RESEARCH ARTICLE
Cenozoic Methane-Seep Faunas of the
Caribbean Region
Steffen Kiel1,2*, Bent T. Hansen3
1 Georg-August-Universität Göttingen, Geoscience Center, Geobiology Group, Goldschmidtstr. 3, 37077,
Göttingen, Germany, 2 Naturhistoriska riksmuseet, Department of Palaeobiology, Box 500 07, 104 05,
Stockholm, Sweden, 3 Georg-August-Universität Göttingen, Geoscience Center, Department of Isotope
Geology, Goldschmidtstr. 3, 37077, Göttingen, Germany
* steffen.kiel@nrm.se
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 dat-
ing 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 Pleuro-
phopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep com-
munities 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 lucinidMeganodontia.
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 (Pego-
physema). In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godi-
neau 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 fac-
ultative chemosymbiotic and need to derive a significant proportion of their nutrition from
suspended organic matter.
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 1 / 33
OPEN ACCESS
Citation: Kiel S, Hansen BT (2015) Cenozoic
Methane-Seep Faunas of the Caribbean Region.
PLoS ONE 10(10): e0140788. doi:10.1371/journal.
pone.0140788
Editor: David P. Gillikin, Union College, UNITED
STATES
Received: March 5, 2014
Accepted: September 30, 2015
Published: October 15, 2015
Copyright: © 2015 Kiel, Hansen. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are
credited.
Funding: Financial support was provided by the
Deutsche Forschungsgemeinschaft through grants
Ha1166/17-1 and Ki802/6-1, and by the Open Access
Publication Funds of the Georg-August-University
Göttingen. The funders had no role in study design,
data collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
Introduction
Methane seeps on the deep-sea floor harbor dense faunal communities whose dominant mem-
bers rely on chemosynthetic bacteria for nutrition [1, 2]. First discovered in the Gulf of Mexico
in the 1980s, they are now recognized at virtually all continental margins worldwide [3, 4].
Although the rise of the modern, mollusk-dominated vent and seep fauna began during the
Cretaceous, the most common taxa at present-day vents and seeps originated in the early
Cenozoic [5–9]. Biogeographically the Cenozoic fossil record of methane seeps is strongly
skewed toward the active continental margins of the Pacific Ocean [10–13]; fossil occurrences
in the Atlantic realm are restricted to the Caribbean region [14, 15] and the Mediterranean
basin [16, 17]. The fossil record of the Caribbean region is of particular interest in this context
because this area has long served as a gateway for faunal exchange between the Atlantic and
Pacific oceans [18, 19].
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
VanWinkle, 1919 [20, 21], from Cuba, which was considered as a mix of marine and freshwa-
ter 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.
Here we report new seep faunas from Colombia, Cuba, the Dominican Republic, Trinidad,
and Venezuela, and our attempts to improve the dating of some of the known faunas from Bar-
bados, Cuba, Trinidad, and Venezuela (Fig 1), based on strontium isotope stratigraphy. A com-
prehensive taxonomic account on the mollusk species of the Caribbean Cenozoic seep faunas
is beyond the scope of the present paper and will be published separately.
Sr isotope stratigraphy is based on the observation that (i) marine carbonates record the
87Sr/86Sr-ratio of the seawater in which they formed, and (ii) those ratios have changed through
Earth’s history. Thousands of measurements of samples with known biostratigraphic ages have
been compiled into a Phanerozoic Sr-isotope curve that can be used, within certain limits, to
infer the age of a marine carbonate sample based on its 87Sr/86Sr-ratio [26]. We have recently
tested whether this approach can be applied to fossil methane-seep carbonates [27]. Methane
seeps pose the potential risk that the seeping fluid carries Sr with a 87Sr/86Sr-ratio quite differ-
ent from that of ambient seawater [28], which could corrupt the utility of the Sr isotope signa-
ture of the seep carbonate for stratigraphic purposes. However, 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
The new faunas reported here are from the collection of the Paleontological Research Institu-
tion (PRI) in Ithaca, USA, and the Naturhistorisches Museum Basel (NMB), Switzerland. All
taxonomic identifications and assignments presented here were made by SK, except when
noted otherwise. Additional material for Sr isotope stratigraphy and thin sectioning was pro-
vided by the Smithsonian Natural History Museum (USNM) in Washington, DC, USA, for the
Palmar-Molinera-road site in Colombia, and the Elmira asphalt mine site in Cuba [15]. The
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 2 / 33
fossil occurrences are identified as ancient methane seeps based on (i) their faunal content, typ-
ically large lucinid, vesicomyid, and mytilid bivalves, (ii) the carbon isotope values (δ13C) of
the associated carbonate, which tend to be very negative, and (iii) distinct carbonate fabrics of
the associated carbonate (when available). The oxygen isotope signature (δ18O) of the associ-
ated carbonate is used as an indicator for the degree of diagenetic alteration of the carbonate,
which is used to assess the reliability of the Sr isotope signature [27, 31]. No permits were
required for the described study, which complied with all relevant regulations.
Strontium isotopic compositions of representative samples were analyzed on unspiked sam-
ples. The samples were weighted into Teflon vials and dissolved in a mixture of 5 ml HF and
HNO3 (3:2) with a PicoTrace digestion system. This form of digestion may imply that tiny
amounts of detrital and/or meteoric material are dissolved as well, and therefore the obtained
ratios represent maximum ages. The solutions were processed by standard cation-exchange
techniques for purification of the Sr fractions. Sr was loaded with 0.5N H3PO4 on pre-condi-
tioned double Re filaments. Measurements of isotopic ratios were performed on a ThermoFin-
nigan Triton mass spectrometer in static mode (GZG Göttingen, Dept. Isotope Geology). The
mean 87Sr/86Sr ratio obtained for the Sr standard SRM NBS987 during the period of analytical
work was 0.710272 ± 0,000039 (n = 8, 2σ). All Sr isotopic ratios were normalized to an
86Sr/88Sr ratio of 0.1194 over the course of this study. Total procedure blanks were consistently
below 150 pg. 87Sr/86Sr ratios given as “87Sr/86Sr [corr.]” in Table 1 are corrected for blank and
mass fractionation, and after these corrections the 87Sr/86Sr ratios were adjusted to 0.710248
for the NBS987 which is the normalization ratio for the LOWESS curve and look-up table
Fig 1. Locality map showing the seep faunas reported herein. 1: Cantera Portugalete and Elmira asphalt mine, Cuba; 2: Cañada de Zamba, Dominican
Republic; 3: Bath Cliffs and Joes River, Barbados; 4: Bronte Estate, Freeman’s Bay, Godineau River, and Jordan Hill, Trinidad; 5: Buenavista de Maicillal,
Caujarao, Corro Colorado, La Piedra and Puerto Escondido, Venezuela; 6: Mata Cana and Sta. Clara, Colombia.
doi:10.1371/journal.pone.0140788.g001
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 3 / 33
Table 1. Strontium isotope data and derived ages.
[Sample number], origin of sample 87Sr/86Sr
[corr.]
