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3 Department of Biological Sciences, Kent State University, Kent, Ohio 44242; 4 New York Botanical Garden, Bronx, New York 10458-5126; 5 United States Geological Survey, National Center, MS 926A, Reston, Virginia 22092
Received for publication July 13, 1999. Accepted for publication January 3, 2000.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSCOMPOSITIONDISCUSSIONLITERATURE CITED |
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Key Words: Cuba • Eocene • palynoflora • Saramaguacán Formation
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSCOMPOSITIONDISCUSSIONLITERATURE CITED |
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; Hollick, 1928
; Leon, 1929
), and some later ones published on individual Mesozoic plant fossils (Piazopteris; Areces-Mallea, 1991
; Vakhrameev, 1965, 1966
), there have been no sustained investigations on plant megafossil floras from Cuba in modern times (Borhidi, 1996
, p. 257).
A study of plant microfossils was begun by Areces-Mallea (1985, 1987, 1988, 1989, 1990
; Areces-Mallea and García Rodríguez, 1990
), and in 1993 the samples were sent to the KE (Kent State University) palynology laboratory for completion of the project. The material consisted of unprocessed rock, slides of processed material, and photographs. The palynomorphs were from a core 
30 cm long from the Saramaguacán Formation in the Sierra de Maraguán in east-central Cuba (Provincia de Camagüey), 2.5 km north of the road between Guanábana (Camagüey) and Sibanicú; Figs. 78, 79, 81). A buff-colored section of the core about 8 cm long yielded the plant microfossils.
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, personal communication) provides the following information on the age and stratigraphic position of the Saramaguacán Formation. The stratigraphic sequence is described as follows: Magantilla Formation (Miocene)
Saramaguacán Formation
San Jacinto member
Santa Rosa member
El Capataz member
Guanábana member
Maraguán Formation (middle Eocene)
The Maraguán Formation is considered middle Eocene in age based on planktic and benthic foraminifera. The samples are part of the El Capataz member of middle late Eocene age because the benthic foraminifera Nummulites floridensis is present. This species is known also from the Santa Rosa member at the type section of the Saramaguacán Formation, and the Paleocene to middle Eocene benthic foraminifera Ranikotalia (Nummulites) bermudezi is known from the San Jacinto member.
Study of the Saramaguacán assemblage is complicated by the fact that several of the original specimens shown in the photographs are on slides presently in Cuba and are not available for study. In some cases similar specimens were recovered from material processed at KE and from which the morphology and size of the specimens in Cuba could be determined. Others, however, had to be described and identified from the photographs alone. In these instances, the subtle differences between colporate and colpor(oid)ate (pores poorly developed), psilate-scabrate-microreticulate, and estimates of size and other quantitative features were often difficult to make depending on the preservation, orientation of the grains, and the focal level of the photographs. In cases where the morphology is distinctive, and similar to that of previously named specimens described from other Cenozoic palynofloras in the Gulf-Caribbean region, those names are used at the appropriate taxonomic level [viz., genus or genus/species; e.g., Undulatisporites, Pteris dentata (Nagy) Frederiksen, Arecipites, Liliacidites, etc.]. In instances where identity to previously described taxa is not clear from the photographs, the morphologically-based nomenclature developed by van der Hammen (1956)
is used (e.g., Peripollenites, Retiatricolpites). Eventually it may be possible to apply a more uniform nomenclature if the actual specimens become available for examination, but this appears unlikely in the near future. Considering the biogeographic importance of Cuba, the dearth of recent information on its vegetational, environmental, and geological history (there is a relatively recent geologic map of Cuba; Borkowska et al., 1988
) and the fact that the available data do provide some insight on these histories, the results and preliminary interpretations are presented pending access to additional material.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSCOMPOSITIONDISCUSSIONLITERATURE CITED |
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. Samples at the CIDP (Centro de Investigación y Desarrollo del Petróleo, Havana, Cuba) were processed through HCl and HF to dissolve minerals. Schultze's reagent followed by KOH was used to remove organic debris. Palynomorphs were concentrated by flotation in a ZnCl2 solution (specific weight 1.96), then stained with safranin and mounted in glycerine jelly. All specimens were examined and photographed at 400x magnification with a MBI-15 (Russian) microscope using ORWO NP-15 black and white film under blue light. Samples at KE were processed by standard methods described by Gray (1965)
and Traverse (1988)
. The sediments were processed through HCl, HF, and HNO3 to remove mineral and organic debris, then acetolyzed (nine parts acetic anhydride to one part concentrated H2SO4), preceeded and followed by rinses in glacial acetic acid. Some residues were mounted unstained in glycerine jelly while others were stained with safranin and mounted in Protexx. The specimens at KE were examined and photographed at 400x magnification with a Leitz Orthoplan Photomicroscope using Ilford black and white film. Identifications were made by comparisons to a pollen and spore reference collection of 24 000 slides and a stratigraphic collection of previously studied Tertiary palynofloras from the Gulf/Caribbean region. Other identifications, primarily of distinctive morphological types from the southeastern United States, northern Mexico, Jamaica, Panama, and northern South America, are based on descriptions and illustrations in the literature. Location of specimens on the slides is by ESF (England Slide Finder) coordinates. In the descriptions "Photograph" designates microfossils presently available only from pictures provided by Areces-Mallea. Slides, residues, unprocessed samples, negatives, and duplicate prints are in the palynological collections at KE; other materials are in the Museo Nacional de Historia Natural in Habana, Cuba. |
COMPOSITION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSCOMPOSITIONDISCUSSIONLITERATURE CITED |
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Verrucatosporites usmensis van der Hammen (Figs. 2, 3). Reniform; monolete, laesura located on concave side of spore, straight, 25 µm long, narrow, extending 2/3 length of spore; inner margin entire(?); verrucate, verrucae conspicuous, shape irregular, 2–3 µm in diameter; size 35 x 25 µm. Photograph.
