The Burrowing Activities of Certain Crabs and Their Geologic Significance

Abstract

On the sandy and muddy beaches bordering the northwestern part of Taiwan (Formosa) there are great numbers of active crabs. Certain of these have the habit of burrowing deeply, the most common burrowers being Ocypoda ceratophthalma Fabricius and Ilyoplax formosensis Rathbun. Interested by their activities, I made plaster-of-Paris (gypsum) casts of some burrows at Tansui, a bathing place near Taihoku, the metropolis of Taiwan. Fortunately, the effort was successful, and I obtained a number of models of the burrows though many were incomplete. Most of these closely resemble the pipes commonly found in certain Tertiary sandstones of Taiwan (Plate 1, Fig. 2; Plate 2, Fig. 5). Most of these are not properly pipes; they are irregularly crooked rods measuring up to a few scores of centimeters in length and one to a few centimeters in diameter. Some stand almost perpendicular to the planes of stratification, but others are variably inclined. Some of them branch. My conclusion was that such sandstone rods would be produced if crab burrows were filled with sediment and the beach sand itself were converted into a hard sandstone. This was suggested by observations at the beach south of the city of Shintiku, southwest of Taihoku, where part of the youngest Tertiary sandstone of the island is exposed along the beach. This sandstone