Pleistocene pteropod limestones dredged from the East Yucatan Scarf

Palaeogeography, Palaeoclimatology, Palaeoecology, 30(1980): 97--105

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© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

PLEISTOCENE PTEROPOD LIMESTONES DREDGED FROM THE EAST YUCATAN SCARP GIUSEPPE BUCCHERI, RAIMONDO CATALANO and BRUCE HEEZEN~-

Istituto di Geologia, Corso Tukory, 131 Palermo (Italy) Lamont-Doherty Geological Observatory, Palisades, N.Y. (U.S.A.) (Received October 9, 1979)

ABSTRACT Buccheri, G., Catalano, R. and Heezen, B., 1980. Pleistocene pteropod limestones dredged from the East Yucatan Scarp. Palaeogeogr., Palaeoclimatol., Palaeoecol., 30: 97--105. A pteropod-rich fauna represents the bulk of the Pleistocene rocks dredged along the East Yucatan Scarp from a depth of 500--700 m. Many of the 14 pteropod taxa and the two heteropod taxa identified occur also in analogous Quaternary associations from the Caribbean Sea and Mexico Gulf. Paleoecological and paleoclimatic analyses indicate:(a) the whole pteropod fauna is indigenous and lived in warm to temperate water; (b) the associated planktonic foraminifers confirm these indications. The pteropod sediments belong to the Globigerina calida calida subzone (Globorotalia truncatulinoides zone, Upper Pleistocene). Previous authors correlated the abundance of pteropods in the Caribbean during the past 120,000 years area with cold climate; in our Yucatan fauna, on the contrary, the abundance of pteropods s e e m s t o correspond to a warm-temperate climate.

INTRODUCTION

During a cruise of the R/V Eastward {March, 1972), two dredge hauls from depths of 500--700 m along the East Yucatan Scarp (Fig.l) yielded about 40 kg of cobbles and pebbles of Pleistocene limestone. These Fe-Mn encrusted fragments consist of well-bedded pteropod-bearing biocalcirudites and biocalcarenites in beds up to 15 cm thick; they are more or less weakly cemented and alternate in some samples with thin layers of calcilutite with planktonic foraminifera. The biocalcarenites and biocalcirudites are composed of indigenous and displaced biogenic components. The indigenous specimens, belonging to an open-shelf depositional environment, are represented almost entirely by pteropods and heteropods. Other molluscs (Limopsis minuta, Calliostoma sp., Ovulacteon meeki, Puncturella sp., Perotrochus amabilis, Pleurotoma sp.), brachiopods (Terebratulidae), corals, echinoids and otoliths are also present. Among the displaced components, most common are molluscs, such as

98

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Fig.1. Map showing locations of the dredged pteropod limestones.

Margarites aff. olivaceus margaritatus, Polinices draconis, Pteropurpura vokesae, Granulina aff. ovuliformis, Alvania sp., Hyalina aff. avenacea, Marginella sp., Arca sp., chitons (fragments), colonial corals (fragments), echinoids ("sand dollars"), worms, and foraminifers (Peneroplis sp., Lenticulina sp.). Some of the fossils are quite abraded but a few are well preserved. These materials come from reef or forereef depositional environments and were displaced from their original setting and transported down slope to a deeper, open marine environment. The calcilutites consist of a micritic matrix in which planktonic fossils are embedded. The sparse p t e r o p o d and the rich planktonic foraminiferal fauna are well preserved. These rocks, and their biogenic content, again indicate an open-shelf depositional environment. The preservation and abundance of pteropods and heteropods (constituting almost the 70% of the rock) gave us the o p p o r t u n i t y to study their paleontological composition, stratigraphic value and climatologic significance.

