higher up the hanging-wall dip slopes. The same principles apply during early phases of inversion tectonics. The part of the master fault that is above the hanging-wall detachment cutoff may constitute a buttress that causes displacement to backthrust along any available detachment into accommodation structures such as emergent ramps. This structural style is characterized by compressional structures within the graben while there is minor or even no sign of inversion on the graben margin faults. These geometries could be accounted for by other processes, for example, localized deep-seated fault-controlled structures within graben, or salt redistribution. However, fieldwork and analog models demonstrate the admissibility of triangle zone kinematics across a range of tectonic settings in the presence of detachment layers that are thin relative to the overall stratigraphy — typically tens to hundreds of meters in thickness. These models can guide seismic interpretation of unusual fold structures in extensional and inverted graben. Seismic interpretation examples were evaluated from the North Sea and Saudi Arabia.

Reprint of “The possibility of underground gasification of lignite from Polish deposits”

The paper focuses on the possibility of underground gasification of lignite from Polish deposits. Lignite deposits in Poland are part of the European Lignite Formation. The profile of coal bearing sediments in Poland is several hundred meters (Paleocene–Pliocene), but it is fragmented vertically and is not complete at any point. It includes marine and brackish sediments, as well as Paleogene and Neogene land sediments. Lignite deposits originated both in platform areas and sedimentary basins in orogenic belts. The coals form extensive seams or lenses ranging from few meters to several dozen meters in thickness. There are 90 documented lignite deposits in Poland.Currently, geological resources of lignite are about 26,132Mt. On the Polish Lowland, ten lignite (eight major and two accompanying) seams have been distinguished within the Paleogene and Neogene stratigraphic columns. Only three of them (1st Mid-Polish, 2nd Lusatia, 3rd Ścinawa), and locally-five (additionally 2ndA Lubin and 4th Dąbrowa) are important from the economic point of view.The annual production of lignite in Polish open cast mines amounts to 65.0Mt per year, while it is primarily used by power plants. However, chemical processing of lignite is not yet developed. It is planned that pilot plants are to be developedfor underground lignite gasification in the near future. The geological structure of the Tertiary coal-bearing formation in the Polish Lowland was the basis for the development of guidelines and parameters for criteria verification of resource base (ortho-lignite) for underground coal gasification (UCG) in Poland. Lignites from the Polish coal deposits havethe characteristics of low rank coal (mean Rr 0.2–0.35), an average carbon content at around 62–65% C, high moisture content (>50%) and net calorific value (NCV) 6–20MJ/kg (mean 8.0MJ/kg).Petrographic composition of lignite (>80% humic components) makes it a preferred material for chemical processing. The available resources and lignite deposits have been verified on the basis of the assumed geological and technological criteria. Since the geologic and reservoir conditions are accompanied by the requirements of environmental protection, protection of groundwater reservoirs of drinking water and distance requirements between the gasification plants and residential buildings, roads and transmission lines, a significant reduction in coal resources suitable for underground gasification in Poland occurred. The aforementioned criteria were applied to the initial verification of lignite resources in the Polish deposits. The deposits useful for underground gasification are mainly located in the area from Głogów up to Ściniawa and Legnica. Some individual deposits are scattered in different locations (e.g. Węglewice, residual part of the Turów deposit).

