Footpaths: pedogenic and geomorphological long-term effects of human trampling

Footpaths are of the oldest and most widely distributed forms of human imprint on the landscape. These elongated features are the result of continuous usage of a certain route for walking, at time scales ranging from days to centuries or millennia. In this qualitative investigation, we take a holistic approach combining micromorphology (including voids analysis), chemical soil parameters (such as selective iron oxide dissolution), and remote sensing (spatial distribution and orientation of footpaths in the landscape) to evaluate the long-term residues and environmental effects resulting from the formation of footpaths. Our diverse case studies incorporate footpaths used for recreational and transport purposes in temperate and sub-humid climates from both recent and historical perspectives. A reduction of the large pores was observed down to 3 cm below current and historical surfaces compared to control areas without footpaths. The lower porosity subsequently hinders of the supply of oxygen and/or water into the sub-surface and encourages water stagnation on the compacted footpath surface. These processes result in higher amounts of pedogenic Fe oxides and, at times, macro-organic residues under footpaths and hindering of soil formation. As an additional result of compaction, surface runoff is promoted. The latter may either trigger the initiation of gullies directly downslope from footpaths or lead to incision of the footpaths themselves. Incised footpaths are more likely to occur when the footpath is oriented parallel to the stream network. Once an incised footpath is formed, it may reduce gully erosion susceptibility downslope as the incised footpath acts as a channel that decreases a footpath’s ‘overbank’ flow. With a better understanding of footpaths as landscape units we can (1) pose archaeological questions related to human environmental interaction, (2) assess carbon storage potential under footpaths and (3) use incised footpaths as possible measures against gully erosion

Palaeoenvironmental research at Hawelti–Melazo (Tigray, northern Ethiopia) – insights from sedimentological and geomorphological analyses

The sites of Hawelti–Melazo in the Tigray region of the northern Ethiopian Highlands is an archaeological hotspot related to the D'mt kingdom (ca. 800–400 BCE). The existence of several monumental buildings, which have been excavated since the 1950s, underline the importance of this area in the Ethio-Sabaean period. We investigated the geomorphological and geological characteristics of the site and its surroundings and carried out sedimentological analyses, as well as direct (luminescence) and indirect (radiocarbon) sediment dating, to reconstruct the palaeoenvironmental conditions, which we integrated into the wider context of Tigray. Luminescence dating of feldspar grains from the May Agazin catchment indicate enhanced fluvial activity in the late Pleistocene, likely connected to the re-occurring monsoon after the Last Glacial Maximum (LGM). The abundance of trap basalt on the Melazo plateau, which provides the basis for the development of fertile soils, and the presumably higher groundwater level during the Ethio-Sabaean Period, provided favourable settlement conditions. The peninsula-like shape of the Melazo plateau was easily accessible only from the east and northeast, while relatively steep scarps enclose the other edges of the plateau. This adds a possible natural protective function to this site.</p

Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment

Intraplate regions characterized by low rates of seismicity are challenging for seismic hazard assessment, mainly for two reasons. Firstly, evaluation of historic earthquake catalogues may not reveal all active faults that contribute to regional seismic hazard. Secondly, slip rate determination is limited by sparse geomorphic preservation of slowly moving faults. In the Vienna Basin (Austria), moderate historical seismicity (Imax, obs&thinsp;∕&thinsp;Mmax, obs = 8∕5.2) concentrates along the left-lateral strike-slip Vienna Basin Transfer Fault (VBTF). In contrast, several normal faults branching out from the VBTF show neither historical nor instrumental earthquake records, although geomorphological data indicate Quaternary displacement along those faults. Here, located about 15 km outside of Vienna, the Austrian capital, we present a palaeoseismological dataset of three trenches that cross one of these splay faults, the Markgrafneusiedl Fault (MF), in order to evaluate its seismic potential. Comparing the observations of the different trenches, we found evidence for five to six surface-breaking earthquakes during the last 120 kyr, with the youngest event occurring at around 14 ka. The derived surface displacements lead to magnitude estimates ranging between 6.2&thinsp;±&thinsp;0.5 and 6.8&thinsp;±&thinsp;0.4. Data can be interpreted by two possible slip models, with slip model 1 showing more regular recurrence intervals of about 20–25 kyr between the earthquakes with M ≥ 6.5 and slip model 2 indicating that such earthquakes cluster in two time intervals in the last 120 kyr. Direct correlation between trenches favours slip model 2 as the more plausible option. Trench observations also show that structural and sedimentological records of strong earthquakes with small surface offset have only low preservation potential. Therefore, the earthquake frequency for magnitudes between 6 and 6.5 cannot be constrained by the trenching records. Vertical slip rates of 0.02–0.05 mm a−1 derived from the trenches compare well to geomorphically derived slip rates of 0.02–0.09 mm a−1. Magnitude estimates from fault dimensions suggest that the largest earthquakes observed in the trenches activated the entire fault surface of the MF including the basal detachment that links the normal fault with the VBTF. The most important implications of these palaeoseismological results for seismic hazard assessment are as follows. (1) The MF is an active seismic source, capable of rupturing the surface despite the lack of historical earthquakes. (2) The MF is kinematically and geologically equivalent to a number of other splay faults of the VBTF. It is reasonable to assume that these faults are potential sources of large earthquakes as well. The frequency of strong earthquakes near Vienna is therefore expected to be significantly higher than the earthquake frequency reconstructed for the MF alone. (3) Although rare events, the potential for earthquake magnitudes equal or greater than M = 7.0 in the Vienna Basin should be considered in seismic hazard studies

