Paleosol Horizons Research Articles

The impact of Last Glacial climate variability in west-European loess revealed by radiocarbon dating of fossil earthworm granules

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard-Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continental lowlands, numerous high-resolution records of loess and paleosols sequences show a consistent environmental response to stadial-interstadial cycles. However, the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with Greenland interstadials. To overcome this problem, a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of Nussloch (Germany). Its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every Greenland interstadial identified in isotope records with specific soil horizons. Furthermore, eight additional minor soil horizons dated between 27.5 and 21 ka only correlate with minor decreases in Greenland dust records. This dating strategy reveals the high sensitivity of loess paleoenvironments to Northern Hemisphere climate changes. A connection between loess sedimentation rate, Fennoscandian ice sheet dynamics, and sea level changes is proposed. The chronological improvements enabled by the radiocarbon "earthworm clock" thus strongly enhance our understanding of loess records to a better perception of the impact of Last Glacial climate changes on European paleoenvironments.

Geology, mineralogy, and geochemistry of late Miocene paleosol and calcrete in the western part of the Central Anatolian Volcanic Province (CAVP), Turkey

The late Miocene was characterized by high global temperatures and partly to nearly complete desiccation of the Mediterranean Sea throughout the latter part of the Messinian age (the Messinian salinity crisis). The non-marine paleoenvironmental and paleoclimatic records from the Mediterranean area are highly limited in their spatial range. Late Miocene river flood-plain sediments in the Central Anatolian Volcanic Province (CAVP) of central Turkey consist of siliciclastic and pyroclastic sediments with paleosols and calcrete. Five lithofacies were identified as (A) massive conglomerate, (B) trough-cross-bedded sandstone, (C) massive mudstone, (D) disrupted mud, (E) and disrupted matrix-supported conglomerate. The paleosols were composed predominantly of smectite and illite with smaller amounts of feldspar, quartz, opal-A, pyroxene and amphibole, and the calcretes were composed mainly of calcite, with smaller amounts of feldspar, quartz and opal-A, and minor amounts of smectite, chlorite and illite. Authigenic clay minerals and micritic calcite coating on the detrital grains and soil peds and pendant cement in the calcrete and paleosol horizons were evidence of a vadose zone. In contrast, the large equant spar drusy mosaics were formed in phreatic environments. The weathering of ignimbrite and marble led to the depletion of SiO2, CaO, Al2O3, Fe2O3, TiO2, and K2O through the precipitation of smectite and illite in the paleosols, and CaO in the form of micrite and calcite in the calcrete horizons. Field observations, mineralogy, geochemistry and the results of δ18O and δ13C isotopic analysis reveal that alternating wet and dry periods resulted in an upward increase in precipitation of authigenic smectite and illite within the late Miocene sections, under the influence of geochemical and pH fluctuations in phreatic or vadose water within the river flood-plain paleoenvironment.

Evidence for cosmic airburst in the Western Alps archived in Late Glacial paleosols

Abstract Previous evidence for fragments of a cosmic airburst in the Western Alps has been shown to reside in weathering rinds in surface clasts of Late Glacial (LG) (mid-LG-post Allerod) deposits and in Ah horizons of several associated paleosols. In contrast to outlying strata, Younger Dryas (YD) paleosol horizons contain minor reworked airburst evidence that includes melted quartz/pyroxene grains, carbon spherules, glass-like carbon, and with minor differences in microbial populations. New data from LG paleosol profiles show REEs elevated above crustal abundance in several profiles of mid-Late Glacial age, along with elevated Pt concentrations, similar to those found at the YD Boundary in the Greenland Ice Sheet. Pt/Pd ratios that are elevated above background suggest an exogenic influx of Pt from meteoritic ablation and/or airbursts. An increasing number of localities with sedimentary time lines coeval with an airburst (12.8 ka) indicate the event was intercontinental, producing widespread conflagrations archived in local sediment sequences. This is the first instance worldwide in which evidence of the black mat event has been found both in weathering rinds and in paleosols in the Alps, with such information being applicable to reconnaissance beyond Earth such as in the case of Mars.

