Small-scale cyclic deposition in the Frasnian (Upper Devonian) of the Holy Cross Mountains, Poland
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Date
2014-12
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Publisher
Instytut Geologii UAM
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Abstract
In sections exposing Frasnian limestones at five outcrops in the Holy Cross Mountains, five lithofacies (L1 to L5) that
represent upper slope to basinal environments are identified. These lithofacies are characterised by dark-coloured micritic
limestones–marly shale couplets with many light-coloured intercalations of fine- to coarse-grained limestones (=
event beds). This lithofacies pattern characterises mostly low-energy domains punctuated by storm episodes. In addition,
these upper-slope to basinal lithofacies are arranged into small-scale, coarsening-upward beds and cycles. The
cycles are locally composed of fining/thinning-upward beds. The small-scale cycles have a calculated duration of 19 to
42 kyr. The differential thickness of beds and cycles within and between sections was probably caused by differential
subsidence and local tectonics. Possible evidence of tectonic activity is also related to a difference in number of cycles
recorded in the time-equivalent sections. The recognised cyclicity shows sea-level fluctuations and a few deepening
episodes. Some of them are correlated with the Timan global eustatic events. However, local tectonics and episodic subsidence
may have played a significant role in recording brief deepening pulses. Thus, low-amplitude sea-level changes
were major factors in platform generation and evolution in the Frasnian of the Holy Cross Mountains modified by local,
block-related subsidence.
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Keywords
sedimentology, carbonate platform, limestones, shallowing-upward cycles, event beds
Citation
Geologos, 2014, 20, 4, s. 239-258.
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ISBN
978-83-232187-4-6
ISSN
1426-8981