99 FAUNAL ANALYSIS From a taxonomic point of view, thirteen species and one subspecies of pteropods and two species of heteropods have been identified: Pteropoda Limacina inflata (d'Orbigny) Limacina bulimoides (d'Orbigny) Limacina lesueurii (d'Orbigny) L imacina trochif ormis (d'Orbigny) Creseis acicula Rang Hyalocylis striata (Rang) Styliola subula (Quoy and Gaimard) Clio pyramidata Linneo Clio cuspidata (Bosc) Diacria quadridentata (Lesueur) orbignyi (Rang) (Souleyet) Cavolinia longirostris (Lesueur) f. strangulata (Deshayes) Cavolinia inflexa (Lesueur) Cuvierina columneUa (Rang) Peraclis reticulata (d'Orbigny) Heteropoda Atlanta peronii Lesueur Atlanta cfr. quoyii Gray The bulk of the population is composed of Limacina inflata and Styliola subula (which represent about 60% of the biogenous fraction). Atlanta peronii, Limacina bulimoides, Limacina trochiformis, Diacria quadridentata orbignyi, Limacina lesueurii are abundant, while Cavolinia inflexa, Hyalocylis striata and Creseis acicula are scarce. Clio cuspidata and Peraclis reticulata are very rare. Recorded for the first time as fossils in the Caribbean area are: Atlanta peronii, Cavolinia longirostris f. strangulata, Cuvierina columnella, Clio cuspidata and Diacria quadridentata orbignyi. Some species, among which Limacina trochiformis, L. bulimoides, L. lesueurii, Creseis acicula and Clio cuspidata are believed to be chiefly epipelagic (Menzies, 1958; Rampal, 1975), whereas Clio pyramidata [here represented by three different forms: f. pyramidata (mainly), f. convexa, f. lanceolata] and Peraclis reticulata are believed to be chiefly mesopelagic (Tesch, 1946; Menzies, 1958, Rampal, 1975), and finally Styliola subula and Limacina inflata are believed meso- and infrapelagic (Rampal, 1975). COMPARISON WITH PTEROPOD ASSOCIATIONS OF THE ADJACENT AREAS The dredged fauna has been compared with Quaternary pteropod associations from the adjacent Caribbean areas studied by Herman (1971), Jung (1973) and Le Roy and Hodgkinson (1975). The faunal association known from the Caribbean Sea (Herman, 1971) consists of fifteen pteropod species but not one species of heteropod. It

100 differs from our fauna with the absence of heteropods and of Cavolinia longirostris, Hyalocy lis striata, Cuvierina columnella, Peraclis reticulata and for the presence of Diacria trispinosa, Creseis virgula constricta and Clio polita. The association from the Cariaco Trench at DSDP Site 147 (Jung, 1973) consists of fourteen pteropod species that, when compared with the Yucatan fauna, show some differences marked by the absence of Clio cuspidata, Diacria quadridentata orbignyi, Cuvierina columnella and of the heteropods; and by the presence of Creseis virgula conica, Creseis virgula constricta and Diacria trispinosa form major. The association from the northern Gulf of Mexico (Le Roy and Hodgkinson, 1975) consists of sixteen taxa and differs from the Yucatan fauna by the absence of species such as Atlanta quoyii (Heteropoda), Limacina bulimoides, Limacina trochiformis and Clio cuspidata (Pteropoda) and by the presence of Cavolinia uncinata, Clio balantium, Creseis virgula, Creseis virgula conica, Diacria trispinosa and Diacria trispinosa major. Notwithstanding the differences in provenance, lithology and depth, it is clear that: (a) our associations, and those described by the previous authors, show many forms in common and comparable species frequency; and (b) the number of individuals of pteropods in our samples appears greater than the medium value usually found by the other authors. STRATIGRAPHY

To define the stratigraphic position of these pteropods and heteropods more precisely we examined the associated planktonic foraminifers; the following were identified: G lobigerina calida calida Parker Globigerina bulloides d'Orbigny Globigerina rubescens Hofker G lobigerina pachyderma (Erhemberg) Globigerinoides ruber (pink) (d'Orbigny) G lo b igerino ides trilo bus (Reuss) G lobigerinoides elogantus (d'Orbigny) Globigerinoides tenellus Parker Globigerinoides conglobatus (Brady) G loborotalia truncatulinoides (d'Orbigny) G loborotalia truncatulinoides pachyteca Blow G loborotalia inflata (d'Orbigny) Globorotalia crassaformis crassaformis (Galloway and Wissler) Globorotalia crassaformis ronda Blow Globorotalia crassaformis oceanica Cushman and Bermtldez Globorotalia crassaformis viola Blow Globorotalia hessi Bolli and Premoli Silva Globorotalia menardii Parker, Jones and Brady Globorotalia scitula (Brady) G lo b igerinita glutinata (Egger) Hastigerina siphonifera involuta (Cushman)

