ABSTRACT

Birdseyes, birdseye limestone, fenestrae, fenestral fabric, shrinkage pores, and loferites are considered similar if not synonymous when occurring in lime mudstone or syndepositional dolomite, especially in association with mudcracks and stromatolites. Compaction experiments indicate, however, that in the absence of early cementation, these rugs can be completely obliterated, whereas mudcracks and stromatolites remain relatively unchanged.

Lumping of burrows and root tubes under the general terms birdseyes or fenestrae, such as for example tubular fenestrae, burrow fenestrae, or root-tube fenestrae, is discouraged. They should be called burrows or root tubes because the birdseyes, fenestrae, and shrinkage pores are so intimately associated with tidal flats in the minds of most geologists. Submarine cementation of pelletal and oolitic botryoidal grainstone under 5 to 6 m of water on the Bahama Banks has resulted in rugs provocatively similar to many birdseyes and fenestrae generally attributed to peritidal conditions in the literature. Birdseyes and fenestrae in ancient grainstones cannot therefore be reliably identified without consideration of the sedimentary sequence and assoc ated sedimentary structures.