Deep-water carbonate strata of Cambro-Ordovician age in western Newfoundland are composed of interstratified conglomerates and thinly bedded calcarenites, lime mudstones, and shales. Early lithification has preserved an abundant but simple algal flora in shallow-water clasts within both conglomerates and deep-water slope sediments. Large boulders contain sheets of Girvanella and arborescent clusters of Epiphyton, but only Girvanella as intraclasts, rafts of intertwined tubules, single tubules, and oncolites can be distinguished in calcarenites.

Preservation of Girvanella in boulders varies from distinct tubules to "structure grumeleuse" (clotted fabric) in which patches of micrite mask any evidence of former algal structure. Comparison of Girvanella in boulders and calcarenite grains indicates that much carbonate sand consists of broken and abraded Girvanella sheets. In contrast, Epiphyton thalli appear to be comminuted to form silt- and sand-size micrite peloids.

An extension of these findings is that many peloids, peloidal intraclasts, and much structure grumeleuse in early Paleozoic carbonates, both shallow and deep water, are derived from calcareous algae. These

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algae may have been just as important for producing carbonate sediment during the early Paleozoic as codiacean algae are in the modern ocean. This algal contribution is difficult to recognize in most ancient sediments probably because absence of early interparticle cementation, allows compaction, filling of tubules with micrite cement, or micritization.

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