2se δ13C (PDB)
[‰]
δ18O (PDB)
[‰]
Age [numerical, stage]
[Sr-1] Barbados, NMB loc. 10147, G17898, peloidal
micrite
0.708306 0.000007 -15.3 1.4 22.05 (+0.8/-0.55), lower
Aquitanian
[Sr-1] Barbados, NMB loc. 10147, G17898, peloidal
micrite
0.708335 0.000012 -15.3 1.7 21.6 (+0.7/-0.7), middle Aquitanian
[Sr-3] Barbados, NMB loc. 10147, G17899, micrite 0.708509 0.000010 -14.3 -1.2 18.75, lower Burdigalian
[Sr-4] Barbados, gastropod shell, NMB loc. 10039,
H20157
0.707745 0.000017 2.6 1.4 37.6 (+n.a./-3), basal Priabonian
[Sr-4] Barbados, gastropod shell, NMB loc. 10039,
H20157
0.707750 0.000010 2.1 1.3 37.2 (+n.a./-0.9), basal Priabonian
[Sr-6] Colombia, Mata Cana, micrite 0.707535 0.000007 -36.6 -1.9 * below Cenozoic Sr isotope
curve
[Sr-7] Colombia, Mata Cana, micrite 0.707493 0.000016 -32.8 -1.9 * below Cenozoic Sr isotope
curve
[Sr-8] Colombia, Sta. Clara, micrite 0.707507 0.000006 -23.0 -5.9 * below Cenozoic Sr isotope
curve
[Sr-9] Colombia, Sta. Clara, micrite 0.707556 0.000014 -24.5 -5.7 * below Cenozoic Sr isotope
curve
[Sr-10] Colombia, Palmar-Molinera, rim cement,
USNM 558830
0.708663 0.000005 -52.5 -5.9 16.85 uppermost Burdigalian
[Sr-10] Colombia, Palmar-Molinera, rim cement,
USNM 558830
0.708688 0.000006 -50.8 -5.8 16.5, uppermost Burdigalian
[Sr-12] Colombia, Palmar-Molinera, rim cement,
different sample
0.708631 0.000013 -45.0 -3.8 17.3, upper Burdigalian
[Sr-13] Cuba, Elmira Asphalt mine, micrite from
concretion
0.707731 0.000007 -28.2 -0.3 39.0 (+1/-4), Bartonian
[Sr-14] Cuba, Elmira Asphalt mine, micrite from
concretion
0.707697 0.000006 -28.7 -0.4 49.25 (+n.a./-1.65), upper
Ypresian
[Sr-15] Cuba, Elmira Asphalt mine, Unio? bitumen
shell
0.707705 0.000007 -2.4 -1.8 48.8 (+n.a./-1.6), upper Ypresian
[Sr-16] Cuba, Cantera Portugalete, white micrite 0.708459 0.000005 -7.0 1.7 19.4 (+0.4/-0.9), basal Burdigalian
[Sr-17] Cuba, Cantera Portugalete, micrite 0.708450 0.000005 -9.2 0.6 19.5 (+0.5/-0.6), basal Burdigalian
[Sr-18] Trinidad, Godineau River, bivalve shell 0.708855 0.000006 -16.9 -2.9 11.1, basal Tortonian
[Sr-19] Trinidad, Godenau River, micrite 0.708952 0.000007 -20.7 3.7 6.35 (+2.65/-0.35), middle
Messinian
[Sr-20] Trinidad, Freeman's Bay, light micrite 0.709027 0.000011 -14.5 -1.8 * 5.3, Miocene-Pliocene boundary
[Sr-21] Trinidad, Freeman's Bay, brown micrite 0.709120 0.000007 -20.0 -2.3 * 1.3, Pleistocene
[Sr-22] Trinidad, Jordan Hill, micrite 0.708936 0.000008 -43.7 2.6 7.7 (+2/-1.3), uppermost Tortonian
[Sr-23] Trinidad, Jordan Hill, micrite 0.708918 0.000007 -29.3 0.0 8.8 (+1.2/-1.8), upper Tortonian
[Sr-24] Venezuela, Corro Colorado, micrite 0.708481 0.000014 -22.0 -2.7 19.1 (+/- 0.5), lower Burdigalian
[Sr-25] Venezuela, Corro Colorado, micrite 0.708394 0.000004 ND ND 20.5 (+0.75/-0.7), uppermost
Aquitanian
[Sr-26] Venezuela, Buena Vista de Maicillal, micrite 0.708342 0.000018 -21.4 -2.4 21.45 (+0.65/-0.7), Aquitanian
[Sr-27] Venezuela, Buena Vista de Maicillal, micrite 0.708292 0.000028 -21.8 -2 22.3 (+0.8/-0.65), basal Aquitanian
[Sr-28] Venezuela, Buena Vista de Maicillal, micrite 0.708354 0.000011 -21.3 -2.6 21.25 (+0.7/-0.75), Aquitanian
[Sr-29] Venezuela, Caujarao, micrite 0.708394 0.000033 -23.0 -4.3 20.5 (+0.75/-0.7), uppermost
Aquitanian
[Sr-30] Venezuela, La Piedra, micrite 0.708971 0.000008 12.4 -5.9 6.45 (+2.6/-0.8), Messinian
[Sr-31] Venezuela, La Piedra, micrite 0.708868 0.000005 -2.1 -6.5 10.75 (+2.45/-1.35), lower
Tortonian
[Sr-32] Venezuela, Puerto Escondido, micrite 0.708946 0.000006 -26.5 -3.6 7.2 (+2.1/-1.1), Tortonian/
Messinian
(Continued)
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 4 / 33
version 5.0 [26]. All 87Sr/86Sr ratios are reported with their 2 σ internal precision. For further
details see [32]. Samples for Sr isotope analyses were either taken from the shells of mollusks,
or from matrix micrites or rim cements of the seep carbonates that contain the mollusks. The
latter carbonate phases often preserve an unaltered Sr isotope signal [27] and the samples were
checked for diagenetic alteration using their oxygen isotope signature (Table 1).
Samples for carbon and oxygen isotope analyses were extracted using a hand-held micro-
drill and carbonate powders were reacted with 100% phosphoric acid at 75°C using a Kiel III
online carbonate preparation line connected to a ThermoFinnigan 252 mass spectrometer. All
values are reported in per mil relative to V-PDB by assigning a δ13C value of +1.95‰ and a
δ18O value of –2.20‰ to NBS19. Reproducibility was checked by replicate analysis of labora-
tory standards and is better than ± 0.05‰.
Barbados
Fossil seep faunas in Barbados have been the subject of various studies, but the identity of the
taxa and their stratigraphic ages are still poorly understood. An unusual mollusk fauna was
reported from Eocene, oil-indurated mudstones of the Joes River Formation in Barbados [24].
Later, Harding [25] reported an early Miocene carbonate-hosted seep fauna with various
bivalves and worm tubes from the nearby Bath Cliffs area, and identified the ‘Joes River’ fauna
as seep related and as being of Miocene instead of Eocene age. A new geologic framework was
adopted for these faunas by Gill et al. [14]: the fauna of the Joes River Formation was regarded
as belonging to the diapiric mélange, and the carbonate-hosted fauna reported by [25] as
belonging to the Suboceanic Fault Zone. Furthermore, they suggested that both faunas could
have any geologic age between Eocene and Miocene [14]. To improve the dating of these fau-
nas, five Sr isotope measurements were made (Table 1): three on the micritic matrix of carbon-
ates associated with Pleurophopsis- and Bathymodiolus-like bivalves from the Oceanic
Formation (samples Sr-1 to Sr-3), now the Suboceanic Fault Zone (Fig 2; Basel Museum local-
ity 10147; from the East facing side of Bissex Hill near Cambridge, considered Middle-Early
Eocene), and two on a mudstone-hosted shell of an abyssochrysoid gastropod from the Joes
River Formation (samples Sr-4 and Sr-5), now diapiric mélange (Basel Museum locality 10039;
western branch of Spa River, between Spa and Richmond Ridge, considered as middle Eocene).
The two samples from the gastropod (samples Sr-4 and Sr-5) indicate an early late Eocene
age (basal Priabonian, 37.2 to 37.6 Ma). This is consistent with the previously suggested Eocene
age [24] for the fauna associated with the Joes River Formation, which consists chiefly of large
lucinid bivalves, a large bivalve of unknown affinity, the nuculanid bivalve Nuculana senni
Kugler, Jung and Saunders, 1984, and a large abyssochrysoid gastropod now assigned to the
genus Ascheria [24, 33]. This late Eocene mudstone-hosted association will be referred to as
‘Joes River fauna’ in the following text. The three samples from the carbonates of the ‘Oceanic
Formation’ (samples Sr-1 to Sr-3) indicate an early Miocene age, the two more reliable ones
Table 1. (Continued)
[Sample number], origin of sample 87Sr/86Sr
[corr.]