Growth of cyclone Viyaru and Phailin – a comparative study

The tropical cyclone Viyaru maintained a unique quasi-uniform intensity during its life span. Despite being in contact with sea surface for >120 hr travelling about 2150 km, the cyclonic storm (CS) intensity, once attained, did not intensify further, hitherto not exhibited by any other system over the Bay of Bengal. On the contrary, the cyclone Phailin over the Bay of Bengal intensified into very severe cyclonic storm (VSCS) within about 48 hr from its formation as depression. The system also experienced rapid intensification phase (intensity increased by 30 kts or more during subsequent 24 hours) during its life time and maximum intensity reached up to 115 kts. In this paper, a comparative study is carried out to explore the evolution of the various thermodynamical parameters and possible reasons for such converse features of the two cyclones. Analysis of thermodynamical parameters shows that the development of the lower tropospheric and upper tropospheric potential vorticity (PV) was low and quasi-static during the lifecycle of the cyclone Viyaru. For the cyclone Phailin, there was continuous development of the lower tropospheric and upper tropospheric PV, which attained a very high value during its lifecycle. Also there was poor and fluctuating diabatic heating in the middle and upper troposphere and cooling in the lower troposphere for Viyaru. On the contrary, the diabatic heating was positive from lower to upper troposphere with continuous development and increase up to 6∘C in the upper troposphere. The analyses of cross sections of diabatic heating, PV, and the 1000–500 hPa geopotential metre (gpm) thickness contours indicate that the cyclone Viyaru was vertically tilted (westward) and lacked axisymmetry in its structure and converse features (axisymmetric and vertical) that occurred for the cyclone Phailin. In addition, there was a penetration of dry air in the middle troposphere of Viyaru, whereas high moisture existed in the middle troposphere of Phailin. The vertical wind shear (5–10 ms−1) near the core of the storm region between 850 and 200 hPa was favourable for both the systems but was higher in the northern region of the cyclone Viyaru. The divergent development of these thermodynamic features conspired to produce converse characteristic of the two cyclones.

Arctic–alpine blockfields in the northern Swedish Scandes: late Quaternary – not Neogene

Abstract. Autochthonous blockfield mantles may indicate alpine surfaces that have not been glacially eroded. These surfaces may therefore serve as markers against which to determine Quaternary erosion volumes in adjacent glacially eroded sectors. To explore these potential utilities, chemical weathering features, erosion rates, and regolith residence durations of mountain blockfields are investigated in the northern Swedish Scandes. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay / silt ratios, secondary mineral assemblages, and imaging of chemical etching of primary mineral grains in fine matrix are each used for this purpose. Secondly, erosion rates and regolith residence durations of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surfaces. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite consistent variability according to slope position. In addition, average erosion rates of ~16.2 and ~6.7 mm ka−1, calculated for the two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few metres in thickness, within a late Quaternary time frame. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. The persistence of autochthonous blockfields over multiple glacial–interglacial cycles confirms their importance as key markers of surfaces that were not glacially eroded through, at least, the late Quaternary. However, presently blockfield-mantled surfaces may potentially be subjected to large spatial variations in erosion rates, and their Neogene regolith mantles may have been comprehensively eroded during the late Pliocene and early Pleistocene. Their role as markers by which to estimate glacial erosion volumes in surrounding landscape elements therefore remains uncertain.

The possibility of underground gasification of lignite from Polish deposits

The paper focuses on the possibility of underground gasification of lignite from Polish deposits. Lignite deposits in Poland are part of the European Lignite Formation. The profile of coal bearing sediments in Poland is several hundred meters (Paleocene–Pliocene), but it is fragmented vertically and is not complete at any point. It includes marine and brackish sediments, as well as Paleogene and Neogene land sediments. Lignite deposits originated both in platform areas and sedimentary basins in orogenic belts. The coals form extensive seams or lenses ranging from few meters to several dozen meters in thickness. There are 90 documented lignite deposits in Poland.Currently, geological resources of lignite are about 26,132Mt. On the Polish Lowland, ten lignite (eight major and two accompanying) seams have been distinguished within the Paleogene and Neogene stratigraphic columns. Only three of them (1st Mid-Polish, 2nd Lusatia, 3rd Ścinawa), and locally-five (additionally 2ndA Lubin and 4th Dąbrowa) are important from the economic point of view.The annual production of lignite in Polish open cast mines amounts to 65.0Mt per year, while it is primarily used by power plants. However, chemical processing of lignite is not yet developed. It is planned that pilot plants are to be developedfor underground lignite gasification in the near future. The geological structure of the Tertiary coal-bearing formation in the Polish Lowland was the basis for the development of guidelines and parameters for criteria verification of resource base (ortho-lignite) for underground coal gasification (UCG) in Poland. Lignites from the Polish coal deposits havethe characteristics of low rank coal (mean Rr 0.2–0.35), an average carbon content at around 62–65% C, high moisture content (>50%) and net calorific value (NCV) 6–20MJ/kg (mean 8.0MJ/kg).Petrographic composition of lignite (>80% humic components) makes it a preferred material for chemical processing. The available resources and lignite deposits have been verified on the basis of the assumed geological and technological criteria. Since the geologic and reservoir conditions are accompanied by the requirements of environmental protection, protection of groundwater reservoirs of drinking water and distance requirements between the gasification plants and residential buildings, roads and transmission lines, a significant reduction in coal resources suitable for underground gasification in Poland occurred. The aforementioned criteria were applied to the initial verification of lignite resources in the Polish deposits. The deposits useful for underground gasification are mainly located in the area from Głogów up to Ściniawa and Legnica. Some individual deposits are scattered in different locations (e.g. Węglewice, residual part of the Turów deposit).

