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The reddened granitoid facies in the basement of the Polish Sudetes exhibits two categories of alteration spatially arranged with respect to fractures: (1) saussuritization and sericitization within light-colored facies in the interior of fracture-bounded blocks and (2) albitization and hematization in reddened facies occurring adjacent to fracture walls. These alterations are associated with the chloritization of primary ferromagnesian minerals and the development of secondary minerals such as quartz, K-feldspar, apatite, prehnite, calcite, and titanite. We link these parageneses and the observed zonation to a unique alteration event consisting of an interplay of chemical reactions of variable spatial extent. The complete albitization of the feldspars (plagioclase and K-feldspar) adjacent to fractures points to a significant supply of Na for albite neoformation and the availability of oxygen to form the associated hematite. The dating of the iron oxides by paleomagnetism and the secondary monazite associated with the albitized facies by U-Th-Pbtotal unambiguously indicates their post-Variscan ages. In this context, the alterations are related to a regionally widespread post-Variscan paleosurface. The weathering profiles formed in phreatic groundwater environments downgradient of highlands that provided a hydrological head. Sodium supply likely originated from gigantic salt playas that characterized Permian and Triassic lowlands. Weathering was interrupted by the Mesozoic transgression. The recognition of these weathering profiles over extensive parts of the Variscan Belt provides the basis for reconstructing the post-Variscan paleosurface and constraining Triassic and post-Triassic geodynamics, including erosion rates and geomorphological evolution of the Paleozoic massifs in Europe. [ABSTRACT FROM AUTHOR]

Based on detailed stratigraphic correlation and framework studies for FLK-W, in lowermost Bed II and containing the oldest Acheulian artifacts (dated to 1.7 Ma) in Olduvai Gorge, it is possible to document significant changes in the paleolandscape. This study uses outcrops up to 1.6 km from the FLK-W locality to aid in the understanding of the environmental setting available to Acheulian tool-makers. The reconstruction of the FLK-W isochronal paleosurface also provides a means to correlate FLK-W with other contemporary sites found at other lowermost Bed II localities. These sites, such as HWK, HWK-E and HWK-EE are associated with Oldowan artifact assemblages. The reconstruction of the sedimentary environment and geomorphology of the paleosurface indicates these sites are all part of the same fluvial system, although located at different sections along its course. The Oldowan levels are found in a set of small, shallow braided channels. The Acheulian artifacts are associated with a deeper, wider channel formed by the merging of several channels within the drainage network. Based on this analysis, water may have been more readily available at FLK-W and there might have also been a thicker vegetation cover when compared to the Oldowan localities. The sedimentologic and geomorphic contexts appear to help explain the typological/technological variability observed within this section of Bed II. [ABSTRACT FROM AUTHOR]

The Atacama Desert on the western margin of the Central Andes is one of the driest and oldest deserts in the world. It is defined by a distinct and ancient surface, known as the Pacific Paleosurface (PPS) or Atacama Paleosurface. The age of this surface is determined as the time at which sediment deposition ceased, and the surface was effectively abandoned. Early studies suggested that this abandonment took place between 14 and 10 Ma, and was related to both the uplift of the Andes and the onset of hyperaridity in the region. Here we provide a regional re-examination of the PPS, compiling existing work on the underlying geology, sedimentology, surface exposure dating, and seismic profiling. We also present new multispectral satellite maps of the PPS and 45 new cosmogenic 3 He and 21 Ne surface exposure ages in order to constrain the formation age, and the preservation and incision history of the paleosurface. We conclude that the PPS is not a single paleosurface, but instead is a mosaic of smaller surfaces that were formed by aggradational and degradational processes over 19 million years (or more) and should be termed collectively as the Pacific Paleosurfaces. The time at which individual paleosurfaces formed is related to regional climate, where the location of each is controlled by regional tectonic activity. Cosmogenic surface exposure ages suggest that the surfaces are a record of regional scale climate events. [ABSTRACT FROM AUTHOR]