These spores are also widespread in Gulf/Caribbean Cenozoic deposits (Germeraad, Hopping, and Muller, 1968
). They are produced by many genera in several families of ferns and have broad stratigraphic and geographic ranges.
Triletes
Lygodiumsporites adriennis (Potoníe and Gelletich) Frederiksen (Fig. 4). Oblate, amb triangular, apices rounded; trilete, laesurae straight, 15 µm long, extending 3/4 distance to spore margin; laevigate; wall 2 µm thick; size 45 µm. Photograph.
These spores are also encountered in the literature under the name Deltoidospora. The particular type described here is more similar to the modern Acrostichum than to typical Lygodium but the biological affinities are uncertain.
Trilete fern spore type 1 (Fig. 5). This spore is similar to Lygodiumsporites adriennis and may represent the same taxon but it is noticeably smaller (30 µm). Photograph.
Undulatisporites concavus Kedves (Figs. 6, 7). Oblate, amb concavo-triangular, apices rounded; trilete, laesurae slightly sinuous, 15 µm long, extending nearly to spore margin, inner margin entire, bordered by lip 2–3 µm in width; indistinctly verrucate; wall 2 µm thick; size 32 µm. Photograph.
Similar spores are described by Frederiksen (1980a
, p. 31, plate 2, fig. 6) from the upper Eocene Jackson Group of the southeastern United States.
cf. Pteris dentata (Nagy) Frederiksen (Pteridaceae; Fig. 8). This specimen is fragmentary but enough remains to recognize it as a spore of the tropical fern Pteris. Frederiksen (1980a
, p. 32, pl. 3, figs. 5, 6) described similar spores from the Jackson Group (upper Eocene) of the southeastern United States, and they are frequent in Tertiary deposits throughout the Gulf-Caribbean area. Photograph.
Monosulcates
Arecipites (Palmae; Figs. 9–15). Greatest diameter often slightly off of equator (grains then wedge-shaped); monosulcate, sulcus straight, narrow, 30–40 µm long, extending entire length of grain, inner margin entire to slightly lobate to dentate; finely reticulate, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm or less); tectate-perforate, columellae just evident in median optical section (at 400x magnification), wall 1–2 µm thick; size 42–54 x 25–32 µm. Slide A4, ESF X-36 (Fig. 10); Slide A2, ESF Z-36,1; slide Y-25, S-32; and photograph.
Palm pollen is the most diverse and numerically the most abundant plant microfossil in the Saramaguacán assemblage. Although several studies have been made on the pollen of modern palms (Harley, 1989, 1990
; Harley and Morley, 1995
; Thanikaimoni, 1966
), the size of the family (estimated 2500 species), its pantropical distribution, and the subtle morphological differences in pollen between many taxa still make it impossible to identify most fossil specimens to genus. Among the Saragaguacán fossils there are slight differences in size, wall thickness, and distinctiveness of the microreticulum and all specimens are presently referred to the form genus Arecipites.
Liliacidites (Figs. 16, 17). Monosulcate, sulcus straight, narrow, 33 µm long, extending nearly entire length of grain, inner margin entire to slightly dentate due to overlying sculpture elements; reticulate, muri smooth, sinuous, width (1 µm) considerably less than diameter of lumina (4–5 µm) producing a delicate, open reticulum; tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 1–2 µm thick; size 42 x 18 µm. Photograph.
