Sequence stratigraphy of an apparently non-cyclic carbonate succession: Recognizing subaerial exposure in largely subtidal sequences, M. Ordovician, East Tennessee
- ABB Environmental Services, Inc., Knoxville, TN (United States)
- Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geological Sciences
A 400 meter thick succession of Middle Ordovician non-cyclic carbonates occurs at four on-shelf localities exposed along a 6 km transect on the northwest limb of the Copper Creek allochthon of East Tennessee. By using paleobathymetric analysis the authors were able to unravel the sequencing of stratigraphic units in this succession. Inflection points in water-depth curves indicate stratigraphic intervals that, on further detailed analysis, also contain subtle indicators of subaerial exposure. Seven surfaces of subaerial exposure or drowning define six third order sequences in the entire Middle and Upper Ordovician. They have analyzed in detail the lower four and the lower part of the fifth third order sequences and their contained 22 fourth order sequences that appear to be correlative across the shelf. These third and fourth order sequences, contain many fifth order or meter-scale packages, here termed sub-sequences. Sub-sequences are not correlative from place to place and many of these are probably the result of fine scale, lateral environmental migration. Stratigraphic sequences and sub-sequences represent shallowing-upward packages similar to cycles. However, these sequences and sub-sequences differ from the usual cycles in that they mostly lack peritidal caps, and evidence for exposure and shoaling is subtle and generally revealed only through detailed microscopic examination. A Fischer plot, substituting sub-sequences for cycles, supports interpretations previously made for this succession based on other lines of evidence and helps clarify new observations revealed through water-depth analysis.
- OSTI ID:
- 5807577
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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