Late Quaternary loess-like paleosols and pedocomplexes, geochemistry, provenance and source area weathering, Manasbal, Kashmir Valley, India

The late Quaternary loess and loess-like deposits in Kashmir Valley are natural archives that have preserved paleoclimate and paleoenvironmental records of the region. We present a loess-like paleosol located along the margin of the Manasbal Lake, Ganderbal, which was studied in detail for understanding the pedological processes and reconstructing the late Quaternary soil formation. In this paper we present loess-like paleosol formation of a nearly 10.6m thick sequence exposed along the margin of Manasbal Lake, Ganderbal District, Srinagar, Kashmir. Geochemical and textural data of this loess-like sedimentary sequence fluctuate reflecting the varied depositional processes operating in the valley, differential intensity of weathering, and processes of pedogenesis. Weathering indices such as chemical index of alteration, chemical index of weathering, and plagioclase index of alteration reveal weak to moderate weathering of the parent material. Provenance discrimination diagrams of the present study disclose that the Manasbal loess-like paleosol sediments are derived from the mixed source rocks suggesting a variety of provenance with variable geological settings, which apparently have undergone weak to moderate recycling processes. The Manasbal paleosol horizons have been dated by the optically stimulated luminescence (OSL) method to the marine isotope stages mid-MIS-3 (41.7±8.0ka) and late-MIS-2 (14.6±3.8ka). During the MIS-3 period, the climate was wetter, forming a strong AhBtk paleosol as inferred from the geochemical data. A steady increase in the CaCO3 content and C/N ratio in the paleosols from 6.50m (MIS-3) indicates arid and drier climatic conditions. The area around Manasbal Lake incised because of climate change and neotectonic activity since post-14ka.

Late Glacial erosion and pedogenesis dynamics: Evidence from high-resolution lacustrine archives and paleosols in south Bohemia (Czech Republic)

Sediments from three paleolakes and two paleosol horizons in south Bohemia, Czech Republic, provide evidence of climate change and landscape evolution in central-eastern Europe on millennial to centennial timescales over the Late Glacial (~16–11.5ky). Based on a combination of geochemical, sedimentological and geophysical proxy indicators, along with the pollen record and soil micromorphology, we propose a relationship between vegetation cover, soil development, and erosional processes. Four major and two minor environmental stages, identified in all investigated paleo-lakes, were broadly correlated with the Late Glacial climatostratigraphy. Short-term (decadal to centennial) climatic deteriorations between the Bølling and Allerød, and within the Allerød, have been correlated with the Older Dryas and the Intra-Allerød Cold Period (IACP) respectively. B horizons of two (gleyic) podzols discovered under aeolian sand dunes in the lake catchments were dated to the Allerød interstadial and were parallelized with Usselo soils – pedostratigraphical marker horizons of west- and northern-central Europe. The upper parts of these soils have signs of colluvial processes. According to the radiocarbon dating, the erosion occurred at 13,155±150cal. yr BP and can be associated with the IACP event, which is marked by a significant input of allogenic material into the lake basins. We attribute the significant increase in the iron and consequent phosphorus content in the lake sediments during the Allerød to the podzolization that occurred with the humid interstadial conditions.

Chromium geochemistry of the ca. 1.85Ga Flin Flon paleosol.

