Fachbereich Geowissenschaften

The World Reference Base for Soil Resources and the FAO Guidelines for Soil Description are tools to identify, describe and classify a soil by diagnostic horizons, diagnostic properties, diagnostic materials, and other soil features. While bedrock and residual fragments can be defined by their lithology and abundance, the parent material of soil formation is not clearly classified. Therefore a substrate classification was implicated in descriptions of layered soils, because these consist often of allochthonous, polygenetic and heterogeneous substrates. Results of soil investigations in Yemen developed into a substrate classification key for parent materials that focuses on parameters of substrate variety. Primarily, the present approach was developed to describe layered soils on the Island of Socotra, but it is assumed to be valid for any semi-arid region in the Tropics and Subtropics. To assess the operational reliability of the system, it was applied to classify parent materials of soils from Yemen mainland and Jordan. The classification key is partly based on the FAO Guidelines, and partly on the German Soil Mapping Guidelines. The substrate variety includes lithology, weathering intensity, stratigraphical unit and substrate form. Different substrate varieties within one profile are called substrate orders and closely relate to sedimentary bedding. The proposed classification key is based additionally on parameters such as geogenesis and relief position. It can be used separately from soil description. However, soil identification and description become more precise by using this classification system. This contribution should be understood as a first approach to an international substrate classification.

Pedostratigraphic and soil morphological data show a well-preserved and wide spread palaeosol at the southwestern margin of the Ar-Rub' al-Khali, Ma'rib, Yemen. The marker horizon of the buried soils is considered as a new proxy of Holocene climate change that is characterised by alternation of e.g. low and high precipitation. The humic palaeosol mainly represented by Ahb and ABb horizons indicates soil development in a more humid climate during the Early Holocene in Southern Arabia as compared to overlying sediments (cover sediments). These cover sediments are obviously a result of increasing aridity from 5800 to 5950 yrs BP on. The early Holocene palaeosol is characterised by AMS 14 C, soil chemical and geochemical data. The pedogenic status quo of this palaeosol is a very important proxy for the interpretation of regional palaeoclimate fluctuations and of the southward shift of the ITCZ in Southern Arabia.

Krotovinas, the burrows of small mammals, are common phenomena in steppe landscapes, and for a long time they have been a major point of discussions about the genesis of Holocene Chernozems. In addition, krotovinas provide a very valuable archive of the biological activities of soil, which is essential when stratigraphical ambiguities are to be solved. Despite this, krotovinas have received little attention within pedostratigraphical research. Using the example of the Upper Palaeolithic excavations Kostiënki and Borshchevo in the Middle Russian Steppe an integrative soil scientific approach highlights the importance of burrowing small mammals and of krotovina fillings resulting from both bioturbation and soil erosion in the Late Pleistocene. Based on field and laboratory data of sediments inside and outside krotovinas and 14 C dating results from two sections, this systematic approach demonstrates the high value of the burrow fillings: black and humus-speckled fillings belong to deep burrows of hamsters dating to the period of Early Holocene Chernozem formation at the very beginning of the Preboreal (10-8 ka cal BC). Greyish sediments originate either from Ag-Bg horizons of the "Gmelin soil" (25-22 ka) or from other as yet unknown Late Valdai paleosols; these fillings are the result of the activities of shallow-burrowing lemmings. In addition, burrow fillings have provided optimal material for worms. Also, fossil bones and teeth found within krotovina fillings give new insights into the occurrence of Cricetus cricetus and Lagurus lagurus in this part of the Middle Russian steppe.

The application of sediment description in excavations helps to interpret sedimentary archives on archaeological sites. Although there are a few standardised approaches for describing deposits in excavations, stratigraphic records carried out by archaeologists can differ significantly from those carried out by geoscientists. In order to compare the results of both types of records, anthropogenic deposits of the Sabaean town of Sirwah, Yemen were investigated with regard to sedimentological criteria. Apart from field description and radiocarbon dating, the texture, structure and chemical data were studied in order to demonstrate whether or not they are suitable for determining post-sedimentary modifications and for refining stratigraphy as developed by archaeologists. The comparison of sediment units and cultural layers of a selected part of an archaeological section demonstrates that a stratigraphic record carried out according to a soil manual substantiates depositional history. In addition, the paper gives some new insights into the occupation and building history of the unique Sabaean culture at the Ramlat As-Sab'atayn desert margin of Yemen in the first millennium BC.

The excavations of the Upper Palaeolithic sites of Kostenki and Borshchevo, located in the Middle Russian Plain, bear several meters of loess-derived colluvial deposits of the Middle and Late Valdai, which cover alluvial sediments of the Don floodplain. At least four cultural layers and more than three paleosol units occur within the colluvial deposits. A high number of krotovinas is most obvious, mainly the burrows of Cricetus cricetus and Lagurus lagurus, which on first view seem only to disturb sediment and soil stratigraphy. To disprove this assumption, the present paper investigates the significance of krotovina fillings within soil research by applying micromorphological analysis. The study gives insight into different filling materials, soil forming processes inside abandoned and filled burrow systems, and surrounding material. In some cases, krotovina fillings in this part of the Middle Russian Plain can be areas of bulking and compaction, of preferential paths of infiltration followed by calcium carbonate depletion, and of drying followed by secondary calcification. Further, burrows are paths for second and third generations of soil faunal activities.

