52 NEW MEXICO GEOLOGICAL SOCIETY TENTH FIELD CONFERENCE MISSISSIPPIAN STRATA ON THE EAST SIDE OF THE DATIL PLATEAU By

PREVIOUS WORK Herrick (1904, p. 311) named the Mississippian strata of the Magdalena Mountains the "Graphic-Kelly limestone" after the two leading mines of the area. Gordon (1907, p. 62-63) renamed these strata the "Kelly limestone" after the mining town of Kelly on the west side of the Magdalena Mountains. G. H. Girty (in Gordon, 1907, p. 58) identified fossils collected by Lee from the southern Ladron Mountains, which he considered to be of early Mis-sissippian age. Loughlin and Koschmann (1942) in their study of the Magdalena Mountains collected two small lots of Mississippian fossils, which G. H. Girty noted as being unlike, suggesting marked differences of age. Noble (1950, p. 38; also Kelley and Silver, 1952, p. 86-87) proposed the name "Caloso formation " for the entire Mis