Timing of the last interglacial in Northern Europe derived from Optically Stimulated Luminescence (OSL) dating of a terrestrial Saalian–Eemian–Weichselian sedimentary sequence in NE-Germany

Based on the results of palynological and geochemical analyses, a sediment section near the village of Vevais (north-eastern Brandenburg) is assumed to encompass a succession of Saalian, Eemian and Weichselian sediments and is expected to cover a time span from Marine Isotope Stage (MIS) 6 to MIS 2. It is regarded as a key site for the study of the last interglacial cycle in north-eastern Germany. Palynological analyses had revealed an almost complete record of the Eemian (MIS 5e) preserved within a succession of lake marls exposed in the sediment sequence, but results from numerical dating methods were still missing. Within this study five samples from sand layers within the profile have been analyzed using luminescence dating techniques in order to set up a geochronometrical time frame for the Eemian interglacial. First results from Optically Stimulated Luminescence (OSL) dating of quartz showed severe age underestimation of some samples with regard to their relative stratigraphical position to the Eemian lake marls. Radionuclide analyses revealed disequilibria within the 238U decay chain and inconsistencies concerning the 40K content for most of the samples. In order to overcome these dosimetric problems, additional Infrared Stimulated Luminescence (IRSL) and post-Infrared Yellow OSL (post-IR YOSL) measurements from feldspar were conducted and a ‘subtraction dating’ method was successfully applied. Hence, it was for the first time possible to set up a time frame for the Eemian interglacial inferred from luminescence dating techniques of a terrestrial sedimentary archive in north-eastern Germany. The onset of the Eemian was dated to 126 ± 16 ka. The termination and beginning transition from the Eemian to the Weichselian cold stage was dated to 108.9 ± 7.8 ka. These results are in excellent agreement with the marine isotope record as well as with the results of the analysis of the continuous varve record of Lago Grande di Monticchio, with a period of 17.7 ± 0.2 ka from the onset at 127.2 ± 1.6 ka BP for the Eemian interglacial

Implications from Sedimentary records in Fluvial Terraces for Geomorphological Evolution in the Puli Basin, Taiwan

Fluvial terraces play an important role for research on previous geomorphic processes as their sediments can record various sedimentation stages. In the mountains of central Taiwan, however, the formation time of sediments in the Puli Basin is still unclear. In this study, we investigate the fluvial sediments of a fluvial terrace in the Taomi River catchment in the Puli Basin in terms of sedimentology and geochronology and consider their implications for geomorphic evolution in the Puli Basin. Optically stimulated luminescence (OSL) dating shows that fine-grained and homogeneous sediment in the studied fluvial terrace was deposited at 12.3 ± 1.7 ka and 12.0 ± 2.1 ka. These dating results are consistent with the age of 14.5 ± 0.4 ka cal B.P. from the radiocarbon dating of a charcoal fragment. A third OSL age of 8.7 ± 1.4 ka suggests that the overlying fluvial gravels started to form in the early Holocene.Based on the dating results and the sedimentological and geomorphic characteristics of the fluvial terrace under study, a preliminary model of the geomorphic evolution of the Taomi River catchment is proposed: I. The fine-grained sediment had been deposited at the end of the Late Pleistocene. II. In the early Holocene, fluvial gravel deposits were formed, probably caused by a climatic shift (from dry to wet). III. Huge-scaled incision of the Taomi River took place possibly associated with rapid Holocene river incision. IV. Incision stopped, and the studied fluvial terrace was formed. Later, young fluvial terraces, as derived from the analysis of a high resolution DTM, related to episodic incision of the river were formed. The modern river channel is 20 m below the studied outcrop.<br/

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Abstract Screening for fecal occult blood by means of guaiac tests has an unsatisfactory sensitivity for the detection of colorectal neoplasms. The immunological determination of human hemoglobin in feces has a higher sensitivity and specificity, but hemoglobin is degraded during its transport through the gastrointestinal tract. We compared the hemoglobin test to a newly developed immuno-chemiluminometric (ILMA) assay for quantifying the hemoglobin-haptoglobin complex in feces which shows high stability against degradation. From each of 621 patients with gastrointestinal complaints before scheduled colonoscopy we collected two 1-ml samples from a single stool; there were no dietary restrictions. The sensitivity for detecting colorectal carcinomas proved 87% with hemoglobin. With the hemoglobinhaptoglobin complex it was 87% at a cutoff level of 1.5 µg/g feces, 83% at 2.0 µg/g feces, and 78% at 2.5 and 3.0 µg/g feces. The sensitivity for detecting large adenomatous polyps was 54% with hemoglobin, 76% with the hemoglobin-haptoglobin complex at a cutoff point of 1.5 µg/g feces, 73% with the hemoglobin-haptoglobin complex at 2.0 and 2.5 µg/g feces, and 65% with the hemoglobin-haptoglobin complex at 3.0 µg/g feces. The optimal cutoff point for the hemoglobin-haptoglobin complex was estimated to be 2.0 µg/g stool. The specificity for hemoglobin (99%) was significantly higher than that for the hemoglobin-haptoglobin complex at 2.0 µg/g feces (96%). Immunological determination of the hemoglobin-haptoglobin complex in feces has a comparable sensitivity as the fecal hemoglobin assay for colorectal carcinomas and a significantly higher sensitivity for adenomatous polyps but a significantly lower specificity. Its use for colorectal cancer prevention is currently being evaluated in a screening study