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
cycles.
next to an author's name indicates that all files or directories associated with their ETD are accessible from the Virginia Tech campus network only.
![[VT]](http://scholar.lib.vt.edu/images/ETD-db/restricted.gif)
