Sinkhole development in the Sivas gypsum karst, Turkey

Ergin Gökkaya*, Francisco Gutiérrez, Mateja Ferk, Tolga Görüm

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

The extensive gypsum karst of Sivas, Turkey is one of the most outstanding examples of bare gypsum karst in the world. It displays a number of remarkable geomorphic features, including: (1) two stepped planation surfaces cut-across folded gypsum developed during an initial phase of slow base level deepening punctuated by periods of stability; (2) unusual deeply entrenched gypsum canyons related to a subsequent phase of rapid fluvial incision and water table lowering; (3) a polygonal karst of superlative quality mainly developed in the upper surface; (4) relict valleys disrupted by sinkholes in the lower erosional surface; (5) a large number of bedrock collapse sinkholes mostly associated with the lower surface; and (6) numerous cover subsidence sinkholes developed in the valley floors. This work analyses the spatial distribution, characteristics and evolution of the sinkholes within the broad Plio-Quaternary geomorphological and paleohydrological evolution of the epigene karst system dominated by autogenic recharge. A cartographic sinkhole inventory has been produced in an area covering 2820 km2 with morphometric data and including 295 bedrock collapse sinkholes and 302 cover subsidence sinkholes. The different sinkhole types show a general spatial zonation controlled by the hydrogeological functioning of the different sectors: (1) solution sinkholes (polygonal karst) in the upper recharge area; (2) bedrock collapse sinkholes in the lower denudation surface and close to the base level, where well developed caves are inferred; and (3) cover subsidence sinkholes, with high densities probably associated with areas of preferred groundwater discharge. The morphology of the bedrock collapse sinkholes, varying from small cylindrical holes to large and deep tronco-conical depressions with gentle slopes reflect to geomorphic evolution of these sinkholes that reach exceptionally large hectometre-scale diameters. Their evolution, involving substantial enlargement and deepening, is attributed to the solutional removal as solute load of large volumes of gypsum by downward vadose flow. This type of morphological evolution with significant post-collapse solutional denudation differs from that observed in carbonate rocks characterised by lower solubility and erodibility. The analysis of historical imagery reveals that bedrock collapse sinkholes currently have a very low probability of occurrence and that buried cover subsidence sinkholes are used for urban development creating risk situations.

Original languageEnglish
Article number107746
JournalGeomorphology
Volume386
DOIs
Publication statusPublished - 1 Aug 2021

Bibliographical note

Publisher Copyright:
© 2021 The Authors

Funding

The work conducted by FG has been supported by project CGL2017-85045-P ( Ministerio de Ciencia e Innovación , Spanish Government). The contribution by MF has been supported by the Slovenian Research Agency (research programme P6-0101 ; research project N1-0162 ). This paper is a part of the first author's Ph.D. Thesis. The work conducted by FG has been supported by project CGL2017-85045-P (Ministerio de Ciencia e Innovaci?n, Spanish Government). The contribution by MF has been supported by the Slovenian Research Agency (research programme P6-0101; research project N1-0162). This paper is a part of the first author's Ph.D. Thesis.

FundersFunder number
Ministerio de Ciencia e Innovaci?n
Javna Agencija za Raziskovalno Dejavnost RSP6-0101, N1-0162
Ministerio de Ciencia e Innovación

    Keywords

    • Collapse
    • Evaporite karst
    • Morphometry
    • Sinkhole hazard
    • Solutional denudation

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