Cyclic Sedimentation in Middle and Upper Holder (Upper Pennsylvanian) Formation, New Mexico: ABSTRACT

Abstract

The Middle and Upper Holder Formation (Upper Pennsylvanian), Sacramento Mountains, New Mexico, comprises terrigenous and carbonate facies that accumulated on a narrow open-marine to restricted-marine shelf. Differential subsidence of the shelf combined with eustatic sea level changes caused cyclic deposition. Deposition began with a varying supply of terrigenous sediments from shifting delta lobes. Several carbonate facies, lateral equivalents of the terrigenous strata, are distinguished on the basis of their allochemical constituents. Bioclastic wackestones to grainstones with cortoids and oncoids characterize open-marine intervals. Laminoid-fenestral mudstones and wackestones with oncoids were common in restricted-marine intervals. Fusulinids and algal and peloidal grainstones are common marginal-marine facies. Restricted-marine sediments were deposited after clastic influxes and during marine transgressions. The division between the Middle and Upper Holder members can be placed beneath a channel conglomerate an unconformity that developed on a restricted platform. Deposition of predominantly restricted-marine sediments with erosional clastic influxes characterize the Upper Holder. The upward increase both in reworked and encrusted allochems might End_Page 541------------------------------ reflect regional changes in paleogeography that caused progressive exposure of the platform. Rates of sea level rise were high and punctuated by periods of decreased rates or near stillstand as indicated by restricted-marine and clastic deposition with unconformities. The duration of these stable periods of relative sea level increased through time. End_of_Article - Last_Page 542------------