Abstract

Limestones are continuous wavy thin beds to isolated centimeter-scale pods; commonly have flat bottoms and ripple-form tops; typically are internally current- or wave-ripple cross-laminated; and are composed of peloidal grainstones. Dolostones interbedded with these limestones are typically continuous on the outcrop scale; drape underlying limestone ripple-forms; are commonly mudcracked; and are composed of 10-40 mu dolomite rhomobohedrons in a carbonate-clay matrix. Some ribbon rocks are disrupted by filled tubes, soft sediment deformation features, and abrupt lateral changes in rock type. Three observations suggest that the limestone-dolostone alternations of ribbon rocks reflect original carbonate sand-mud alternations. This interpretation is strongly amplified by comparing Conococheague ribbon rocks to examples of lenticular and wavy bedding from mixed siliciclastic sand and mud flats from the modern North Sea. An overall interpretation of Conococheague cycles as the regressive deposits of carbonate tidal flats.--Modified journal abstract.

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