2se δ13C (PDB)
[‰]
δ18O (PDB)
[‰]
Age [numerical, stage]
[Sr-33] Venezuela, Puerto Escondido, micrite 0.708979 0.000008 -24.5 -1.4 6.25 (+1.25/-0.75), Messinian
* = derived ages that are considered unrealistic because the oxygen isotope signal suggests diagenetic alteration; ND = do data; n.a. = not applicable
because the value was below the Cenozoic Sr isotope curve.
doi:10.1371/journal.pone.0140788.t001
Fossil Caribbean Seep Faunas
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indicate a lower early Miocene (Aquitanian) age, consistent with the age given by [25]. These
early Miocene faunas will be referred to hereafter as the ‘Bath Cliffs fauna’.
Colombia
One Cenozoic seep deposit has been reported from Colombia so far, called Palmar-Molinera-
road locality, based on a small collection deposited in the Smithsonian Natural History
Museum in Washington, DC. It consists mainly of a solemyid bivalve, two lucinid bivalves
including Elongatolucina peckmanni Kiel, 2013 and the mussel Bathymodiolus palmarensis
Kiel, Campbell and Gaillard, 2010 [15, 34, 35]. Here we report new petrographic data for this
deposit, and two new seep faunas based on collections made by Axel A. Olsson in the 1940s,
now deposited in the PRI.
The Palmar-Molinera-road site
Paleoecology and stratigraphic age. Thin sections made from voucher material from this
locality show a micritic matrix with glauconitic grains, oval fecal pellets, detritus such as fora-
miniferan tests and gastropod shells, and signs of bioturbation (Fig 3A). Former voids with
banded and botryoidal rim cements and filled by sparry calcite are common. In an attempt to
improve the stratigraphic age of the Palmar-Molinera-road locality, three Sr isotope measure-
ments were made from rim cements in two different samples (samples Sr-10 to Sr-12). They
indicate an early Miocene age (late Burdigalian, 16.5 to 17.3 Ma) rather than an Oligocene age
as indicated on the label associated with this collection.
Mata Cana
Location and stratigraphic age. The labels for this collection read “Mata Cana” or “Mata-
cona”, and “San José ls., Field along cut rd., Lower Oligocene”. Considering Olsson’s (1940)
statement about the frequent occurrence of carbonate lenses with the Pleurophopsis fauna in
the Sinú River basin mentioned above, this could possibly refer to Mata de Caña, about 20 km
S of Lorica in the Department Córdoba, along the Sinú River, at 9°04’30” N, 75°49’30”W.
The carbonate consists mostly of a peloidal micrite with microdetritus and abundant signs
of bioturbation. It also contains a few small vugs that lack rim cements but are filled by sparry
Fig 2. Petrography of an early Miocene seep carbonate from Barbados, NMB locality 10147. Scanned
thin section, note cross section of vesicomyid bivalve on right side.
doi:10.1371/journal.pone.0140788.g002
Fossil Caribbean Seep Faunas
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Fig 3. Petrography of the Oligocene seep carbonates from Colombia. Scanned thin sections. A: Palmar-
Molinera Road. B. Mata Cana. C. Sta. Clara.
doi:10.1371/journal.pone.0140788.g003
Fossil Caribbean Seep Faunas
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calcite (Fig 3B). The carbon isotope values range from –37.2 to –29.6‰ (Fig 4), indicating
methane seepage [36]. The corresponding oxygen isotope values have a narrow range from –
3.4 to –1.8‰ and thus indicate some diagenetic alteration; the two Sr isotope measurements
(samples Sr-6 and Sr-7) fall below the Sr isotope curve for the Cenozoic (Table 1).
Fauna. Few fossil specimens are preserved with recrystallized shell; most are internal
molds. Crustacean claws, possibly of Callianassa Leach, 1814, are abundant in this collection,
and there is a crustacean carapace. Bivalves are also common and comprise the lucinids Elon-
gatolucina Gill and Little, 2013 and a rounded-oval species with fine concentric sculpture, a
very elongate solemyid resembling Solemya belensis Olsson, 1931 from Oligocene seep deposits
Fig 4. Cross-plot of stable carbon and oxygen isotope data. Barbados, Colombia, Cuba and the Dominican Republic.
doi:10.1371/journal.pone.0140788.g004
Fossil Caribbean Seep Faunas
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in Peru [37], and the nuculid Truncacila Schenck, 1931; there is a high-spired gastropod, a nau-
tiloid, and a crustacean carapace belonging to a? goneplacoid crab. The fauna is summarized in
Table 2 and illustrated in Fig 5.
Sta. Clara, loc. 303
Location and stratigraphic age. The label associated with this collection reads “Sta. Clara,
sinú, 7225 i, flfs. ls., 303, 22-IV-40”. A screening of Axel Olsson’s field notes (Xerox copies in
the USNMCenozoic mollusk type collection) revealed no information about these potential
locality numbers. But in a report on the Oligocene of western Columbia Olsson (1940, p. 250)
writes that “The (middle) Oligocene beds are succeeded by shales, very similar to the Uscari and
Tapaliza of Panamá and Costa Rica and at several places, particularly in the Sinú, contain lime-
stone lenses carrying the Pleurophopsis fauna.” [23]. The collection includes elongate vesicomyid
bivalves that were typically referred to as Pleurophopsis by Olsson [37] and it is therefore assumed
to be from the Sinú River basin. Indeed, Oligocene accretionary prism sediments crop out over
wide areas of the Sinú River basin and are referred to as Floresanto Formation [38].
The carbonate consists of fine peloidal and detrital micrite, and shows evidence of bioturba-
tion. Pyrite-rimmed dissolution features are common, and there are occasional small voids that
lack rim cements (Fig 3C). The carbon isotope values fall within a narrow range of –24.5 to –
22.9‰ (Fig 4), indicative of hydrocarbon seepage [36]. The corresponding oxygen isotope val-
ues range from –6.3 to –5.7‰ and thus indicate considerable diagenetic alteration and as
above, the two Sr isotope measurements (samples Sr-8 and Sr-9) fall below the Sr isotope curve
for the Cenozoic (Table 1).
Fauna. Fossils are preserved either with recrystallized shell or as internal molds with
chalky surface. The fauna consists of the vesicomyid bivalves Pliocardia sp. (common) and
Pleurophopsis sp., the lucinid Elongatolucina sp., an unidentified, small oval bivalve that exter-
nally resembles NucinellaWood, 1851, and the thyasirid Conchocele adoccasa (Van Winkle,
1919). This latter species was originally regarded as belonging to Thyasira Lamarck, 1818 [21]
but its large size, rectangular outline and two posterior ridges and sulcus clearly place this spe-
cies in Conchocele Gabb, 1866 [39, 40]. The two gastropods from this site are a neogastropod
and the seguenzoid Cataegis godineauensis (VanWinkle, 1919); the latter species was originally
regarded as belonging to SolariellaWood, 1842, but with its strong spiral sculpture and fine
commarginal ribblets it clearly shows affinities to extant species of Cataegis [41]. A summary
of the fauna is provided in Table 3 and it is illustrated in Fig 6.
Cuba
Cenozoic seep deposits occur in northwestern Cuba in the vicinity of the capital Havana. A
presumably Oligocene site with an unusual fauna consisting of the large, globular gastropod
Table 2. List of taxa fromMata Cana, Colombia.