101 Neogloboquadrina dutertrei (d'Orbigny) Orbulina universa d'Orbigny The presence of Globorotalia truncatulinoides, Globorotalia hessi and Globigerina calida calida indicates the Globigerina calida calida subzone (Globorotalia truncatulinoides zone) (see Bolli and Premoli Silva, 1973). PALEOCLIMATOLOGIC IMPLICATIONS Diacria q uadridentata and Cavolinia longirostris have been found in equatorial waters (Tesch, 1946); Atlanta peronii, Crescis acicula, Limacina bulimoides, Cuvierina columnella and Cavolinia inflexa were found in warmer seas (Tesch, 1946; Van Der Spoel, 1967) and Styliola subula is a common and ubiquitous thermophile species in the world oceans (Rampal, 1975). According to Chen and B~ (1964), Limacina bulimoides, Limacina inflata, Limacina lesueurii, Clio pyramidata and Styliola subula are subtropical, cold-tolerant forms, whereas Limacina trochiformis, Creseis acicula, Hyalocylis striata, Cavolinia inflexa and Cavolinia longirostris are subtropical, warm-tolerant forms. Clio pyramidata is found in temperate waters (Chen, 1968; Rampal, 1975). Thus, the whole Yucatan fauna assemblages studied here are regarded as belonging to warm-temperate waters based on the dominance of warm-water species and the absence of typical cold-water species such as Limacina retroversa and Limacina helicina (Tesch, 1946, Chen and B~, 1964; Van Der Spoel, 1967; Chen, 1968). Furthermore, among the foraminifera recognized here, Globigerina calida calida, Globigerina pachyderma (dextral coiling), Globorotalia menardii {very rare), Globigerinoides conglobatus, Globigerinoides ruber (pink) are considered to be warm- to temperate-water species, confirming the climatic inference already drawn from the pteropods. When compared with the standard climatologic curves used for the marine Pleistocene of the Caribbean area, the Yucatan fauna (belonging to the Globigerina calida calida subzone) appears to be included in the X zone (warm stage) of Ericson and Wollin (1968) and in the oxygen isotopic stage 5 (Emiliani, 1966, 1971) (Fig.2). In fact, according to R5gl and Bolli (1973), in the Caribbean, the G. calida calida subzone corresponds to the larger part of the X zone which spans an age range of about 80,000--130,000 years (inferred from fig.7, p. 1233 of Ericson and Wollin, 1968) and of about 75,000--128,000 years (Broecker and Van Donk, 1970). It means that our fauna (falling in the G. calida calida subzone) certainly falls in the X zone. The comparison with the Caribbean pteropod faunas (Chen, 1968; Jung, 1973), belonging to the time interval corresponding to stage 5, shows that in the coeval Yucatan fauna, both species diversity and the relative number of individuals are greater. Hence we have a very rich pteropod association in a climatically warm stage (X zone = stage 5).

102 BOLLI & THIS PAPER C H E N 1968 PREMOLI S I LVA, YUCATAN SCARP CARl BBEAN SEA

, 1973, "PLANKT. FORAMS

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Fig.2. Stratigraphic and climatologic relationships of the Yucatan pteropods. The diagram shows the stratigraphic position and the inferred paleoclimatic conditions for the pteropods dredged from the East Yucatan Scarp. The abundance of pteropods in the Yucatan fauna is in contrast with faunas in the Caribbean of the same age described by Chen (1968). The Yucatan p t e r o p o d fauna is further correlated with the standard temperature curves of Emiliani ( 1 9 6 6 ) a n d Ericson and Wollin (1968).

PLATE I

1. Limacina inflata (d'Orbigny). Umbilical view, × 40. 2. Limacina lesueurii (d'Orhigny): a, front view, × 20; b, apical view, X 20.

