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Plate II. Basinal and Offbank Facies

(A) Spiculitic wackestone basinal strata composed of very light and delicate mon-
axon spicules (25 microns across), now partly calcified in black, organic-rich,
siliceous micrite, standard microfacies 1; facies P-l1, Chapter VII. The sediment
accumulated below wave base in water more than 30 m deep, quiet, with sufficient
current to orient the spicules but not to winnow the micrite and calcisilt. The
facies occurs on the basinal side of the Wolfcampian Townsend-Kemnitz reef in
Lea County, New Mexico. See Figs. VI-19 to VI-22. Sample: Shell ETA-5,
10337ft; thin section, x 36

(B) Microbioc1astic peloidal calcisilt, standard microfacies 2. The sediment is
composed of ofT-bank debris partly indigenous and partly drifted off a bank of
very low relief. Currents which deposited the silt grains also winnowed the lime
mud. Note the mm laminae grading from tiny echinodermal bioclasts up to dark
peloids or fine-grained lithoclasts. Cure section, Middle Jurassic, southeast Paris
basin, Burgundy, France. Photograph courtesy of Bruce Purser and Koninklijke
Shell Exploration and Production Laboratory, The Netherlands. See Figs. X-7
and X-8 for location of the section and calcisilt facies. Thin section, x 36