HOW UNIQUE IS THE MANZANITA LIMESTONE MEMBER, CHERRY CANYON FORMATION (PERMIAN, GUADALUPIAN, WORDIAN), NORTHERN DELAWARE BASIN, NEW MEXICO AND WEST TEXAS?

Outcrop studies in the Guadalupe and Delaware Mountains over more than 60 years suggest the Manzanita Member is different than other basinal, deep water Wordian and Capitanian limestone tongues which grade shelfward into the Getaway Bank, Goat Seep Reef or Capitan Reef. Stratigraphic position indicates that the Manzanita is younger than the Goat Seep and older than the Capitan. It has been correlated with part of the shelfal Shattuck Member of the Queen Formation. In the Delaware Mountains the Manzanita forms a cuesta that extends across the basin but appears to pinch out shelfward along the west face of the Guadalupe Mountains. Its carbonate beds are mud-rich and commonly include bentonite beds considered to be altered volcanic ash. Some workers interpret it as a lowstand deposit but its environment of deposition remains controversial.

In the subsurface the Manzanita is present over the entire northern Delaware Basin where it has been penetrated by thousands of wells. On wireline logs it is identified as the carbonate-rich unit (containing at least three gamma log kicks interpreted as bentonites) lying below the widespread Hegler (“Two Finger”) Limestone Member of the Bell Canyon Formation. Although reservoirs have been studied locally where oil is produced from sandstones associated with the Manzanita, there is no published regional study, until now. Our regional study identifies several unique characteristics of the Manzanita. Based on sequence stratigraphy and basin margin relationships, we place the subsurface-defined Manzanita in one high frequency sequence that includes at least five siliciclastic to carbonate cycles. The basal Mz-1 cycle contains one and the Mz-3 cycle contains two thin bentonites that are very useful in well-to-well correlation. The cycles are best developed east of the Huapache Fault zone and are thinner and amalgamated to the west in the more positive Guadalupe Mountain block. Although the carbonate beds change thickness gradually, the lowstand siliciclastic beds may vary significantly over short distances. Unlike exposures along the west face of the Guadalupe Mountains, the Manzanita locally thickens to over 100 meters in the subsurface along the northern and eastern margin of the Delaware Basin where it cannot be distinguished in wireline logs from the Capitan Formation.