Gridino melange zone of the Belomorian eclogite province: Succession of tectonic events and structural position of mafic dyke swarms

Based on relationships between Paleoproterozoic mafic dykes, lithotectonic complexes, and tectonic structures of the Gridino Zone in the Belomorian eclogite province of the Fennoscandian Shield, deformations have been divided into groups differing in age and the succession of tectonic events has been reconstructed. The formation of Neoarchean eclogite-bearing melange was related to disintegration of large eclogite sheets in the course of near-horizontal ductile flow accompanied by syntectonic granitoid magmatism, multiple migmatization, and granulite-to amphibolite-facies metamorphism. The exotic blocks, including eclogites, were incorporated into TTG gneisses as sheets and lenses up to a few hundreds of meters in thickness and oriented conformably with gneissic banding. As a result of ductile flow, the lithotectonic complexes were transported at the level of discrete brittle-ductile deformations expressed as strike-slip faults and associated folds. Under conditions of a relatively rigid medium, individual structural elements underwent rotation approximately through 90° in plan view. Under the extension regime in the Early Paleoproterozoic, several swarms of mafic dykes were injected into the already cold framework rocks, as is evident from dyke morphology. The dykes crosscut all predated structures, included turned blocks, and are therefore important reference points for subdivision of Neoarchean and Paleoproterozoic processes. The Svecofennian postdyke tectonic activity was accompanied by local shearing and boudinage of metabasic rocks, development of quartz and pegmatite veins along tension cracks, disharmonic folding, and discrete retrograde metamorphism up to amphibolite-facies conditions. The postdyke deformations did not exert a substantial effect on the previously formed regional structure.

Mass-transport deposits in a Variscan wedge-top foreland basin (Pisuerga area, Cantabrian Zone, NW Spain)

Large-scale mass-transport deposits (MTDs) from two wedge-top depocentres in a Variscan foreland-basin system (Cantabrian Zone, Iberian Massif, northern Spain) have been studied to gain a better understanding of the processes involved in comparable deposits found in modern submarine environments. The well-exposed outcrops allow documenting the composition, internal organization and lateral changes of the MTD units, and, additionally, to know their frequency and significance in a tectonically active depositional setting. The synorogenic 5000 m-thick succession that contains these resedimented units comprises seven major tectonically controlled sequences, whose bounding unconformities were recognised by seismic-scale stratal patterns, such as fault-propagation and growth-fold geometries (wedging, truncation and onlap). These major sequences range between 4 and 0.4 Myr in duration and between 1300 and 200 m in thickness and display an overall shallowing-upward trend, from a basal MTD and deep-water sediments (prodeltaic mudstone wedges, turbidites) to shallow-marine carbonates and deltaic deposits. Each major sequence consists of one or more transgressive–regressive high-frequency sequences, up to several hundred metres in thickness, showing rapid lateral changes of facies associations across the wedge-top depocentres. The MTD units are composed of megaclasts (up to 2 km long and 360 m thick) embedded in mudstones, matrix- and clast-supported breccias and conglomerates with variable internal organization, and subordinate turbidite sandstones, deposited from slides, and gravity flows from cohesive debris flows to high-density turbidites. These en masse deposits originated from the failure of shelf to slope reaches and some of them constitute multiepisodic units resulting from several large-scale collapse events. These collapses could have been triggered by several factors, mainly related to the growth of fault-propagation anticlines during thrust emplacement. The ensuing tectonic overload would lead to strong flexural subsidence and to the modification of the basin profile. Both the major sequences and the MTD units are a useful tool for correlating the highly deformed and faulted successions across the three fault-bounded synclines and establishing a coherent stratigraphic framework.

