LATE CRETACEOUS SILICEOUS SPONGES FROM EL RAYO FORMATION, PUERTO RICO

Abstract

This paper presents sponges from the Late Cretaceous El Rayo Formation, Puerto Rico. Siliceous sponges are common fossils in the Late Cretaceous of Europe (see for example Schrammen, 1910–1912; Moret, 1926; Weidenmayer, 1994; Pisera, 1999). So far only rare siliceous sponges from the Late Cretaceous of the Caribbean region have been reported: lithistid ? Jerea Lamouroux, 1821, hexactinellids Ventriculites Mantell, 1822, and Plocoscyphia Reuss, 1846 from Trinidad (Thomas, 1935; Trechmann, 1935), and Callopegma Zittel, 1878 from the Cariblanco Formation, Puerto Rico (Howell, 1966). The sponges studied by us are heavily silicified and thus only their approximate determination was possible, but among bodily preserved sponges they are undoubtedly lithistids with tetraclone and rhizoclone desmas. Among loose spicule material, fragments of hexactinellid skeleton dominate, tetraclone and dicranoclone lithistids desmas are common, and hexactinellid lychniscosid skeletons are very rare. The island of Puerto Rico is the easternmost island of the Caribbean Greater Antilles (Fig. 1.1), a complex island arc with accreted terranes. The island is composed of Lower Jurassic to Lower Cretaceous ophiolites, Lower Cretaceous to Eocene island arc volcanic and sedimentary rocks, Middle Oligocene to Pliocene terrigenous clastics, and limestone unconformably overlying the older rocks along the north and south coasts (Santos, 1999). The pre-Oligocene rocks are divided into the southwest, central, and northeast igneous provinces (Fig. 1.2). Figure 1 — 1 , Location of the island of Puerto Rico. 2 , Location of the study area on the Sabana Grande Quadrangle. CMF–Cerro Mula Fault Zone; GSPRFZ–Great Southern Puerto Rico Fault Zone. The paleogeographic setting of the earliest island arc volcanism differed in each of the three igneous provinces (Santos, 1999). The southwest igneous province is separated from the rest of the island by the Great Southern Puerto Rico Fault Zone (Fig. 1.2). It contains …