| A Middle Pennsylvanian outcrop in Pikeville (eastern Kentucky) was investigated to interpret factors controlling hierarchy of fluvial architectural elements within an incised valley. A photo-mapping of the channel elements helped to identify major facies, and to interpret different autocyclic and allocylic factors. Backstripping revealed true dimensions of the units and magnitude of local subsidence. When the incised valley formed, the sea-level was low, which resulted in a sediment bypass. Subsequently, an increasing sea-level was estimated from measurements of accommodation space. With rising sea-level and increasing accommodation space, the valley fill transitioned from a non-amalgamated to an amalgamated fluvial stacking pattern. Forward stratigraphic simulations revealed local tectonics, base level, compaction, discharge, and sediment concentration as key formative processes, and helped to quantify them. The discharge and velocity of the Middle Pennsylvanian rivers were interpreted to be moderate. The sediment concentration was high in the channel waters, and together with discharge, was found to have main control on architecture of the units. This had implications for storage of carbon and paleoclimate studies. Middle Pennsylvanian rivers flowed through tropical rain forests with a high concentration of sediments, and a significant portion of that flux could have been particulate organic carbon derived from the densely vegetated forests. Removal of surficial carbon might have contributed to climate cooling, and eventual Pennsylvanian glaciation. Also, formations containing that organic carbon could be significant hydrocarbon source rocks. |
