Ontogenetic morphometrics of some Upper Cretaceous foraminifera ...
fore, organisms that depended on algae as a principal nutrient source, such as bivalves, would have been adversely affected. It is therefore being proposed that E. antarctica shows that its growth was restricted, due not to the environmental temperature regime, but to the fact that its growing season would have been very short compared to that at lower latitudes. In this case, bivalve growth patterns could be very useful as palcolatitude indicators. This research was supported by National Science Foundation grant DPP 84-16783. References
Eisma, D., W.G. Mook, and H.A. Das. 1976. Shell characteristics, isotopic composition and trace-element contents of some euryhaline
Ontogenetic morphometrics of some Upper Cretaceous foraminifera from the southern high latitudes BRIAN T. HUBER
Byrd Polar Research Center
and
Department of Geology and Mineralogy Ohio State University Colunibus, Ohio 4321()
Several factors have impeded efforts toward improving the Upper Cretaceous planktonic foraminiferal biostratigraphy of the southern high latitudes: (1) rarity of thermophilic taxa used in the standard zonal schemes, (2) apparently slow evolutionary rates, and (3) high morphologic variability of several indigenous planktonic species. The latter factor has caused considerable taxonomic confusion in studies of Upper Cretaceous globigerine foraminifera from Deep Sea Drilling Project hole 511 (Falkland Plateau) and Seymour Island (Antarctic Peninsula). Specimens from these localities, which were previously classified as Rucoglobiçerina rugosa (Plummer), R. pilula Belford, R. pustulata Bro;dinnimann, R. rotundata Bro;dinnimann, and Hedbergella montnouthensis (Olsson) by Sliter (1976), Krasheninnikov and Basov (1983) and Huber, Harwood, and Webb (1983), show considerable intraspecific morphologic overlap, and they differ significantly from the original type descriptions (Huber in press). The proper taxonomic designation of these morphotypes is important because they dominate the antarctic and Falkland Plateau planktonic foraminiferal assemblages. Their original taxonomic assignments were based only on external characteristics of the foraminiferal shells, without regard to the ontogenetic features preserved within. To achieve taxonomic stability within this group, it became apparent that more detailed morphologic information was needed. New methods were used to observe the developmental ontogeny of the Falkland Plateau and Seymour Island specimens and compare them with topotypes of the species listed. One procedure involves a series of test dissections and observations under the scanning electron microscope using techniques sim1987 REVIEW
molluscs as indicators of salinity.
Palaeogeography, Palaeoclimatology, Palaeoecology, 19, 39-62. Kennett, J.P. 1977. Cenozoic evolution of antarctic glaciation, the cir-
cum-antarctic ocean, and their impact on global paleoceanography.
Journal of Geophysical Research, 82(27), 3843-3859. Panella, C., and C. MacClintock. 1968. Biological and environmental rhythms reflected in molluscan shell growth. Journal of Paleontology, 42(5, part II), 64-80. Tilzer, MM., and Z. Dubinsky. 1987. Effects of temperature and day length on the mass balance of Antarctic phytoplankton. Polar Biology, 7, 35-42. Urey, H.C., H.A. Lowenstam, S. Epstein, and C.R. McKinney. 1951.
Measurement of paleotemperatures and temperatures of Upper Cretaceous of England, Denmark, and the southeastern United States.
Geological Society of America Bulletin, 62, 399.
