In the Mammoth Cave area, groundwater moving via conduit flow emerges along many springs adjacent to the Green River, such as Turnhole Spring, Echo River Spring, and River Styx Spring.


The River Styx Spring is located due west of & downhill from Mammoth Cave's historic entrance.  The rocks at River Styx Spring are part of the upper St. Louis Limestone (Meramecian Stage, Middle Mississippian) and include the interval normally containing the Lost River Chert Bed.  The chert bed is mostly absent here due to a lateral facies change.  River Styx Spring itself is an overflow exit conduit for the Echo River Spring.


All of the springs near local base level can experience water flowing away from the Green River.  This happens when the level of the Green River rises during flood events.  Water levels can rise significantly in level F during Green River flood events.  Occasionally, even portions of level E can be backflooded (for example, River Hall).


River Styx Spring



River Styx Spring



River Styx (looking ~W)




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