Fractionation of stable Cr isotopes has been measured in Archaean paleosols and marine sedimentary rocks and interpreted to record the terrestrial oxidation of Cr(III) to Cr(VI), providing possible indirect evidence for the emergence of oxygenic photosynthesis. However, these fractionations occur amidst evidence from other geochemical proxies for a pervasively anoxic atmosphere. This study examined the Cr geochemistry of the ca. 1.85Ga Flin Flon paleosol, which developed under an atmosphere unambiguously oxidising enough to quantitatively convert Fe(II) to Fe(III) during pedogenesis. The paleosol shows an extreme range in Cr isotope composition of 2.76 ‰ δ53/52 Cr. The protolith greenstone (δ53/52 Cr: -0.23 ‰), the deepest weathering horizon (δ53/52 Cr: -0.15 to -0.23 ‰) and a residual corestone in the upper paleosol (δ53/52 Cr: -0.01 ‰) all exhibit Cr isotopic compositions comparable to unaltered igneous rocks. The most significant isotopic fractionation is preserved in the areas influenced by oxidative subaerial weathering (i.e. increase in Fe(III)/Fe(II)) and the greatest loss of mobile elements. The uppermost paleosol horizon is both Cr and Mn depleted and offset to significantly 53 Cr-enriched compositions (δ53/52 Cr values between +1.50 and +2.38 ‰), which is not easily modelled with the oxidation of Cr(III) and loss of isotopically heavy Cr(VI). Instead, the currently preferred model for these data invokes the open-system removal of isotopically light aqueous Cr(III) during either pedogenesis or subsequent hydrothermal/metamorphic alteration. The 53 Cr enrichment would then represent the preferential dissolution or complexation of isotopically light aqueous Cr(III) species (enhanced by lower pH conditions and possibly the presence of complexing ligands) and/or the residual signature from preferential adsorption of isotopically heavy Cr(III). Both scenarios would contradict the widely held assumption that only redox reactions of Cr can generate large magnitude isotopic fractionations and, if substantiated, non-redox isotope effects would complicate the conclusive fingerprinting of ancient atmospheric O2 from Cr isotope data alone.

Sedimentary facies analysis of a high-frequency, small-scale, peritidal carbonate sequence in the Lower Jurassic of the Tripolis carbonate unit (central western Crete, Greece): Long-lasting emergence and fossil laminar dolocretes horizons

The study examines a Lower Jurassic (late Liassic) cyclic lagoonal–peritidal stratigraphic unit outcropping in central western Crete (Tripolis unit), which corresponds to the eastern (internal) part of the mainland Gavrovo-Tripolis platform, the most significant external platform of the Hellenides. The studied Tripolis carbonate sequence consists of meter-scale, shallowing-upward successions of restricted inner-carbonate platform facies, including cyclically repeated subtidal, intertidal and supratidal facies, that are separated by erosion surfaces (elementary cycles). Each cycle starts with relatively open-marine facies, which are overlain by shallower, more restricted facies (tidal flat progradation). The lithofacies association includes dolomitic intraclastic–peloidal–bioclastic wackestones–packstones/floatstones and grainstones/rudstones dominated by a restricted shallow-marine fauna (bivalves, gastropods, ostracods and seldom benthic foraminifers), representing a shallow subtidal to intertidal, moderately high-energy environment within an inner-platform setting (peritidal environment to restricted lagoon). This lithofacies association has been intermittently subaerially exposed and has undergone diagenetic processes in an inter- or supratidal environment, exhibiting features of vadose diagenesis and pedogenesis due to long-lasting exposure along certain horizons. The peritidal facies are capped by dolocretes controlled by root-activities (laminar dolocretes, peloidal–pisoid dolocretes and massive dolocretes), marking the end of each depositional cycle, and, thus, distinguishing the successive episodes of a prolonged subaerial exposure period and birth of paleosol horizons. Dolocretes consist a diagenetic facies, characterized by several vadose and pedogenic fabrics, including fenestral cavities with geopetal structures, “flower spar” to blocky sparry cement in primary pores, micritic coatings, crudely pelleted walls, alveolar-septal texture, infills of rootlet moulds, inter-granular micritic bridges, meniscus cement, sinuous desiccation cracks, circum-granular cracking and in-situ brecciation. The stratigraphic distribution of the cyclothems, suggests relative sea-level control on the peritidal cyclicity controlled by uniform tectonic subsidence and eustasy (allocyclic processes), in an inner- ramp-to-shelf carbonate setting with tidal flat and restricted lagoon depositional environment. However, a combination of allocyclic with autocyclic processes controlling accommodation space and sediment accumulation, should be also taken in consideration. The studied high-frequency cycles are interpreted to have been formed during the falling stage and correspond to lowstand systems tract (LST) sediments, which consists part of a regressive peak of the Lower/Middle Jurassic Transgressive–Regressive Facies Low Frequency Cycle (2nd order). Due to the absence of massive evaporites, dolomitization has been attributed to reflux of slightly increased-salinity marine fluids (i.e. penesaline), that are driven into the underlying lagoonal–peritidal carbonate sediments during periods of long term sea-level fall in a marginal marine setting.

