Paleosols

Palaeoclimate of the Late Jurassic of Portugal: comparison with the Western United States

by Timothy Myers

Myers, T.S., Tabor, N.J., Jacobs, L.L., and Mateus, O. (in press) Sedimentology

Investigation of the palaeoclimatic conditions associated with Upper Jurassic strata in Portugal and comparison with... more Investigation of the palaeoclimatic conditions associated with Upper Jurassic strata in Portugal and comparison with published palaeoclimate reconstructions of the Upper Jurassic Morrison Formation in western North America provide important insights into the conditions that allowed two of the richest terrestrial faunas of this period to flourish. Geochemical analyses and observations of palaeosol morphology in the informally named Upper Jurassic Lourinhã formation of western Portugal indicate warm and wet palaeoclimatic conditions with strongly seasonal precipitation patterns. Palaeosol profiles are dominated by carbonate accumulations and abundant shrink-swell (vertic) features that are both indicative of seasonal variation in moisture availability. The δ18OSMOW and δDSMOW values of phyllosilicates sampled from palaeosol profiles range from +22.4‰ to +22.7‰ and -53.0‰ to -37.3‰, respectively. These isotope values correspond to temperatures of formation between 32°C and 39°C ± 3°, with an average of 36°C, which suggest surface temperatures between 27°C and 34°C (average 31°C). On average, these surface temperature estimates are 1°C higher than the highest summer temperatures modelled for Late Jurassic Iberia using general circulation models. Elemental analysis of matrix material from palaeosol B-horizons provides proxy (chemical index of alteration minus potassium) estimates of mean annual precipitation ranging from 766 to 1394 mm/year, with an average of approximately 1100 mm/year. Palaeoclimatic conditions during deposition of the Lourinhã formation are broadly similar to those inferred for the Morrison Formation, except somewhat wetter. Seasonal variation in moisture availability does not seem to have negatively impacted the ability of these environments to support rich and relatively abundant faunas. The similar climate between these two Late Jurassic terrestrial ecosystems is probably one of the factors which explains the similarity of their vertebrate faunas.

A Bán-halom komplex tájökológiai és paleotalajtani felmérése – Survey of the biotical and abiotical landscape factors of the Bán-halom kurgan and its surrounding territory

by Ákos Pető

Barczi, A. - Tóth, Cs. - Tóth, A. - Pető, Á., 2009. A Bán-halom komplex tájökológiai és paleotalajtani felmérése. Tájökológiai Lapok [Hungarian Journal of Landscape Ecology] 7(1): 191-208. (in Hungarian with English abstract)

Palaeoenvironmental reconstruction of Hungarian kurgans on the basis of the examination of palaeosoils and phytolith analysis

by Ákos Pető

Barczi, A. - Golyeva, A.A. - Pető, Á., 2009. Palaeoenvironmental reconstruction of Hungarian kurgans on the basis of the examination of palaeosoils and phytolith analysis. Quaternary International 193: 49-60.

Late Jurassic paleoclimate of Central Africa

by Timothy Myers

Myers, T.S., Tabor, N.J., and Jacobs, L.L. (2011) Palaeogeography, Palaeoclimatology, Palaeoecology 311: 111-125

Paleopedology and geochemical analysis of Upper Jurassic deposits in the Stanleyville Group of Central Africa indicate... more Paleopedology and geochemical analysis of Upper Jurassic deposits in the Stanleyville Group of Central Africa indicate harsh Late Jurassic paleoclimates in the interior of Gondwana. Subsurface samples collected from the Samba borehole near the center of the Congo Basin show only weak morphological evidence of pedogenesis, but are characterized by an abundance of shrink-swell (vertic) features and rare calcium carbonate nodules, indicating seasonal variations in moisture availability and net soil moisture deficiency, respectively. X-ray diffraction analysis of paleosol matrix material reveals the presence of analcime and the clay mineral palygorskite, strong indicators of hot, arid climatic conditions. The δ18O and δD values of clay minerals from paleosol profiles range from +22.3‰ to +25.4‰ and −44.4‰ to −39.6‰ SMOW, respectively, and correspond to crystallization temperatures between 25°C and 40°C. These crystallization temperatures compare favorably with austral summer surface temperature estimates for Central Africa that result from Late Jurassic global circulation models. Calculations of soil CO2 production using the δ13C values of pedogenic carbonates and plant-derived organic matter produce lower CO2 production estimates for the Stanleyville Group relative to the roughly contemporary Morrison Formation of the western U.S. These low soil CO2 production estimates provide further support for arid Late Jurassic climate conditions in the Congo Basin. The paleoclimatic conditions inferred here from the Stanleyville Group are similar to those reconstructed from other Upper Jurassic African continental localities between 5°S and 20°S paleolatitude. However, penecontemporaneous terrestrial coastal sites within this latitudinal belt of Gondwana retain evidence of generally wetter conditions, suggesting that those regions may have received more rainfall than the continental interior. The paleoclimatic setting reconstructed here from geologic indicators and geochemical proxies suggests that general circulation models accurately predict unique paleoenvironmental conditions that lack modern analogs.

