New Mexico Geological Society Annual Spring Meeting — Abstracts

The Morrison Formation in the Lamy area (T15N, R10E) consists of 183 m of variegated mudstones, sandstones, siltstones and conglomerate. Based on lithologic characteristics and stratigraphic position, the Recapture, Westwater Canyon, Brushy Basin and JackpileSandstone members can be recognized. The Recapture overlies gypsum or limestone of the Todilto Formation and consists of 81.3 m of pale reddish-brown mudstones and fine-grained sandstones. Overlying the Recapture are 48 m of medium-grained sandstones and minor mudstones of pale greenish-yellow color. This sandstone sequence, which also includes rare, conglomerates, is assigned to the westwater Canyon Member. The Brushy Basin consists of 37 m of variegated grayish-red purple and pale olive mudstones. overlying the Brushy Basin is 10 m of white coarse-grained kaolinitic sandstone assigned to the Jackpile Sandstone Member. Above the Jackpile is a 2 cm-thick ferrugenous zone, which weathers moderate brown in color, overlain by 7 m of medium-grained white sandstone. This upper sandstone sequence may be correlated with the Encinal Canyon Member of the Dakota Formation.

The stratigraphic section at Lamy represents the easternmost outcrops of the Morrison which can be correlated with the sequence on the Colorado Plateau. Forty miles east at Romeroville Gap (T15N, R16E) the members of the Morrison which are present at Lamy cannot be recognized. However, in most of east-central New Mexico, the Morrison section is homotaxial with that on the Colorado Plateau. The evidence from Lamyand Romeroville indicates that the homotaxial relationship is not the result of depositional continuity of facies across central New
Mexico.