The Mississippian System of north-central New Mexico
— Augustus K. Armstrong and B. L. Mamet

The generalized map of the total thickness of Mississippian rocks (fig. 1) shows disconnected areas of Mississippian rock that are remnants of extensive sheets; these sheets were dissected and beveled in northern and central New Mexico in Namurian (Chesterian) time and over the entire state by erosion on structurally active features in Pennsylvanian and Permian time.

 

Flooding of the state by Mississippian seas began in early Tournaisian time (pre-Zone 7) in the southwestern and south- central part of the state, forming the Escabrosa carbonate platform. By the end of Tournaisian (Osagean) time, epicontinental seas had flooded the northern and central parts of the state. Two low islands may have existed, the Zuni highlands and remnants of the transcontinental arch, the Pedernal highlands (fig. 1). The Espiritu Santo Formation (figs. 2-4) is composed of carbonate tidal deposits in the Sangre de Cristo, Sandia, Nacimiento and San Pedro mountains of north-central New Mexico (Armstrong, 1967; Armstrong and Mamet, 1977a, 1978; Vaughan and others, 1977). The Leadville Limestone is the time-stratigraphic equivalent in the San Luis basin and is an eastern extension of the Redwall Limestone of Arizona. The end of Tournaisian (Osagean) time is marked by a marine regression, a regional uplift, and extensive erosion of the Tournaisian (Osagean) carbonate deposits (figs. 2-4).

 

The geographic and stratigraphic extent of this hiatus at the end of the Tournaisian (Osagean) is shown in Figures 2-4. A major regional marine transgression occurred in middle Visean (Meramecian) time and is represented by the massive encrinites of the Hachita Formation in the southwestern part of the state, the deeper water carbonate rocks of the Rancheria Formation of Laudon and Bowsher (1949) in the southern San Andres and Sacramento mountains, and in north-central New Mexico by the Turquillo and Manuelitas members (Meramecian) of the Tererro Formation. Late Visean carbonate rocks of Zone 16i (Chesterian) also are distributed widely in disjunct outcrops. These are the Cowles Member of the Tererro Formation, the upper part of the Rancheria Formation, and the lower part of the Paradise Formation.

Marine sedimentation ceased in northern and central New Mexico at the end of Zone 16i time. In southwestern New Mexico, marine sedimentation continued into Zone 19. There, the Paradise Formation (fig. 2) is a series of shallow-water, shoaling to nearshore, oolitic carbonate rocks and plant-fossil- bearing, crossbedded sandstone and siltstone. The Helms Formation to the east is a deeper-water facies of the Paradise Formation (Armstrong and Mamet, 1978).

 

The Log Springs Formation (Armstrong, 1955) of the San Pedro, Nacimiento, Jemez and Sandia mountains unconformably overlies the Arroyo Penasco Group, and in turn, is truncated by limestone of Pennsylvanian (Zone 20) age (fig. 3). The Log Springs Formation is composed of terrigenous, red-brown, iron-rich shale, siltstone and lithic to arkosic conglomerate formed of angular cobbles of Precambrian and Mississippian rocks. It is interpreted as being post-Zone 16i and pre-Zone 20, or Namurian (Chesterian) in age, and represents in part a regolith and tectonically derived sediments washed into small basins adjacent to uplifted, faulted and tectonically active highlands (figs. 2-4).