BIOSTRATIGRAPHIC EVALUATION OF A SEQUENCE STRATIGRAPHIC BOUNDING SURFACE: THE CARDINAL/LEYLAND UNCONFORMITY ('E5/T5 SURFACE') IN THE CARDIUM FORMATION (UPPER CRETACEOUS; UPPER TURONIAN-LOWER CONIACIAN) AT SEEBE, ALBERTA

摘要

The recent paper by Hall et al. (1994) have made an important advance in understanding the biostratigraphy of the Cardium in the Seebe area. However, their correlation with the subsurface depends on "one large whorl fragment" of an ammonite where "the fragmentary nature of the specimen, poor preservation, and lack of complete information about its morphology preclude definite identification with that species [Prionocyclus quadra-tus]" (Hall, pers. comm., 1994). Their correlation raises more problems than it solves in terms of introducing more erosion surfaces and necessitating a very unlikely scenario, mudstone deposition closer to the shoreline and sandstone and conglomerate deposition 150 km or more offshore. Their biostratigraphy at Seebe gives reasonable time for the regression and transgression that formed the E5/T5 surface in our interpretation. Their biostratigraphy has no bearing on the mappability of the topography of the E5 surface in the subsurface.