An Integrated Appraisal of Burgan Reservoir in Soroosh Oil Field, Using Petrographic and Petrophysical Approaches

The Burgan Formation in northwest of the Persian Gulf is applied to lower part of Albian age Kazhdumi Formation, where is dominated by coarse to medium terrigenous facies. It is the most susceptible siliciclastic unit in the area to hydrocarbon reservoir. This reservoir is studied in a well of Soroosh oil field with best available data to determine its facies characteristics, sequence stratigraphy and reservoir quality. Based on the petrographic results and log data, 7 facies are determined in the formation, which are mainly composed of sandstone and shale. These facies are classified into three facies associations (FA) based on their sedimentological properties and environmental conditions. The first FA consists of sandstone, siltstone and shale, mostly developed in the lower part of formation, and is related to a fluvial environment. The second FA consists of fluvial sandstones and sandwich by marine shales and is related to fluvial-dominated shallow marine setting (estuary to delta). The third FA consists of limestones of chemical and biochemical origin and is related to a marine condition. According to their reservoir quality, these facies associations show a decreasing trend in porosity and permeability values from FA1 to FA3. The first FA is more abundant in the lower part of the Burgan Formation where causes a good reservoir quality trait. FA2, presenting a medium reservoir quality, is more frequent in the middle parts of studied formation and FA3 is found almost in the upper parts. Based on the results from this study, three 3rd order sequences have been identified. Sequences 1 and 3 are partial but the sequence 2 is the main and most complete one of the formation in the studied area. The paleosol horizons are used for relative sea level change analysis of the formation in sequence stratigraphic studies.

Magnetic stratigraphy constraints on the Matuyama–Brunhes boundary recorded in a loess section at the southern margin of Chinese Loess Plateau

Although the Matuyama-Brunhes boundary (MBB) in the Chinese Loess Plateau (CLP) is very important in reliably correlating Quaternary loess with other sediments in the world, particularly with marine and polar ice cores, its exact stratigraphic position remains controversial. Previous investigations usually placed the MBB between paleosol unit S8 and loess unit L8 in various locations. To better understand the spatial differences in the MBB position, a high-resolution paleomagnetic study was conducted in a loess section of the Lantian Basin at the southern margin of the CLP. The results show that the MBB is situated in the middle of the relatively weak paleosol unit S7, consistent with a recent report on the MBB based on a Be-10 study from the Xifeng and Luochuan loess sections of the central CLP. However, the regional anomalously low magnetic susceptibility in paleosols S7 and S8 indicates that it is more reliable to determine the paleoclimate boundaries between loess and paleosol horizons of this segment with median grain size. Then, the MBB in the Yushan section can be correlated with the bottom of paleosol S7, corresponding to the older part of interglacial marine isotope stage 19. This result temporally reconciles the striking discrepancy of the position of the MBB recorded in between loess and other typical sedimentary sequences, and further confirms that the stratigraphic position of the MBB could spatially vary to a certain extent due to regional sedimentary or paleoclimatic conditions in the marginal areas of the CLP. In the Yushan section, the high-frequency variations of paleomagnetic directions during a long period of similar to 31 ka before the MBB, however, could not be attributed to a genuine response to the true geomagnetic behaviour. Moreover, the climate offset defined by the magnetic susceptibility and median grain size of the section can be preliminarily attributed to the regional geology and paleoenvironment background. A multiproxy-based stratigraphic division is considered very necessary when paleomagnetic and climatic boundaries are defined exactly in a specific area of the southern CLP.

