Miocene biostratigraphic framework and paleogeography of Barro Colorado Island, Isthmus of Panama

León, Santiago, Montes, Camilo, Mora-Rojas, Laura, Cárdenas, Andrés, Luque, Javier, Buchs, David M. ORCID: https://orcid.org/0000-0001-8866-8125, Trejos-Tamayo, Raúl, Vallejo-Hincapié, Felipe, Rodríguez-Abaunza, Alejandra, Marulanda, Sebastián and Jaramillo, Carlos 2026. Miocene biostratigraphic framework and paleogeography of Barro Colorado Island, Isthmus of Panama. Palaeogeography, Palaeoclimatology, Palaeoecology 701 , 114168. 10.1016/j.palaeo.2026.114168

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Abstract

Barro Colorado Island (BCI), in central Panama, is one of the sites with the longest-running biological and ecological studies of tropical rainforests. Its geology, however, has received less attention, even though it offers clues to the evolutionary history of its biota and landscape. Here, we reconstruct the Neogene paleoenvironmental history of BCI, based on new field, petrographic, geochronological, foraminiferal, molluscan, and calcareous nannofossil data. We link two main environmental shifts to the evolution of Canal Basin in the context of the emergence of the Isthmus of Panama. A first shift from terrestrial to marine conditions is recorded by the transition from coarse, volcanic-rich fluvial deposits of the lower Bohio Formation to fossil-bearing deltaic and shallow-marine sediments of the upper Bohio Formation. A newly dated volcaniclastic deposit interbedded with marine deposits firmly places the upper Bohio Formation in the Early Miocene (23.2 ± 0.6 Ma). Coeval terrestrial volcaniclastic deposits in the vicinity of BCI indicate a landscape of scattered volcanic highs surrounded by marine platforms in the Canal Basin. Continued basin deepening and flooding until ca. 19 Ma is recorded by transgressive deposits of the Culebra Formation and its marine equivalent, the Caimito Formation in BCI. A second environmental transition during the latest Early Miocene reflects a return to terrestrial settings, represented by deltaic-to-fluvial deposits of the upper Culebra and Cucaracha formations. At the same time, marine sedimentation persisted locally in BCI, indicating an asymmetric topographic growth in the Canal Basin. Since ∼16 Ma, BCI has likely remained a subaerial topographic high. These environmental shifts align with regional tectonic and magmatic reorganizations driven by interactions among the Caribbean, Nazca, and South American plates, which shaped the Miocene paleogeography of the Isthmus of Panama.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences Schools > Physical, Chemical & Environmental Sciences
Publisher:	Elsevier
ISSN:	0031-0182
Date of First Compliant Deposit:	1 September 2026
Date of Acceptance:	21 August 2026
Last Modified:	01 Sep 2026 10:01
URI:	https://orca.cardiff.ac.uk/id/eprint/189259

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