Cyclic carbonates of Phanerozoic carbonate platforms formed under global green-house to ice-house conditions
- Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences
Carbonate platforms that formed under global green-house conditions (Late Cambrian-Early Ordovician, Early Silurian to Middle Devonian, Triassic and Cretaceous) are characterized by layer-cake cycle stacking patterns, dominance of high frequency precessional cycles with an autocyclic component, widespread tidal flat caps on the shallow platform, and few major sequence bounding unconformities. Sea level fluctuations are small (10 m or so) and dominated by precessional (15 to 24 k.y. periods) and lesser 100 and 400 k.y. eccentricity forcing of climate. At the other extreme, cyclic carbonate platforms that formed under global ice-house conditions with major continental glaciation (Pennsylvanian-Early Permian, Miocene-Holocene), have erosionally capped cycles lacking tidal flat facies except near regional shorelines. Downdip cycles show interlayering of deeper water and shallow water facies. Cycles have a highly shingled distribution on ramps, and layer cake stacking on flat topped platforms. On rimmed platforms, reefal facies may be bundled with aggrading to prograding to downstepping geometries. Sea level fluctuations are large (up to 100 m) and dominated by 100 and possibly 400 k.y. eccentricity forcing of climate, but may also show 40 k.y. forcing. Precessional cycles are rare. Intermediate between these extremes may be high frequency, moderate amplitude cycles of the Late Middle to Late Ordovician and Mississippian which have both disconformable and conformable caps, and lack tidal flat facies except in HSTs or locally in down ramp positions. Sea level fluctuations likely are 20 to 40 m and may relate to obliquity and eccentricity forcing of climate (40 to 400 k.y.).
- OSTI ID:
- 6830044
- Report Number(s):
- CONF-9404221-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 26:4; Conference: 43. annual meeting of the Southeastern Section of the Geological Society of America, Blacksburg, VA (United States), 7-8 Apr 1994; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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