Lopes, V., Freitas, M.C., Andrade, C., Taborda, R., Ramos, R. and Oliveira, M.A. 2013. A GIS-assisted reconstruction of the Holocene transgressive paleosurface of Pederneira lowland (W Portugal) The Last Glacial Maximum low stand and coeval re-incision of the Portuguese hydrographic network created the space and defined the shape of the main morphological features available to accommodate the inundation resulting from the Holocene transgression and the marine sediments deposited in tune with changing base levels. The reconstruction of the transgressive paleosurface is relevant in paleoenvironmental studies, namely to establish the paleobasin morphology and evaluate accommodation volume. In the case of the study area (Pederneira lowland), the geological data set available to reconstruct that surface consists of borehole logs carried out for geotechnics and groundwater and three cores performed for paleoenvironmental reconstruction. The borehole data scatter non-uniformly across the lowland providing spatially biased information. The surveying of several Transient Electromagnetic Method (TEM) profiles yielded inconclusive results in separating sediment units below and above the transgressive surface due to poor contrast in sediment resistivity and high conductivity of groundwater. This study addresses a method for estimating that paleosurface using the combination of a standard geostatistical interpolation procedure (kriging) with a conceptual geomorphological model. The geomorphological model comprised the sketching of a paleoriver drainage system in which the position of the thalwegs was defined departing from present-day slope morphology and depths estimated by adjusting a mathematical curve describing their longitudinal profile to control points. Final adjustments to the paleodrainage system were constrained by borehole data and expert judgment. This methodology proved to be effective in an area where limited objective geological and geophysical data are available. [ABSTRACT FROM AUTHOR]

The combination of magmatic, structural and fission track (FT) data is used to unravel Oligocene/Miocene near-surface tectonics in the internal Western Alps. This includes reburial of parts of the already exhumed Sesia-Lanzo Zone and their subsequent re-exhumation. We define blocks mainly on the base of their Oligocene-Miocene cooling history (FT data) and on published paleomagnetic data. The preservation of a paleosurface allows a detailed reconstruction of the exhumation, burial and re-exhumation of different tectonic blocks. Near-surface, rigid block rotation is responsible for the reburial of the Lower Oligocene paleosurface in part of the Sesia-Lanzo Zone (the Cervo Block) and for the conjugate uplift of deeper portions of the Ivrea-Verbano Zone (the Sessera-Ossola Block). This block rotation around the same horizontal axes produces in the currently exposed portions of the two blocks, quite different temperature/time paths. While the surface of the Cervo Block is buried, the lower part of the Sessera-Ossola Block is uplifted. The rotation is constrained between the age of emplacement of the Biella Volcanic Suite on top of the Sesia-Lanzo Zone (32.5 Ma) and the intrusion of the Valle del Cervo Pluton (30.5 Ma). After this relative fast movements, the concerned blocks remained in (or underneath) the partial annealing zone of zircon until in Aquitanian times they were rapidly uplifted into the partial annealing zone of apatite. The further stage of exhumation out of the partial annealing zone of apatite extends over the entire Miocene. At that time, units of the external Western Alps underwent fast exhumation (external Briançonnais, Valais). In addition to the well-known post-collisional deformation in the axial- and external Western Alps, the internal units (i.e., the upper plate) hold an apparent stable position in terms of exhumation. [ABSTRACT FROM AUTHOR]

