Paleosol Morphology Research Articles

The Far-Field imprint of the late Paleozoic Ice Age, its demise, and the onset of a dust-house climate across the Eastern Shelf of the Midland Basin, Texas

The late Paleozoic is a period of pronounced climatic and tectonic change, characterized by the onset and disappearance of continental-scale glaciers across polar Gondwana, the formation of Pangea, and widespread large igneous province volcanism. The low-latitude equatorial tropics are assumed to be places of persistent warm and wet climatic conditions throughout the Phanerozoic, which through intense silicate weathering, exert a major influence on Earth’s climate via the consumption of atmospheric carbon through carbonic hydrolytic weathering, formation of clay minerals and deliverability of alkalinity to ocean basins. Here we investigate the late Paleozoic sedimentary record of the Eastern Shelf of the Midland Basin in order to refine the climatic and provenance record of this region. The Eastern Shelf of the Midland Basin was situated within the equatorial tropics throughout the late Paleozoic and was connected to the open ocean through a network of fluvial systems that drained into the marine Midland Basin. We present new U-Pb zircon geochronology (19 samples, 2591 analyses) and sedimentary petrography (11 samples, 5800 grain counts), which we integrate with previously published paleobotany, paleosol chemistry and clay mineralogy to provide a holistic climate and tectonic record from this region. We observe major changes in sedimentary processes that we attribute to the formation of Pangea, eustatic changes linked to a dynamic high-latitude glaciation and teleconnections with low latitude hydrology, and a long-term shift in the Earth climate system all of which result in a dynamic sediment provenance history. Late Pennsylvanian and earliest Permian deposits are enriched in zircons with local affinity and interpreted to reflect local uplift and repeat incision across the basin margin, the latter a result of glacioeustatic forcing during an “everwet” climate. A major paleoenvironmental shift occurs in the late early Permian, which is reflected by the transition from fluvial to mixed fluvial-aeolian and ultimately aeolian dominant sedimentation by the late Permian. The transition from fluvial to aeolian dominant sedimentation is accompanied by a change in clay chemistry, sedimentary rock textual maturity, paleosol morphology and a threefold increase in Paleozoic zircons in the mid to late Permian strata. Widespread loess deposits across equatorial Pangea during the Permian have been used to argue for the possibility of equatorial glaciers situated in highland settings during the early Permian. Conversely, our data suggest initiation of a substantial component of aeolian deposition across the field areas, which is coincident with widespread ice loss across high latitude Gondwana, and ultimately highlights the teleconnections between high latitude glaciation and the low latitude hydrologic cycle.

Paleoecology During the Creation of a Large Boldyrevo Kurgan of the Yamnaya Culture in the Southern Cis-Urals, Russia

This study focuses on a short-term pedochronosequence of Kurgan № 1 at the Boldyrevo IV kurgan cemetery in the Orenburg Region of the Southern Cis-Urals. According to archaeological findings, the kurgan was built over several decades by people of the Yamnaya (Pit-Grave) culture of the Early Bronze Age (around 5500 BP), with the exact time of its building to be confirmed by radiocarbon dating and further archaeological information. A comparative analysis of the four earthen constructions of the kurgan and the paleosols buried under those constructions was conducted. Results suggest that the kurgan building period was accompanied by the following changes in paleosol morphology and physicochemical properties: the humus horizon acquired a tonguing-like lower boundary, decreased organic carbon content and magnetic susceptibility, while the whole profile was characterized by increasing degree of zooturbation; the impregnation by carbonates in the middle part of the profile and the contents of carbonate carbon, gypsum, and exchangeable sodium increased. Similar trends of morphological and physicochemical changes were observed in the materials of the kurgan constructions. Based on these findings it can conclude that the climate went through aridization rise during the period of the kurgan building. The paleobotanical data from palynological and microbiomorphic analyses indicate that there was a tendency for paleoclimate aridization and, possibly a cooling trend during the studied period of the Yamnaya culture, which was probably more arid than the modern climate.