Monosulcate pollen of this type has not been described from the Paleogene of the southeastern United States or from northern South America. Despite the etymology of the generic name its affinities can only be ascribed to the monocotyledons (Liliaceae, Amaryllidaceae, Bromeliaceae, et al.).
Retimonocolpites type 1 (Figs. 18, 19). Monosulcate, sulcus straight, 50 µm long, extending entire length of grain, inner margin dentate due to overlying sculpture elements, narrow margo formed by finer sculpture bordering sulcus; reticulate, muri smooth, slightly sinuous, width (1 µm) narrow in relation to diameter of lumina (5 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 2 µm thick; size 75 x 40 µm. Slide A4, ESF S-25; photograph.
González-Guzmán (1967
, pp. 51–52, pl. XXV, figs. 2, 2a) describes and illustrates a specimen from the lower to middle Eocene of the Tibú area of Colombia that appears similar to the Saramaguacán specimen.
Retimonocolpites type 2 (Figs. 20, 21). This specimen differs from R. type 1 in being distinctly smaller (45 µm). Photograph.
Retimonocolpites type 3 (Figs. 22, 23). This specimen is distinguished by the open and fine reticulum and its comparatively small size (30 µm). Photograph.
Retimonocolpites type 4 (Fig. 24). This specimen is small (20 µm) and densely microreticulate. Photograph.
Retimonocolpites(?) type 5 (Fig. 25). The distinguishing features of R.(?) type 5 are the apparent small echinae (e.g., evident along the bottom margin of the specimen illustrated). Slide X24, ESF P-34,2–4.
Tricolpates
Cupuliferoidaepollenites liblarensis (Thompson) Potonié (Fig. 26). Prolate; tricolpate, colpi equatorially arranged, meridonallly elongated, equidistant, straight, 23 µm long; psilate to faintly scabrate; tectate, wall homogeneous in median optical section (at 400x magnification), moderately thick (2 µm); size 26 x 16 µm. Slide A4, ESF R-27.
A similar specimen is described and illustrated by Frederiksen (1980a
, pp. 46–47, pl. 9, fig. 23) from the Upper Eocene Jackson Group of the southeastern United States. Its biological affinity is unknown but possibly with the Fagaceae.
Fraxinoipollenites cf. F. scoticus (Simpson) Frederiksen (Fig. 27). Prolate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 30 µm long, inner margin entire; reticulate to slightly striato-reticulate, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, individual columellae just evident in median optical section (at 400x magnification), wall 1 µm thick; size 33 x 24 µm. Slide A1, ESF N-40,2.
Frederiksen (1980a
, p. 48, pl. 10, fig. 18) describes and illustrates a similar specimen from the upper Eocene Jackson Group of the southeastern United States. Despite the etymology of the generic name the biological affinity is unknown and probably not with Fraxinus.
Echitricolpites (Fig. 28). Prolate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 22 µm long, inner margin slightly dentate due to overlying sculpture elements; minutely and densely echinate, echinae short (1 µm or less); tectate, wall homogeneous in median optical section (at 400x magnification), 1–2 µm thick; size 35 x 30 µm. Slide X24, ESF N-38,2.
Retitricolpites type 1 (Fig. 29). Prolate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 24 µm long, costae colpi 2 µm wide; finely reticulate, muri smooth, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae evident in optical section (at 400x magnification), short, relatively thick (0.5 µm), wall 1 µm thick; size 36 x 26 µm. Slide A4, ESF X-40,2.
Retitricolpites type 2 (Fig. 30). Prolate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, 50 µm long, narrow costae colpi 1 µm wide, inner margin slightly dentate due to overlying sculpture elements; finely reticulate, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 1 µm thick; size 54 x 34 µm. Slide X24, ESF Q-34.
This specimen differs from R. type 1 in being larger (54 µm vs. 36 µm) and the wall is thinner relative to the size of the grain.
Retitricolpites type 3 (Fig. 31). Prolate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 27 µm long, inner margin dentate due to overlying sculpture elements; finely reticulate, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), long (2–3 µm), wall 3 µm thick; size 46 x 30 µm. Slide Y25, ESF R-40,4
Retitricolpites type 4 (Fig. 32). Prolate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 39 µm long, inner margin slightly dentate due to overlying sculpture elements; finely reticulate to striato-reticulate, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), short, broad, apices rounded, wall 1 µm thick; size 54 x 32 µm. Slide X24, ESF M-36,3–4.
