Paper No. 18-3
Presentation Time: 1:30 PM-5:30 PM
GEOLOGIC STRIP MAP OF THE K-T BOUNDARY SECTION EXPOSED AT MOSCOW LANDING, TOMBIGBEE RIVER, SUMTER COUNTY, WESTERN ALABAMA
The Moscow Landing section exposed along the west bank of the Tombigbee River, eastern Sumter County, Alabama, is well known for its quality outcrops encompassing the Cretaceous-Paleocene transition, which include purported megawave deposits and deformational features associated with the K-T boundary impact event. Various authors have described this stratigraphic sequence and provided detailed cross-sections that include boundary-event deposits and structures. However, to our knowledge, a detailed map of the section has not been produced previously. As part of our ongoing ichno-sedimentologic investigations at this locality, we have mapped the narrow belt of Cretaceous and Paleocene strata exposed in the Moscow Landing section. The map was produced in the field by tracing features on enlarged Google Earth images acquired on February 15, 2015, when the river level was only slightly above that at the time of mapping. Owing to narrow width (50-100 ft) of exposures normal to the river shoreline relative to the length of the mapped shoreline (~1 mile), the map was prepared in nine partly overlapping segments or strips, each of which encompass ~650 of shoreline length. The map depicts the distribution of stratigraphic units and faults. Mapped units include, in ascending order, the upper part of the Maastrichtian Prairie Bluff Chalk, including a thin (~10-15 cm), partly phosphatic fossil lag bed therein; several distinct, discontinuous (0-2 m thick) “Clayton sand” bodies linked to megawave deposition or related sea-level changes; the Lower Paleocene Clayton Formation (~8 m thick), including a chalk marker bed in its upper part; and the Paleocene Porters Creek Formation (5+ m). Structural features include 19 faults, most of which strike WNW, dip to the NE or SW at 35-66 degrees, and mainly reflect normal offset. At least three of the faults offset the Prairie Bluff Chalk and the Clayton sand beds but are truncated at the base of the Clayton Formation. While strata generally dip very gently (1-4 degrees) to the south, dips are locally steeped and reversed, particularly adjacent to faults. The Moscow geologic strip map presented here should be of use by those visiting the Moscow Landing site, for student or societal field trips or for other purposes.