Cenozoic Methane-Seep Faunas of the Caribbean Region.

Steffen Kiel,Bent T Hansen,David P Gillikin

doi:10.1371/journal.pone.0140788

Steffen Kiel, Bent T Hansen + Show 1 more

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https://doi.org/10.1371/journal.pone.0140788

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Abstract

We report new examples of Cenozoic cold-seep communities from Colombia, Cuba, the Dominican Republic, Trinidad, and Venezuela, and attempt to improve the stratigraphic dating of Cenozoic Caribbean seep communities using strontium isotope stratigraphy. Two seep faunas are distinguished in Barbados: the late Eocene mudstone-hosted ‘Joes River fauna’ consists mainly of large lucinid bivalves and tall abyssochrysoid gastropods, and the early Miocene carbonate-hosted ‘Bath Cliffs fauna’ containing the vesicomyid Pleurophopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep communities from the Sinú River basin in Colombia consist of lucinid bivalves including Elongatolucina, thyasirid and solemyid bivalves, and Pleurophopsis. A new early Miocene seep community from Cuba includes Pleurophopsis and the large lucinid Meganodontia. Strontium isotope stratigraphy suggests an Eocene age for the Cuban Elmira asphalt mine seep community, making it the oldest in the Caribbean region. A new basal Pliocene seep fauna from the Dominican Republic is characterized by the large lucinid Anodontia (Pegophysema). In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godineau River fauna consisting mainly of lucinid bivalves, and the limestone-hosted Freeman’s Bay fauna consisting chiefly of Pleurophopsis, Bathymodiolus, and small gastropods; they are all dated as late Miocene. Four new seep communities of Oligocene to Miocene age are reported from Venezuela. They consist mainly of large globular lucinid bivalves including Meganodontia, and moderately sized vesicomyid bivalves. After the late Miocene many large and typical ‘Cenozoic’ lucinid genera disappeared from the Caribbean seeps and are today known only from the central Indo-Pacific Ocean. We speculate that the increasingly oligotrophic conditions in the Caribbean Sea after the closure of the Isthmus of Panama in the Pliocene may have been unfavorable for such large lucinids because they are only facultative chemosymbiotic and need to derive a significant proportion of their nutrition from suspended organic matter.

Highlights

Methane seeps on the deep-sea floor harbor dense faunal communities whose dominant members rely on chemosynthetic bacteria for nutrition [1, 2]
The Cenozoic fossil record of methane seeps is strongly skewed toward the active continental margins of the Pacific Ocean [10,11,12,13]; fossil occurrences in the Atlantic realm are restricted to the Caribbean region [14, 15] and the Mediterranean basin [16, 17]
Unusual faunal assemblages have been reported for a long time from the Caribbean region, including examples from Trinidad that were dominated by the enigmatic bivalve Pleurophopsis Van Winkle, 1919 [20, 21], from Cuba, which was considered as a mix of marine and freshwater taxa [22], from Colombia, where the ‘Pleurophopsis fauna’ was reported from the Oligocene of the Sinú River basin [23], and a fauna from the Joes River area in Barbados, which “appears to be a specialized one, perhaps requiring an unusual environment for its existence” [24]

Summary

Introduction

Methane seeps on the deep-sea floor harbor dense faunal communities whose dominant members rely on chemosynthetic bacteria for nutrition [1, 2]. Unusual faunal assemblages have been reported for a long time from the Caribbean region, including examples from Trinidad that were dominated by the enigmatic bivalve Pleurophopsis Van Winkle, 1919 [20, 21], from Cuba, which was considered as a mix of marine and freshwater taxa [22], from Colombia, where the ‘Pleurophopsis fauna’ was reported from the Oligocene of the Sinú River basin [23], and a fauna from the Joes River area in Barbados, which “appears to be a specialized one, perhaps requiring an unusual environment for its existence” [24] These and other, similar faunas were subsequently identified as ancient methane seep faunas [14, 15, 25], but the still poor age determinations and taxonomic identifications of these faunas have so far prevented a rigorous analysis of the evolution of seep faunas from the Caribbean/ Gulf of Mexico region, as well as their role in the biogeographic evolution of the seep fauna in general. This does not seem to the case as most tested Recent seep carbonates carry the marine Sr isotope signature [29, 30], and our tests with a wide range of Phanerozoic seep carbonates indicated that diagenetic alteration, not initial contamination, is the main issue in this approach [27]

Material and Methods

Discussion