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Retitricolpites type 6 (Figs. 37, 38). Oblate; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, 15 µm long (apex to equator), tapering to acute apex, margin entire; psilate (microreticulate?); tectate (tectate-perforate?), columellae evident in median optical section (at 400x magnification), wall 1–1.5 µm thick; size 30 (Fig. 38) to 50 µm (Fig. 37). Photograph.
Reticulataepollis cf. intergranulata (Potonié) Krutzsch (Figs. 35, 36). Oblate-spheroidal, amb circular; tricolate, colpi equatorially arranged, meridionally elongated, equidistant, short, 5 µm (apex to equator), inner margin entire; reticulate, muri smooth, sinuous, width of muri (1 µm) narrow in relation to diameter of lumina (2–3 µm), lumina polygonal, floor granular; tectate-perforate, columellae evident in median optical section (at 400x magnification), long (3 µm), wall 3 µm thick; size 30 µm. Photograph.
Otherwise comparable specimens among modern and fossil taxa often have a pore along the colpus but this feature is obscure in the photograph. Frederiksen (1980a
, p. 60, pl. 14, figs. 23–26) describes and illustrates similar specimens from the upper Eocene of the southeastern United States.
Tricolporoidates
Retitricolporoides type 1 (Figs. 39–41). Prolate; tricolporoidate, colpi equatorially arranged, meridionally elongated, equidistant, straight, narrow, 34 µm long, extending nearly entire length of grain, inner margin entire, costae colpi 3 µm wide; reticulate, reticulum regular, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), apices rounded, wall 2 µm thick; size 35 x 28 µm. Photograph.
This generalized type of prolate, tricolpor(oid)ate, reticulate grain is widespread throughout the Cenozoic in the Gulf/Caribbean region. It is produced by members of the Anacardiaceae, Euphorbiaceae, Rutaceae, and others. If a distinct pore is present, as there appears to be in a similar grain illustrated in Fig. 50, the moderately large size and comparatively heavy wall suggest possible affinities with Coccoloba (Polygonaceae).
Retitricolporoidies type 2 (Figs. 42, 43). This specimen is similar to R. type 1 but it has a slightly thinner wall and is smaller (25 µm). Photograph.
Retitricolporoidies type 3 (Figs. 44, 45). Prolate; tricolporoidate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 34 µm long, extending 3/4 length of grain, inner margin slightly dentate due to overlying sculpture elements; finely reticulate and in places arranged into a slightly swirled pattern, muri smooth, slightly sinuous, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 2 µm thick; size 40 x 32 µm. Photograph.
Striatricolpites cataumbus González Guzmán (Leguminosae, Caesalpinioideae; Figs. 46, 47). Prolate; tricolporoidate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 30 µm long, extending 3/4 to nearly entire length of grain, inner margin entire; striate, striae sinuous, densely arranged; tectate, wall 1 µm thick; size 40 x 27 µm. Photograph.
These grains are similar to those produced by Crudia although the biological equivalency of the modern taxon and these ancient microfossils is not certain. The microfossils are frequent but not abundant in early and middle Tertiary deposits of the Gulf-Caribbean region, and megafossils (fruits) have been found in the Eocene of the southeastern United States (Herendeen and Dilcher, 1990
).
Tricolporates
Retitricolporites type 1 (Fig. 49). Prolate; tricolporate, colpi equatorially arranged, meridionally elongated, equidistant, straight, 42 µm long, extending 3/4 to nearly entire length of grain, inner margin entire, narrow costae colpi (1–2 µm wide), pores situated at mid-point of colpus, equatorially elongated (1 x 4 µm); finely reticulate, muri smooth, straight, width of muri approximately equal to diameter of lumina (1 µm); tectate-perforate, columellae just evident in median optical section (at 400x magnification), wall 2 µm thick; size 48 x 27 µm. Slide A4, ESF V-27,1–3.
Retitricolporites type 2 (Fig. 48). Prolate; tricolporate, colpi equatorially arranged, meridionally elongated, equdistant, straight 45 µm long, narrow costae colpi (1–2 µm wide), pores situated at midpoint of colpus, equatorially elongated, 4 x 9 µm; finely reticulate to striato-reticulate, muri smooth, slightly sinuous, width of muri approximately equal to diameter of lumina (1 µm) to lumina slightly elongated; tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 1 µm thick; size 60 x 34 µm. Slide X24, ESF L-35,4.
Retitricolporites type 3 (Fig. 50). This grain is similar to those described under Retitricolporoidites but a faint pore is more evident (center of left colpus in Fig. 50). Photograph.
