Page 379 - Carbonate Facies in Geologic History

366 Summary

PLATY ALGAE· SACRAMENTO MlS LOW. ORO SPONGE. ALGAL •
NEW MEXICO El PASO, TEX
Tubular, Bioclastic flank beds
chambered farams

platy algae
Orgonic veneer
and flank bed
• J SILURIAN,
IOWA

Halimeda
Nerinea Chandradanta Penicillus
Ganialithan

Cladaphyllia
Foroms
CRETACEOUS CAPRINIDS. RODRIGUEZ KEY, HOLOCENE
GA TESVlllE, lEX flORIDA
Fig.XII-4. Five examples of shelf mounds, summarizing variations in evolving growth facies
as diagrammed in Fig. IV-9, IV-27, VI-25, and XI-4. Facies 1- 7 are characterized in Fig.XII-5.
For general legend see Fig. III-I

particular buildups. For practical field reasons it is usually impossible to observe
outcropping beds just under a mound. In oil fields, production is generally from
the tops of the buildups and few wells penetrate the mound base. Our best clue for
determining the probable origin is perhaps the relationships of trends to regional
paleogeography.

Mound Facies Sequence

Whatever their origins, many mounds developed on shelves and in shallow basins
consistently show a vertical and lateral sequence of textural and organic facies.
This is because the processes which create them are sufficiently rapid to cause
shelf mounds normally to grow into wave base from deeper and quieter water.
These processes may be summarized as follows:
1. Mechanical accumulation of both fine and coarse sediment through cur-
rent and wave action. Probably the most important process localizing mound
growth.