Palaeosol stratigraphy across the Permian-Triassic boundary, Bodga Mountains, NW China: Implications for palaeoenvironmental transition through Earth's largest mass extinction

by Timothy Myers

Thomas, S.G., Tabor, N.J., Yang, W., Myers, T.S., Yang, Y., and Wang, D. (2011) Palaeogeography, Palaeoclimatology, Palaeoecology 308: 41-64

Upper Permian and Lower Triassic palaeosols from northeastern Tethyan localities exposed within the Bogda Mountains,... more Upper Permian and Lower Triassic palaeosols from northeastern Tethyan localities exposed within the Bogda Mountains, NW China, provide a wealth of information regarding long-term palaeoclimatic and palaeoenvironmental variations. Wuchiapingian palaeosols are characterized by intense redoximorphy, accumulation of vascular plant matter, accumulation of clay minerals and Fe-oxides, slickensides, and clastic dikes, suggesting a soil moisture regime that ranged from perennially wet to distinctly seasonal in soil moisture budget. Changsinghian to early Induan palaeosols include subsurface accumulations of clay and carbonate as well as surficial accumulations of organic matter, indicative of sub-humid to sub-arid soil moisture and variable soil moisture regimes. Induan to Olenekian palaeosols contain pedogenic CaCO3 accumulations and gypsum pseudomorphs, indicating a drier environment characterized by net soil moisture deficiency. Elemental composition of palaeosol matrix was used to estimate palaeoprecipitation through the chemical index of alteration minus Potassium (CIA-K) proxy. Estimates from various Wuchiapingian strata indicate relatively stable palaeoprecipitation. During the late Changsinghian and early Induan, palaeoprecipitation appears to have decreased from 1100 to 230 (±180)mm/year over less than 100 m of vertical stratigraphic section. In the Induan and Olenekian, palaeoprecipitation appears much less stable than in Wuchiapingian, with values vacillating from 290 to 1014 mm/year. The transition to a relatively unstable precipitation state coincides generally with the Permian–Triassic boundary, and may reflect climatic disturbances associated with the end-Permian extinction event in addition to altered atmospheric circulation patterns resulting from regional tectonics, moisture availability, and expansion of the subtropical high pressure belt.

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

by J.Sébastien Steyer

A palaeoenvironmental analysis of Permian sediments in Minorca (Balearic Islands, Spain) with new palynological and megafloral data

by Antoine Bercovici

Bercovici, A., Diez, J. B., Broutin, J., Bourquin, S., Linol, B., Villanueva-Amadoz, U., López-Gómez, J., Durand, M. (2009). A palaeoenvironmental analysis of Permian sediments in Minorca (Balearic Islands, Spain) with new palynological and megafloral data. Review of Palaeobotany and Palynology, v. 158, pp. 14-28.

Plant fossils are rarely preserved within the Upper Permian of western Europe as the majority of continental deposits... more Plant fossils are rarely preserved within the Upper Permian of western Europe as the majority of continental deposits consists of siliciclastic redbeds. Because organic matter such as plant debris and palynomorphs is destroyed by oxidizing conditions, these red sedimentary facies were often considered as “devoid of life”. This paper presents new palaeobotanical data from the Upper Permian strata of Minorca (Balearic Islands, Spain). In addition, a rich and diverse “Thuringian” palynoflora was recovered from the Permian sediments, and several megafloral taxa are recorded. Additionally, a detailed sedimentological analysis of the studied section is provided. The Permian succession shows a general evolution from a ponded floodplain environment to sand-sheet rivers flowing across a semi-arid alluvial plain. Additionally, new palaeobotanical elements, added to the study of palaeosols, allow reconstruction of Late Permian plant growth within the terrestrial environment, as well as a palaeoenvironment reconstruction of the preserved sedimentary interval. At the transition between ponds and alluvial plain deposits, root systems surprisingly similar to those known in extant mangroves are described for the first time within Permian deposits. As there are no other palaeobotanical remains preserved in association, the type of plant that inhabited this environment remains conjectural.

Plio-Pleistocene red clay deposits in the Pannonian basin: A review

by János Kovács

Grain-size analysis of the Neogene red clay formation in the Pannonian Basin

by János Kovács

Comparative study on the Late Cenozoic red clay deposits from China and Central Europe (Hungary)

by János Kovács

Chemical weathering intensity of the Late Cenozoic 'Red Clay' deposits in the Carpathian Basin

by János Kovács

Human and natural impacts on fluvial and karst depressions of the Maya Lowlands

by Duncan Cook

Published in a special issue of Geomorphology in 2008. Co-authored with Timothy Beach, Sheryl Luzzadder-Beach and Nick Dunning.