Trisyncolporate
Myrtaceidites cf. parvus Cookson and Pike (Myrtaceae; Fig. 51). Oblate, amb triangular, apices acute; trisyncolporate, colpi equatorially arranged, meridionally elongated, equidistant, 14 µm long (apex to equator), straight, margin slightly diffuse, fused at the poles, pores indistinct; scabrate; tectate, size 25 µm. Photograph.
These grains are similar to those produced by Eugenia, Myrcia, and other genera of the Myrtaceae but they can not be assigned to any one modern genus. They are frequent but never abundant in the Gulf/Caribbean Tertiary. The Saramaguacán specimens differ from M. parvus described and illustrated by Frederiksen (1980a
, p. 58, pl. 14, figs. 9–11) in being more distinctly triangular and scabrate.
Brevitricolpates/Brevitricolporates
Bombacadites cf. tilioides Krutzsch (Bombacaceae; Figs. 52–55). Oblate, amb triangular, apices rounded; tricolporate, colpi equatorially arranged, meridionally elongated, equidistant, situated in interapical area, short (6 µm, apex to equator), costae pori (3 µm wide), pores situated at midpoint of colpus, meridionally elongated; reticulate in polar region grading to more finely reticulate/scabrate at apices; tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 2 µm thick; size 48 µm. Photograph.
The biological affinities of these grains are with the Bombacaceae which is presently a family typical of warm-temperate to tropical environments. They are common in the Saramaguacán flora, and similar microfossils are frequent in the Tertiary of the Gulf/Caribbean region. Frederiksen (1980a
, p. 59, pl. 14, fig. 15) reports pollen of B. nacimientoensis (Anderson) Elsik from the Eocene of the southeastern United States; [see also Elsik (1968)
for a record from the Paleocene Rockdale lignite of Texas]. Germeraad, Hopping, and Muller (1968)
report a different form [B. annae (van der Hammen) Leidelmeyer] in the Paleocene of the Maracaibo region of Venezuela. Because the Saramaguacán form slightly differs from typical B. tilioides, Areces-Mallea (1985)
described it as a different species (B. mirabilis Areces). González Guzmán (1967)
does not list it for the Eocene of the Tibú area of Colombia, but it is reported by Lorente (1986)
for the Upper Tertiary of Venezuela. Generally, the Saramaguacán specimens are more similar to those from the southeastern United States than to those from northern South America.
B. type 1 (Fig. 56). This specimen differs from B. tilioides in being more uniformly and finely reticulate. If the reticulum is interpreted as uniform across the entire surface the specimen would be identified as B. nanobrochatus Frederiksen. If the reticulum is viewed as slightly finer at the corners it would be B. fereparilis Frederiksen. Both species, like B. tilioides, are known from North America (Frederiksen, 1983
). Slide A1, ESF A-24,4.
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, p. 170, pl. 3, fig. 31) from the Paleogene of the southeastern United States. Photograph. Basopollis/cf. Choanopollenites sp. (Fig. 58). Oblate, amb triangular, apices acute; tricolporate, colpi equatorially arranged, meridionally elongated, equidistant, situated at apices, straight, short (6 µm), vestibulate, conspicuously protruding (7–8 µm), pores situated a midpoint of colpi, distinct annulus (3–4 µm wide); finely verrucate/fossulate; tectate-perforate, wall 2 µm thick; size 32 µm. Photograph.
This grain belongs to the Normapolles group of pollen, an extinct assemblage with affinities possibly with the Juglandaceae, and characteristic of eastern North America and western Europe during the Cretaceous and Paleogene. It was described from Cuba as Basopollis by Areces-Mallea (1989)
, while Frederiksen (personal communication) believes it is similar to Choanopollenites as described by Tschudy (1973)
. It represents one of the several elements of the Cuban Eocene flora with affinities to North America.
Retibrevitricolpites (Figs. 59, 60). Oblate-spherioidal, amb circular; tricolpate, colpi equatorially arranged, meridionally elongated, equidistant, short (2–3 µm apex to equator), inner margin entire, surrounded by costae colpi (2 µm wide); finely reticulate, muri smooth, straight, width of muri approximately equal to slightly wider than diameter of lumina (1 µm); tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 2 µm thick; size 25 µm. Photograph.
Porocolpopollenites (Fig. 61). Oblate, amb oval-triangular, apices acute; tricolporate, colpi equatorially arranged, meridionally elongated, equidistant, situated at apices, straight, short (3 µm apex to equator), pores situated at midpoint of colpi, surrounded by costae porae 3 µm wide; finely reticulate; tectate-perforate, columellae evident in median optical section (at 400x magnification), wall 1 µm thick; size 32 µm. Photograph.
