Taxonomyand paleoecologyof late Neogene benthic foraminiferafrom the Caribbean Sea and eastem equatorial Pacific Ocean Lennart Bornmalm SCANDINAVIAN UNI VERSITYPRESS II �I� Oslo � Copenhagen � Stockholm � Boston FOSSILS AND STRATA An international monograph series of palaeontology and stratigraphy Owner Lethaia Foundation, Oslo. Administrative Council: Hans Jørgen Hansen, Copenhagen, David Bruton, Oslo, Christina Franzen, Stockholm, Stefan Bengtson, Uppsala. Editor Stefan Bengtson, Dept. Palaeozoology, Swedish Museum ofNatural History, Box 50007, S-104 05 Stockholm, Sweden; tel. +46-8 666 4220; fax +46-8 666 4184; e-mail [email protected]. Publisher Scandinavian University Press, P.O. Box 2959, Tøyen, N-0608 Oslo 6, Norway. Programme Fossils and Strata is an international series of monographs and memoirs in palaeontology and stratigraphy, published in cooperation between the Scandinavian countries. It is issued in Numbers with individual pagination. Fossils and Strataforms part ofthe same structured publishingprogramme as the journals Lethaia and Boreas. These two journals are fully international and accept papers within their respective sectors ofscience without nationallimitations or preferences. Fossils and Strata,however, is an outlet for more comprehensive systematic and regional monographs emanating primarily fromthe five countries of Norden. Contributions from other countries may also be included if this series is deemed appropriate with regard to distribution and availability. Articles can normally only be accepted if they are heavily subsidized by the national Research Council in their country of origin or by other funds. All income is re-invested in forthcoming numbers of the series. Although articles in German and French may be accepted, the use ofEnglish is stronglypreferred. An English abstract should always be provided, and non-English articles should have English versions of the figurecaptions. Abstracts or summaries in one or more additional languages may be added. Many regional or systematic descriptions and revisions contain a nucleus of results which are of immediate and general interest in international palaeontology and stratigraphy. It is expected that authors of such papers willto some extent duplicate their publication in the form of an article for a journal, in the firstplace Lethaia or Boreas. Sales Individual numbers and standing subscriptions may be ordered from Scandinavian University Press (postal address as above; e-mail address [email protected]). Prices (subject to revision) are listed on the back side of each issue. IPA members generally have a 50% discount on older issues (ask for information fromScandinavian University Press). Allprices exclude postage and handling. LETHAlA An international journal of palaeontology and stratigraphy An international journal of Quaternary research Scandinavian University Press, p.o. Box 2959, Tøyen, N-0608 Oslo 6, Norway Taxonomy and paleoecology of late Neogene benthic foraminifera from the Caribbean Sea and eastern equatorial Pacific Ocean LENNART BORNMALM Bornmalm, L. 1997 02 15: Taxonomy and paleoecology of late Neogene benthic fo raminifera from the Caribbean Sea and eastern equatorial Pacific Ocean. Fossils and Strata, No. 41, pp. 1- 96. Oslo. ISSN 0300-9491. ISBN 82-00-37666-4. Benthic foraminifera (l47 taxa) were investigated from the Caribbean Sea (Deep Sea Drilling Project; DSDP Hole 502A, depth 3,051 m) and eastern equatorial Pacific Ocean (DSDP Hole 503B, 3,672 m) over an interval between the terminal Miocene and the basal Pleistocene (5.5- 1.7 Ma). To determine the influenceover time of the Central American Isthmus (closure of the Isthmus of Panama occurring some time between 3.5 and 3.0 Ma) on the benthic fauna, the composition and diversity of the fauna as well as many physico-chemical variables were con­ sidered. The latter include changes in coarse-fraction (>63 �m), calcite dissolution (estimated from the degree of fragmentation of planktic fo raminifera), accumulation rates of benthic fo raminifera (BFAR, used as an index of the flux of organic matter to the sea floor), CaC03 con­ tent, and stable isotopes in planktic and benthic fo raminifera. In the Caribbean Hole 502A, the 0180 of planktic foraminifera increased at about 4.2 Ma relative to the benthic values and also relative to the planktic and benthic values in the Pacific Hole 503. This change may reflect increasing surface-water salinity in the Caribbean Sea as a result of restricted surface-water exchange between the Atlantic and Pacific caused by the emergent Panama Isthmus. Most of the physico-chemical va riables in Hole 502A have similar trends to those in the PacificHole 503 between late Miocene and 3.85 Ma. Afterthat, Hole 503 continued to show a typical equatorial Pacific