Afloramientos carboníferos en la quebrada La Herradura, Provincia de San Juan (oeste de Argentina), revisados: edad de las transgresiones.

At the outcrops of the Tupe Formation in the La Herradura Creek, San Juan Province, two transgressive events are recorded, which range from few meters to tens of meters in thickness. These strata correspond to the stratotype of the faunal Tivertonia jachalensis-Streptorhynchus inaequiornatus Biozone. An evaluation of the timing of the two marine transgressions is made on the basis of palynological assemblages and available radiometric ages. A short-lived transgression is recorded in the latest Bashkirian-early Moscovian, and then a substantial sea level fall took place forming an irregular incision surface. Later, a major high eustatic sea-level occurred during the middle Moscovian resulting in a more important marine ingression. The palynological assemblages associated to the older transgressive event indicate the presence of the Raistrickia densa- Convolutispora muriornata (DM) Biozone (Subzone B). Palynofloras referred to the Subzone C of the DM Biozone characterize the strata of the younger transgression that also bear marine fauna of the Tivertonia jachalensis-Streptorhynchus inaequiornatus Biozone. Correlations with other Pennsylvanian outcrops in the region give support to the stratigraphic scheme here proposed.

Nucleation and growth of the Naica giant gypsum crystals

The Cave of Giant Crystals in the Naica mine (Mexico) is one of the most amazing displays of mineral beauty ever created in nature. In addition to the colossal crystals of gypsum, which in some cases exceed eleven meters in length and one meter in thickness, the scenery fashioned by the crystalline beams that thrust through the darkness of the cave from floor to ceiling with a luster like moonlight is a unique example of harmony based on crystal symmetry. We review the crystallogenesis of this remarkable and challenging phenomenon of mineralization near equilibrium that can be used to teach the basics of nucleation and crystal growth.

Storm‐dominated shelf‐edge delta successions in a high accommodation setting: The palaeo‐Orinoco Delta (Mayaro Formation), Columbus Basin, South‐East Trinidad

AbstractPliocene age deposits of the palaeo‐Orinoco Delta are evaluated in the Mayaro Formation, which crops out along the western margin of the Columbus Basin in south‐east Trinidad. This sandstone‐dominated interval records the diachronous, basinwards migration of the shelf edge of the palaeo‐Orinoco Delta, as it prograded eastwards during the Pliocene–Pleistocene (ca 3·5 Ma). The basin setting was characterized by exceptionally high rates of growth‐fault controlled sediment supply and accommodation space creation resulting in a gross basin‐fill of around 12 km, with some of the highest subsidence rates in the world (ca 5 to 10 m ka−1). This analysis demonstrates that the Mayaro Formation was deposited within large and mainly wave‐influenced shelf‐edge deltas. These are manifested as multiple stacks of coarsening upward parasequences at scales ranging from tens to hundreds of metres in thickness, which are dominated by storm‐influenced and wave‐influenced proximal delta‐front sandstones with extensive, amalgamated swaley and hummocky cross‐stratification. These proximal delta‐front successions pass gradationally downwards into 10s to 100 m thick distal delta front to mud‐dominated upper slope deposits characterized by a wide variety of sedimentary processes, including distal river flood and storm‐related currents, slumps and other gravity flows. Isolated and subordinate sandstone bodies occur as gully fills, while extensive soft sediment deformation attests to the high sedimentation rates along a slope within a tectonically active basin. The vertical stratigraphic organization of the facies associations, together with the often cryptic nature of parasequence stacking patterns and sequence stratigraphic surfaces, are the combined product of the rapid rates of accommodation space creation, high rates of sediment supply and glacio‐eustasy in the 40 to 100 Ka Milankovitch frequency range. The stratigraphic framework described herein contrasts strikingly with that described from passive continental margins, but compares favourably to other tectonically active, deltaic settings (for example, the Baram Delta Province of north‐west Borneo).

