Wighart von KOENIGSWALD, Martin WALDERS & Martin SANDER:
An unusually rich horizon with animal tracks of Late Pleistocene age was discovered in the unconsolidated sediments of the Emscher river near Bottrop-Welheim. The lithostratigraphic position of the track horizon is in the lowermost »periglaziale Lößaue« (periglacial loess floodplain) unit which belongs to the Weichsel glaciation. Biostratigraphically, the track horizon can be dated as middle Weichselian. Luminescens dating supports this age assignment.
About 600 footprints covering an area of about 150 m2 represent one water fowl and several cold-period mammals. About half of all footprints can be combined into 30 trackways, 16 of which can be assigned to the reindeer, Rangifer tarandus. The animals crossed the area individually and not as a herd. Two trackways were made by large bovids (Bison or Bos), but another 10 trackways can only be ascribed to large ungulates. Of these, two are parallel and contemporaneous and probably represent horses (Equus sp.). Especially impressive are the trackways of two large carnivores, the cave lion, Panthera leo spelaea, and the wolf, Canis lupus. Travelling speeds were estimated from the pace in the trackways. The results indicate that the predators as well as their prey crossed the area in a slow walk, presumably at different times. The track horizon does not record a hunt.
Based on the differential preservation of the footprints, the progressive drying up of the floodplain mud as well as local moisture gradients can be reconstructed. The faunal inventory documented by the track horizon is reviewed within the stratigraphic framework of the Late Pleistocene of Central Europe. The time of disappearance of the individual taxa as they approach the Pleistocene-Holocene boundary received special attention.
Wighart von KOENIGSWALD & Martin WALDERS:
Based on the mammal remains from the older and younger »Niederterrasse« (alluvial plain) of the Emscher river, the »Knochenkies« (bone gravel) unit is determined to be of early to middle Weichselian age. Small faunal admixtures from the Saale glaciation and the Eemian interglacial are likely present as well. The »Schneckensand« (snail sand) unit of the older »Niederterrasse« and the »periglaziale Lößaue« (periglacial loess floodplain) unit of the younger »Niederterrasse« are also of middle Weichselian age. The track horizon at the base of the periglacial loess floodplain therefore is of late middle Weichselian age which is in agreement with the luminescence dating. The track horizon accordingly originated before the maximum extend of the Weichsel glaciation.
At Bottrop-Welheim in Westfalia a horizon of mammal tracks was found in Upper Pleistocene sediments of the Lower Terrace of the river Emscher. The horizon is rich in tracks from individuals and species such as Panthera leo spelaea which is unique to Middle Europe. The horizon is paleontologically and biostratigraphically of last glacial age.
12 samples were taken from three profiles above and below the mammal track horizon. Systematic investigations were carried out to study the reliability of thermoluminescence (TL) and infrared stimulated luminescence (IRSL) dating methods for fluviatile sediments, and to determine the age of the animal tracks. The dating approach is based on 35 luminescence ages which have been determined by TL and IRSL using the additive dose and partial bleach methods as well as bleaching experiments. Quartz and light mineral coarse grains (100-200 µ) were used for the dating. The annual dose was estimated by gammaspectrometry in the laboratory.
The dating approach showed large uncertainties when fluviatile sediments were dated by TL because of unsufficient bleaching before sedimentation, hence erroneous high ages have been obtained. The systematic dating approach showed that TL and IRSL age determination of fluviatile sediments was a function of the depositional environment and dependant on the fluviatile dynamics of the river Emscher. A variety of apparent residual levels for the quartz and light mineral coarse grains were obtained since the minerals had received only a brief light exposure under the fluviatile conditions. TL dating seems to be less suitable for dating of fluviatile sediments. The additive dose method was performed on all samples, however only five samples were analysed by the partial bleach method.
The IRSL dating results show a better agreement with the stratigraphy of terrace sediments in comparison with the TL signal since the IRSL signal was more sensitive to sunlight.
At Bottrop-Welheim the following ages were determined for the sediments of the Lower Terrace of the river Emscher: IRSL ages of 35-42 ka were obtained for the sandy and silty layer of the »periglaziale Lößaue« whereas the younger sand layers of the »Ältere Talsande« showed ages between 13.8 and 18.8 ka. All ages are interpreted as maximum ages because of insufficient bleaching before sedimentation. The IRSL ages for the light mineral fraction are in general agreement with the stratigraphy. Stratigraphically the mammal track horizon belongs to the upper part of the Middle Weichselian or lower part of the Upper Weichselian. The sedimentation age of the »Ältere Talsande« belongs to the upper part of the Upper Weichselian.
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