Paleoclimate-induced stress on polar forested ecosystems prior to the Permian–Triassic mass extinction

The end-Permian extinction (EPE) has been considered to be contemporaneous on land and in the oceans. However, re-examined floristic records and new radiometric ages from Gondwana indicate a nuanced terrestrial ecosystem response to EPE global change. Paleosol geochemistry and climate simulations indicate paleoclimate change likely caused the demise of the widespread glossopterid ecosystems in Gondwana. Here, we evaluate the climate response of plants to the EPE via dendrochronology snapshots to produce annual-resolution records of tree-ring growth for a succession of late Permian and early Middle Triassic fossil forests from Antarctica. Paleosol geochemistry indicates a shift in paleoclimate towards more humid conditions in the Early and early Middle Triassic relative to the late Permian. Paleosol morphology, however, supports inferences of a lack of forested ecosystems in the Early Triassic. The plant responses to this paleoclimate change were accompanied by enhanced stress during the latest Permian as determined by high-resolution paleoclimate analysis of wood growth intervals. These results suggest that paleoclimate change during the late Permian exerted significant stress on high-latitude forests, consistent with the hypothesis that climate change was likely the primary driver of the extinction of the glossopterid ecosystems.

Climate-Controlled Coastal Deposition of the Early Permian Liangshan Formation in Western South China

During the late Paleozoic ice age, tropical coastal depositions have been widely linked to high-frequency sea-level variations, but their linkage with the associated climate change was not fully understood. In the early Permian, two deglaciations occurred in the late Sakmarian and late Artinskian, respectively. During the late Artinskian deglacial warming and transgression, coal-bearing siliciclastic successions of the Liangshan Formation were developed in South China. Three facies associations were recognized from the Liangshan Formation successions in western South China and ascribed to coastal alluvial plain, estuarine, and deltaic environments. Detailed analysis of sedimentology, paleosol morphology, and sandstone petrology suggest a relatively dry-to-wet climate shift and estuarine to deltaic facies transition in the lower Liangshan Formation. This climate shift and facies transition can be temporally correlated based on regional stratigraphic correlations, although precise age constraints are needed to test this correlation. The estuarine interval of the lowest Liangshan Formation signified a rapid transgression during the late Artinskian deglaciation and likely formed during a relatively arid climate with locally small fluvial systems, which provided limited sediment supply. The subsequent transition to and initiation of deltaic deposition was broadly associated with the inferred climate shift and could be primarily resulted from a climate wetting-induced great increase in sediment supply, irrespective of the deglacial sea-level rise.

When does large woody debris influence ancient rivers? Dendrochronology applications in the Permian and Triassic, Antarctica

Accumulations of woody debris and in situ forests in and near ancient river systems are studied in Permian through Triassic strata of Antarctica. These Permian and Triassic fossil ecosystems represent paleo-polar and paleo-high-latitude environments, respectively, and therefore represent unique ecosystem end-members for assessing the role of woody debris in influencing fluvial deposition and paleoecologic processes. A new application of dendrochronology, the cross-dating of ring widths from individual trees, is applied to these fossil woods to develop a chronology of wood growth in the transported woody debris relative to in situ stumps. Cross-matching of woody debris relative to in situ stumps for the Permian indicates that woody debris deposition in river channels was contemporaneous with the development of vegetated macroforms in in-channel fluvial deposits. In contrast, Triassic woody debris occurs without evidence of vegetated in-channel macroforms, yet the volume and areal distribution of woody debris is greater than that measured in the Permian. Floral diversity increased dramatically across the Permian–Triassic transition in Antarctica, in addition to an increase in tree density in Triassic forests relative to Permian forests. However, these observations do not clearly explain the difference between the woody debris influence on Permian river systems relative to Triassic river systems. Paleoclimate simulations, however, indicate that the Permian polar environment was in surplus of water during the austral summer relative to the Triassic, consistent with paleosol morphology, suggesting that paleoclimate variation exerted a prominent control on vegetation-river dynamics.

Paleosols and host rocks from the Middle–Upper Permian reference section of the Kazan Volga region, Russia: A case study