Species Max. size (mm) N of specimens
Solemya aff. belensis Olsson 1931 53.7 2
Truncacila sp. 8 2
Elongatolucina sp. 83.5 2
Oval lucinid 48 7
High-spired gastropod 34.5 1
Nautiloid 37 1
?Goneplacoid carapax 20 1
Crustacean claws 18 6
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Elmira cornuatietis Cooke, 1919, an elongate veneriform bivalve of uncertain affinities
described as Unio? bitumen Cooke, 1919, the lucinid Cubatea asphaltica (Cooke, 1919) and
possible abyssochrysid gastropods, was reported from the Elmira asphalt mine at Bejucal [15,
34]. Here we report and discuss Sr-isotope ages for the Elmira asphalt mine locality, and
describe a new seep fauna of early Miocene age from near the village of Jamaica in the Havana
province.
Fig 5. The Oligocene Mata Cana seep fauna from Colombia. A, B: The lucinid Elongatolucina sp. (PRI 68645, 68646). C: Oval lucinid bivalve (PRI 68647).
D, E: The solemyid Solemya cf. belensis (Olsson, 1931) (PRI 68648). F: The nuculid Truncacila sp. (PRI 68649). G: Carapace of a ?goneplacoid crab (PRI
68650). H: Crustacean claw (PRI 68651). I: Tall neogastropod (PRI 68652).
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Fossil Caribbean Seep Faunas
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Elmira asphalt mine site
Stratigraphic age. Three Sr isotope measurements were made (Table 1), two from a small
calcareous concretion (samples Sr-13 and Sr-14), one from the shell of the bivalve Unio? bitu-
men (sample Sr-15). One date from the concretion indicates an upper middle Eocene age (sam-
ple Sr-13, Bartonian, 39 Ma), while the other and the bivalve shell indicate an Early Eocene age
(samples Sr-14 and Sr-15, late Ypresian, 48.4 to 49.25 Ma). According to the map of French &
Schenk [42], both Eocene and Oligocene sediments crop out in the area of Bejucal, and in his
Table 3. List of taxa from Sta. Clara, Colombia.
Species Max. size (mm) N of specimens
Oval bivalve (Nucinella?) 22.5 3
Conchocele adoccasa (Van Winkle 1919) 72 3
Elongatolucina sp. 86 2
Pleurophopsis sp. 59.5 2
Pliocardia sp. 44 12
Cataegis godineauensis (Van Winkle 1919) 7 1
Neogastropod 32 1
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Fig 6. The Oligocene Sta. Clara seep fauna from Colombia. A: The vesicomyid Pleurophopsis sp. (PRI 68653). B: The thyasiridConchocele adoccasa
(VanWinkle, 1919) (PRI 68654). C: The vesicomyid Pliocardia sp. (PRI 68655). D: Oval bivalve resemblingNucinella? (PRI 68656). E: The lucinid
Elongatolucina sp. (PRI x13). F: The seguenzoid Cataegis godineauensis (VanWinkle, 1919) (PRI 68657). G: Neogastropod (PRI 68658).
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original report on the locality, Cooke wrote [22] that “The fossils are doubtfully referred to the
Oligocene”, without providing any basis for this assignment. The fossil assemblage at this site
is rather unusual compared to those described here and elsewhere for the Caribbean Cenozoic
and it may therefore indeed be older than Oligocene. Even the early Eocene age is not contra-
dicted by the fauna: the Unio? bitumen is as-yet difficult to place taxonomically, the only other
occurrence of the gastropod Elmira Cooke, 1919 is at a late Cretaceous seep deposit in Japan
(Takami Nobuhara and SK, unpublished observation), and gastropods resembling the abysso-
chrysoid from the Elmira asphalt mine are mostly found in Cretaceous and Eocene seep depos-
its [43–45].
Cantera Portugalete
Location and stratigraphic age. This material was collected by Dorothy K. Palmer during
her pioneering work on the stratigraphy and geology of Cuba. All specimens have the number
802 written onto them, which most likely is Palmer’s locality number. The description of this
locality is “Habana Province, Cantera Portugalete, 1 km. N of Jamaica. Ls chips. 1/9/32” [46].
The village of Jamaica is just NW of San José de las Lajas, about 30 km SE of Havana, at 22°
58’44”N, 82°10’11”W. The sediments in this area belong to the early Miocene Husillo Forma-
tion and represent a “carbonate and carbonate-terrigenous sequence” that was deposited in a
deep marine channel between present-day western and central Cuba [47, 48]. The Husillo For-
mation contains indurated, dark gray, massive rocks [47, 49] like those associated with the fos-
sils concerned here. Two samples for Sr isotope stratigraphy were taken from the carbonate
that forms the internal molds of two bivalves (samples Sr-1 and Sr-17), and both indicate a
basal Burdigalian age (19.4 to 19.5 Ma), consistent with the early Miocene age of the Husillo
Formation (Table 1).
Fauna. Few fossils preserve recrystallized shell material, most are internal molds. The
most conspicuous species is the large (up to 120 mm long) lucinid bivalveMeganodontia sp.
The other species are an up to 90 mm long vesicomyid bivalve resembling Pleurophopsis litho-
phagoides Olsson 1931, a small (44.5 mm) lucinid resembling the extantMyrteopsis? lens Ver-
rill and Smith, 1880 from the western Atlantic Ocean, and a mytilid that reaches 56 mm in
length. The mytilid species is unusual among seep-inhabiting mussels because it does not
resemble any extant or fossil bathymodiolin, but instead has a terminal umbo and the curved
outline of species belonging to Brachidontes orMytilus. A species of Brachidontes is here
reported from a seep deposit at La Piedra in Venezuela (see below), which is also associated
with a largeMeganodontia. The Cuban species may thus also belong to Brachidontes. The
fauna is summarized in Table 4 and illustrated on Fig 7.
Paleoecology. The carbon isotope signature of the carbonate attached to the fossils or
composing the internal molds ranges from –10 to –4.4‰ (Fig 4). These are less negative values
compared to the other seep deposits reported herein and are not necessarily indicative of a seep
limestone. However, during the precipitation of seep carbonate the typically very negative orig-
inal isotope signature of the seeping methane is ‘diluted’ by mixing with other carbon sources
Table 4. List of taxa from Cantera Portugalete, Cuba.
Species Max. size (mm) N of specimens
Meganodontia sp. 120 3
Myrteopsis? sp. 44.5 8
Pleurophopsis aff. lithophagoides Olsson, 1931 90 7
Mytilid 56 5
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(i.e., marine bicarbonate) [36]. Considering that (i) the Husillo Formation is largely a carbonate
sequence the addition of marine carbonate was likely to be very high, and (ii) the fauna consists
largely of chemosymbiotic bivalves, the Cantera Portugalete fauna is here interpreted to have
lived at a methane seep, possibly with low rates of seepage and diffuse fluid flow.
Fig 7. The Early Miocene Cantera Portugalete seep fauna from Cuba. A-C: The lucinidMeganodontia sp. (A and B; PRI 68659. C; PRI 68660). D-G: The
lucinid bivalveMyrteopsis? sp.; three views of a specimen with preserved shell and hinge (D-F; PRI 68661) and internal mold showing adductor muscle scars
(G; PRI 68662). H, I: Mytilid (PRI 68663). J, K: Pleurophopsis cf. lithophagoidesOlsson 1931 (PRI 68664).
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Dominican Republic
Location and stratigraphic age
The material from NMB loc. 16813 is from the Gurabo Formation, found in the Cañada de
Zamba of the Río Cana, in the Cibao Valley in the northern Dominican Republic. The Gurabo
Formation in the Río Cana section has been assigned an age that ranges from 5.7 to 4.3 Ma,
mostly early Pliocene [50], and the section with Basel loc. 16813 is in the lower part of the Gurabo
Formation, very close to the Miocene-Pliocene boundary (Donald McNeill, pers. comm. 2015).
