Missing history (16–71 Ma) of the Galápagos hotspot: Implications for the tectonic and biological evolution of the Americas

Abstract

We present the results of volcanological, geochemical, and geochronological studies of volcanic rocks from Malpelo Island on the Nazca plate (15.8-17.3 Ma) belonging to the Galápagos hotspot tracks, and igneous complexes (20.8-71.3 Ma) along the Pacific margin of Costa Rica and Panama. The igneous complexes consist of accreted portions of ocean island and seamount volcanoes and aseismic ridges, representing the missing (primarily subducted) history of the Galápagos hotspot. The age and geochemical data directly link the Galápagos hotspot tracks on the Pacific Ocean floor to the Caribbean large igneous province (ca. 72-95 Ma), confirming a Pacific origin for the Caribbean oceanic plateau from the Galápagos hotspot. We propose that emplacement of this oceanic plateau between the Americas and interaction of the Galápagos hotspot tracks with the Central American Arc played a fundamental role in the formation of land bridges between the Americas in Late Cretaceous-Paleocene and Pliocene-Holocene time. The land bridges allowed the exchange of terrestrial faunas (e.g., dinosaurs, mastodons, saber-tooth cats, and ground sloths) between the Americas and served as barriers for the exchange of marine organisms between the central Pacific Ocean and the Caribbean Sea and the central Atlantic Ocean.

From seamount accretion to tectonic erosion: Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica

“…[58] Accretion of the Osa Igneous Complex and Osa Mélange from the Farallon to the Caribbean plate is implied by the geochemical and isotopic composition of the their igneous component [Hauff et al, 1997;Hoernle et al, 2002].…”

“…The Osa and Quepos igneous complexes are interpreted to be part of the subsequent Galapagos hot spot track after the oceanic plateau migrated to the east [Hauff et al, 1997[Hauff et al, , 2000. Younger, 20-38 Ma, accreted Galapagos terranes have been found in the western Panama Azuero Peninsula, where Hoernle et al [2002] hypothesized the hot spot track to have been subducted between $25 and 8-5 Ma. The volcanic stratigraphy in Quepos unit provides evidence for the emergence of a submarine volcanic edifice above sea level and the formation of an ocean island volcano [Hauff et al, 2000] prior to accretion in the inner fore arc.…”

“…Basalts intrude the limestones, but they do not cause contact metamorphism, indicating that the carbonates were still unlithified and water-rich at the time of intrusion (Figure 3c). Shallow water carbonates are common in the Bahia Drake (Playa Colorado) area close to the Osa Igneous Unit [Di Marco et al, 1995;Hoernle et al, 2002]. These limestones have been interpreted as clastic aprons associated with island volcanoes suggesting drowning of former ocean island volcanoes before they were accreted [Hoernle et al, 2002].…”

“…Wildberg [1984] proposed an island arc affinity for the ophiolites present in the inner part of the Osa Peninsula and around Golfito. Petrographic work since then, however, has documented that the oceanic igneous rocks of Golfito and Osa do not belong to the same oceanic environment [Hauff et al, 1997[Hauff et al, , 2000Hoernle et al, 2002].…”

“…[11] The Osa Igneous Unit represents rock bodies formed between 65-60 Ma (Paleocene) and 45-40 Ma (Eocene) Hoernle et al, 2002] and subsequently accreted before $25 Ma to the Pacific margin of Costa Rica after the eastward dipping subduction along the western margin of the CLIP initiated at $90 Ma [Hoernle et al, 2002] (Figure 2). Volcanology, petrology, and sedimentology of igneous rocks and associated sediments suggest that the Osa Igneous Unit once formed part of an aseismic ridge similar to the Cocos Ridge presently being subducted beneath the Osa Peninsula.…”