Age of karst processes

Objectives of the course

Karst and cave sediments are a relatively special type of geological material. The karst environment is as much inclined to the preservation of paleontological remains as to their disintegration. On one hand, karst regions are known as being rich with sites of paleontological remains but on the other the majority of cave fill is completely sterile, particularly sediment from inside caves. A second problem is the decomposition and mixing of various cave sediments that erase their original record. For this reason it is necessary to undertake the dating of karst processes using various dating methods. Since the karst and caves have developed since the Archeozoic, almost all dating methods can be employed, except of course those used to date igneous and metamorphic rock. The methods used to determine directly the age of cave sediments are based on physical, chemical, and biological factors and classic geological and stratigraphic approaches. Students will become familiar with various dating methods, which we can divide into six categories: (1) sidereal (chronological or annual) methods, which determine the chronological record or counts annual events; (2) isotopic methods, which measure changes in isotopic elements relative to radioactive disintegration and/or rays/decay; (3) radiogenic methods, which measure the cumulative effects of radioactive decay such as damage to crystals and electronic energy belts//drops in electronic energy/; (4) chemical and biological methods that measure the results of time-dependent chemical or biological processes: (5) geomorphic methods, which measure the cumulative results of complex and reciprocal physical, chemical, and biological processes on the earth’s surface; and (6) comparison methods, which determine age by comparing various properties that are independent of time. The results of dating can be classified into four classes: numerical age, calibrated age, relative age, and correlated age. The evaluation of results acquired through the various dating methods depends on other geological records, the geological context, and awareness of the reliability and limits of the methods. The unreliability of the methods can results from analytical errors, the natural variability in samples, mistakes in identifying the geological context, calibration errors, or an incorrect hypothesis. During the course, the students will also become familiar with paleokarst, stratigraphic gaps, problems of dating the onset of karstification, various phases in the filling of caves, the development of karst forms, etc. The time scale defined by the development of the karst surface and cave passages extends from ten to one hundred ka.

Prerequisites

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Assessment methods

Oral exam.

Course contents

• Introduction
• Dating methods
• Sidereal Methods
• Isotopic methods
• Radiogenic methods
• Chemical and biological methods
• Geomorphic methods
• Correlative methods
• Error possibilities of methods and evaluating their results
• Dating paleokarst
• Dating various periods of karstification and filling phases in karst areas

Recommended reading

• Bosák, P., Ford, D.C., Glazek, J. & Horaček, I., (Ed.)1989: Paleokarst. A Systematic and Regional Review. Elsevier-Academia, Amsterdam –Praha.
• Bosák, P., 2002: Karst processes from the beginning to the end: how can they be dated? in Gabrovšek, F. (Ed.) Evolution of Karst: From Prekarst to Cessation, Carsologica, Založba ZRC, 191-223, Ljubljana.
• Bosák P., Pruner, P., Mihevc, A. & Zupan Hajna, N., 2000: Magnetostratigraphy and unconformities in cave sediments: case study from the Classical Karst, SW Slovenia. Geologos, 5, 13-30, Poznań.