The Urzhumian (Wordian) and Severodvinian (Capitanian) reference section of the Monastery Ravine (Kazan Volga region, Russia), contains two siltstone lithofacies: (a) laminated and (b) massive. Depositional settings of the laminated siltstones can be interpreted as perennial to ephemeral lakes; depositional settings of the massive siltstones are interpreted as floodplains with soil cover and periodical silt influx in wet seasons. The bulk geochemistry of siliciclastics has revealed a high degree of weathering of both types of siltstone. The similar chemical composition, mineralogy, and grain size suggest the same provenance of silt material. Geochemical data indicate eastern source rocks, which are the Permian red beds of the Cis-Ural plains.The main genetic types of paleosols hosted in the massive siltstones in the studied section, include moderately developed Vertisols and Calcisols with drab-colored root traces, calcareous nodules, low chroma mottles, angular blocky peds and slickensides. These pedofeatures indicate in general a semi-arid climate with clear seasonality of rainfall. Major oxides of the paleosol matrix were used to estimate paleoprecipitation through the bases to alumina (ΣBases/Al) ratio and chemical index of alteration minus potassium (CIA-K) proxies. Estimates from Urzhumian paleosols indicate relatively low mean annual precipitation (MAP) of 390mm/yr. The transition to the Severodvinian paleosols is marked by a noticeable MAP increase up to 777mm/yr. This climate moistening coincides with changes in the morphology of paleosols from dolomitic with low redoximorphy to calcitic with gley horizons. The pedogenic carbonate nodules consisting of dolomicrite (5–10μm) are very common in the Urzhumian paleosols and their morphology, micromorhology and isotopic features indicate the pedogenic origin of dolomite.Sedimentological and paleopedological features of the studied siltstones, as well as the location of the Volga-Ural basin in a mid-latitude position (25–32°N) indicate a monsoonal character of precipitation during the Middle Permian.

Plio-Pleistocene paleosols: Loess-paleosol sequence studied in the Beregovoye section, the Crimean Peninsula

The loess-paleosol sequence exposed in the Beregovoye section (southwest of the Crimean Peninsula) has been thoroughly studied. Detailed analysis of the paleosol morphology, physical properties and chemical composition, micromorphology and other characteristics made it possible to identify types of paleosols formed in the Pliocene and Pleistocene. The results obtained gave us an insight into the climate and environments of the past. According to them, the climate of the Pliocene optimum was extremely hot and wet, and the soil zonality was hardly pronounced practically over entire Central and Eastern Europe. At the final phase of the Pliocene the climate became drier, though the rainfall amount was still greater than in the Holocene. During the Early Pleistocene the soil development followed the Mediterranean type, the climate being still warm, though less humid than in the Pliocene. There are two peaks of catastrophic changes in the evolution of the climate and environments distinctly traceable in the Beregovoye section: first – corresponding to the global change recorded between the Pliocene and Pleistocene and second, falling on the initial phase of the modern (Holocene) soil formation.

Vegetation response during the lead-up to the middle Miocene warming event in the Northern Rocky Mountains, USA

The mid-Miocene climatic optimum (MMCO; initial warming beginning ca. 18Ma and with peak warming ca. 17–14.75Ma) constitutes the Earth's most recent greenhouse episode, characterized by a transient shift to higher global atmospheric CO2 levels and warmer, possibly wetter, climatic conditions. Combined with the spread of grass-dominated habitats, it has been suggested that the MMCO lead to significant turnover and modernization of fauna and flora. However, records documenting local vegetation change during the MMCO are rare, hence this hypothesis remains largely untested. Herein, we combine phytolith assemblages and δ13C records from paleosol organic matter from the Railroad Canyon section (RCS), eastern Idaho, to provide the first direct, detailed, and continuous, long-term record of vegetation composition and structure in a single basin during the lead-up to the MMCO (22.9–15.2Ma; late Arikareean–early Barstovian). Phytolith assemblage analysis indicates that grasses, primarily C3 pooids, dominated early–middle Miocene vegetation. Potential C4 PACMAD grasses were present by ca. 21.6–20.7Ma (late Arikareean) and vary in abundance (0.4–17.2% of diagnostic phytoliths) through the section. Although relatively rare overall, PACMAD grasses decrease significantly through time, in parallel with declining diatom abundances and an increase in pooid grasses. In contrast, paleosol δ13Corg indicates 0–29.1% C4 vegetation but no consistent temporal change. Where both phytolith- and isotope-based estimates are made from the same paleosol, they are within error most (82%) of the time; thus, the apparent discrepancy in temporal trends could either be due to differences in the resolution of the two records, or could be explained if many PACMADs were not C4 grasses, but instead water-loving C3 species. Overall, these data suggest that open-habitat mosaic vegetation with grass-dominated grasslands and open woodlands occurred in the North Rocky Mountains, USA, by at least the early Miocene, more comparable to the timing for the spread of grass-dominated habitats in the Great Plains than previously thought. Additionally, phytolith data suggest that overall vegetation structure remained relatively stable throughout the RCS, inconsistent with published paleosol morphology data. This points to regionally unique floral patterns decoupled from global climate change leading into the MMCO.