Fauna and paleoecology
The fauna consists of numerous large (up to 115 mm long) specimens of Anodontia (Pegophy-
sema) sp., possibly a precursor to the very similar Recent Caribbean A. (P.) schrammi (Crosse,
1876) (Fig 8). One of the specimens has some hard micritic matrix adhering to it, which shows
a carbon isotope signature of –28 to –20‰ (Fig 4). Especially the lower value indicates the oxi-
dation of hydrocarbons including methane during the formation of this carbonate.
Trinidad
The Cenozoic seep faunas of Trinidad reported so far were found along the shore of Freeman’s
Bay to the West of San Fernando, in the vicinity of the mouth of Godineau River. Here they
Fig 8. The early Pliocene seep-cemented lucinid bivalve Anodontia (Pegophysema) sp. from Cañada de Zamba, Dominican Republic. A: view on left
valve showing the very elongate anterior adductor muscle scar and the impression of the pallial blood vessel (NMB 17900). B, C: same specimen as in Fig A,
in dorsal view (B) and view on right valve (C).
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were collected as float material on the beach, as mentioned in various reports [14, 20, 21, 51]
and indeed, many of the samples investigated here have numerous small extant barnacles
attached to them. The fossils were reported to be associated with sediments of the Lengua For-
mation, which were either considered as middle Miocene [52] or late Miocene [53]. They were
reported from two different lithologies (Fig 9) associated with two different preservational
Fig 9. Petrography of the seep carbonates from Trinidad. Scanned thin sections. A: Godineau River. B:
Freeman’s Bay. C: Jordan Hill.
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styles: (i) from a large, isolated, impure limestone block on the costal mudflat where fossils
occur as internal molds, and (ii) from often brecciated, oil-impregnated calcareous mudstone
lenses surrounded by greenish, unctuous and slickensided clays in the adjoining coastal section
where the fossils occur as black, oil-impregnated specimens often with original shell material
[14, 51]. The impure limestone block was given its own lithostratigraphic unit, the “Freeman’s
Bay limestone Member”, the oil-impregnated calcareous mudstone lenses were interpreted as
having formed at mud diapirs [14]. Despite these differences, paleoecologic interpretations
were considered as difficult to reach and the available fossils were reported as a single seep
fauna [14].
Based on the material available at the NMB and the PRI, we separate two ecologically dis-
tinct types of seep faunas in the Miocene of Trinidad: the dark, bitumen-impregnated fauna is
coined ‘Godineau River fauna’ because the boxes containing this fauna at the PRI were labeled
Godineau River, whereas the fauna associated with the white limestone is referred to as ‘Free-
man’s Bay fauna’. Two further collections with a typical Freeman’s Bay fauna were recovered,
Bronte Estate and Jordan Hill, from an area to the East of San Fernando, towards Princess
Town. Our Sr-isotope work indicates a late Miocene age for the Godineau River and Jordan
Hill faunas (Table 1), which supports the stratigraphic scheme of Erlich et al. [53].
Godineau River fauna
Stratigraphic age. Two Sr isotope measurements were made: one sample was from the cal-
careous mudstone and indicates a middle Messinian age (sample Sr-19, 6.35 Ma), the other is
from the aragonitic shell of the possible vesicomyid bivalve, which gave a basal Tortonian age
(sample Sr-18, 11.1 Ma). The corresponding oxygen isotope value of the latter sample (Table 1)
indicates slight diagenetic alteration of this material by meteoric water, thus the Messinian age
derived from the apparently unaltered calcareous mudstone is here considered the more reli-
able. However, both dates suggest a late Miocene age for the Godineau River fauna.
Fauna and paleoecology. The Godineau River fauna consists exclusively of very large,
infaunal or semi-infaunal chemosymbiotic bivalves (Table 5, Fig 10): the thyasirid Conchocele
adoccasa reaching 87 mm length, the lucinids Nipponothracia sp. reaching 167 mm in length
and Elliptiolucina sp. reaching 85 mm length, and an unidentified species that may (or may
not) belong to the Vesicomyidae, reaching 140 mm length. In thin section, the oil-impregnated
calcareous mudstone is composed of monotonous micrite with rare planktonic foraminiferans
(Fig 9A). Its carbon isotope signature ranges from –25.8 to –20.2‰, with corresponding oxy-
gen isotope values ranging from 3.7 to 4‰ (Fig 11), indicating that the limestone formed due
to methane oxidation with a considerable amount of marine bicarbonate mixed in [36].
Freeman’s Bay
Stratigraphic age. Two Sr isotope measurements were made on two differently colored
micrites (samples Sr-20 and Sr-21, Table 1). The accompanying oxygen isotope values were
slightly negative, suggesting diagenetic alteration by meteoric waters, and the ages derived
Table 5. List of taxa fromGodineau River, Trinidad.
Species Max. size (mm) N of specimens
Conchocele adoccasa (Van Winkle 1919) 87 8
Nipponothracia sp. 167 8
Elliptiolucina sp. 85 2
Vesicomyid? sp. 140 8
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from the Sr isotope ratios were younger than reasonable considering the biostratigraphic
framework of this locality.
Fauna and paleoecology. The fauna consists largely of the vesicomyid bivalve Pleurophop-
sis unioides VanWinkle, 1919 and P. u. var. fernandensis VanWinkle, 1919 that reach just
over 80 mm length. The validity of the genus Pleurophopsis had been questioned because of its
poorly preserved type material [54], but was considered valid by other authors [55, 56]. The
material investigated during the present study indicates that it is indeed a valid and distinctive
genus; further details will be published in a forthcoming paper. Minor elements of the Free-
man’s Bay fauna include the lucinid bivalves Cubatea sp. and an unidentified lucinid, which
are here reported for the first time from this fauna, Conchocele adoccasa, which is the only spe-
cies shared between the Freeman’s Bay and Godineau River faunas, a nuculanid bivalve, and
four gastropods: Cataegis godineauensis (Van Winkle 1919), Cantrainea sp., Provanna sp., and
a limpet (Table 6, Fig 12). In addition, a bathymodiolin mussel has been reported [14, 21].
The Freeman’s Bay fauna was characterized by Van Winkle as “very peculiar and unlike any
known” [21] and later interpreted as a fossil seep fauna [14, 57]. Evidence for this interpreta-
tion has never been provided, and it was presumably based on the abundance of chemosymbio-
tic bivalves. The carbon isotope signature of the limestone ranges from –20 to –14.5‰, with
corresponding oxygen isotope values ranging from –2.8 to –1.7‰ (Fig 11), consistent with the
interpretation that methane oxidation was involved in the formation of the carbonate.
Fig 10. The late Miocene Godineau River seep fauna in Trinidad. A: The thyasiridConchocele adoccasa (VanWinkle, 1919) (PRI 68665). B: The lucinid
Nipponothracia sp. (PRI 68666). C-E: The lucinid Elliptiolucina sp.; specimen with preserved shell and hinge (C, D; PRI 68667), internal mold showing
anterior adductor muscle scar (E; PRI 68668). F-H: A possible vesicomyid; external view (F, G; PRI 68669) and interior of fragment showing anterior adductor
muscle scar (H; PRI 68670).
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Petrographically the Freeman’s Bay limestone shows abundant traces of bioturbation and bio-
clasts (Fig 9B), unlike the Godineau River material.
Bronte Estate
Location and stratigraphic age. The locality description for NMB locality 10228 reads
“Lengua Formation, Freeman’s Bay limestone Member. Naparima area, Bronte Estate, Man-
ager House. Quarry near trigonometric station W of Naparima.” Today there is a ‘Bronte vil-
lage, Naparima’ just south of the Jordan Hill Presbyterian school, exactly where the Lengua
Formation crops out according to Kugler’s map [51]. It is therefore assumed that the fossils
reported here were collected in this area. Due to the (assumed) close proximity to the Jordan
Hill site, this locality is considered to be of late Miocene age.
