Pg. 294, 320-321. Upper Mud sandstone --brown shaly micaceous sandstone, 0 to 5 feet thick, underlying Lower Belcher shale. Rests on Upper Mud shale, which consists of 20 to 50 feet of red shale overlying Lower Mud sandstone. The latter sandstone consists of 0 to 5 feet of greenish-gray or brown sandstone, resting on Lower Mud shale (red and variegated or dark-green and sandy shale 15 to 40 feet thick, which rests on Glady Fork sandstone). All are members of Bluestone group [Bluestone formation], and all are exposed on Mud Fork of Bluestone River in Tazewell Co., VA, about 1 mi north of Bailey Station, also in Mercer Co., WV.
[The Bluestone group is a term used by some geologists to include same rocks as Bluestone formation of USGS reports (US geologic names lexicon, USGS Bull. 896, p. 222).]

Source: US geologic names lexicon (USGS Bull. 896, p. 1448).

Pg. 184, pl. 15. Mud Fork member of Bluestone formation. Reger (1926) [West Virginia Geol. Survey Rpt. Mercer, Monroe, and Summers Counties, p. 294, 320-321] subdivided the 90- foot succession of red beds immediately above Glady Fork sandstone into 4 units which he named Lower Mud shale, Lower Mud sandstone, Upper Mud shale, and Upper Mud sandstone. The four units are herein grouped into single member named Mud Fork member of Bluestone formation. Recognized in southwestern Virginia and southeastern West Virginia. Thickness at type section 91 feet. Underlies Belcher member (new). Age is Late Mississippian (Chesterian).
Type section: along Road 656 about 1.5 mi north of Bailey, Burkes Garden quadrangle, Tazwell Co., VA. Named from Mud Fork, a tributary of Bluestone River.

Source: US geologic names lexicon (USGS Bull. 1200, p. 2651-2652).