Polygenetic History of Paleosols In Middle-Upper Pennsylvanian Cyclothems of the Illinois Basin, U.S.A.: Part II. Integrating Geomorphology, Climate, and Glacioeustasy

Abstract Distinct lateral and stratigraphic trends in paleosol morphology and clay mineralogy, in conjunction with the stable-isotope composition of sub-millimeter-scale spherulitic siderite (sphaerosiderite) and flint-clay kaolinite in middle–upper Pennsylvanian cyclic coal-bearing strata of the Illinois basin (IB) presented herein provide proxy records of middle–late Pennsylvanian equatorial terrestrial environments. Collectively, these data provide a better understanding of the polygenetic history of ancient soils preserved in cyclic strata and indicate that low-latitude Pennsylvanian IB soil profiles were influenced by a combination of autogenic and allogenic controls. Lateral variations in paleosol morphology from the interior of the basin to the northern margin indicate that soil development was dominantly influenced by autogenic controls, such as differences in local paleohydrology (i.e., groundwater fluctuations) and subsidence rates across the basin. Conversely, allogenic controls (i.e., glacioeustasy and climate) are interpreted to be principally responsible for the preservation of features in gleyed Protosols, gleyed Vertisols, and gleyed calcic Vertisols that occur in the interior of the IB. These paleosols are characterized by a polygenetic development history that includes (1) an initial period of soil formation in well-drained environments with seasonal wetting and drying of the profile, followed by (2) a subsequent period of waterlogging and development of reducing conditions. Paleosols that lack evidence for extensive periods of waterlogging are restricted, with the exception of two examples, to the northern margin of the basin, and they become abundant in the stratigraphic record near the middle–upper Pennsylvanian boundary (uppermost Desmoinesian). The stratigraphic distribution of these paleosols, in conjunction with a decrease in the relative abundance of kaolinite in the < 2 µm size fraction of IB paleosols near the Desmoinesian–Missourian (D-M) boundary, is interpreted to reflect a shift in the overall low-latitude regional climate to drier conditions. The stable-isotope compositions of sphaerosiderite and flint-clay kaolinite in middle–upper Pennsylvanian strata of the IB provide an additional proxy record of past equatorial terrestrial environments and are used to constrain the magnitude of paleoclimate change across the D-M (∼ Moscovian–Kasimovian) boundary. Sphaerosiderite δ18OV-PDB and δ13CV-PDB values range from −3.6‰ to −0.5‰ and −12.8‰ to −3.2‰, respectively. In particular, sphaerosiderite δ18O values from the B horizons of paleosols display an approximate −1.5‰ shift across the D-M boundary. This stratigraphically short isotopic shift occurs across the D-M boundary, on the order of one cyclothem (∼ 400 kyr), and is followed by a subsequent shift on the order of one cyclothem, back to more positive siderite δ18O values. The average δ18OV-SMOW and δDV-SMOW values of kaolinite isolated from the < 0.2 µm size fraction of a latest Desmoinesian flint-clay breccia are +21.0‰ and −46.5‰. These values correspond to a latest Desmoinesian crystallization temperature of 27 ± 2°C and a meteoric-water δ18OV-SMOW value of −3.1‰. Combination of sphaerosiderite δ18O values and co-occurring flint-clay kaolinite δD and δ18O values suggest a possible warming of up to 6°C across the D-M boundary, corresponding to an approximate temperature change of siderite crystallization from 27 to 33°C. This temperature increase, in conjunction with distinct stratigraphic trends in the clay mineralogy and morphology of IB paleosols, is consistent with previous paleoclimate interpretations, and it suggests that low-latitude Pennsylvanian paleoclimate became drier and warmer across the D-M boundary.

