The allochthonous nature of lower Mississippian Waulsortian mounds in the Sacramento Mountains, New Mexico
Katherine A. Giles

Abstract:

Waulsortian mounds comprise a distinctive assemblage of carbonate facies organized into a mounded geometry that is interpreted as forming as a result of in situ biohermal growth in a moderately deep water setting (>100 m). However, depositional features of well-exposed mounds in the Sacramento Mountains, New Mexico, indicate generation primarily by gravity-driven sedimentologic processes with biohermal growth either absent or playing a subsidiary role in mound development. The Sacramento mounds are interpreted here to have been generated by downslope movement and accumulation of allochthonous sediment resulting from a combination of gravity-driven sedimentary processes such as translation (glide and slump), creep, debris flow, grain flow, and turbidity current. Characteristics of the Sacramento mounds that are consistent with a gravitydriven allochthonous origin are: (1) dominance of debris flows and turbidites throughout mound core and flank facies, (2) abundant slump folds and elastic injection dikes within the mounds, (3) stratigraphic mix of non-compacted, early-cemented facies with severely overcompacted, late-cemented facies, (4) presence of extraclasts within debris flow units, and (5) the complete absence or localized distribution of framework or sediment-binding organisms within the mounds. Though the Sacramento mounds appear to have been generated primarily by allochthonous sediment accumulations, they also provided a substrate for local colonization by deep-water biotic communities of bryozoans, sponges, and microbes.


Citation:

  1. Giles, Katherine A., 1998, The allochthonous nature of lower Mississippian Waulsortian mounds in the Sacramento Mountains, New Mexico, in: Las Cruces Country II, Mack, G. H.; Austin, G. S.; Barker, J. M., New Mexico Geological Society, Guidebook, 49th Field Conference, pp. 155-160.

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