Title page for ETD etd-11012008-063546
|Type of Document
||Khetani, Amy B.
||Sequence stratigraphy and the development of a clinoformal carbonate ramp on an abandoned delta system :Mississippian Fort Payne--Salem Interval, Kentucky
||Master of Science
|Read, James Fredrick
|Bambach, Richard K.
|Eriksson, Kenneth A.
- clinoformed carbonate ramp
- sequence stratigraphy
- abandonded delta
- Appalachian Basin
|Date of Defense
Middle Mississippian ramp carbonates in Kentucky (Fort Payne to Salem interval)
form a large scale depositional supersequence (0 to 500 feet thick, approximately 8 m. y.
duration). It formed on and in front of the abandoned Early Mississippian Borden deltaic
marine paleoshelf, which had up to 100 m of relief above the adjacent starved basin. Major
facies consist of marine quartz sandstone and shale; peritidal carbonates; high-energy ramp
margin, crinoidal-bryozoan grainstones; deeper ramp mounds, skeletal grainstone/packstone sheets and channel-fills interlayered with shale or calcisiltite; and slope deposits
of siliceous calcisiltite. Regional slopes on the paleoshelf edge and ramp margin are 0.5 to
2.5 mIkm (less than 0.25 degrees), although clinoforms of 2 to 10 degrees occur locally
associated with mounds and depositional lobes. The supersequence LST is dominated by
mounds interlayered with green shaly, deeper ramp facies. The mounded units are located
in a fairway that is normal to the Borden margin but parallel to the Appalachian Grainger
deltaic shelf. No TST is evident, except for a glauconite horizon capping the Borden
paleoshelf. The supersequence HST consists of at least eight third-order sequences (each
approximately 1 m.y. duration), the older ones downlapping onto the shelf 20 to 30 m
deep, the younger ones downlapping into the deeper basin (over 150 m water depth).
Sequences show marked toplap with the upper sequence boundary. The third-order
sequences locally have lowstand sands, some of which may be associated with a paleodrainage system off the Borden paleo shelf. They lack recognizable TSTs, but have
well-developed prograding HST units of nearshore shale and peritidal dolomite, skeletal
packstone/grainstone banks, and siliceous calcisiltite slope facies. The supersequence
correlates with a global sea level cycle in the lower Visean terminating in a major sea-level
fall. The highly clinofonned toplapping supersequence reflects this long term, sea-level fall
which prevented space from being created on the old delta top. The third-order sequences,
although mappable between the sections, are not easily correlated with global third order
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