NEW REGIONAL CORRELATION OF TROPICAL NEOGENE SEQUENCES OF COASTAL ECUADOR AND CENTRAL AMERICA

The Neogene history of paleobiological, paleoceanographic and tectonic changes in tropical America rests in large part on the chronology and paleoenvironments of its formations. This study correlates the ages and paleoenvironments of newly sampled fossiliferous deposits of coastal Ecuador (forearc Borbón and Manabí basins) and the Caribbean and Pacific sides of Central America, including the Chucunaque and Sambu basins of Pacific eastern Panama, Charco Azul Group of Pacific Panama–Costa Rica, Limon Basin of Caribbean Costa Rica, and Bocas del Toro and Panama Canal basins of Caribbean Panama. Below we highlight the new results from Ecuador.

The stratigraphic succession examined spans lower Oligocene–Pleistocene, middle bathyal to shallow neritic sediments, and includes several significant unconformities. BORBON BASIN: Sections of the middle to upper bathyal Pambil Fm. are lower Oligocene to lower Miocene. The unconformably overlying outer–middle neritic Angostura Fm. is of late Miocene age (~11–8.3 Ma, ages of Berggren et al. 1995); the hiatus is >10 m.y. in one section and 16 m.y. in another. At Punta Verde, the middle Miocene, bathyal Viche Fm. unconformably underlies the Angostura Fm.; the hiatus is >1.4 m.y. The outer neritic–upper bathyal lower Onzole Fm. overlies the Angostura Fm. and ranges from 10.7–5.6 Ma in age. Further south, the mid-Pliocene, middle bathyal upper Onzole Fm. ranges ~4–2.8 Ma in age. MANABI BASIN: Samples examined from the bathyal Tosagua Fm. are middle and upper Miocene (the latter equivalent to the Portoviejo Fm.). In the south it is directly overlain by the Pleistocene Canoa Fm., separated by an unconformity of >14 m.y. The Pleistocene, inner neritic Tablazo Fm. overlies and possibly intergrades with the Canoa Fm. The upper Miocene Guayacan Fm. (10.9–6 Ma) is directly overlain by the upper Miocene (8.3–6 Ma) Bahia Fm. The neritic Jama Fm. is also upper Miocene (8.6–5.3 Ma). These results extend and refine those of previous studies.