Part 4 - Berg - Hughes Center

the high iron content seems to support the existence of the pre-Norphlet unconformity.
From subsurface control, it appears as though the salt is laterally continuous and
underlies parts of Texas, Arkansas, Alabama, and Mississippi, and nearly all of Louisiana
(Andrews, 1960). A maximum thickness of 1,300 ft was recorded in the Placid No. 3
Freeman-Smith (Sec. 14, T. 16 S., R. 13 W.), Calhoun County, Arkansas, and more than
3,300 ft (still in salt at total depth of 14,890 ft) in the C.V.O.C. No. 2 Banks well (Sec.
34, T. 21 N., R. 10 W.), Webster Parish, Louisiana. The thickness is believed to be
associated with salt flowage, and may have been the result of basinward thickening of the
salt. An original deposition of about 5,000 ft of bedded salt has been postulated but
because of the topographically irregular floor of the basin, the thickness was not uniform
(Parker and McDowell, 1955; Andrews, 1960). Bishop (1967) reported that precipitation
of as much as 5,000 ft of Louann Salt was the result of concentrated marine waters
flowing periodically into the basin, more or less isolated from the open sea by barrier
bars. The CaCO3 and CaSO4 were precipitated, and the produced concentrated brines of
NaCl were deposited in the basin.
Upper Jurassic Louark (Norphlet, Smackover, Haynesville-Buckner)
Norphlet Formation
The Norphlet unconformably overlies the Louann Salt and older units near the
margins of the basin where the Louann was not deposited or has been removed by
erosion. Based on the relation of the Norphlet to the overlying Smackover, it has been
assigned to the Upper Jurassic (Hazzard et al., 1947; Bishop, 1967). The Norphlet of
Arkansas, Louisiana, and Texas attains a maximum thickness of about 150 ft and is
composed primarily of red and gray shale and sandstone. The northernmost area of
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