The Ramlat as-Sab'atayn desert margin near Ma'rib, Yemen, displays well-preserved Early Holocene paleosols that are documented by micromorphological and pedological data. The buried soils, which are represented by Ahb horizons, indicate soil formation mostly before 8.3 cal ka BP. In contrast, sandy cover sediments without signs of pedogenesis appeared between 8.3 and 6.6 cal ka BP due to increasing aridity. Characteristic micromorphological features of the cover sediments are a single grain microstructure, crystallitic b-fabric, predominant occurrence of fresh sideromelane, and remnants of microlayers. Micromorphological pedogenic features in the buried Ah horizons include a subangular blocky microstructure, undifferentiated b-fabric as a result of enrichment of organic matter and decalcification, and the predominant occurrence of completely altered sideromelane. Most of these horizons appeared to be nearly completely decalcified so that in parts a stipple speckled b-fabric and neoformed clay coatings could be detected as a result of stronger weathering and soil formation. Pedogenic data provide important information about Holocene climate fluctuations, including the amount of precipitation, which was calculated on the basis of geochemical data from buried A, AB and B horizons. The buried paleosols represent moist climate conditions with precipitation ranging from 400 to 600 mm a-1. RESUMEN En los márgenes del desierto Ramlat as-Sab'atayn, cerca de Ma'rib (Yemen), se encuentran paleosuelos del Holoceno Inferior bien conservados que se documentan con datos micromorfológicos y edáficos. Los suelos enterrados, representados por horizontes Ahb, indican que se formaron mayoritariamente antes de hace 8,3 ka. Por el contrario, los sedimentos arenosos que los cubren sin rasgos de edafogénesis se depositaron posteriormente debido a una aridez creciente hasta hace 6,6 ka. Los rasgos micromorfológicos de los sedimentos arenosos están caracterizados por una microestructura granular sencilla, una fábrica birrefringente cristalítica, presencia predominante de sideromelana fresca y remanentes de microláminas. Los horizontes Ah enterrados tienen una microestructura en bloques subangulares, una fábrica birrefringente no diferenciada como resultado del enriquecimiento en materia orgánica y del proceso de descalcificación, y la presencia predominante de sideromelana completamente alterada. La mayoría de estos horizontes están casi descalcificados, por lo que en algunas partes se observa una fábrica birrefringente de motas en mosaico y revestimientos de arcilla neoformada como resultado de una fuerte meteorización y edafogénesis. Los datos edáficos aportan información importante sobre las fluctuaciones climáticas del Holoceno, en particular la cantidad de precipitación calculada a partir de los datos geoquímicos de los horizontes enterrados A, AB y B. Los paleosuelos enterrados indican condiciones de un clima húmedo con precipitaciones que varían entre 400 y 600 mm año-1 .

Semiarid tropical regions are very suitable to study the polygenesis of layered substrates and soils. To determine relic and recent soil features of tropical soils, pedons in the northern part of Socotra Island, Yemen, were investigated. The aim of the study was to create developmental stages of widely distributed soils, which in particular are layered Cambisols and Calcisols. In most layers of those investigated soils, denudative components occur, which clearly indicate the relocation of coverloams and coverclays with an incorporation of extraneous materials, such as small pieces of relic clayey loams with different shapes. These fragments indicate strong chemical weathering, preceding erosion, and redistribution and/or embedding into younger sediments. Calcium carbonate found at a depth of up to 30 cm in 52% of the layered soils is very typical of an increasing aridity in parts of the semiarid tropics, particularly in areas with high groundwater levels and interflow. In addition, oxidation features and clay illuviation in noncalcareous substrates were detected. At the end, two major soil developmental stages of layered Cambisols and Calcisols were defined and demonstrated at two selected profiles. We assume that patterns of soil polygenesis depend not only on the composition of the respective substrates but also on changing climate conditions. Geochemical and soil physical methods as well as micromorphological analysis were used to describe and classify the soils.

Inhabited dry tropical regions are principally seen as vulnerable areas, especially if people have limited access to suitable land, fresh water and crop seeds. From the traditional, but also from the scientific point of view in some cases, it might be considered to be exceptional, indeed pointless, for people to try to improve land in such an arid environment. But for people living directly on a hypersaline coastline, experiments in crop cultivation are necessary to produce additional fruits and vegetables, using either traditional or adapted techniques of land cultivation. Soil investigations in a kitchen-garden situated on the northern coast of Soqotra Island, Yemen, show that one year of cultivation increased Corg contents from 0 up to 0.7%, and Pav contents from 100 mg kg-1 up to 230 mg kg-1 in the garden beds. A general decrease in slightly soluble salts - explained by irrigation with fresh water - is already obvious after only one year: decreasing from 6.7% slightly soluble sa...

Pedology is a discipline with a wide range of applications in geology, geomorphology, archaeology, geoarchaeology and geography. Especially paleopedology aims are to answer questions about climatic changes, rates of pedogenic processes, pedostratigraphy, suitability of former surface soils and human occupation. In combination to other disciplines, pedology aims to advance geoscientific methods at different scales, and during the last decades, (paleo)pedological research increasingly touched archaeological fields whereby soil research was mostly somehow included in geoarchaeology. When the term 'archaeopedology' was introduced in the 1940s, researchers were already aware of the importance of the subject 'soil' as being a key figure when answering questions of site formation history, cultural chronology and environmental change. The present paper aims to reintroduce this term to the scientific community and to accentuate the importance of buried soils within geoarchaeological research. Shown by two different studies, one from Upper Palaeolithic sites in the Ueckermünder Heide/Germany and one from ancient Yeha/Ethiopia the archaeopedological approach highlights the importance of pedological research on-and off-site excavations by clearly bridging a gap between archaeology, geoarchaeology and (paleo)pedology.