Recognition of ancient tidal deposits and facies successions changes according to stratigraphic context. Examples from upper cretaceous gallup clastic wedge, New Mexico

Abstract

A high-resolution genetic stratigraphic study was conducted on the four corners area, New Mexico, USA. Sedimentologic and stratigraphic observations made on the Gallup Clastic Wedge help us to learn about 1. how tidal influenced or dominated deposits are incorporated into the stratigraphic record, 2. how they are expressed in outcrops 3. the way they change according to stratigraphic position. 

Seven facies were used to characterize facies successions influenced by tidal processes. They reflect an intermediate-scale paleogeomorphic change from wave dominated to tidal influenced environments. In the Gallup, shoreface differ from tidal influenced deposits in that tidal deposits occur within a context of intermediate scale increasing Accomodation/Sediment Supply (A/S) conditions. Additionally, Three facies were used to characterize facies succession dominated by tidal processes. They reflect a large scale paleogeomorphic change from wave dominated to tidal dominated environments. In the Gallup Clastic Wedge, tidal dominated deposits differ from tidal influenced deposits in that the tidal dominated occur within a context of large scale increasing A/S conditions.

Vertical facies successions are a product of translation of geomorphic elements downslope and migration of laterally linked subenvironments. Preservational trends from tidal deposits associated with base level fall differ from those deposited in base level rise conditions. Tidal influenced deposits, related with large scale base level fall trends are more amalgamated, less wide, and more homogeneous that tidal dominated deposits, associated to large scale base level rise conditions. Examples of how identify tidal influenced environments are shown. 

Quantification of geometric and dimensional attributes of tidal influenced deposits provides additional information to be carefully considered in reservoir characterization, and simulation.