Geochemistry of a paleosol horizon at the base of the Sausar Group, central India: Implications on atmospheric conditions at the Archean–Paleoproterozoic boundary

A paleosol horizon is described from the contact of the Sausar Group (∼2400 Ma) and its basement (Tirodi Gneiss; >2500 Ma) in Central India. Physical evidence of pedogenesis is marked by the development of stress corrosion cracks, soil peds, corestone weathering and nodular rocks. XRD and SEM-EDX data indicate the presence of siderite, ankerite, uraninite, chlorite, alumino-silicate minerals, ilmenite, rutile and magnetite, in addition to quartz, feldspar and mica. The chemical index of alteration, the plagioclase index of alteration, and the chemical index of weathering show an increasing trend from parent rock to the paleosol and indicate a moderate trend of weathering. The A-CN-K plot indicates loss of feldspars, enrichment in Al2O3 and formation of illite. Different major element ratios indicate baseloss through hydrolysis, clay formation, leaching of some elements, and more precipitation with good surface drainage. The paleosol is depleted in HREE in comparison to the parent rock indicating high fluid-rock interaction during weathering. The paleosol samples show flat Ce and Eu anomalies, low ΣREE, and high (La/Yb)N, indicative of a reducing environment of formation. Reducing condition can also be inferred from the concentration of elements such as V, Co, Cu, Pb, and Zn in the paleosol profile. Although enriched in Fe and Mg, the overall geochemical patterns of the paleosol indicate oxygen deficient conditions in the atmosphere and development by weathering and leaching processes associated with high precipitation and good surface drainage at the time of development of this paleosol during the Archean–Paleoproterozoic transition.

Holocene floodplain soils along the Río Mamoré, northern Bolivia, and their implications for understanding inundation and depositional patterns in seasonal wetland settings

The Llanos de Moxos (LM) in the Bolivian Amazon basin host one of the largest seasonally inundated savannah landscapes on Earth. Very little is known of this area with regard to sedimentary dynamics, soil formation, or their relationship to longer-term climatic and hydrological variability in this setting. Here we present a detailed study of three floodplain depositional sequences building up the inundation savannah along the Mamoré River in the central LM. Pleistocene sands and silts (unit 1) are overlain by thick overbank deposits of mostly Holocene age (unit 2) on both sides of the Mamoré River, and underline the importance of extensive flooding processes for the late Quaternary sedimentary and geomorphic evolution of the LM. The fine-grained distal overbank sediments show signs of strong modification by hydromorphic processes and reflect spatial and temporal variations in flood inundation patterns. In addition, widespread dark gray to blackish soil and paleosol horizons are intercalated with the overbank sediments, but lack evidence for significant weathering. These horizons are likely the result of cumulative incorporation of organic material under conditions of particularly low sedimentation rates. Therefore, their formation should be linked to processes such as channel migration, longer-term meanderbelt evolution, avulsive drainage reorganization, changes in sediment supply or climatically induced variations in flooding type, frequency or magnitude. The common occurrence of these floodplain soils in the early to mid-Holocene may thus reflect the combined effects of hydrological, geomorphic and sedimentary changes during a drier mid-Holocene.

Environmental significance of lungfish burrows (Gnathorhiza) within Lower Permian (Wolfcampian) paleosols of the US midcontinent

Abstract Burrows of the lungfish Gnathorhiza occur in the fine-grained strata of the Lower Permian (Wolfcampian) Blue Spring Shale Member, of the Matfield Formation near Manhattan, Kansas. Thousands of lungfish burrows occur in three beds of a compound paleosol profile, with the vast majority confined to a single bed several meters below the Florence Limestone Member of the Barneston Limestone (Chase Group). The burrows, a high percentage of which contain lungfish bones, occur in a 145 m long lens-shaped unit comprised of clayey siltstone that exhibits platy to subangular-blocky peds, and downward and laterally branching thin rhizoliths. The uppermost paleosol horizon in each level is gleyed, indicating that there was standing water for part of the year. The paleoecosystem represented by these units formed in a low-lying terrestrial coastal paleolandscape with subtle topography and imperfectly drained paleosols equivalent to present-day aquents. These paleosols are part of a pedogenic sequence recording an upward climatic trend from semi-arid to monsoonal.