3. Limacina bulimoides (d'Orbigny): a, front view, × 40; b, rear, × 40. 4. Limacina trochiformis (d'Orbigny) front view, x 40. 5. Diacria quadridentata (Lesueur) orbignyi (Rang) (Souleyet) ventral view, × 22.5. 6. Cauolinia longirostris (Lesueur) f. strangulata (Deshayes) lateral view, x 10. 7. Peraclis reticulata (d'Orbigny) front view, X 10. 8. Hyalocylis striata (Rang) dorsal view, X 15. 9. Clio pyramidata Linneo dorsal view, X 7.7. 10. Clio cuspidata (Bosc). Embryonic part of shell, x 15. 11. Styliola subula (Quoy and Gaimard) dorsal view, x 9.

PLATE I

lO3

104 A c c o r d i n g t o Chen (1968), in the last 1 2 0 , 0 0 0 years p t e r o p o d s in the Caribbean and G u l f o f M e x i c o were m o r e a b u n d a n t in cold periods and rare or a b s e n t in warm times. Thus, a c c o r d i n g to the criteria f o r Caribbean z o n a t i o n (based e i t h e r o n a l t e r n a t i o n s o f warm- and c o l d - w a t e r species or o n the p r e s e n c e or t o t a l absence o f p t e r o p o d specimens), p t e r o p o d s should be very rare or a b s e n t in samples f r o m stage 5. Finding such a rich p t e r o p o d f a u n a f r o m the Y u c a t a n Scarp, signifying a w a r m stage b u t assigned t o stage 5 (= X zone), seems to challenge the value and significance o f the z o n a t i o n s p r o p o s e d b y C h e n f o r the Caribbean. ACKNOWLEDGEMENTS This m a n u s c r i p t describes a small p o r t i o n o f the d a t a which were c o l l e c t e d during the a u t h o r ' s (R. Catalano) association with t h e late Dr. B r u c e C. H e e z e n w h o c o l l e c t e d a considerable a m o u n t o f d a t a f r o m the Caribbean area which will be p r e s e n t e d in a series o f studies o n r e l a t e d stratigraphy, s e d i m e n t o l o g y and sea-floor mapping. T h e a u t h o r s are i n d e b t e d to R o d o l f o Sprovieri, University o f P a l e r m o , f o r his h e l p f u l assistance in d e t e r m i n i n g the p l a n k t o n i c f o r a m i n i f e r a . T h a n k s are also due to Prof. E d w a r d s Winterer (Scripps I n s t i t u t i o n o f O c e a n o g r a p h y ) f o r his h e l p f u l suggestions, E n r i c o D i S t e f a n o (University o f P a l e r m o ) f o r his technical assistance and C h a r l o t t e Schreiber, w h o revised and i m p r o v e d the m a n u s c r i p t .

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105 Deep Sea Drilling Project, XV. U.S. Government Printing Office, Washington, D.C., pp. 753--756. Le Roy, D. O. and Hodgkinson, K. A., 1975. Benthonic Foraminifera and some Pteropoda from a deep water dredge sample, northern Gulf of Mexico. Micropaleontology, 21(4): 420--447. Menzies, R. J., 1958. Shell-bearing pteropod gastropods from Mediterranean plankton (Cavolinidae). Pubbl. Staz. Napoli, 30 fasc. 3: 1--21. Rampal, J., 1975. Les Th~cosomes (Mollusques pelagique). Systematique et Evolution. Ecologie et Biogeographie mediterraneennes. These presentee a l'Universite de Provence, Aix, Marseille I, 485 pp. Rogl, F. and Bolli, H. M., 1973. Holocene to Pleistocene planktonic Foraminifera of leg 15, site 147 (Cariaco Basin (Trench), (Caribbean Sea) and their climatic interpretation. In: Initial Reports of the Deep Sea Drilling Project, XV. U.S. Government Printing Office, Washington, D.C., pp. 553--615. Tesch, J. J., 1946. The Thecosomatous Pteropods. I. The Atlantic: The Carlsberg Found. Ocean. Exped. Round the World 1928--1930 and Previous Dada Exped., Dana Rep., No. 28: 1--82. Van der Spoel, S., 1967. Euthecosomata: a Group With Remarkable Developmental Stages (Gastropoda, Pteropoda). J. Noorduijn en Zoon N.V., Gorinchem, 249 pp.