A mid Miocene to early Pleistocene multi-level cave as a gauge for tectonic uplift of the Swabian Alb (Southwest Germany)

摘要

A recently discovered deep cave (Laierhohle) within a plateau of Upper Jurassic limestone is the deepest (126 m) of the southwest German Swabian Alb providing a unique gauge for crustal tilting and isostatic uplift of the southwest German crust from late Mid Miocene to earliest Pleistocene. Horizontal levels are considered a product of a stationary palaeo-water table; vertical shafts are related to base-level fall which in turn may be the result of uplift and/or incision. We correlate speleogenetic with dated geomorphic features and thus come to a chronology of events. The Laierhohle 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 time-span 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.