Paleoenvironment and Human Occupation in the Maya Lowlands of the Usumacinta River, Southern Mexico

Paleosol sequences along the lowest terraces of the Usumacinta River in southern Mexico were used to reconstruct Holocene environmental changes and examine human–environmental interactions. Study sections were correlated through paleosol morphology, radiocarbon dating, and artifact seriation of Formative, Classic, and Postclassic ceramics. The oldest paleosols have gleyic features. Although they contain hard carbonate concretions dating to 5450–5380 cal. yr B.P., these Gleysols formed in the Late Pleistocene to Early Holocene. Carbonates were deposited later. The uppermost paleosols lack gleyic features, the oldest of which contains vertic features, dating to 2000–2700 cal. yr B.P., and contains abundant Formative period ceramics. The upper two paleosols are morphologically less developed and are strongly affected by human activities; radiocarbon ages and ceramic assemblages indicate that they belong to the Maya Classic and Postclassic periods. Stable carbon isotope values from the decalcified organic matter vary among paleosols of different ages and sites. δ13C values are highest (−16 to −20‰) in the Formative period paleosol. Although it is possible that maize cultivation could contribute to the isotopic signatures, we believe that the δ13C values indicate the dominance of drought‐resistant C4 and CAM vegetation due to their association with vertic soils. The Classic period paleosol has a slightly lower isotopic value (−20 to −22‰), while the Postclassic paleosol shows the lowest values (−22 to −23‰), suggesting reforestation of the floodplain. These results indicate that the Early Holocene paleosols formed in a humid climate similar to that of today, which transitions toward dryer conditions around 5500 cal. yr B.P. In the Late Holocene (approximately 3000 B.P.) an increase in seasonality occurs. This condition favored the formation of Vertisols, suitable for agriculture.

Eocene vegetation and ecosystem fluctuations inferred from a high-resolution phytolith record

A thorough understanding of the ecosystem factors that can act as drivers of vegetation change, an important factor for projecting impacts of future climate change, requires adequately distinguishing between plant community changes that occur on the local scale or over ecological time scales, and long-term trends. Phytolith assemblages have the potential to provide this information, but little work has been done so far to test their ability to do so in deep time. We examined vegetation patterns inferred from phytoliths (plant silica microfossils) from a single section of the Renova Formation, Timberhills region, Montana, dated to 39.2 ± 3 Ma (late middle Eocene). The section is composed of fl uvial sediments overprinted by paleosols including Alfi sols, Entisols, Inceptisols, and composite paleosols. Phytolith assemblages from 27 paleosol samples were used to reconstruct a high-resolution vegetation history for the area and were compared with paleosol data. Phytoliths are predominantly from forest plants and include tropical elements such as palms (Arecaceae) and gingers (Zingiberales), suggesting a paratropical forest . The high-resolution sampling records heterogeneous vegetation including shifts among closed forest, moderately open forest (forest gaps, edges, and woodland), and grass-dominated habitats. Grasses are interpreted as early open-habitat plants tolerant of drier conditions, but they appear to be replaced by forest vegetation with time, resulting in poor correspondence between paleosol type and phytolith assemblage at some stratigraphic levels, where paleosol morphology indicates a forest ecosystem and the phytolith assemblages indicate a changing grass-forest mixture as a function of depth within the profi les. This is the fi rst study that has used phytoliths to construct a high-resolution record of vegetation from deep time, and we demonstrate that dense sampling and multiproxy approaches to paleo environmental reconstruction are necessary to capture vegetation heterogeneity in time and across microhabitats.

The Permian Moradi Formation of northern Niger: Paleosol morphology, petrography and mineralogy