character, whereas Hole 502A was affected by local tectonics and bottom-water exchange between Caribbean Sea and the Atlantic. The increased BFAR at 3.85 Ma in Hole 502A may indicate increased productivity of the surface water in the Caribbean Sea, but it could als o be a result of a decrease in dissolution and intensifiedventilation of the bottom water. The increased 0180 and ol3C values in the benthic fo raminifer record, increased coarse-fraction CaC03 content, as well as decreased fragmentation of planktic fo raminifera are probably related to greater inflowof Upper North Atlantic Deep Water (UNADW) to the Caribbean Sea since 3.85 Ma, most likely initiated by increased northward transport of warm, high-salinity waters to high latitudes via the Gulf Stream, which in turn was caused by progressive upliftof the Central American land bridge. The fluctuationsin the physico-chemical parameters in Hole 503 are overall iarger than in Hole 502A, which probably is a result of dissolution signals caused by vertical oscillations of the Iysocline in Hole 503 because of the deeper location of this site. The increased planktic and benthic foraminifer oxygen isotope values from 3.2 Ma in Hole 503 probably reflect oceanographicand c1imatic changes in the Antarctic area from this time. Q­ mode principal component analysis on benthic fo raminifer abundances (accumulation rates of selected species) distinguished two major faunal groups in both Hole 502A and Hole 503. Nut­ tallides umbonife ra is the most abundant species and makes up one group, while the other group is made up of both Cibicidoides wuellerstorfi and Oridorsalis umbonatus in Hole 502A, and only o. umbonatus in Hole 503. In Hole 502A C. wuellerstorfiand o. umbonatus are abun­ dant in the interval between 4.2 and 3.7 Ma. From about 3.7 Ma N. umbonife ra increased and became the most abundant benthic species. In Hole 503 N. umbonife ra was the most abundant species between 4.8 and 2.1 Ma, except for a few intervals where O. umbonife ra was more fre­ quent. These changes in the abundance of N. umbonife ra may be due to (I) changes in volurne of different water masses, (2) changes in productivity, and/or (3) a transitory shift in an envi­ ronmental preference of N. umbonife ra. However, in both Hoies 502A and 503 there is no sig­ nificantcorrelation among dissolution, CaC03 content, BFAR, and the variation in the abun­ dance of N. umbonife ra. DBenthicfo raminife ra, biostratigraphy, paleoecology, paleoceanography, late Neogene, Isthmus of Panama, Deep Sea Drilling Project, DSDP Sites 502 and 503, Caribbean Sea, Colombia Basin, eastern equatorial Pacific Ocean, Guatemala Basin. Lennart Bornmalm, Department of Marine Geology, University ofGiitebor g, P. o. Box 7064, S- 402 32 Giiteborg, Sweden; 25th February, 1995. Contents Introduction ...................................................................... .. .... .... ...... ......... 3 Genus Glandulina d'Orbigny, 1839 .............................................. 39 Study area ..............................................................................................4 Subfamily Oolininae Loeblich & Tappan, 1961 ................................4 0 Material and methods ...........................................................................5 Genus Fissurina Reuss, 1850 .......................................................... 40 Acknowledgements ....................... ........ ............................. ................. 1 O Genus Oolina d'Orbigny, 1839 ...................................................... 43 Results ...................................................................................................... II Genus Parafissurina Parr, 1947 .................................................... .44 Coarse-fraction analysis ...................................................................... 11 Superfamily Robertinacea Reuss, 1850; Family Epistominidae Fragmentation patterns .............. ................................................. ....... 11 Wedekind, 1937 ......................................................................... 45 Benthic foraminifer acculation rates (BFAR) ... ................................. ll Genus Hoeglundina Brotzen, 1948 ................................................ 45 Calcium carbonate con tent ................................................................ 13 Superfamily Buliminacea jones, 1875; Family Bolivinitidae Stable isotopes ..................................................................................... 13 Cushman, 1927 .......................................................................... 46 Diversity ofthe benthic fo raminifer faunas ....................................... 13 Genus Bolivina d'Orbigny, 1839 ..................................................