High Resolution Sequence Stratigraphy Fluvial Aggradational Cycles in the Late Cretaceous Dilco Member of the Crevasse Canyon Formation, Seboyeta, New Mexico

Paralic environments occur at or near sea level, demarcating the unique transition between marine and non-marine environments. The high degree of variability, complexity, and increasing importance placed in distinguishing modern paralic environments have led to greater subdivision within them. However, the plethora of classifications allocated to these modern sub-environments are juxtaposed to the lack of classifications allocated to ancient sub-environments. Detailed sequence stratigraphic analysis on what was initially interpreted to be continuously aggrading coastal plain facies with a lack of fluvial channel sandstones, reveal 17 unique facies and 6 facies associations within the upper Cretaceous Dilco Member of the Crevasse Canyon Formation, north of Seboyeta New Mexico. Furthermore, these facies associations cumulatively combine to represent 14 fluvial aggradational cycles (FACs), 6 FAC sets, and two paralic sequences. These paralic stratal units indicate a higher degree of cyclicity related to the Dilco member than previously thought and reveal the level of detail that can be used in classifying ancient paralic environments. Furthermore, facies analysis led to the observation that at least one multistory channel outcrops north of Seboyeta and subsequently demarcates a sequence boundary in one of the measured sections. The development time of pertinent FACs are estimated to range from 50 years to 5,550 years and reflect autogenic controls. FAC sets in this study are estimated to range from 500 years to 15,000 years and were interpreted to be associated with significant channel avulsion in addition to base level changes related to climate controls that subsequently alter the amount of glacial ice and/or water held in aquifers. Lastly, the estimated duration for the most representative paralic sequence is less than 32,000 years and is interpreted to be associated with glacial and aquifer-eustasy caused predominantly from Milankovitch cycle driven climate change.