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Quaternary International 162–163 (2007) 1–2
The Soil Record of Quaternary Climate Change The terrestrial response to climate dynamics varies greatly and may occur over many scales and time frames. Soils and paleosols provide unique records of ecosystem changes through time. Of particular interest are those components of pedogenic systems that can be utilized as reliable proxies of past environmental conditions. Integrated signals from proxies such as stable isotopic ratios, micromorphic characteristics, geomorphic processes, dendrochronology, phytoliths and other biologic components can be invaluable in interpreting changing climate. Because soil processes vary in time and space across the landscape, the proxy climate record is distributed unevenly. The resulting variability preserved in the soil record must also be explained. Modeling is an important tool in addressing the variability of pedogenic processes and a mechanism for linking processes at different scales. The papers collected in this volume are a selection from those presented in a symposium entitled ‘The Soil Record of Quaternary Climate Change’ at the 2003 International Quaternary Association meeting in Reno, Nevada. In the symposium, we addressed the climate record reﬂected in soils with an emphasis on process modeling. This volume takes an international view of the relation between soils and climate with presentations at many scales. The papers are a unique collection of research from every continent except Antarctica and integrate soil climatic proxies with related subjects from archeology to land preservation. Stable carbon isotopes as proxies in plant community reconstructions have become established in the literature. Johnson and his co-authors take a slightly different approach to this method by addressing the variability in carbon isotope signals both vertically and across the landscape. Although more questions result from this study than may have been answered, the authors clearly show that strategies for stable isotopic sampling and investigation need to be carefully considered when using stable isotopes as plant community and climatic proxies. Leavitt and his co-authors compared radiocarbon ages with stable carbon isotope depth proﬁles throughout the Great Plains of the USA to develop paleoclimate proxies for C3 and C4 plant communities. They produced regional snapshots of environmental change on the Great Plains at 1000-year intervals during the Holocene. 1040-6182/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.quaint.2006.11.010
Durand and his co-authors examined calcretes in Precambrian silicates on the semiarid Mysore Plateau in Karnataka State of South India in an initial attempt to reconstruct paleo-rainfall trends. Their study is unique in that (a) it is based largely on non-biologic continental records in India that exceed one glacial–interglacial cycle and (b) the carbonate source. Calcretes often develop from eolian inﬂux of carbonate dust but in this study, calcium was supplied exclusively by silicate mineral weathering, an occurrence rarely investigated in the literature. Micromorphology of pedogenic calcretes was examined in concert with geochemistry. The micromorphic evidence provided the better indicators for detectable paleoclimatic change and landscape evolution on the plateau. In the arid eastern region of the Thar Desert in northern India, Achyuthan and her co-authors used stable isotopic chemistry of pedogenic carbonates in thick dunes as proxies to develop a Quaternary paleoclimatic history of the region. Their results suggest a strong relation between vegetation, greater summer rains and stronger Asian monsoons during interglacial periods and colder temperatures, weaker monsoons, and greater winter rains during glacial maxima. Amit and her co-authors working in ephemeral stream channels of the southern Arava Valley in the Dead Sea Rift of Israel develop a deﬁnition for a morphostratigraphic unit that is described as more pedologic then sedimentary. Found in the active channel at the lower limit of scour and ﬁll, it is termed a ‘‘ﬂuvial pedogenic unit’’. Similar units are found on Holocene and older Late Pleistocene terraces. The presence of carbonate in some of these units led the researchers to develop a climatic history for the Late Pleistocene and Holocene in this present-day hyper-arid zone. In contrast to the processes associated with calcrete formation in the Mysore Plateau of India, Sweeney and his co-authors showed that Eureka Flat proved to be a signiﬁcant dust source for loess in the Palouse region of south-central Washington State in the USA. The geometry of the Flat provided an excellent depositional valley for glacial outburst ﬂoods that swept through the region during the Pleistocene, alternating with a deﬂation surface before and after glacial maxima.
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Geiss and Zanner chose a magnetic susceptibility technique to examine 40 loessial soil proﬁles in the Midwestern USA. They were able to show a correlation between precipitation gradient and magnetic properties across the region in modern soils where upper horizons were enriched in ﬁne-grained magnetic minerals. However, they found that pedogenically produced magnetic minerals inﬂuenced correlations negatively. Botha and Porat assess the soil-landscape dynamics of an extremely large dunal area on the southeastern African coastal plain in Maputaland using both a relative dating technique, a soil development index (SDI), and a quantitative technique, infrared stimulated luminescence (IRSL). They found that morphological relationships in the dune ﬁelds could be reﬁned using the SDI. IRSL illustrated the very complex interactions of intermittently mobile dune systems and soil-forming intervals. The authors show that a formerly simplistic concept that dune age increases from the shore inland is a poor model for the development of the coastal dune ﬁelds during the Quaternary. Leopold and Vo¨lkel examine the archival attributes of colluvial soils in reconstructing Holocene climate in Europe. They deﬁne colluvial soils in a speciﬁc manner but still conclude that colluvial soils are extremely complex and alone cannot yield speciﬁc climatic information. They note that the long history of land use change has also complicated attempts to use colluvial soils as climate proxies. Dlussky studied the interglacial polygenetic paleosols known as IPP in the Russian Plain of Eastern Europe. Geographic zonality and shifts in soil zones are described for two phases of the IPP for the ﬁrst time and are assessed as early as the Middle Pleistocene ‘‘Likhvin’’ Interglacial using paleosol stratigraphy and micromammalian faunal distributions. Dlussky compares the two phases of the IPP to modern-day soil and climatic zones. Favier-Dubois provides access to a very remote part of Argentina in southern Patagonia and Tierra del Fuego,
locations few of us will ever be privileged to visit. He integrates soil stratigraphic mapping techniques with archeology, pollen, lake sediment records, and paleohydrologic evidence, a multi-proxy approach to develop a case for a Middle to Late Holocene climatic scenario and compare it with the historical and recent past. Appropriately enough, we end this volume with the study of land, land planning and cultural heritage of paleosols. Land planners are just now beginning to follow in the footsteps of scientists and eco-preservationists like Aldo Leopold and soil scientist Hans Jenny. Costantini and his co-authors describe a semi-quantitative technique used to score selected soil characteristics for their cultural value and risk to society if permanently lost. This unusual technique provides policy-makers a means of assigning value to preservation of landscapes in rapidly urbanizing areas. Finally, the editors of this volume wish to acknowledge the signiﬁcant effort and time invested by our many colleagues who willingly reviewed the manuscripts. Without their contributions, these papers would not have been published. Among them are: Peter Almond, Ron Amundson, Richard Baker, Peter Birkeland, Jim Bockheim, John Dormaar, Artigas Duran, David Favis-Mortlock, Martin Fey, Glen Fredlund, David Grimley, Margaret Guccione, Bruce Harrison, Tony Hartshorn, Vance Holliday, Eugene Kelly, Rebecca Kraimer, Les MacFadden, Michael Machette, Alex Makeev, Joe Mason, Dennis Nettleton, Lee Nordt, Merith Reheis, Richard Reynolds, Michael Roberts, Randy Schaetzl, Jim Swinehart, Sampat Tandon, Larry Tiesen, Eric Verrecchia, Sharon Waltman, and Marcelo Zapati. Ms. Rachel West provided English language editing. Thank you all.
Carolyn Olson USDA-NRCS, Washington, DC, USA E-mail address: [email protected]