engleski

Conceptual response of cave systems to relative changes of sea-level

Relative sea-level changes must have profound effects on karst processes. As the sea-level rises or falls, so does the base-level, and that is what leaves its mark in cave systems. In caves, we can often see sediments with complex history of deposition and erosion. Usually, these are attributed to changes in hydrological regime within a cave, or to climate changes. But, how the fluctuating sea-levels may have influenced subterranean terrestrial environments? As the relative sea-level falls or rises, it also drives falls or rises of the base -level, but also causes seaward or landward translation of the graded profile of fluvial systems. The relative rise of sea-level causes landward translation of the graded profile, which causes creation of new accommodation space in the lower part of fluvial systems, but also "negative" accommodation space (erosion) in their upper parts. This is recorded by headward erosion which creates debris for deposition in available accommodation space, also underground, and accretion of fluvial systems. Caves will be filled with sediments, some completely. The opposite process, relative sea-level fall will cause seaward translation of the graded profile, which will cause creation of "negative" accommodation space and erosion in the lower part of alluvial systems, but also creation of new accommodation space in the upper part of the profile. This would be a trap for debris and will be recorded as aggradation of alluvial fans, but downstream the alluvial systems will be sediment-free and subjected to erosion, also underground. In caves this would cause erosion of older sediments, and deeper incision of hydrologically active cave channels. As the relative sea-level oscillates in rhythm of Milanković's cycles, the cave sediments will gain complex history of repeated depositional and erosional episodes, which can be correlated with terrestrial and marine records of global sea-level change.

Sea-level change; eustasy; graded profile; accommodation space; base-level change

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