Volcanic contribution to emergence of Central Panama in the Early Miocene

Abstract

Formation of the Panama Isthmus, that had global oceanographic and biotic effects in the Neogene, is generally associated with tectonic uplift during collision of the Panama volcanic arc with South America. However, new field, geochemical and geochronological data from the Culebra Cut of the Panama Canal suggest that volcanism also contributed to the Isthmus emergence in the Early Miocene. This volcanism is recorded in a newly-recognised Central Panama volcanic field that includes several phases of development. Early activity of this field along the Panama Canal was associated with proximal effusive to explosive felsic products during formation of subaerial stratovolcanoes and possible domes ca. 21 Ma. This was followed by a period of marine transgression ca. 21–18 Ma, with more distal volcanism documented by tuffs that deposited in marine to terrestrial environments. Finally, proximal mafic volcanism formed tephra cones in a monogenetic field ca. 18(-?) Ma. This was associated with phreatomagmatic processes in a coastal environment, with remarkable kilometre-wide subvolcanic peperitic intrusions. We propose based on these observations that formation of the Central Panama volcanic field was critical in shaping regional topography, and that this could have actively contributed to obstruction and closure of an interoceanic strait in Central Panama.

Volcanic shutdown of the Panama Canal area following breakup of the Farallon plate

“…2. Ar-Ar ages presented in this manuscript and Buchs et al (2019) have consistent plateau and isochron ages that are also remarkably consistent with stratigraphic controls along the Gaillard Cut. Fig.…”

“…Field work and sampling were conducted during 6 field campaigns between 2015 and 2018 in (i) the Gaillard Cut and Pacific Locks area of the Panama Canal (286 localities), and (ii) nearby forested and urbanised areas in Central Panama (452 localities) (Buchs et al, 2019). Our survey was designed to provide new, systematic constraints on volcanic processes recorded in new exposures of the Gaillard Cut and Pacific locks area created during widening of the Canal since 2008, as well as their possible lateral equivalents along nearby rivers and roadcuts in Central Panama.…”

“…The location of new analyses of igneous rocks that are considered in this study is illustrated in Supplementary Fig. S1 (coordinates in Table S2 and Buchs et al, 2019). A revised lithostratigraphy and volcanic constraints on the newlyi trodu ed Ce tral Pa a a Vol a i Field are detailed i Buchs et al (2019).…”

“…Fig. 2 presents a synthesis of other Ar-Ar and U-Pb geochronological constraints from igneous rocks of the Canal area (Bloch et al, 2016;Buchs et al, 2019;MacFadden et al, 2014;Montes et al, 2012a;Rooney et al, 2011) and volcanic arcs of Panama (Baker et al, 2016;Lissinna, 2005;Montes et al, 2012b;Wegner et al, 2011;Whattamet al, 2012), which were included in our interpretations and model.…”

“…Final emergence of the Panama Isthmus is generally interpreted to be related to tectonic uplift due to collision of the Panama volcanic arc with South America (Coates et al, 2004;Farris et al, 2011;Montes et al, 2012a;Montes et al, 2015). However, magmatism and volcanic construction could also have played a significant role in the emergence of volcanic cordilleras (Buchs et al, 2019;Wörner et al, 2005), but the effects and extent of these processes remain poorly investigated in most of the Isthmus. Because of the peculiar topography of Central Panama and its role in the final emergence of the Isthmus, it is significant to characterise the origin and evolution of magmatism in the Canal area.…”