This grain is similar to those of the modern genus Symplocos described by Frederiksen (1980a)
from the Eocene of the southeastern United States. It is similar also to one listed as "unidentified porocolpate pollen" by Elsik and Dilcher (1974
, pl. 29, figs. 84–85) from the middle Eocene of Tennessee.
Monoporate
Graminidites gramineoides (Meyer) Krutzsch (Gramineae; Fig. 62). Spherical, amb circular; monoporate, pore circular, 3 µm in diameter, inner margin entire, surrounded by annulus 2 µm wide, outer margin diffuse; psilate to scabrate; tectate, wall 1–2 µm thick, homogeneous in median optical section (at 400x magnification); size 30 µm. Photograph.
Pollen of the Gramineae (also known in the stratigraphic literature as Monoporites annuloides van der Hammen; see, e.g., Germeraad, Hopping, and Muller, 1968
, p. 294, pl. 3, fig. 3) is common in parts of the Saramaguacán section, as judged from the number of photographs of specimens processed at Havana, but none were found in the material processed in the KE laboratory so percentages could not be calculated. Certainly, ferns, grasses, palms, and Bombacaceae were prominent in the middle Eocene vegetation of east-central Cuba.
Diporate
Psiladiporites redundantis González Guzmán (Moraceae; Fig. 63). Elliptical, amb oval; diporate, pores situated at opposite poles of the grain, circular, 3 µm in diameter, sourrounded by faint annulus 1 µm in diameter; scabrate; tectate, wall 1 µm thick, homogeneous in median optical section (at 400x magnification); size 23 x 20 µm. Photograph.
These grains are similar to ones produced by several members of the Moraceae. In addition to the occurrence in South America (González Guzmán, 1967
), similar grains are known from the Eocene of Panama (Graham, 1985
, p. 518–519, fig. 58) and from Paleogene sediments of the Gulf Coast of the southeastern United States [Frederiksen, 1988
, p. 48, pl. 1, fig. 17; Elsik, 1974
, pl. 2, figs. 35, 36 reports a somewhat similar type from the Eocene of the Texas Gulf Coast as Ficus? Spp. (Moraceae)].
Triporates
Brosipollis cf. striata Frederiksen (Fig. 64). Oblate, amb triangular; triporate, pores situated at apices of grain, circular to oval, 4 µm in diameter, equatorially arranged, equidistant, protruding 5 µm, surrounded by annulus 2–3 µm wide; scabrate to possibly faintly striate; tectate, wall homogeneous to columellae just evident in median optical section (at 400x magnification), 2 µm thick; size 33 µm (excluding pores). Slide Y25, ESF U-38,3.
Frederikson (1988
, p. 52, pl. 3, figs. 23–26; pl. 4, figs. 1–3) describes the species from the Paleogene of the Gulf Coast of eastern United States and considers its affinities probably to be with Bursera, which has finely striate pollen.
Triporopolllenites type 1 (Fig. 65, 66). Spherical, amb circular; triporate, pores equatorially arranged, equidistant, circular (3 µm in diameter), inner margin entire, surrounded by costae pori (1–2 µm wide), outer margin of annulus slightly diffuse; scabrate; tectate, wall 2 µm thick; size 45 µm. Photograph.
Triporopollenites type 2 (Figs. 67, 68). Oblate-spheroidal, amb circular; triporate, pores equatorially arranged, equidistant, circular, 3 µm in diameter, inner margin entire, surrounded by costae pori 2 µm wide; scabrate; tectate, wall 2 µm thick, columellae evident in median optical section (at 400x magnification); size 40 µm. Photograph.
These grains are similar to Celtis (Celtipollenites) listed by Frederiksen (1988
, pl. 3, figs. 7–11) from the upper middle Eocene Lisbon Formation of southeastern United States.
Periporate
Lymingtonia cf. L. rhetor Erdtman (Nyctaginaceae; Figs. 69, 70). Oblate, amb polygonal (eight sided); periporate, pores equally spaced, circular, 4 µm in diameter, inner margin entire; scabrate (or psilate with heads of columellae apparent through thin tectum); tectate, wall 2–3 µm thick; size 45 µm. Photograph.
Frederiksen (1980a
, p. 44, pl. 9, figs. 1–3; see also Elsik and Dilcher, 1974
) describes and illustrates a similar specimen from the upper Eocene Jackson Group of the southeastern United States. The grains are similar to some Nyctaginaceae (e.g., Phaeoptilum).
Pericolporate
Pericolporites (Figs. 71, 72). Oblate spheroidal, amb circular; pericolporate, apertures equidistant, colpi 20 µm long (apex to mid-point of pore), margin slightly diffuse, tapering to acute apex, pores situated at mid-point of colpus, circular, 3 µm in diameter, inner mrgin entire, annulus 2–3 µm wide; scabrate; tectate, wall 2 µm thick, homogeneous to columellae just evident in median optical section (at 400x magnification); size 45 µm. Photograph.
