Karstbase Bibliography Database
Karstbase Bibliography Database
In south western Germany the karstified plateau of the Swabian Alb consisting of Upper Jurassic limestones hosts numerous caves, dolines, and dry valleys. Known strath terraces, conglomerates, volcanoes, and impact craters within the study area already provided important time stamps for former studies reconstructing landscape history. It is widely understood, that spatial distribution of most karst features is closely related to the palaeo-water-table and its discontinuous lowering over time, which in turn is the result of incision and/or uplift. The situation of the Swabian Alb at the northern rim of the Northern Alpine Foreland Basin and east of the Rhine Graben valley is the reason for this uplift. Many caves can be used as gauge for vertical displacement, considering horizontal cave passages as product of a stationary palaeowater-table and vertical sections as result of falling base level. In contrast recent studies deal with a different type of speleogenesis independent of base level. This hypogenic speleogenesis must be discussed for the caves of the Swabian Alb. The recently discovered cave named Laierhöhle near Geislingen/Steige is a typical 3d-maze providing several horizontal levels. Passage pattern and distinctive corrosion features match with morphologies (feeders, rising wall- and ceiling channels, outlets) characteristical for hypogenic speleogenesis. However, artesian situations, hydrothermal water or confined aquifers as critical conditions for hypogenic speleogenesis can not be verified. Other features like horizontal passages, water table markers, key-hole-features, and massive stratified sediment bodies are pointing to an epigenic, water-table related speleogenesis. In this study therefore a mixed model for speleogenesis of Laierhöhle is presented, assuming a strong initial deep-phreatic corrosion along fractures and fissures, followed by intensive widening at the palaeo water-table resulting in the formation of horizontal passages. Correlations between horizontal cave-levels, valley-bottoms, strath-terraces, local conglomerates and other caves lead to new and more precise data on the fluvial history, changing drainage pattern, and the uplift of parts of southwest Germany.
In the course of Examinations of cave sediments spherical metallic particles were detected. These magnetic spherules are ablation-products from meteorites during impact. After fallout and flushing into karstic voids and caves the spherules got archived till today. Spherules within Laierhöhle, Laichinger Tiefenhöhle and Mordloch are supposed to originate from the impact event producing the impact craters Steinheimer Becken and/or the Nördlinger Ries 14.59 Ma ago. Within most of the cave sediments spherules are accompanied by crystals of titano-magnetite, which built during volcanic activity of the Urach-Kirchheim volcanic field. Both spherules and titano-magnetites are proxies for re-deposited Mid Miocene Sediments. In this study I could correlate speleogenetic with dated geomorphic features and thus came to a chronology of events. The Laierhöhle records five episodes of long-term stability of the karst water table covering the time-span from late Middle Miocene until the Pliocene/Pleistocene transition. The first two stable episodes can be dated to the late Middle Miocene and Late Miocene (horizontal levels 1 and 2a). An episode responsible for the formation of level 2b falls within Early Pliocene time. Levels 3a and 3b are spatially well separated but must have formed within a relatively short timespan towards the end of the Pliocene. In the working area, total depth of penetrative karstification was in the order of 120 m. This penetration has been accomplished over a period of approximately 12 Ma resulting in an average uplift rate of 0.01 mm/a.