Pg. J5 (fig. 3), J7-J8 (fig. 4), J11-J13, J37. Leaning Rock Formation of Perdido Group. Rocks previously assigned to Perdido Formation (McAllister, 1952). Consists of interbedded, commonly deformed, dark-gray, cherty micrite, chert, mudstone, and shale. Thickness 83 m. Underlies Mexican Spring Formation (new) of Perdido Group; contact placed at base of lowest siltstone or sandstone. Overlies Tin Mountain Limestone. Is basal formation of Perdido Group. Age is late Early Mississippian (Osagean; Lower TYPICUS to MEHLI-Lower TEXANUS conodont zone of Poole and Sandberg, 1991; Mamet foraminiferal zones 7-12).
Type section: near Rest Spring in Cottonwood Mountains, about 4 km east of mouth of Perdido Canyon, between 6,160 and 6,240 ft elevation, in northwest corner of sec. 31, T. 13 S., R. 42 E., Lat. 36 deg. 45 min. 30 sec. N., Long. 117 deg. 26 min. 27 sec. W., White Top Mountain 7.5-min quadrangle, Inyo Co., Death Valley National Monument, eastern CA. Named from Leaning Rock Peak about 3 km southeast of type section.

Source: Publication.