Stephanoporate
Malvacipollis tschudyi Frederiksen (Figs. 73–75). Oblate-spheroidal to spherical, amb circular; stephanoporate, pores circular, 2 µm in diameter, inner margin entire, equidistant, surrounded by narrow costae pori; echinate, echinae short (2 µm), straight; tectate, wall 1–2 µm thick, columellae just evident in median optical section (at 400x magnification); size 30–35 µm (excluding spines); Slide Y25, ESF U-38,2; and photograph.
This pollen type is common in the fossil assemblage but it is not always possible to determine aperture number and arrangement from those represented only by photographs. The biological affinities are possibly with the Malvaceae.
Nonaperturate
Retipollenites cf. confusus González Guzmán (Figs. 76, 77). Spherical, amb circular; nonaperturate; reticulate, reticulum coarse (open), heavy, muri thick (2 µm), flat, smooth, slightly sinuous, lumina 3–4 µm in diameter; tectate-perforate, columellae coarse (clearly evident median in optical section at 400x magnification), spaced 3–4 µm, 3 µm long; size 45 µm. Photograph.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSCOMPOSITIONDISCUSSIONLITERATURE CITED |
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). The models of Pindell and Barrett (1990)
and Pindell (1994)
are widely accepted, as are those derived from earlier, unpublished versions (e.g., Ross and Scotese, 1988
), although criticisms and modifications have recently been proposed (Iturralde-Vinent, 1994
; Meschede, 1998
; Meschede and Frick, 1998
; G. Draper, Florida International University). With regards specifically to Cuba its history is becoming more clear, especially as earlier reconstructions showing movement of the island over great distances from the south are discarded. For example, Corrall (1939)
shows Cuba and other islands of the Greater Antilles located along the north coast of South America as recently as the late Miocene (Borhidi, 1996
, p. 257).
The current concensus is that western and central Cuba were separate until early to middle Eocene time. The northern part consisted of the Bahama Bank, a continental margin that was composed of Jurassic to Cretaceous shallow, continental platform to deeper-water, continental rise deposits; the southern part consisted of a Cretaceous volcanic island arc (Draper and Barros, 1994
; Lewis and Draper, 1990
). The arc collided with the continental margin in early to middle Eocene time causing widespread thrust faulting and folding of the Bahamian sediments and the emplacing of both ocean crust and the arc onto the Bahamian margin.
The tectonic evolution of the Oriente region (Holguin-Granma-Santiago-Guantanamo provinces; Fig. 78) is still controversial. The ophiolites (ocean floor material) seem to have been emplaced at the very end of the Cretaceous onto arc crust rather than continental crust. It is likely that Oriente was joined to northern Hispaniola and formed a separate block that did not dock against central Cuba until the Eocene (G. Draper, Florida International University). The block includes the present Sierra Maestra region (Fig. 79). Since the middle Eocene Cuba has mostly been tectonically quiescent (Draper and Barros, 1994
). The Saramaguacàn locality is west of the suture and was part of the island arc. Hispaniola separated in the middle to late Eocene with activation of the Cayman Trough fault system. The on-continent continuation of the Cayman Trough is the Polochic-Montagua fault system of northeastern Guatemala (Fig. 79).
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) and often consitutes 90% of palynofloras in lignites deposited under brackish-water conditions. Earlier, in the Paleocene and early Eocene, a different pollen type (Brevitricolpites variabilis) often reaches these same percentages in brackish-water lignites and presummedly it is the ecological equivalent of Rhizophora. Neither Rhizophora nor B. variabilis pollen was recovered from the Saramaguacán flora. The absence of mangroves, the composition of the flora, the light brown color and fine-grained texture of the sediments, and the geologic history indicates the Saramaguacán assemblage represents an inland swamp or marsh community growing along the northeastern margin of the proto-Cuba island arc which was then near its present position.
Paleoclimates
Relatively little can be said about the middle Eocene terrestrial climates of Cuba based on plant microfossil evidence because the palynomorphs mostly can not be referred to modern taxa. Even when generic identifications are possible it is not certain that these ancient entities are biologically equivalent or had the same ecological requirements as similar modern forms. Nonetheless, several lines of independent evidence provide an approximation of terrestrial Eocene paleoclimates in the northern Caribbean region. The composition and numerical representations of the flora are shown in Table 1. The most abundant microfossils, based on counts of processed material at KE, and on the number of photographs from samples presently housed in Cuba, are Palmae, ferns, Bombacaceae, and grasses. Two genera that can most reliably be assigned to modern genera are the tropical fern Pteris and the primarily Amazonian rain forest genus Crudia. Collectively, the composition of the palynoflora suggests a warm-temperate to tropical climate.
