Stable isotope investigations on speleothems from different cave systems in Germany.

Stabile Isotopen-Untersuchungen an Speläothemen aus verschiedenen Höhlensystemen in Deutschland.

by Peter Nordhoff
Doctoral thesis
Date of Examination:2005-06-13
Date of issue:2005-07-20
Advisor:Prof. Dr. Bent T. Hansen
Referee:Dr. Bettina Wiegand
Referee:Prof. Dr. Martin Sauter
Referee:Prof. Dr. Jürgen Schneider
Persistent Address: http://dx.doi.org/10.53846/goediss-3575

 

 

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Abstract

English

Seven speleothems from six independent cave systems in Germany were investigated on their suitability as paleoclimatic archives. The caves are located in the Jurassic Limestones of the Swabian/Franconian Alb (southern Germany) and in a small-scale Devonian (reef) complex of the Harz Mountains (northern Germany). Based on the chronological control using 234U/230Th (TIMS) ages, δ18O/δ13C timeseries of the speleothems were established and related to known paleoclimatic events. Results of the present-day assessment of the cave systems demonstrated that the cave temperature responses; the stable isotopic abundances of the dripwater, and present-day cave calcites reflect mean annual surface air temperatures as well as established isotopic equilibrium conditions during cave calcite precipitation. However, existing biases have been monitored but most of them may be deduced to anthropogenic influences like mining operations (Zaininger-Cave, Swabian Alb) or showcave business (Hermann’s- and Baumann’s-Cave, Harz Mountains). Although the scenarios leave partially an imprint on present-day spelean calcites, like the indicated non-equilibrium conditions at the Zaininger-Cave, their temporal imprint is restricted very much to the last couple of decennial years and thus assumed not to influence the paleorecords at all. Since the δ18O compositions of present-day calcite precipitates are primarily controlled by temperature, the sites may thus be suitable for paleoclimatic investigations from a today perspective. Since the paleorecords of the Hermann’s- and Baumann’s-Cave stalagmites (Harz Mountains) display ages, which are not in chronological order, a construction of timeseries was not possible. Past stable isotopic equilibrium conditions of the remaining paleorecords were verified using the single layer ”Hendy-Test” as well as δ18O/δ13C regression analyzes of the subsample profiles. Late Pleistocene growth periods were found in the Paleocave Hunas Stalagmite (79373
Keywords: speleothem; stalagmites; stalactites; dripwater; Germany; Swabian Alb; Franconian Alb; Harz Mountains; paleoclimate; δ18O/δ13C; stable isotopes; 234U/230Th; TIMS; Zaininger Cave; Hintere Kohlhalden Cave; Baumanns-Cave; Herrmanns-Cave; Mühlbach-Cave; Paleocave Hunas; hendy test; equilibrium conditions; kinetic fractionation; OIS2; Younger Dryas; Bölling/Alleröd; T1; Pleistocene; Holocene; 8.2 kyr.; Holocene Climatic Optimum
Schlagwörter: Speläotheme; Stalagmiten; Stalaktiten; Tropfwasser; Deutschland; Schwäbische Alb; Fränkische Alb; Harz; Paläoklima; δ18O/δ13C; stabile Isotope; 234U/230Th; TIMS; Zaininger Höhle; Hintere Kohlhaldenhöhle; Baumannshöhle; Herrmannshöhle; Mühlbachquellhöhle; Höhlenruine Hunas; thermodynamische Equilibrium; kinetische Fraktionierung; OIS2; Jüngere Dryas; Bölling/Alleröd; T1; Pleistozän; Holozän; 8.2ka; Holozänes Optimum
 
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