A new marine magnetotelluric measurement system in a shallow-water environment for hydrogeological study

We have developed a new marine magnetotelluric (MT) measurement system that can reduce noises caused by sea wave motions and can be applied to measurements under very shallow seawater areas, such as a coastal region with a sea depth of 10 to 100 m. The difficulties of geophysical exploration in shallow water and coastal areas include (1) fishery activity, (2) limitations of survey vessel size, and (3) motion noise caused by sea waves. In order to overcome these difficulties, we selected a MT method that uses natural EM fields without transmitting an electric current in seawater, which enables the method to be used in areas with active inshore fisheries. In addition, the developed marine MT system is very short, which reduces motion generated by sea waves, and compact, which enables light-draft small survey boat operation. We conducted offshore data acquisition using a new MT measurement system and an onshore MT survey at the Horonobe coastal area, Hokkaido, Japan. High-quality data were successfully obtained in both onshore and offshore field surveys. Two-dimensional (2D) inversion for field data from onshore to sea bottom reveals that a quaternary sedimentary layer of a few hundred meters in thickness, which was determined by well logging to be a freshwater layer, extends horizontally offshore for several kilometers under the sea. The results obtained herein demonstrate that the newly developed marine MT measurement system can be used to clarify the geoelectrical structures of brackish/fresh groundwater distributions and in coastal areas. • We have developed a new magnetotelluric system for very shallow seawater region. • High-quality data were obtained in field surveys at coastal area. • 2D inversion reveals the geoelectrical structure from onshore to sea bottom. • The new system can be used to estimate groundwater distributions in coastal areas.

Late Miocene to recent morphotectonic evolution and potential seismic hazard of the northern Lerma valley: Clues from Lomas de Medeiros, Cordillera Oriental, NW Argentina

Abstract The Lomas de Medeiros are low relief hills located at the northern extreme of the Lerma valley, where new structural, morphological and topographic key data have been collected and integrated with the available stratigraphic and geochronological data in order to elucidate the morphotectonic evolution of the region during the last ~ 10 Ma. In this area, Pliocene to Lower Pleistocene conglomerates and siltstones (Piquete Formation) are deformed delineating an asymmetrical anticline with eastward vergence, axial plane trending N10°E, and progressive unconformities at the backlimb. Syntectonic sedimentation has been documented as related to N–S trending normal faulting near the fold axis as well. Middle Pleistocene to Holocene thick fluvial conglomerates cover unconformably the Piquete Formation as strath terraces with a few meters of thickness. The higher and oldest terrace has been uplifted more than 160 m respect to the top of Calvimonte Formation conglomerates (~ 0.33 Ma), its stratigraphic correlate at the undeformed Lerma valley. Detailed topographic profiles of the terraces show evidences of progressive uplifting by folding and the presence of scarps related with reverse faulting. The anticline has been modeled using the fault propagation folding mechanism with a blind ramp dipping 32° to the west and a decollement level located 2.7 km below the surface, at the contact between the Cenozoic cover and the Paleozoic basement. The integration of these observations with previously published data allowed to establish the morphotectonic evolution of this region during the last 10 Ma. Folded and faulted Middle Pleistocene to Holocene terraces at Lomas de Medeiros and Upper Pleistocene deposits uplifted at Mojotoro range are strong evidences of the seismogenic potential of the faults related with these morphostructures. Applying relationships with the subsurface rupture length, earthquakes with maximum moment magnitudes (M w ) of 6.5, 7.0 and 7.1 have been estimated for Medeiros, Lesser and Mojotoro faults respectively.

Sofalica Region (GAZIANTEP) Chromium on Microgravity Anomalies Modelling of Normalized Full Gradient and Nonlinear Inversion

In this study, the province of Gaziantep, Sehitkamil district, there are thought to be chrome-metallic mine in the village of Sofalica the localization of gravity and economical method was to investigate whether it has a reserve. Approximately 189 hectares of land gravity measurements over the measurement point in the study area was 220. By differentiating regional and residual Bouguer gravity map of the generated residual maps were obtained on areas likely to be created on the source. The inversion method of pre-NTG was required for the selection model is the appropriate start. On the structure of polygon slices as a result of application received in the form of the inversion in the range of 125 meters and 450 meters long, 25 meters to 70 meters in thickness in the range of existence of geometric structures have been identified.