This paper begins to differentiate the major drivers and chronology of erosion and aggradation in the fluvial and... more This paper begins to differentiate the major drivers and chronology of erosion and aggradation in the fluvial and fluviokarst landscapes of the southern and central Maya Lowlands. We synthesize past research on erosion and aggradation and add new data from water, soils, radiocarbon dating, and archaeology to study the quantity, timing, and causes of aggradation in regional landscape depressions. Geomorphic findings come from many excavations across a landscape gradient from upland valleys, karst sinks, and fans into the coastal plain floodplains and depressions. Findings from water chemistry show that sources in the uplands have low quantities of dissolved ions but water in the coastal plains has high amounts of dissolved ions, often nearly saturated in calcium and sulfate. We found significant geomorphic complexity in the general trends in upland karst sinks. In a few instances, sediments preserve Late Pleistocene paleosols, buried 2–3 m, though many more have distinct middle to late Holocene paleosols, buried 1–2 m, after c. 2300 BP (Maya Early to Late Preclassic). From 2300–1100 BP (Late Preclassic to Classic Periods), the landscape aggraded from five main mechanisms: river flooding, climatic instability, accelerated erosion, ancient Maya landscape manipulation, and gypsum precipitation from a rise in a water table nearly saturated in calcium and sulfate ions. Evidence exists for two or three high magnitude floods, possibly driven by hurricanes. Moreover, lake-core and geophysical studies from the Petén Lakes region have shown high rates of deposition of silicate clays (‘Maya Clays’) starting and peaking during the Maya Preclassic and continuing to be high through the Late Classic. The main driver on upland karst depressions, the Petén lakes, upland valleys, and fans was accelerated soil erosion, but water table rise, probably driven by sea-level rise, was the main driver on the wetlands of the coastal plain because the aggraded sediments here are dominantly composed of gypsum, precipitated from the groundwater. This latter mechanism represents a little recognized mechanism of aggradation over a large region. These large scale environmental changes occurred during periods of intensive ancient Maya land use and climatic instability, both of which may have contributed to erosion by increasing runoff. Despite these geomorphic changes, ancient Maya farmers adapted in several key cases.

Impacts of the ancient Maya on soils and soil erosion in the central Maya Lowlands

by Duncan Cook

Co-authored with Tim Beach, Nick Dunning, Sheryl Luzzadder-Beach and John Lohse

Assessing pedogenic calcite stable-isotope values: Can positive linear covariant trends be used to quantify palaeo-evaporation rates?

by Darren Gröcke

Chemical Geology, 256, 46–51, doi:10.1016/j.chemgeo.2008.07.022

Palaeoclimate models suggest enhanced evaporation rates in subtropical regions (15–30° latitude) during... more Palaeoclimate models suggest enhanced evaporation rates in subtropical regions (15–30° latitude) during greenhouse-world conditions, however, there are no empirical data to support these estimates. Laboratory evaporation experiments have shown that calcites precipitated from variably saturated solutions yield a positive linear covariant trend (PLCT) in δ18Ocalcite versus δ13Ccalcite values. The goal of the present controlled laboratory experiments is to develop a method to quantify regional palaeo-evaporation rates from palaeosol calcrete PLCTs. Samples of powdered CaCO3 were dissolved in de-ionized water in pressure sealed containers with a range of elevated atmospheric pCO2 concentrations for 24 h. The solution was then allowed to evaporate completely from an open container within an incubator with the time of calcite crystallization noted, and aliquots removed for analysis every 24 h. The precipitated calcite produced an array of δ18Ocalcite versus δ13Ccalcite values that fall upon a PLCT projected from a theoretical meteoric calcite line (MCL). Water analyses yielded δ18Owater enrichments from an initial value of −4.75‰ VSMOW ranging up to between +10.0‰ and +14.8‰. The experimental results show that solutions formed under higher pCO2 conditions precipitated calcite very early on during evaporation, and thus have δ18Ocalcite and δ13Ccalcite values that are slightly enriched relative to the MCL. The solutions that formed under low pCO2 conditions precipitated calcite after much of the fluid had evaporated, and thus yield more enriched δ18Ocalcite and δ13Ccalcite values. Repeat trials with varying temperature and relative humidity show that the PLCT is steeper under both higher temperature and low relative humidity. The wide range of pCO2, temperature and relative humidity conditions used simulate meteoric phreatic and meteoric vadose conditions that may affect a calcrete horizon over time during numerous dissolution/precipitation reactions. The results of these experiments show that a dominant factor in the precipitation of vadose calcite is the saturation state of the fluid with respect to CaCO3, while the primary factors affecting the magnitude and steepness of the PLCT are vadose zone temperature, relative humidity, the starting δ18Owater value and saturation state of the fluid with respect to CaCO3. Since the pCO2 of the rooting zone is cross-controlled by the local soil and surface ecology, the magnitude of the PLCT enrichment may not be a direct proxy for palaeo-evaporation rates.