Fig 11. Cross-plot of stable carbon and oxygen isotope data. Filled symbols: Trinidad, open symbols: Venezuela.
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Fauna and paleoecology. The fauna consists of Pleurophopsis unioides var. fernandensis
reaching 110 mm in length, and probably two Bathymodiolus species, the elongate one reach-
ing 40 mm in length, the short one reaching 29.3 mm in length (Table 7, Fig 13). The carbonate
adhering to the fossils is whitish-ochre colored micrite; material for thin sectioning was not
available. Its carbon isotope signature ranges from –30.2 to –23‰, clearly indicating than
methane oxidation was involved in the formation of the carbonate. The corresponding δ18O
values range from –5.8 to –4.8‰ (Fig 11).
Jordan Hill
Location and stratigraphic age. The labels of this small collection read “Jordan Hill
House” and “Trinidad GDH”, suggesting that it was collected by Gilbert Dennison Harris.
Today there is a Jordan Hill Presbyterian primary school on the Manahambre road, about half-
way between San Fernando and Princes Town, at 10°15'22"N, 61°24'29"W, and it is assumed
that the material was collected around here. Kugler’s map [51] indicates the upper Cipero For-
mation in this area, which ranges into the late Miocene [53]. However, the Lengua Formation
crops out just a kilometer or so to the SW and SE [51], and could thus also be a source of the
material reported here. Two samples for Sr isotope stratigraphy indicate a late Tortonian age
(samples Sr-22 and Sr-23, 7.7 and 8.8 Ma).
Fauna and paleoecology. The fauna (Table 8, Fig 14) is very similar to the Freeman’s Bay
fauna except for a small, possible vesicomyid bivalve having the general outline of the genus Iso-
rropodon Sturany, 1896 (Fig 14C). Today this genus has a wide geographic distribution but has
so far not been reported from the western Atlantic Ocean [58]; the genus was also present in an
early Miocene seep deposit in the northeastern Pacific Ocean [59]. The lithology of the Jordan
Hill seep deposit differs from both the Freeman’s Bay and Bronte Estate seep deposits by contain-
ing more diverse carbonate phases and especially by the presence of various vugs lined with
banded rim cements; such cements have not been seen in the Freeman’s Bay and Bronte Estate
deposits (Fig 9C). Furthermore, the Jordan Hill seep carbonate shows a wider range in its carbon
isotope signature, ranging from –43.7 to –12.3‰ (Fig 11), consistent with its more diverse car-
bonate phases. The very negative carbon isotope signature clearly indicates that biogenic meth-
ane (rather than thermogenic methane) was involved in the formation of the carbonate [36].
Venezuela
Cenozoic seep faunas in Venezuela are found in the Falcon Basin at or near the present-day
coast of the Caribbean Sea, and here the moderate to deep-water deposits within the Agua Sal-
ada Group. A single Cenozoic seep deposit has so far been reported, from Puerto Escondido in
Table 6. List of taxa from Freeman’s Bay, Trinidad.
Species Max. size (mm) N of specimens
Nuculanid 7 2
Conchocele adoccasa (Van Winkle 1919) 21 1 external mold
Pleurophopsis unioides Van Winkle 1919 83 ca. 40
Pleurophopsis u. var. fernandensis Van Winkle 1919 81 5
Cubatea sp. 57.5 4
Cantrainea sp. 8 2
Cataegis godineauensis (Van Winkle 1919) 9 2
Provanna sp. 8.5 10
Limpet gastropod 6 1
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Estado Falcón, consisting of solemyid, bathymodiolin, thyasirid, lucinid and vesicomyid
bivalves, and a few gastropods, considered as being of Miocene age [14, 60]. The new material
reported here is from the collection of the NMB and includes four new sites and new data on
the Puerto Escondido site reported earlier [14]. All new sites are presumed to be from the Agua
Salada Group in the Estado Falcón, including three from the Pozón Formation, one from the
Guacharaca Formation, and one from the Riecito Limestone. They are considered to range in
age from Early Oligocene to middle Miocene. Most locality data are from the NMB locality reg-
ister, addition information and opinions were provided by Oliver Macsotay (pers. comm.
2014), a specialist of the Cenozoic stratigraphy of Venezuela [61].
Fig 12. Examples of the late Miocene Freeman’s Bay seep fauna from Trinidad. A, B: The lucinid Cubatea sp. (PRI 68671). C, D: Lucinid bivalve (PRI
68672). E: The vesicomyid Pleurophopsis unioides var. fernandensis VanWinkle, 1919 (PRI 68673). F, G: Pleurophopsis unioides VanWinkle, 1919 (PRI
68674).
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Table 7. List of taxa from Bronte Estate, Trinidad.
Species Max. size (mm) N of specimens
Pleurophopsis u. var. fernandensis 110 5
Bathymodiolus sp. ‘short’ 29.3 6
Bathymodiolus sp. ‘elongate’ 40 2
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Paleoecology
The Venezuelan fossils in the NMB collection had very little or no carbonate matrix adhering
to them, thus thin section preparation was not possible and only carbon and oxygen isotope
data are available for environmental reconstructions. These isotope data were very similar
among the sites (with the exception of La Piedra, discussed below). Therefore, their implica-
tions are summarized here, instead of reiterating them at each site description. The δ13C values
range from –26.5 to –9.5‰, with the majority of values between –22 and –15‰ (Fig 11). These
values indicate carbonate precipitation induced by the oxidation of hydrocarbons, but are not
necessarily indicative of methane as sole hydrocarbon [15, 36]. However, the characteristic,
very negative δ13C signature of methane can be diluted by marine carbonate in carbonate-rich
settings [62]. The Venezuelan sites reported here were formed in tropical marl- and limestone,
middle to outer shelf settings where a strong input in marine carbonate can be expected. Hence
we assume that the sites reported here formed at ancient hydrocarbon seeps where methane
formed an important part of the hydrocarbons.
Buenavista de Maicillal
This small collection (Basel loc. 15781) obtained by Paul Leuzinger is from Buenavista de Mai-
cillal in the Mirimire area in the Estado Falcón. It belongs to the Pozón Formation of the Agua
Salada Group and here to “its Husite member, composed of marly clays interbedded with
Fig 13. The late Miocene Bronte Estate seep fauna from Trinidad. A: The mytilid Bathymodiolus ‘short’
(NMBG17955). B. The mytilid Bathymodiolus ‘elongate’ NMBG17956). C: The vesicomyid Pleurophopsis
unioides var. fernandensis VanWinkle 1919 (NMBG17953).
doi:10.1371/journal.pone.0140788.g013
Table 8. List of taxa from Jordan Hill, Trinidad.
Species Max. size (mm) N of specimens
Pleurophopsis unioides var. fernandensis Van Winkle 1919 110 1
Bathymodiolus cf. palmarensis Kiel et al. 2010 30 7
Vesicomyid bivalve 26 1
Cataegis godineauensis (Van Winkle 1919) 9 1
Cantrainea sp. 12.5 1
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foraminifera marls, with scattered glauconite. The paleodepth based on ostracods is 100–170 m
[63]” (Oliver Macsotay pers. comm. 2014). Its age is given as ‘mid-late Miocene?’ (label), as
middle to late Oligocene (NMB locality register) or early Middle Miocene (Oliver Macsotay
pers. comm. 2014). Three samples from the micritic matrix were used for Sr isotope stratigra-
phy (samples Sr-26 to Sr-28) and suggest an Aquitanian age (Table 1). The fauna consists of a
large, globular lucinid bivalve apparently with a thin, elongate anterior adductor muscle scar,
and a possible vesicomyid bivalve (Table 9, Fig 15).