Interplay between depositional facies, diagenesis and early fractures in the Early Cretaceous Habshan Formation, Jebel Madar, Oman

Diagenesis and fracturing can significantly alter petrophysical properties of subsurface carbonate reservoirs, but the impacts of these processes at the inter-well scale are hard to predict. However, the initial distribution of sedimentary facies is easier to predict, and could template future diagenetic transformation and potentially influence fracturing as well. This paper provides a case study investigating the mutual influence of depositional facies on diagenesis and interpreted early fractures in the Berriasian–Valanginian Habshan Formation in Jebel Madar (Oman). The Habshan Formation mostly comprises ooidal limestones but dolomitized beds a few metres in thickness and laterally correlatable over at least 5 km are present. Discordant (vertical) dolomite streaks are present in the limestone but are rare. The various sedimentary and diagenetic processes were investigated using fieldwork, XRD analysis, petrography and geochemistry (major and trace elements, stable carbon and oxygen isotopes and strontium isotopes). The lithologies consist of mud-lean ooidal grainstones, mud-rich ooidal packstones and bioturbated limestones. The changes in the amount of fine-grained sediment suggest changing energy conditions at a backshoal position of a carbonate platform. The mud-lean versus mud-rich depositional textures impacted on early diagenesis by promoting abundant calcite cementation in the mud-lean ooidal grainstones and dolomitization in the mud-rich packstones. The discordant bodies, interpreted as sediment-filled early fractures, are dolomitized in the same way as the mud-rich ooidal packstones. Dolomitization occurred probably during the Valanginian–Hauterivian in a shallow burial setting, and was most likely caused by seepage reflux. Salt-doming post-dated dolomitization of the Habshan Formation. The results of this study document the inter-relationship between sedimentary facies, early diagenesis and early fractures.

Characterization of a deeply buried paleokarst terrain in the Loppa High using core data and multiattribute seismic facies classification

The recognition of paleokarst in subsurface carbonate reservoirs is not straightforward because conventional seismic interpretation alone is generally not sufficient to discriminate karstified areas from their surroundings. In the Loppa High (Norwegian Barents Sea), a protracted episode of subaerial exposure occurring between the late Paleozoic and mid-Triassic—Late Permian to Anisian—resulted in a significant overprinting of the previously deposited carbonate units. Here, we map the extension of the karstified areas using an integrated approach consisting of (1) a core study of critical paleokarst intervals, (2) a three-dimensional (3-D) seismic stratigraphic analysis, and (3) a 3-D multiattribute seismic facies (SF) classification. A core retrieved in the flat-topped Loppa High revealed breccia deposits at least 50 m (164 ft) thick, which probably resulted from cave collapses following the burial of the karst terrain. The SF classification was tested on a 3-D cube to (1) discriminate the respective SF related to the breccia deposits compared with other SF and (2) to estimate their spatial extent. Seismic-facies analysis suggests that breccias occupied the topmost area of the structural high, extending up to 12 km (7 mi) in width, 46 km (29 mi) in length, and tens of meters in thickness. The inference of such a large amount of breccia suggests that a significant part of this terrain was derived from the amalgamation of successive cave-development events—including periods of subaerial exposure and subsequent burial and collapse—resulting in a coalesced collapsed paleocave system. Previous observations from the Loppa High revealed the presence of karst plains associated with sinkholes, caves, and other dissolution phenomena associated with the breccia facies, further suggesting that a large volume of carbonate rocks in this area was affected by subaerial exposure and karstification. Our integrated approach and proposed karstification model could be applied to similar sedimentary basins that accommodate deeply buried carbonate successions affected by protracted episodes of subaerial exposure, where only few wells as well as 3-D seismic data are available.