n Oligocene paleosurface (regolith) lies on top of the high-pressure metamorphic rocks of the Sesia-Lanzo Zone near Biella, NW Italy. Only the saprock, the lowermost part in a regolith profile, is preserved. No evidence for any paleosoil can be observed. Field observations indicate that the regolith developed through in situ mechanical fracturing of the rocks of the Sesia-Lanzo Zone in a continental environment. Density estimations of the regolith and the underlying rocks of the Sesia-Lanzo Zone confirm the field observations and imply that a relatively small amount of alteration minerals was formed. The main detected alteration phases are chlorite, various carbonates, quartz, clay minerals, Fe-oxides, and Fe-hydroxides. Chlorite differing in chemistry and crystallographic ordering demonstrates different stages of alteration. Oxygen and carbon isotopic composition of carbonates suggests temperatures higher than surface conditions. Illite and chlorite thermometry indicates temperatures related to the anchizone (~250-300°C). These data are considered as a robust indication of the re-burial of the regolith together with its substrate and its volcanic cover. The burial is closely related to the tilting of the preserved stratigraphic sequence formed by the rocks of the Sesia-Lanzo Zone, the regolith, and the rocks of the Biella Volcanic Suite (Lanza, in Schweiz Miner Petrogr MItt 57: 281-290, ; Lanza, in Geologishe Rundschau 68: 83-92, ). Furthermore, the burial is consistent with this sequence of subaerial rocks being very close to the intrusion depth of the Valle del Cervo Pluton at the time of its emplacement (4-7 km; Zanoni et al., in Rend Online SGI Note Brevi 1: 199-202, ; Zanoni et al., in Int Geol Rev 52: 1244-1267, and references therein). [ABSTRACT FROM AUTHOR]

Abstract: The results of a study carried out on a coastal area of central–western Liguria (Northern Italy), where metamorphosed basic and ultrabasic rocks outcrop, are presented. The study indicates that a wide area (16km2) was involved in a large scale “deep-seated gravitational slope deformation” (DSGSD). This movement has special features related to the lithology and structure of the involved rock mass, to the Plio-Quaternary uplifting and brittle tectonics, affecting an area where a paleosurface was recognised, and to the continental shelf dynamics. The particular geometry of the DSGSD was recognised on the basis of detailed analyses of the above-mentioned aspects. Due to its characteristics, the deep-seated deformation can be classified as a “lateral spreading”. The current altitude of the Pliocene marine clay outcrops and their deposition bathymetry allowed estimation of the uplift rate of the coastal area. The altitudinal variations of an ancient marine terrace, which was displaced by the DSGSD, were used to reconstruct the chronology of the gravitational movement. A final issue concerns the very large scale and the particular kind of phenomenon, both of which are certainly new in Liguria. [Copyright &y& Elsevier]

Seven lithostratigraphic units were identified from a 180-m-long, up to 6-m-high coastal cliff exposure at Po Chue Tam, Lantau Island, Hong Kong. They include older slope wash, debris-flow deposits, raised beach deposits, slope debris, stream-flood gravels, hyperconcentrated flood gravels and younger slope wash. Laterite profiles had developed in the older slope wash and the debris-flow deposits. The profile in the former includes, from bottom to top, slightly weathered but ferruginized bedrock, a mottled pebble/cobble zone and a vesicular laterite horizon. In contrast, the profile in the latter consists of only debris-flow deposits that contain detrital laterite fragments and underlying slightly weathered bedrock. The deposits have been cemented and indurated.There are no genetic links between the main zones in the laterite profiles. This is evidenced by the sharp bed contact, the absence of a leaching zone in the bedrock, and the general constraint of the main zones by stratigraphic sequences. The present study highlights that both relative accumulation of iron from pedogenic weathering and absolute accumulation of iron from a lateral source through groundwater and/or surface water occur concomitantly and superimpose upon each other. This leads to the development of a polygenetic laterite profile rather than a single, monogenetic profile.Caution should be exercised to ascertain the origin of laterite before attempting to explore the paleoclimatic imprints or reconstruct landscape evolution. Laterites of both pedogenic and groundwater origins can represent paleosurfaces that required prolonged subaerial exposure, quiescent tectonism and climatic stability. [Copyright &y& Elsevier]

Trend surfaces were determined and compared for the bedrock surface, two characteristics of the present topography, and 42 water well log reports of glacially buried carbonaceous horizons within drift from an area in central Michigan. Data almost certainly indicate that the glacially buried Pleistocene organic deposits represent two or more pre-Woodfordian paleosurfaces. Trend surface analysis of buried organic horizons may be useful for recognizing paleosurfaces and separating drift sheets in other areas with limited subsurface data. [ABSTRACT FROM AUTHOR]