A Proxy for Humidity and Floral Province from Paleosols

by Erik Gulbranson

A pedogenic goethite record of soil CO2 variations as a response to soil moisture content

by Erik Gulbranson

PRE-MAZAMA PEDOGENESIS RECORDED IN POST-OUTBURST FLOOD GEOLOGIC DEPOSITS OF THE SCABLAND, COLUMBIA PLATEAU, WASHINGTON

by Brett Lenz

The shallow subsurface of the Scabland region of the Columbia Plateau in central Washington State, displays abrupt... more The shallow subsurface of the Scabland region of the Columbia Plateau in central Washington State, displays abrupt change in mode of deposition and sedimentation rates recorded in Pleistocene and early Holocene pedogenic sequences. Local depositional environment change occurred rapidly as a result of catastrophic flood sedimentation, the source of eolian and alluvial parent materials. Cross-Scabland flooding ceased between 12.8 and 12.1 KBP, while catastrophic floods that were restricted to the Columbia River valley post-date the fall of Glacier Peak tephra (11.2 KBP). Pedogenesis into these flood deposits and thin L1 loess at numerous Scabland locations is recorded in two soil-forming periods. The lower soil, termed the Bishop Paleosol, is characterized by a well-developed A horizon and relatively thin Cambic (Bw) or Argillic (Bt) horizons, depending on the depositional environment. The age of this soil is constrained by its relative position between Mt. St. Helens Set S (12.8±60KBP) and Glacier Peak tephras. Separating the two soils at several locations is a post-Glacier Peak tephra period of eolian deposition which may reflect disbursement of Columbia River Valley outburst flood sediments during the Younger Dryas cooling period. The second period of pedogenesis post-dates deposition of Glacier Peak tephra and pre-dates Mazama (7.7KBP) tephra deposition. This soil, termed the Badger Mountain paleosol, is characterized by multiple, stacked buried A (Ab) horizons, Cambic horizons and well developed Argillic horizons which may qualify as Natric soils. These strong B horizons overprint the deepest buried A horizons and the Bishop paleosol in some exposures. The cap of the Badger Mountain soil is characterized by a zone of extremely well-developed cicada burrowing up to 1m thick, indicating a shift to arid conditions after 11.2KBP.

Archaeological Geology of Upper Pleistocene and Early Holocene Landforms of the Pacific Northwest, USA: Identifying the Colonizer Landscape

by Brett Lenz

While it is generally accepted that the initial Pleistocene human colonizers of the Americas likely entered the... more While it is generally accepted that the initial Pleistocene human colonizers of the Americas likely entered the continents via the Pacific coast, formal models of their entry and dispersion into the continental interior are scarce. The ability to identify colonizer period archaeological sites for development of such models requires that researchers identify landforms of appropriate age and depositional character to target for large-scale archaeological survey. Well-preserved Upper Pleistocene and Early Holocene landforms are present across the Pacific Northwest. From coastal environs to the Palouse, these landforms represent a remnant landscape which initial colonizers explored at some point subsequent to the last glacial maximum. The types of landforms suitable for deposition and preservation of colonizer period archaeological sites include a broad array of settings, including: Coastal environments, characterized by relict Pleistocene-age landscape features shoreward of the submerged continental shelf; Continental ice-marginal and ice-distal depositional environments, where a variety of glaciomarine and long-standing glacial lakes formed behind the retreating Puget Lobe of western Washington State; Interior Scablands where cataclysmic outburst floods created scoured topographic lows that acted as local depositional basins—often holding paleo-lakes and marshes; and the Palouse loess within the Columbia Basin province, where eolian deposition has buried and preserved the Pleistocene and early Holocene landscape. Along the major drainageways, Upper Pleistocene to Early Holocene alluvial chronologies vary locally, but overall regional trends indicate that climate-controlled aggradation initiated between 12.0 to 11.0KBP, forming distinct terraces in the major river systems and their tributaries. Regional soil formation is evidenced by the Bishop Geosol which dates between 13.5KBP and 11.2KBP, present in a broad variety of depositional environments. Upper Pleistocene archaeology is sparse but present across the region; initial colonizers were broad-spectrum foragers whose toolkit included distinctive stemmed and shouldered bifaces, macroblade tools and crescents.

Latest Cretaceous (Maastrichtian) aridity indicated by paleosols in the McRae Formation, south-central New Mexico

by Brenda Buck