Time scales of erosion and deposition recorded in the residual south polar cap of Mars

The residual south polar cap (RSPC) of Mars has been subject to competing processes during recent Mars years of high resolution image coverage: continuing erosion of scarps while the maximum extent grows as well as shrinks (Piqueux, S., Christensen, P.R. [2008]. J. Geophys. Res. (Planets) 113, 2006; James, P.B., Thomas, P.C., Malin, M.C. [2010]. Icarus 208, 82–85). Additionally, the cap has a variety of morphologies and erosion (scarp retreat) rates (Thomas, P.C., James, P.B., Calvin, W.M., Haberle, R., Malin, M.C. [2009]. Icarus 203, 352–375). Do these different forms and competing processes indicate an aging and possibly disappearing cap, a growing cap, or a fluctuating cap, and is it possible to infer the timescales of the processes acting on the RSPC? Here we use the latest imaging data from Mars’ southern summer in Mars year 30 (Calendar year 2011) to evaluate erosion rates of forms in the RSPC over 6Mars years, and to map more fully features whose sizes can be used to predict deposit ages. Data through Mars year 30 show that scarp retreat rates in the RSPC have remained approximately the same for at least 6Mars years and that these rates of erosion also apply approximately over the past 21Mars years. The thicker units appear to have undergone changes in the locations of new pit formation about 30–50Mars years ago. The thinner units have some areas that are possibly 80Mars years old, with some younger materials having accumulated more than a meter in thickness since Mars year 9. Formation of the thicker units probably required over 100Mars years. The upper surfaces of most areas, especially the thicker units, show little change at the few-cm level over the last 2Mars years. This observation suggests that current conditions are substantially different from those when the thicker units were deposited. A prime characteristic of the evolution of the RSPC is that some changes are progressive, such as those involving scarp retreat, while others, such as the geography of initiation of new pits or the areal coverage of ice, appear to be more episodic.

Spatial and thermal characteristics of mountain permafrost, northwest canada

Lewkowicz, A.G., Bonnaventure, P.P., Smith, S.L. and Kuntz, Z., 2012. Spatial and thermal characteristics of mountain permafrost, northwest Canada. Geografiska Annaler: Series A, Physical Geography, ••, ••–••. doi:10.1111/j.1468‐0459.2012.00462.xABSTRACTAn extensive network of monitoring stations was used to develop a mean annual air temperature map for the complex mountainous terrain in the southern Yukon and northern British Columbia, Canada (latitude 59° to 65° N). Air temperature lapse rates measured at screen height from valley bottoms up to treeline are normal in the maritime extreme southwest, normal but weak in much of the region, and inverted in the highly continental northernmost sites. Relationships between air and ground surface temperatures, expressed as freezing and thawing n‐factors, vary significantly with vegetation type and hence elevational band, with the lowest values for the forested zone and the highest for non‐maritime alpine tundra. Equilibrium modelling carried out for one site in the southern part of the region and one in the northern part illustrates the impacts of the differing n‐factors on trends in mean ground surface temperature with elevation. Ground thermal regimes determined at borehole locations vary greatly due to these climatic controls but are also affected by substrate. Valley‐bottom permafrost in the south is scattered, at temperatures just below 0°C, has a depth of zero annual amplitude of 2–3 m (due to latent heat effects) and may be only a few metres in thickness. Permafrost on bedrock summits is cold, has active layers >5 m thick, is >50 m thick and may be locally continuous. Given the range of air temperatures and n‐factors, permafrost is possible throughout the Yukon but higher temperatures southward and stronger lapse rates mean that a lower elevational limit exists in northern British Columbia.

Soil Compaction by Valmet Forwarder Operation at Soil Surface with and without Slash

Soil compaction by machine used in forest harvesting operation caused negative impacts for regeneration and tree growth. This research was intended to analyze the effectiveness of using slash to decrease soil compaction, to analyze soil compaction at various soil depths, and to measure rut depth at soil surface. Valmet 860.1 forwarder was used in this research. Soil compaction was measured through its bulk density, cone index, and rut depth, under the condition with and without slash. The slash comprised of twigs, branches, and leaves as wastes from harvested Acacia mangium that were stacked to a width of about 1 meter in thickness following forwarder traffic. Results indicated that slash was effective in decreasing soil compaction. About 50% increased in soil compaction by a Valmet forwarder could be reduced by using slash coverings at soil surface. The maximum soil bulk density occurred after 5 forwarder passes. Soil compaction also occurred at subsurface soil. After forwarder traffic, increasing cone index was observed at subsurface of various soil depths. Slash was effective in decreasing soil compaction up to 20 cm in soil depth, although soil compaction by forwarder operation was slightly increased until 50 cm of soil depth. Rut was not observed under the slash however rut of about 24 cm in depth was formed at soil surface without slash. Using slash as coverings for forwarder operation reduced soil damaged. Keywords : soil compaction, forwarder Valmet, Acacia mangium , rutted, slash

