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Plate XXII. Late Paleozoic Platy Algal Mound Rock

(A) Platy (phylloid) algal segments occur in typical micrite matrix; facies P6 of
Chapter VII, also see Chapter VI. Cortex shows as dark, poorly preserved, short
columns along the outer edges of crystalline plates. This is a typical codiacean
structure. Tubular foraminifera encrust some plates as well as the tiny chambered
foraminifer Tuberatina and the multi-chambered bell-shaped Tetrataxis. A fusu-
linid is seen in the lower left corner. This "plate rock" is common in Pennsyl-
vanian to middle Permian strata in the southwestern United States. Sample 23-42
is from the Virgilian Holder Formation on the north side of Indian Wells Canyon
on the ridge above Alamogordo, Sacramento Mountains, New Mexico. Thin
section, x 10
(B) Brecciated platy algal lime mud wackestone common in mud mounds
with abundant bioclastic particles; facies P6 of Chapter VII. Crinoids, brachio-
pods, and bryozoans are also common in this sample (see Chapter VI). The brec-
ciation is an early slumping phenomenon. The hardened clasts and fossil frag-
ments are fractured but the fracturing dissipates within the matrix between the
grains. Sample DCWR-2 is from the lower mound at the mouth and on the north
side of Dry Canyon, Sacramento Mountains, New Mexico. See Frontispiece for
location. Thin section, x 4