Caujarao
This collection (Basel loc. 16626) is from Río Mirimire near Caujarao in the Aguide area in
Estado Falcón. According the NMB locality register it belongs to the Guayabal marls of the
Guacharaca Formation. According to Oliver Macsotay (pers. comm. 2014) “This locality
belongs to the La Danta member ([61], p. 336–337), the lowest member of the Guacharaca Fm.
This unit is essentially pelitic, with fine-grained turbidites, of 235–250 m in thickness, and
should be of Early Oligocene age.” A single measurement of Sr isotope ratios (sample Sr-29)
Fig 14. The late Miocene Jordan Hill seep fauna from Trinidad. A: The vesicomyid Pleurophopsis unioides var. fernandensis VanWinkle, 1919 (NMB
G17945). B: The mytilid Bathymodiolus aff. palmarensis Kiel, Campbell & Gaillard, 2010 (NMBG17946). C: The possible vesicomyid bivalve (PRI 68675). D:
The colloniidCantrainea sp. (PRI 68676). E: The seguenzoid Cataegis godineauensis VanWinkle, 1919 (PRI 68677).
doi:10.1371/journal.pone.0140788.g014
Table 9. List of taxa from Buenavista de Maicillal, Venezuela.
Species Max. size (mm) N of specimens
Vesicomyid bivalve 61 1
Large, globular lucinid 86 1
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suggests an uppermost Aquitanian (early Miocene) age; however, the oxygen isotope signature
of the samples indicates some diagenetic alteration (Table 1). The fauna consists of ten moder-
ately sized (up to 77 mm long) specimens of a lucinid bivalve possibly belonging toMegano-
dontia (Fig 15).
Corro Colorado
The labels associated with this locality read “Corro Colorado, near Maicillal de la Costa, due
South on road”and “[unreadable] between Corro Colorado onto road to San Francisco“.
According to Oliver Macsotay (pers. comm. 2014) “this locality, by cartography, belongs to the
Husite Member of the Pozón Formation. The age is Early Middle Miocene.” Two samples (Sr-
24 and Sr-25) were used for Sr isotope stratigraphy and suggests an uppermost Aquitanian to
Fig 15. The Oligocene to Miocene Buenavista de Maicillal and Caujarao seep faunas from Venezuela.
A: A large lucinid bivalve from Buenavista de Maicillal (NMBG18007). B: A possible vesicomyid bivalve from
Buenavista de Maicillal (NMBG18008). C: A large lucinid bivalve from Caujarao (NMBG17996).
doi:10.1371/journal.pone.0140788.g015
Table 10. List of taxa from Corro Colorado, Venezuela.
Species Max. size (mm) N of specimens
Glypturus fragments 18 25
Possible vesicomyid bivalve 61 2
Large lucinid bivalve 80 1
Small lucinid bivalve 38 3
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lower Burdigalian (early Miocene) age, and there is only a slight chance of diagenetic alteration
as indicated by the oxygen isotope signature of only –2.7‰ (Table 1). The fauna includes a rel-
atively large potential vesicomyid bivalve, a large lucinid bivalve, a smaller lucinid, and abun-
dant callianassid shrimp fragments belonging to the genus Glypturus [64] (Table 10, Fig 16).
La Piedra
Location and stratigraphic age. This small collection (NMB loc. 15780) obtained by
Louis Vonderschmidt is from La Piedra in the Isidro area in Estado Falcón. It belongs to the
Pozón Formation of the Agua Salada Group and was regarded as either middle to late Oligo-
cene (NMB locality register) or mid-late Miocene (label). Oliver Macsotay (pers. comm. 2014)
believes that “the fossils came from Policarpo member, composed of marly limestones, clays,
with glauconititc beds at its base. Iron concretions are frequent. [. . .] The paleodepth data
given by [65] based on benthic foraminifera should extend from 200 to 600 meters.” The Poli-
carpio “Greensand”Member is of late Aquitanian (early Miocene) age [65]. Two samples (Sr-
30 and Sr-31) were used for Sr isotope stratigraphy and broadly suggest a late Miocene age
(lower Tortonian to Messinian; Table 1), but with δ18O values as low as –6.5‰ the samples
appear diagenetically altered and hence the Sr isotope age should be treated cautiously.
Fig 16. The early to middle Miocene Corro Colorado seep fauna from Venezuela. A: The large lucinid bivalve (NMBG17995). B, C: The small lucinid
bivalve (NMBG17992, 17993). D: The possible vesicomyid bivalve (G17965). E, F: Claw fragments of the callianassid ghost shrimpGlypturus (NMB
G17967, 17968).
doi:10.1371/journal.pone.0140788.g016
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PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 24 / 33
Fauna and paleoecology. The fauna consists of a large lucinid resemblingMeganodontia,
a small lucinid, and a mytilid belonging to Brachidontes (Table 11, Fig 17). The carbon isotope
values of the associated carbonate are very heterogeneous, ranging from –11.5 to +12.4‰, with
more homogenous corresponding oxygen isotope values between –7.5 to –5.9‰. While the
negative carbon isotope values indicate the oxidation of hydrocarbons, the very positive values
can only be explained my local methane formation, because the CO2 pool utilized during
archaeal methanogenesis becomes enriched in 13C [36, 66, 67]. Such 13C-enriched carbonate
phases are interpreted as having formed after the precipitation of the 13C-depleted carbonate
phases, probably during early burial [36].
Puerto Escondido
The carbonate adhering to a vesicomyid and a Bathymodiolus shell from this locality (NMB
loc. 13968) has a carbon isotope signature as low as –26.5‰ (Fig 11), supporting the suggestion
of [14] that the Puerto Escondido fauna formed at an ancient methane seep deposit. The age of
Fig 17. The Miocene La Piedra seep fauna from Venezuela. A: The lucinidMeganodontia? sp. (NMB
G18003). B: Small lucinid bivalve (NMBG18001). C, D: The mytilid Brachidontes sp. (NMBG18005,
G18006).
doi:10.1371/journal.pone.0140788.g017
Table 11. List of taxa from La Piedra, Venezuela.
Species Max. size (mm) N of specimens
Meganodontia? sp. 125 2
Small lucinid bivalve 21 1
Brachidontes sp. 60 3
doi:10.1371/journal.pone.0140788.t011
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 25 / 33
this fauna was given as ‘Miocene’ [14] and it occurs in the Huso Clay Member of the Pozon
Formation, which, according to the stratigraphic chart of Blow [65] is late Burdigalian (late
Middle Miocene). Two samples (Sr-32 and Sr-33) were used for Sr isotope stratigraphy and
both suggest a Messinian age (upper Late Miocene; Table 1).
Discussion
Stratigraphy of the Caribbean seep faunas
The exact geographic location and therefore also the stratigraphic ages of many of the Carib-
bean seep communities are still not well constrained, and our current understanding is summa-
rized in Fig 18. Although our Sr isotope dating of known and new sites provided new insights
into their stratigraphic ages, it also revealed a number of persistent problems and uncertainties.
The Cuban Elmira asphalt mine site, hesitantly considered Oligocene in previous papers
[15, 22], may be as old as early Eocene, based on our Sr isotope stratigraphy. This would make
it the oldest seep community of the Caribbean region so far. An Eocene age would be consistent
with the presence of the relatively large-sized abyssochrysoid gastropods at this site, which
occur also the late Eocene ‘Joes River fauna’ of Barbados [24], and are generally a common fea-
ture of late Mesozoic to Eocene seep faunas [9, 33, 34, 43, 68].
