. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography GEOLOGIC MAP OF THE ORCHILA ISLAND QUATERNARY LEGEND ~] Ool-ALLUVIUM ~] Oar-ELEVATED REEFS { £°< FT*] Kcd-QUARTZ DIORITE UPPER ggx-i ^ CRETACEOUS? â ujj jj [ -YJgj Kd-DIABASE l-^§0 j nKec-MICASCHISTSaOUARTZITES \SZA\ Kb- PERIDOTITES a GABBROS. JJ K«9-GRANITE GNEISS [ K«o-AMPHIBOLE SCHISTS Figure 39. Geologic map of Orchilla Island (from Schubert, 1970). On the basis of the similarity of the Garanton Stock and the quartz-diorites of Aruba, Ru
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography GEOLOGIC MAP OF THE ORCHILA ISLAND QUATERNARY LEGEND ~] Ool-ALLUVIUM ~] Oar-ELEVATED REEFS { £°< FT*] Kcd-QUARTZ DIORITE UPPER ggx-i ^ CRETACEOUS? â ujj jj [ -YJgj Kd-DIABASE l-^§0 j nKec-MICASCHISTSaOUARTZITES \SZA\ Kb- PERIDOTITES a GABBROS. JJ K«9-GRANITE GNEISS [ K«o-AMPHIBOLE SCHISTS Figure 39. Geologic map of Orchilla Island (from Schubert, 1970). On the basis of the similarity of the Garanton Stock and the quartz-diorites of Aruba, Rutten (1931) suggested that they are probably of the same age. Isotopic age determinations (Rb-Sr and K-Ar) made on the biotites of the quartz-diorites of Aruba gave 73±3 for the formation of these rocks (Priem, e_t jal. , 1966) . Whole-rock K-Ar age determinations on similar rocks in Curacao gave 72±7 (Priem, 1967). The central and eastern part of Blanquilla Island is covered by coralline limestones of Pleistocene and Recent age (Maloney, 1968). Based on the elevations of terraces in the southwestern part of Blan- quilla Island and on their dip towards the northeast, Maloney (1968) suggested that the island was tilted to the northeast in the Pleistocene. Although faults or folds were not reported from Blanquilla Island, there are numerous east-west and northwest-southeast trending faults on Los Hermanos islands (Maloney, 1968; Schubert, 1969a). The writer dredged the talus material off the southwest tip of Blanquilla Island and recovered quartz-diorite, quartz-monzonite, meta- basalt, and marble. Another dredge haul from the western slope of the seamount southwest of Blanquilla Island (11°41'N, 64°5A'W) yielded graphic granite, amphibole-biotite granite, quartz-diorite, and grano- diorite. An age of 81 was determined by K-Ar measurements on the. Please note that these images are extracted from scanned page images that may have been digitall
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