Pedological Iron/Al Extracts, Clast Analysis, and Coleoptera from Antarctic Paleosol 831: Evidence of a Middle Miocene or Earlier Climatic Optimum

An unusual and remarkable find of fossilized Coleoptera exoskeletons, soil organics/plant roots, and microbes—recovered from an alpine-age paleosol in moraine at New Mountain near the Taylor Glacier in the Antarctic Dry Valleys—provides evidence for an ameliorative Early to middle Miocene Climatic Optimum (MMCO). Compared with the microbial analysis of other nearby and somewhat younger paleosols (sites 827–829) in nearby moraine deposits at both New Mountain and Aztec Mountain (sites that are known to contain bacteria and fungi), paleosol horizons at the alpine-age site (831) contain prolific fossil evidence of either an expanded MMCO or an earlier Early Miocene/Oligocene age. Together with fossil filamentous forms of either algae or fungi and bacteria, these Coleoptera exoskeletons make up part of a higher-altitude tundra ecosystem distantly related to a many-fold increase in terrestrial pollen and woody plants that inhabited the Dry Valley Coast ∼15 Ma or earlier. While the age of the 831 paleosol as discussed elsewhere is impossible to assess with precision, the presence of a mix of subround/subangular sands—a high percentage carrying V-shaped percussion cracks—signals significant aqueous transport, with the sediment believed to have been deposited before the transition from warm/wet to cold/dry ice. In addition, fossilized organics—including salt-encrusted earth, roots, and clay/mineral coatings on both sands and biogenic specimens—suggest at least an early cold/semihumid environment conducive to weathering, probably mediated by microbe activity. Other chemical indices reported previously are here analyzed with extractable Fe/Al, which suggests greater antiquity, possibly Early Miocene or Oligocene.

Isotopic and micromorphological studies of Late Quaternary loess–paleosol sequences of the Karewa Group: Inferences for palaeoclimate of Kashmir Valley

Pedogenic carbonates, widespread in paleosols throughout the geological ages, have been widely used to infer climatic conditions and vegetation type during their formation. They are ubiquitous and widespread in the Late Quaternary loess–paleosol sequence of the Kashmir Valley, mostly in the form of carbonate nodules. In the present study, pedogenic carbonates are studied to analyze trends in the stable isotopic composition of carbonate nodules across three well-developed loess–paleosol sections in the Kashmir Valley. The stable carbon isotopic (δ13C) analysis reveals a gradual increase of the C4 vegetation towards the top of the sections. The development of C4 plant biomass towards the top of sections possibly reflects water stress and/or reduced atmospheric pCO2 and increasing aridity. The oxygen (δ18O) isotopic analysis reveals little variation with the values ranging from −6.37‰ to −7.75‰, reflecting stable climatic conditions during the development of pedogenic carbonate nodules. The use of geospatial data including digital elevation model (DEM) and Landsat TM remote sensing imagery have added morphological characterization of the topographic and landform features observed in the area. The tectonic uplift of the Pir Panjal Range, variation in the geometry of Karewa Basin and the slope gradient have played a key role in the spatial variation of loess–paleosol sequences in the valley. The Late Quaternary climate changes, deposition of loessic sediments, formation of the interbedded paleosol profiles and the subsequent denudation processes have resulted in the present day typical geomorphic landscape of the Kashmir Valley. The micromorphological analysis of loess–paleosol horizons reveals cold arid to semi-arid climatic conditions prevailed during the Late Quaternary in the valley.

Pliocene aridity and Neogene landscape evolution recorded by a fluvial sediment system (Campaspe Formation) in northeast Queensland