Fossil seep faunas from Barbados are known from two different rock units: the mudrock-
hosted Joes River fauna from the diapiric mélange, and the carbonate-hosted Bath Cliffs fauna
from the Suboceanic Fault Zone [14]. These faunas are taxonomically distinct and were
recently considered to be of any age between the Eocene and the Miocene, based on the well-
established ages of the enclosing units [14]. Our Sr isotope data, although limited, indicate that
at least some of these faunas are also stratigraphically distinct: our samples of the Joes River
fauna with its large lucinid bivalves and the tall abyssochrysoid gastropods indicate a late
Eocene (basal Priabonian) age, and an early Miocene age for the Bath Cliffs fauna with Pleuro-
phopsis, Cataegis, and associated taxa. However, considering that seep faunas that are ecolog-
ically similar to the Joes River and Bath Cliffs faunas, respectively, occur together in late
Miocene sediments in Trinidad indicates that these different faunal types may just be the result
of different ecological settings [14]. Thus, we cannot exclude the possibility that mudstone-
and carbonate-hosted faunas have coexisted in Barbados from Eocene to Miocene time and we
have just accidentally sampled an Eocene example of the mudstone-hosted fauna and an early
Miocene example carbonate-hosted fauna for our Sr isotope work. Further stratigraphic and
taxonomic work on these deposits and their faunas may solve this question and could certainly
provide further insights into the evolution of the Caribbean seep fauna.
In Colombia, our attempt at Sr isotope stratigraphy failed in cases of the Sta. Clara and
Mata Cana sites. In case of the Palmar-Molinera-road site, it suggests an early Miocene instead
of an Oligocene age as indicated by the sample label. This early Miocene age should be treated
cautiously, because the samples show evidence of diagenetic alteration. However, the similarity
of Bathymodiolus palmarensis to the bathymodiolin found in the Miocene Freeman’s Bay and
Jordan Hill seep limestones in Trinidad supports a Miocene age of the Palmar-Molinera-road
site. Clearly, more detailed stratigraphic work on the Colombian seep faunas would provide
more detailed insights into the evolution of the Cenozoic seep faunas of the Caribbean region.
Sr isotope stratigraphy has proven useful in many, but not all, cases in the present study,
another potential way forward may be dinoflagellate biostratigraphy, as recently used for Cre-
taceous seep carbonates found as float boulders on beaches in northern New Zealand [68].
Among the five Venezuelan sites, a bewildering array of contradicting stratigraphic ages is
indicated by the labels and locality information associated with these fossils, by the personal
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 26 / 33
assessment of an experienced regional geologist, and our Sr isotope stratigraphy approach.
Most ages, however, seem to center around the Miocene (Fig 18).
Biogeography & Evolution
Through the Cenozoic, seep faunas in the Caribbean and Gulf of Mexico region show three
successive faunal associations:
Fig 18. Summary of the geologic ages of the Cenozoic seep faunas from the Caribbean region. Long range indicates uncertainty in dating; note break
in time scale below 40 Ma. Sr associated with stippled lines and whiskers indicate minimum or maximum age based on strontium isotope stratigraphy.
doi:10.1371/journal.pone.0140788.g018
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 27 / 33
i. The Eocene faunas are dominated by lucinid bivalves and large gastropods, namely the glob-
ular Elmira and the tall abyssochrysoids. Similar large gastropods, as well as the lucinid
Fig 19. Geologic ranges of mollusk genera from Cenozoic seeps in the Caribbean region.Note break in time scale below 40 Ma; dotted lines indicate
occurrences outside the seep environment; data for Bathynerita and ‘Calliotropis’ from [14], for Ascheria from [33].
doi:10.1371/journal.pone.0140788.g019
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 28 / 33
bivalves, are known from various Cretaceous to Eocene seep deposits worldwide [34, 35, 43,
44, 68], and S. Kiel and T. Nobuhara, unpublished observations]. The disappearance of the
large gastropods from the Caribbean seeps after the Eocene coincides with their disappear-
ance worldwide, while the lucinid bivalve genera survived into the Oligocene and Miocene,
both in the Caribbean region and in general. Thus the Eocene Caribbean seep fauna is clearly
derived from, and shares a common fate with, the global seep fauna of its time.
ii. The Oligocene to Miocene Caribbean seep faunas consist partly of members of widely dis-
tributed lucinid genera [35], and they also saw the rise of the Pleurophopsis-Cataegis-fauna.
These taxa have not been reported from other well-studied seep faunas of this age, namely
in the western USA [69, 70], Japan [59, 71], and New Zealand [72]. However, this fauna
does show links to the Pacific Ocean, especially during the Oligocene, when Pleurophopsis
and other taxa reported here from Colombia are known from seep deposits in northern
Peru [15, 37].
iii. Arguably the most remarkable faunal change among Caribbean/Gulf of Mexico seep faunas
can be seen between the late Miocene and the modern fauna, when Pleurophopsis disap-
peared along with virtually all lucinid genera (Fig 19).
The latter is noteworthy because present-day Caribbean/Gulf of Mexico seeps are inhabited
mostly by a distinct group of medium-sized (up to 70 mm length) lucinids which so far have
no fossil record [35, 73, 74]. Although the fossil record currently lacks the resolution to narrow
down the exact timing of this extinction, it roughly coincides with the closure of the Isthmus of
Panama [75]. This event resulted in increasingly oligotrophic conditions in the Caribbean Sea
[76, 77] and it is tempting to speculate that this had a negative effect on the large lucinids: Luci-
nids are only facultative chemosymbiotic and derive a significant proportion of their nutrition
from suspended organic matter [78]. Thus a decrease in food availability may have led to the
disappearance of the large lucinids that were used to more eutrophic conditions, and those that
replaced them could not realize such large size. Indeed, at least two of the large lucinid genera
that inhabited Miocene seeps in the Caribbean region (Elliptiolucina andMeganodontia) are
today restricted to the more eutrophic waters of the central Indo-Westpacific [79, 80]. To the
best of our knowledge, there are no studies on the size of suspension feeders on either side of
the Isthmus of Panama before and after its closure, but a general decrease in the maximum size
of tropical lucinid bivalves through the Cenozoic was attributed to decreasing productivity
[81]. Likewise, the generally larger body size among soft-bottom feeding guilds in the western
compared to the eastern North Atlantic Ocean was considered related to the higher productiv-
ity of the western North Atlantic Ocean [82].
Acknowledgments
SK thanks Amanda Millhouse and TomWaller (Washington, DC), Greg Dietl, Leslie L. Ski-
binski, and Judith Nagel-Myers (Ithaca), and Walter Etter and Olivier Schmidt (Basel) for
access to collections under their care, arranging the loans, and their hospitality during my visits
to the USNM, PRI and NMB. We thank Manuel Iturralde-Vinent (Havanna) for help with
Cuban geology, Oliver Macsotay (Valencia) for help with Venezuelan geology, Donald McNeill
(Miami) for help with the geology of the Dominican Republic, Gerhard Hundertmark (Göt-
tingen) and Christian Stocker (Vienna) for photography, Andreas Pack and Dennis Kohl (Göt-
tingen) for stable isotope analyses, Brigitte Dietrich (Göttingen) for her patience and help with
Sr isotope analyses, John McArthur (London) for providing the LOWESS 5.0 look-up table,
Elena Krylova (Moscow) for discussions on vesicomyid bivalves, John Taylor and Emily Glover
Fossil Caribbean Seep Faunas
PLOS ONE | DOI:10.1371/journal.pone.0140788 October 15, 2015 29 / 33
(London) for advise on lucinid bivalves, Emilio Garcia (Lafayette) for providing extant material
from the Gulf of Mexico, Adiël Klompmaker (Gainesville) for help identifying crustacean frag-
ments, Jim Goedert (Wauna) for critically reading an early version of this manuscript, and
Greg Dietl and three anonymous referees for their constructive criticism that very much
improved this manuscript.
Author Contributions
Conceived and designed the experiments: SK. Performed the experiments: SK. Analyzed the
data: SK BTH. Wrote the paper: SK.
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Fossil Caribbean Seep Faunas
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