Hiatus (geology)
A hiatus ( lat. : Hiatus , opening ',' gap ') is a geological layer gap , in the apparently seamless in consecutive ( concordant ) sedimentary rocks - layers portions are missing. This gap, characterized by missing rocks of a certain stratigraphic age, is caused by erosion of already deposited layers or by non-deposition ( omission ). A special case of erosion is subsolution, in which salt deposits , for example, leave layer gaps at their place of origin due to salt migration or dissolution.
In contrast to the discordance , the layers below and above a hiatus do not meet at a more or less large angle, but lie parallel. The layer gaps in the stratification can be detected both by sedimentological - lithostratigraphic criteria and by biostratigraphic criteria such as the absence of biozones .
The term 'hiatus' is also applied - detached from the current shift stack - to the time span in the shift gap. This can be geologically brief: A comparison of the amount of sediments currently deposited in the oceans with the rocks handed down from the geological past shows that in 50 to 90% of the shallow sea sediment non-deposition events of the order of magnitude of several thousand years must occur. In other cases there are gaps in the sequence of rocks corresponding to hundreds of thousands of years or more.
literature
- Hans Füchtbauer: Sediments and sedimentary rocks . 4th edition. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1988, ISBN 3-510-65138-3 , pp. 78 .
Individual evidence
- ↑ Hans Murawski: Geological Dictionary . 8th edition. Enke, Stuttgart 1983, ISBN 3-432-84108-6 , pp. 131 .
- ↑ Füchtbauer 1988, p. 79f.