Campaspe Formation, a surficial, fluviatile, sand-dominated unit, is extensively developed in the Charters Towers region of north Queensland where it covers an area of 11 000 km2, overlying Paleozoic basement and erosional remnants of Paleogene Southern Cross Formation. In the northern part of its distribution, it is interlayered with, and overlain by, flows of Nulla Basalt. It is dated as mid-Pliocene, based on the 3.48 Ma age of the Myrrilumbing Flow interlayered with its upper part, an antiquity consistent with thin ferricrete locally developed at its surface. The formation defines the Campaspe Surface at an elevation of 200–440 m in the present landscape, falling gently from upland to the west towards the current channel of the Burdekin River. This surface is a relict alluvial plain little incised by easterly flowing tributaries of the Burdekin River and has survived, essentially intact, from the early Pliocene. Geometry of the formation is established from some 2000 mineral exploration drill holes and seismic profiling. It has an average thickness of some 60 m, reaching a maximum of over 200 m. It blankets a pre-existing, low relief landscape in which a basement ridge divides it into two sub-basins that mirror the present drainage. The formation consists of poorly sorted sandstone with minor conglomerate and siltstone, and contains paleosol horizons with associated calcrete. Matrix supported sandstone in the succession, indicates deposition in part from hyperconcentrated flows. Sandstones generally show poorly defined planar layering as typical of ephemeral overbank and terminal splay sediment bodies but beds with cross-lamination, indicating fluvial channel bed forms, are also present. They are characterised by pore-filling silt and mud, largely emplaced by post-depositional infiltration, such that the unit produces essentially no groundwater. Facies attributes are consistent with fluvial deposition in ephemeral, dry climate, distributary system, with inefficient cross-drainage discharge that induced aggradation, resulting in a substantial sediment body perched in the landscape. Framework grain compositions show the formation to be mineralogically mature, representing erosional debris derived from intense weathering in an earlier climatic regime recorded, at least in part, by duricrust developed in the fluviatile–lacustrine Southern Cross Formation of Paleogene age. Such duricrust intervals are now upstanding in the landscape, representing erosional remnants from inverted relief developed in a mid-Cenozoic, pluvial, landscape cycle. Paleoclimatic signature of the Campaspe Formation extends the record of Pliocene aridity, widely recognised elsewhere in Australia, to northeast Queensland. In large part the landscape of the Charters Towers district is relict from the early Pliocene and is in the process of readjusting to more pluvial climatic regimes. By implication, Pliocene aridity has, on a small scale, exerted a strong influence on the present physiography of Australian landscapes.

Reassessment of the Microbial Role in Mn-Fe Nodule Genesis in Andean Paleosols

The presence of Mn-Fe nodules in the epipedons (surface horizons) of paleosols of presumed Upper Neogene age in the northwestern Venezuelan Andes have been interpreted as products of inorganic oxidation and reduction processes operating over the full range of glacial and interglacial cycles that affected paleosol morphogenesis. New microscopic/chemical data from combined SEM-EDS-FIB analyses of representative Mn-Fe nodules indicate microbes play an important role in Mn/Fe precipitation leading to their genesis in alpine Mollisols (Argiustolls). Although the prevailing new data are based mainly on fossil forms of filamentous bacteria and fungi and other biogenic pseudomorphs that may represent the former resident bacteria, the presence of extant microbes must await field experiments/collection, followed by a molecular microbiology approach to determine the biological drivers of metal precipitation. As in other terrestrial niche environments, microbes are seen here to play a role, perhaps a key one, in the morphogenesis of paleosols of importance in upper Neogene paleoenvironmental reconstruction.

Late Pennsylvanian aridification on the southwestern margin of Gondwana (Paganzo Basin, NW Argentina): A regional expression of a global climate perturbation

Paleosols of the Paganzo Group preserve a shift from the cool climate of the glaciated high-latitudes of Gondwana to a long-term aridification punctuated by shorter-term fluctuations in moisture regime in the late Carboniferous. A quantitative reconstruction of paleoclimate inferred from the major element chemistry of paleosol horizons and the stable isotope geochemistry of soil-formed minerals and organic matter indicates that the climate varied substantially during deglaciation along the southwestern margin of Gondwana in the Middle Pennsylvanian including two geologically abrupt shifts to notably drier conditions. This dynamic climate terminates in a dry subhumid moisture regime characterized by steppe/dry scrub floral provinces. Quantitative estimates of net primary production during the post-glacial interval inferred from paleosol major element geochemistry are consistent with a mesic soil temperature regime, in agreement with paleotemperatures inferred from pedogenic goethite δD and δ18O. Contemporaneous aridification is well expressed in paleotropical continental records with Middle to Late Pennsylvanian aridification coincident with an abrupt evolutionary change in many marine and terrestrial species. The synchrony of aridification between the high and low paleo-latitudes and concomitant major restructuring of some ecosystems suggests that a paleoclimate change of global nature occurred during the Moscovian and Kasimovian.