Three basic paleosol morphologies, named Type A, Type B and Type C, are described from the middle–upper Permian strata of the Moradi Formation, Tim Mersoi Basin, northern Niger. The Moradi Formation is a typical alluvial redbed succession dominated by red mudrocks with fine to coarse-grained pebbly channel sandstones and matrix-breccias. Type A paleosols are hosted by well-sorted fine to medium grained trough cross bedded and massive sandstones and preserve abundant vertical to horizontal micritic and microspar calcite tubules, interpreted as rhizoliths. Lateral variability of rhizoliths in Type A paleosols, and their close association with fluvial channel-fill sediments suggests they are the roots of grove stands of phreatophytic vegetation that grew within unstable anabranching stream systems. Type B paleosols are hosted by mudrocks and preserve well-developed ped structure, abundant micritic calcite nodules and vertically-stacked micritic calcite nodular bodies, as well as rare calcite with satin-spar texture interpreted as a pseudomorphic replacement of pedogenic gypsum. The morphology of Type B paleosols suggests they were formed in well-drained floodplain deposits on stable landforms. Type C paleosols are similar to Type B but preserve pedogenic structures indicative of soil volume expansion and contraction, as well as more abundant Stage II pedogenic carbonate nodules. The morphology of Type C paleosols suggests that they developed periodically rather than seasonally in poorly-drained deposits that nevertheless occupied a relatively stable part of the landscape such as the plains flanking ephemeral lakes or sabkhas.X-ray diffraction analysis of the <2μm fraction from the Moradi Formation strata indicates that paleosol phyllosilicates are composed of illite, smectite, and occasionally kaolinite and talc. Illite is likely a detrital mineral, whereas smectite and kaolinite are likely pedogenic weathering products. The presence of talc in the Moradi Formation paleosols is unusual. It is limited to paleosol horizons that also preserve evidence for pedogenic gypsum accumulation and is therefore most likely related to a pedogenic weathering process. It is possible that this talc is a relatively low-temperature (~50–100°C) diagenetic alteration product of pedogenic Mg–phyllosilicates such as sepiolite.The range of morphologies, petrographic textures and mineralogy of the paleosol profiles indicates semi-arid to hyper-arid climatic setting. This paleoclimatic reconstruction is in agreement with Middle and Late Permian conceptual paleoclimate models and quantitative general circulation models. Nevertheless, and in spite of an arid climate, Moradi paleosols and their host strata also indicate a relatively shallow groundwater table. Importantly, this shallow groundwater resource undoubtedly helped to support the moderately diverse fossil vertebrate assemblage and large-stature macrophytes preserved in the Moradi Formation.

Way out of Africa: Early Pleistocene paleoenvironments inhabited by Homo erectus in Sangiran, Java

A sequence of paleosols in the Solo Basin, Central Java, Indonesia, documents the local and regional environments present when Homo erectus spread through Southeast Asia during the early Pleistocene. The earliest human immigrants encountered a low-relief lake-margin landscape dominated by moist grasslands with open woodlands in the driest landscape positions. By 1.5 Ma, large streams filled the lake and the landscape became more riverine in nature, with riparian forests, savanna, and open woodland. Paleosol morphology and carbon isotope values of soil organic matter and pedogenic carbonates indicate a long-term shift toward regional drying or increased duration of the annual dry season through the early Pleistocene. This suggests that an annual dry season associated with monsoon conditions was an important aspect of the paleoclimate in which early humans spread from Africa to Southeast Asia.

Paleoclimatic Implications of Crayfish-Mediated Prismatic Structures in Paleosols of the Paleogene Willwood Formation, Bighorn Basin, Wyoming, U.S.A.

Abstract Paleosols at Polecat Bench, northern Bighorn Basin, Wyoming, show prismatic structures not previously described in the Paleogene Willwood Formation. Prisms are densely spaced 15–50 mm diameter cylinders with vertical to slightly sinuous paths up to 400 mm long, subangular to rounded vertical faces, and slightly concave to convex tops. Prism exteriors are coated commonly by < 1-mm-thick clay films; exteriors also commonly show knobby and striated surficial morphologies. Prismatic structures are nearly exclusive to thin-bedded (< 1 m thick) compound paleosols composed of red to red-purple sandy mudrock overlying gray to green-gray heterolithic units composed chiefly of fine-grained sandstone. In addition to prismatic structures, these paleosols are characterized by large gray mottles, slickensides, and calcareous rhizocretions which crosscut or more typically follow prism exteriors. The architectural and surficial morphology of the soil prisms suggest strongly that these are pedogenically modified freshwater crayfish burrows of the ichnospecies Camborygma litonomos. At Polecat Bench, an ~ 40 m interval of the Willwood Formation records a transient episode of global warming known as the Paleocene–Eocene Thermal Maximum (PETM). The PETM interval is characterized by a series of predominantly red, cumulative paleosol profiles and increased soil carbonates. Prismatic soil structures and crayfish burrows are rare or absent in cumulic paleosols typical of the PETM, whereas they are locally abundant in red compound paleosols outside the PETM interval. The changes in paleosol morphology and a sharp decrease in crayfish burrows within the PETM interval suggest significantly improved soil-drainage conditions and lower water tables on the Willwood floodplain during the global warming event.

