Abstract

The Markley Canyon is a large, ancient erosional feature in the Sacramento Valley which has truncated Eocene through Cretaceous sediments. Erosion of the canyon was post-middle Eocene CP14a (and probably CP14b) Subzone based on calcareous nannofossils, post-A-1 Zone based on benthic foraminifera, and occurred primarily during the late-Eocene (CP15 Zone) early to early late Refugian benthic foraminiferal Stage. Filling of the canyon began in the earliest Oligocene CP16a Subzone, latest Refugian Stage, and continued into the early Oligocene upper CP16 Zone, early Zemorrian Stage.

Samples studied from the lower part of the Markley Canyon Fill and from other widespread areas in California demonstrate that the late Refugian, Uvigerina vicksburgensis benthic foraminiferal Zone is in part correlative to the early Oligocene Coccolithus subdistichus (CP16a) calcareous nannofossil Subzone, with no evidence of diachroneity.