R. Shagam, 1972. "Andean Research Project, Venezuela: Principal Data and Tectonic Implications", Studies in Earth and Space Sciences, R. Shagam, R. B. Hargraves, W. J. Morgan, F. B. Van Houten, C. A. Burk, H. D. Holland, L. C. Hollister
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The principal conclusion drawn from an extensive mapping project in the Venezuelan Andes is that these ranges have had a long and complex orogenic history extending at least as far back as the early Paleozoic and probably the late Precambrian. The tectonic evolution of these ranges involved at least three and probably not less than four major orogenic pulses—late Precambrian?, Devono- Mississippian, latest Permian, and post-Paleozoic (principally at the end of the Eocene). Striking results of repeated orogeny include regional parallelism of structural trends, an apparent northwestward migration of the focus of granitic plutonism with time, and an event of high-grade regional metamorphism, only recently recognized, in late Permian time. It is pointed out that current concepts of sea-floor spreading will need elaboration or extension in order to make provision for superimposed orogenies.