Specificity of the morphology of interglacial and interstadial paleosol complexes of the middle and late Pleistocene in the center of the East European Plain

Paleosol studies were conducted on the Moskva-Oka interfluve in the center of the East European Plain. Three paleosol complexes were distinguished in the sequence of soil-loess deposits: the Mezin complex of the Late Pleistocene age and the Kamensk and Inzhavin complexes of the Middle Pleistocene. Each of them consisted of the paleosols of two phases: the earlier interglacial phase and the later interstadial phase. In some cases, the paleosols of these two phases were separated by a thin layer of sediments with distinct features of cryoturbation. Paleosols of the interstadial phases are represented by the dark-colored humus-rich meadowchernozemic and chernozem-like prairie soils. During the interglacial periods in the Middle and Late Pleistocene, the soils with pronounced eluvial-illuvial differentiation of their profiles were developed under forest cenoses. Data on the morphology of paleosols; their physical, chemical, and physicochemical properties (particle-size distribution, pH, humus, carbonates, amorphous and crystallized iron oxides, etc.); and their micro-morphological features studied in thin sections prepared from undisturbed soil monoliths make it possible to judge the character of the pedogenesis during different epochs.

Triassic paleosol catenas associated with a salt-withdrawal minibasin in southeastern Utah, U.S.A.

Catenas for lithified paleosols have been rarely described in the literature because they are seldom preserved and, where present, are difficult to trace laterally. This study focuses on paleocatenas associated with a Triassic salt-withdrawal minibasin (rim syncline). The catenary surfaces formed during an episode of pro-longed landscape stability along a margin of a salt-withdrawal minibasin and were identified by a series of continuous, high-resolution photopanoramas of canyon outcrops. The paleocatenas had paleoslopes of ∼1%, and were laterally extensive over distances ranging from ∼2.8 to ∼7.9 km. Paleocatenas within the Chinle are associated with lateral taxonomic differences in paleosol morphology. A paleocatena formed on the upper boundary of the lower Chinle has well-drained alfisols on its upper slopes and a poorly drained, over-thickened inceptisol at the toe of the slope. A second paleocatena documented within the upper Chinle includes inceptisols with carbonate nodules characterized by thick paleosols on upper slopes and thin paleosols at the toe slope. Solum thickness, horizon thickness, color, and profile development index (PDI) values were evaluated relative to slope position. Solum thickness, E horizon thickness, Bt horizon thickness, and PDI values have relatively robust covariance to slope position, which suggests that they were influenced by pedotopographic factors. The Bw horizon thickness, Bk horizon thickness, and BC horizon thickness have less robust correlation to slope, and may instead, reflect the influence of other soil forming factors. Both paleocatenas were probably unstable, a conclusion supported by evidence for downslope sediment movement. Upper-slope paleosols have truncated surfaces whereas toe-slope paleosols were either buried or over thickened due to cumulic aggradation. Soil development along the paleocatenas was influenced primarily by erosion, deposition and soil-moisture processes, similar to modern catenas. Thus, landscapes associated with these salt tectonic features significantly influenced paleosol morphology in the Chinle.

Loessial deposits in southern South Island, with a definition of Stewarts Claim Formation

Abstract The loess deposits in the southern part of the South Island represent at least four major periods of accumulation. The deposits include the present soil and three well-defined paleosols separating individual loess members. A fourth poorly defined paleosol within the uppermost loess member is considered to represent a minor period of soil formation. The name Stewarts Claim Formation is proposed for the loess deposits of the region. The formation comprises four members: Yellow loess member (the youngest); Brown A loess member; Brown B loess member; and Brown C loess member (the oldest). The distribution pattern and morphology of the loess deposits is described. It is considered that in most localities, paleosols do not have a complete paleo-solum. The break between a paleosol and the overlying loess of the succeeding deposit is marked by a sharp boundary, in many places associated with a discontinuous stone line. The morphology of paleosols is comparable to that of the lower part of the solum or su...

Paleosols and the forest border in Keewatin, N.W.T.

The morphology of paleosols and radiocarbon-dated charcoal from buried surface horizons of soils provide evidence to suggest that between periods of northward forest encroachment tundra climate has dominated areas at least 50 km south of the present forest/tundra border in southwest Keewatin. The present forest/tundra border climate is nearly as severe as any climate that has prevailed in the area since deglaciation.