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). This curve is based on 18O/16O ratios in the shells of marine invertebrates and is, therefore, independent of reconstructions based on fossil plant evidence. More 18O is taken up as the water cools, and deep-sea cores provide a record of the ratios from the past 100 Ma. The curve clearly shows warm climates only slightly cooler than those of the early Eocene thermal maximum. Thus, composition, associated floras, and context information are all consistent in suggesting warm-temperate to tropical climates in the middle Eocene of the Caribbean region.
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Table 1 shows that of the 46 palynomorphs recognized for the Saramaguacán flora, 18 are widespread, 16 are similar to ones reported from the southeastern United States, and only one (Retimonocolpites type 1) is similar to a form described from northern South America. Further comparisions with regions in Mexico, Central America, and other islands of the Antilles (Fig. 81) are constrained by the mostly smaller size and the few middle to late Eocene floras available. The plant microflora of the Guys Hill Member of the Chapelton Formation in Jamaica (Graham, 1993
) is geographically the closest to the Saramaguacán flora and it is about the same age (middle Eocene). However, it was deposited under different ecological conditions as evidenced by the presence of the mangrove Psilatricolporites crassus (Pelliceria) and several marine dinoflagellates. Deltoidospora (Lygodiumsporites), Arecipites (Palmae), and Bombacacidites are abundant in the Chapelton and Saramaguacán floras.
The Burgos Basin flora (Martínez-Hernández, Hernández-Campos, and Sánchez-López, 1980
) in northeastern Mexico (Fig. 81) is also a small assemblage with several palynomorphs similar to those from Saramaguacán. These include Monocolpopollenites (= our Arecipites, Fig. 11), Liliacidites (=possibly our Figs. 16, 17), Bombacacidites, Jussitriporites (=our Brosipollis cf. striata, Fig. 64), and Nudopollis (our Basopollis/cf. Choanopollenites, Fig. 58). The Burgos Basin flora differs in the presence of Ilexpollenites (Ilex) and Momipites (Juglandaceae, cf. Alfaroa, Engelhardia, Oreomunnea).
In the slightly younger middle(?) to late Eocene Gatuncillo flora (Graham, 1985
) in Panama there are several palynomorphs similar to those of the Saramaguacán and other Eocene floras to the north. These include Pteris, Lygodiumsporites (=Trilete fern spore type 3 in the Gatuncillo flora), Arecipites, Striatricolpites catumbus (=Crudia), Cyrtaceidites (=Eugenia/Myrcia), and Psiladiporites (=cf. Ficus). The Gatuncillo flora also includes the mangroves Pelliceria and Rhizophora indicating deposition under coastal brackish-water environments rather than the fresh-water swamp/marsh conditions of the Saramaguacán flora.
All of these floras, collectively and individually, are more similar to one another than to any floras of comparable age known from northern South America. In particular, the Normapolles Basopollis/cf. Choanopollenites (Areces-Mallea, 1990
) is a distinctive form characteristic of eastern North America and has not been reported from sites belonging to the Caribbean or other southern plates. These results are consistent with plate tectonic reconstructions showing the island arc and fragment comprising western and central Cuba as part of the North American plate, and the fragment presently constituting eastern Cuba as originating in the vicinity of the Yucatan Peninsula/northern Central America.
A point that can be raised for preliminary consideration is the extent of paleoendemism (Table 1). Endemics are a characteristic feature of the Caribbean islands. Borhidi (1996
, p. 216) gives the number of endemic plant taxa on Cuba as 3178 or 49.9% of the total flora and 53% of the native flora. Howard (1973)
lists 40 genera found only on Cuba. In all the Tertiary palynofloras studied from northern Latin America there are specimens from each assemblage that presently have not been found in any other. Of the 46 palynomorph types in the Saramaguacán flora 11 (24%) are unique to that flora. There is not a sufficient number of fossil floras known from the Caribbean Basin to determine which forms are likely paleoendemics. As more fossil floras are studied, however, it is worthwhile to track these unique forms which may eventually provide an approximation of the extent of endemism in the Antilles at different times in its history.
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FOOTNOTES |
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2 Author for reprint requests (e-mail: agraham{at}biology.kent.edu
).
6 Current address: Department of Geography, University of Tennessee, Knoxville, Tennessee 37996-1420.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSCOMPOSITIONDISCUSSIONLITERATURE CITED |
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