Part 4 - Berg - Hughes Center

Paleozoic (Pennsylvanian-Permian)
The oldest sediments drilled in the subsurface of north Louisiana are in the late
Pennsylvanian-Permian (310-250 mya) carbonate section over a Sabine Terrane (Lowrie
et al., 1993). An example is found in a crestal area located in Sabine Parish, Louisiana
(Zimmerman, 2000). In southern Arkansas and extending southward to the north side of
the North Louisiana Salt Basin, folded Pennsylvanian-Mississippian sandstone and shale
of the Ouachita are present. Imlay (1942) considered the Morehouse Formation as
representing this unit of rocks in the deeper parts of the basin.
Morehouse Formation
One of the older sedimentary rocks drilled to date in the subsurface of north
Louisiana is the gray shale with rare siltstone and limestone of the Morehouse Formation.
It is found from 9,285 to 10,475 ft in depth in the Union Producing well (No. A-1 Tensas
Delta), drilled in Morehouse Parish (Sec. 8, T. 22 N., R. 4 E) (Imlay, 1942; Bishop,
1967). Because this well was still in the Morehouse Formation at total depth and no other
wells have penetrated it, the exact thickness of the formation is unknown. This well also
indicated that the Morehouse is overlain directly by Werner red beds (Hazzard et al.,
1947; Scott et al., 1961). According to these authors the Morehouse was deposited prior
to the Eagle Mills, and later removed in south Arkansas by pre-Werner erosion. Other
geologists define the Morehouse either as a marine wedge overlying the Eagle Mills or as
a downdip marine facies of that formation.
According to Imlay (1942), a distinctive gastropod and assemblage of other
pelecypods found in cores from the No. A-1 Tensas Delta well suggest a late Paleozoic
age, probably not older than Pennsylvanian, for the Morehouse Formation. In a core from
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