New Mexico Geological Society Annual Spring Meeting — Abstracts

At least two siliclastic facies occur within the exposed lower two-thirds of the Permian red bed Abo Formation where it nonconformably overlies the Precambrian crystalline core of the Zuni Mountains. A ≤ 2 ft thick carbonate micrite-biomicrite/mudstone-wackestone with dominantly molluscan macrofauna occurs within the basal 70 ft of the Abo on both the northeast (NE) and southwest (SW) flanks of the Zuni Mountains. Below the carbonate unit the Abo Formation contains alluvial fan deposits of interbedded gray, tan and red mudrocks and pebbly, moderately to poorly sorted, very coarse-to coarse-grained, dominantly internally structureless sandstones which have erosional lower contacts and locally contain medium scale (5 cm to 1 m) tabular-planar and trough-tangential sets of cross-beds. Higher in the Abo, the abundance of mudrocks increases; thin (< 5 ft) fine-grained overbank sandstones, and thicker medium-grained, braided channel sandstones occur as lenses in the mudrocks.

On the SW flank of the Zuni Mountains the vector mean paleocurrent direction is S40W in the alluvial fan facies and S15W in the overlying
braided channel facies. On the NE flank of the Zuni Mountains the vector mean paleocurrent direction is N28W in the alluvial fan facies
and N13W in the braided channel facies. Both these facies and their paleocurrent directions document the Zuni-Defiance Uplift as the local source area of the Abo Formation in the Zuni Mountains.