Ostracoda (Crustacea) association and a new species (Dolerocypris anatolia nov. sp.) from the Pliocene-Pleistocene Afşin-Elbistan (Kahraman Maraş) Coal Basin of Turkey

Ostracoda (Crustacea) association and a new species (Dolerocypris anatolianov. sp.) from the Pliocene-Pleistocene Afşin-Elbistan (Kahraman Maraş) Coal Basin of TurkeyThe Afşin-Elbistan Coal Basin, which is one of the largest and most important Pliocene-Pleistocene lignite basins of Turkey, is located in Eastern Anatolia. The basin was formed between two normal faults having NE-SW direction and these faults controlled both the sedimentation and the subsidence. The coal horizon of over 50 meters in thickness indicates the balance between the sedimentation and subsidence rates, and was preserved during peat deposition. Coals were generated in this extensive and shallow freshwater lake and evolved from the Pliocene to Pleistocene. Typical faunal and floral assemblages of this ancient Afşin-Elbistan freshwater lake are Ostracoda, Mollusca (Gastropoda and Pelecypoda), spore-pollen and Characeae (gyrogonites). Eleven Cypridoidea species were identified from the investigation area. Eight of them are already known (Candona neglectaSars,Candona iliensisMandelstam,Candonaaff.candida(Müller),Pseudocandona compressa(Koch),Cyclocypris ovum(Jurine),Ilyocypris gibba(Ramdohr),Cypris puberaMüller,Heterocypris salina(Brady)), whereas three belong to open nomenclature —Candonasp. andEucyprissp.;Dolerocypris anatolianov. sp. is proposed as a new species.DolerocyprisKaufmann is one of the largest genera among the freshwater Ostracoda. It has a very wide geographical distribution. Representatives of this genus are actively swimming species found in shallow zones of freshwater lakes and reported from small grassy water bodies with megascopic plants.Dolerocypris anatolianov. sp. is recorded from core samples of the Pliocene-Pleistocene Afşin-Elbistan Coal Basin for the first time.

Extensive surface pedogenic alteration of the Martian Noachian crust suggested by plateau phyllosilicates around Valles Marineris

Thousands of phyllosilicate‐rich outcrops, mainly iron or magnesium‐rich are exposed on Noachian terrains in the Martian southern highlands. We analyzed 90 CRISM observations and more than a hundred HiRISE images located on the plateaus surrounding Valles Marineris. We mapped an extensive Al‐ and Fe/Mg‐phyllosilicate‐rich formation covering at least ∼197,000 km2, for which we introduce the name “Plateau Phyllosilicates.” Tens of meters in thickness, this light‐toned formation crops out at various elevations on top of the Noachian units Npl1 and Npl2, as flat exposures on plateaus and along scarps such as valley walls, chasma walls, pit walls and impact crater rims. The Fe/Mg‐phyllosilicate‐rich lower member of the formation is composed of Fe/Mg‐smectites (nontronite, saponite) and vermiculite. The Al‐phyllosilicate‐rich upper member of the formation contains Al‐smectites (montmorillonite, beidellite) and locally kaolinite and/or halloysite. We suggest that the Plateau Phyllosilicates were mainly formed by pedogenesis related to the weathering of the Noachian bedrock by percolation of meteoric water or melted snow under a temperate and subarid climate during the Noachian Epoch in an alkaline to neutral environment. Kaolinite and/or halloysite may have formed in areas of more intense drainage at the surface under slightly acidic environments during the Noachian and Hesperian Epochs. Fluvial activity and deuteric alteration may have locally contributed to the genesis of phyllosilicates. This study suggests that the alteration of the Noachian basement of the plateaus surrounding Valles Marineris was widespread during the Noachian Epoch, and was still active during the Hesperian Epoch even though the water availability was limited.