Geochemical archive in the three loess/paleosol sections in the Eastern Croatia: Zmajevac I, Zmajevac and Erdut

Abstract The loess record in the Eastern Croatia provides an excellent high-resolution archive of climate and environmental change, providing evidence for the interaction between accumulation and erosion of aeolian and fluvial sediments during the Middle and Late Pleistocene. Impressive loess–paleosol successions up to 30 m thick are exposed by neotectonic movements along SE slope of the Bansko Brdo (=Bansko Hill) (Zmajevac I and Zmajevac) and the steep cliffs of the Danube River (Erdut). The published lithostratigraphical results are complemented by geochemical studies (content of major, trace and REE and pH). In Zmajevac I section three paleosols are intercalated in the loess, in Zmajevac four and in Erdut four paleosols are intercalated in the loess. IRSL age estimates of 17.8 ± 1.9 and 217 ± 22 ka indicate that most of the middle and upper pleniglacial loess record is missing. In all investigated sections, alluvial sediments are intercalated in the loess deposits, indicating periods of fluvial activity. Geochemical characteristics of investigated paleosols explain both the main characteristics and degree of pedogenesis. Paleosol horizons could be clearly distinguished from loess based content of major, trace and REE and on weathering coefficients, such as Ba/Sr and (CaO+Na 2 O+MgO+K 2 O)/Al 2 O 3 .

Paleosols and paleoenvironments of early Mars

Fluviolacustrine sediments filling Gale Crater on Mars show two levels of former exposure and weathering that provide new insights into late Noachian (3.7 ± 0.3 Ga) paleoenvironments of Mars. Diagnostic features of the two successive paleosols in the Sheepbed member include complex cracking patterns of surface dilation (peds and cutans), a clayey surface (A horizon), deep sand-filled cracks with vertical lamination (sand wedges), and replacive sulfate nodules aggregated into distinct bands (gypsic By horizon) above bedded sandy layers (sedimentary C horizon). Shallow gypsic horizon, periglacial sand wedges, and limited chemical weathering are evidence of a hyperarid frigid paleoclimate, and this alternated with wetter conditions for the lacustrine parent materials in Gale Crater during the late Noachian. Depletion of phos- phorus, vesicular structure, and replacive gypsic horizons of these Martian paleosols are fea- tures of habitable microbial earth soils on Earth, and encourage further search for definitive evidence of early life on Mars.

Different paleoenvironments of Late Pleistocene age identified in Verőce outcrop, Hungary: Preliminary results

Complex geomorphological, geological, paleopedological and chronometrical investigations were started to reveal the development of the alluvial section and the loess/paleosol sequence containing remnants of a Late Palaeolithic site near Verőce, Hungary. Different paleoenvironments were identified in the profiles of the abandoned brickyard influenced by different facies in the margin of fluvial–alluvial (Palaeo-Danube) and proluvial (southeast pediment of Börzsöny Mountain) area and the environments affected by the climate fluctuation of Late Pleistocene (loess/paleosol sequence overlying the base of alluvial materials). Sediments possibly deposited by Palaeo-Danube were identified in a basal section of the abandoned brickyard. The alluvial facies was indicated by sand, silt, and clay layers in the sediment sequence. Some parts of the alluvial sediments were covered by loess in the glacial periods intercalated by four paleosol horizons formed during interglacial or interstadial periods. The sedimentation of loess and the forming of paleosols were finished by pedimentation processes (sheet wash, redeposition) indicated by the fine layered material at the top of each paleosol horizon. Another complex fluvial–alluvial section was identified at a different part of the brickyard possibly developed synchronous with the loess/paleosol sequence during the Late Pleistocene. Based on relative and chronometrical dating methods (e.g. archaeological stratigraphy and correlation of the artifacts, 14C and luminescence dating), the development of the loess/paleosol sequence started in marine isotope stage 6 (MIS6) and the youngest layer dated to MIS2.