Geomorphic archives, particularly longitudinal river profiles, are increasingly used as a proxy to reconstruct uplift rates in mountainous regions. Within the Atacama Desert, Northern Chile, slow, long-term erosion creates exceptional preservation of fluvial and alluvial surfaces. This enables river incision patterns to be used on a continental-scale (>250 km) along the western margin of the Andes (18°00'S to 20°15′S) and over a time frame from Miocene to Present day. The data show marked compartmentalisation of fluvial system behaviour with changes in incision rates from south to north creating 3 distinctly different regions. Within these different sectors, incision rates are broadly consistent between rivers suggesting a regional rather than a river specific control on rates. In Sector 1 (18°05′S to 19°20'S) the fluvial systems are exorheic with a terminal base level (the lowest base level to which the river system can erode) in the Pacific Ocean and span the Coastal Cordillera, Longitudinal Valley, Precordillera and western edge of the Western Cordillera. This constrains the total uplift over these regions to a minimum of 1200 m in 11 Myr with incision rates of ~200–120 m/Myr consistent with rapid but sustained uplift of the Andes in the Late Miocene. In Sector 2 (19°20'S to 19°50'S), to the immediate south, the rivers are shorter and terminate in the Longitudinal Valley, spanning only the Longitudinal Valley, Precordillera and the western edge of the Western Cordillera with lower incision rates of 100–50 m/Myr. Comparison of incision rates between Sector 1 and 2 can constrain the uplift of the Coastal Cordillera to 60 m/Myr which is in keeping with previous studies from the region. In southernmost Sector 3 (19°50'S to 20°10'S), the fluvial systems terminate in the Longitudinal Valley and span only the Longitudinal Valley and eastern part of the Precordillera with low incision rates of 50 to 25 m/Myr. Differences between Sectors 2 and 3 are attributable to drainage loss by tectonic beheading of catchments through uplift of the Cordillera de Domeyko fault system, placing a minimum constrain on uplift in this region of 50 to 25 m/Myr. This study demonstrates the applicability of large-scale fluvial archives to access not just the timing of uplift on a continental scale, but also the relative uplift of individual tectonic provinces. • Fluvial archives are reconstructed along the western margin of the Andes from 11 Ma. • Fluvial incision shows compartmentalization with an increase from south to north. • The rate of fluvial incision is stream length across the N to S tectonic provinces. [ABSTRACT FROM AUTHOR]

Geomorphology is an important control on the formation of bauxite. However, geomorphological research on bauxite deposit formation is usually hampered by the lack of systematic detailed data collection. This study focuses on the Wuchuan–Zheng'an–Daozheng (Wu–Zheng–Dao) area of northern Guizhou Province, South China, an area containing bauxite deposits of the Dazhuyuan Formation. These deposits formed during the early Permian in a period associated with the peak timing of the late Paleozoic Ice Age (LPIA). This study used data from 329 drillcores within the Dazhuyuan mining district (DMD) to generate high-precision geomorphological reconstructions for the period of bauxite formation. This includes a series of contour maps showing the total thickness of the bauxite deposit, ore grades, the thickness of Lower (bauxitic claystone) and Upper (bauxite ore) members of the bauxite formation, and the distribution of different types of bauxite ore. These maps indicate that thicker deposits of bauxite are concentrated in deep depressions, whereas no bauxite is found in highly elevated erosional regions. High-grade bauxite ores, including clastic, oolitic, and porous types of mineralization, are located within depressions or in gently sloping areas, whereas low-grade bauxite deposits, including massive bauxite and bauxitic claystone mineralization, are located at the bottom of depressions or are present as thin units within uplifted areas. The geochemistry of the drillcore samples from the study area indicates that leaching is the main control on bauxite ore quality in the study area. Finally, a low groundwater table and water-permeable underlying units provide good drainage, which also contributes to the generation of high-grade bauxite ores. • Geomorphological reconstruction in the Dazhuyuan Mining District, South China • Leaching process rebuilding based on geochemical profiles • Formation model for the early Permian bauxite deposit of the Dazhuyuan Formation [ABSTRACT FROM AUTHOR]