ilar to those described by Huang (1981). Removal of the ventral chamber walls was achieved through the use of a very finely ground needle mounted on a Sensaur micromanipulator, which enables precisely controlled movement in all three dimensions. Examination of the internal morphology using this method reveals valuable information on the ontogenetic changes in (1) wall surface ornament and porosity, (2) apertural position, (3) chamber size, and (4) number of chambers per whorl (figure 1, items 1, 3, 4, 5, and 6; figure 2, items 1, 3, 4, 5, 6, and 7). High resolution X-radiograph images of planktonic foraminifera were produced by adapting techniques described by Arnold (1982) (figure 1, item 2; figure 2, item 2). Equatorial views of the X-ray 1 x images were analyzed using morphometrics software in conjunction with a Leitz orthoplan microscope, a digitizing tablet, and a microcomputer. The chosen parameters include presence/absence and numerical attributes as well as linear and areal measurements which characterize the ontogenetic morphological changes. Internal morphologic characteristics considered as taxonomically useful include: (1) number of chambers in the penultimate whorl, (2) ontogenetic changes in the cross-sectional chamber area and shape, (3) position of the generating curve, and (4) ratio of the penultimate and antepenultimate chamber areas. The advantage of using this method is that data can be generated rapidly from large foraminiferal populations, and it can easily be analyzed statistically. Results of this study indicate that the upper Campanian! Maastrichtian specimens from the Falkland Plateau and Seymour Island, which were previously included in Hedbergella and Rugoglobigerina, are growth morphovariants of a single, new, high-latitude rugoglobigerinid species whose distribution is probably restricted to the southern high-latitude austral province. Specimens which were previously identified as Hedbergella mon;nouthensis at these high latitudes are now considered as juvenile and kummerform adult forms of the new rugoglobigerinid species. The gerontic morphotypes of this taxon, formerly considered as Rugoglobigerina pilula, R. rugosa, R. pustulata, and R. rotundata, show substantial variability in
maximum test diameter, cross-sectional area ratio of the ultimate and penultimate chambers, and position of the generating curve. They differ from typical species of Rugog!ohigerina in that surface ornamentation is predominantly composed of randomly arranged pustules, with only rare occurrence of mendionally aligned costellae. Kummerform chambers occur in moderate frequency and umbilical cover plates (tegilla) are rare. 15
Figure 1. Scanning electron micrographs and X-ray micrograph (item 2) of an upper Campanian specimen of Rugoglobigerina n. sp. showing ontogenetic changes in its morphology. This specimen bears faintly developed meridional costellae on the adult chamber surface and a tegillum. Note the rapid rate of chamber size increase and smoother wall of the pre-adult chambers. ("mm" denotes "millimeter:')
Figure 2. Scanning electron micrographs and X-ray micrograph (item 2) of an upper Campanian specimen of Rugoglobigerina n. sp. from Deep Sea Drilling Project hole 511 (core 24-5, 69-71 centimeters) from the Falkland Plateau. Note that the ontogenetic development of this form is similar to the specimen shown in figure 1. ("mm" denotes "millimeter:') 16
ANTARCTIC JOURNAL
Examination of the pre-adult morphology of planktonic foraminifera using the methods described above provides additional criteria for understanding their taxonomy and phylogenetic relationships. Although this study was concerned with a single time-slice in the Late Cretaceous, analysis of stratigraphic changes in the ontogenetic morphometry of particular taxonomic groups will certainly improve high-latitude biostratigraphy and provide further insight to paleoceanographic and paleoclimatic evolution. Samples provided by the Deep Sea Drilling Project (East Coast Repository, Lamont-Doherty Geological Observatory) are gratefully acknowledged. This research was partially funded by National Science Foundation grants DPP 85-17625 and Di p 84-20622. Jam grateful to the curators at the Scripps Institution of Oceanography for making the Deep Sea Drilling Project samples available to me. References
Arnold, A.J. 1982. Techniques for biometric analysis of foraminifera. Third North American Paleontological Convention, Proceedings, 1, 13-15.
Evidence from the Beardmore Glacier region for a late Paleozoic/early Mesozoic foreland basin
Huang, C. 1981. Observations on the interior of some late Neogene planktonic foraminifera. Journal of Foraminiferal Research, 1(3), 173-190.
Huber, B.T. In press. Upper Campanian-Paleocene foraminifera from the James Ross Island region (Antarctic Peninsula). In R.M. Feldmann and M.O. Woodburne (Eds.), Geology and Paleontology of Seymour Island, Antarctica. (Geological Society of America, Memoir Series 169.) Huber, B.T., D.M. Harwood, and P.N. Webb. 1983. Upper Cretaceous microfossil biostratigraphy of Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 18(5), 72-74.
Krasheninnikov, V.A., and I.A. Basov. 1983. Stratigraphy of Cretaceous sediments of the Falkland Plateau based on planktonic foraminifers, Deep Sea Drilling Project, Leg 71. In W.J. Ludwig, V.A. Krasheninnikov, et al. (Eds.), Initial Reports of the Deep Sea Drilling Project. Washington, D.C.: U.S. Government Printing Office. Sliter, W.V. 1976. Cretaceous foraminifera from the southwest Atlantic Ocean, Leg 36, Deep Sea Drilling Project. In P.F. Barker, I.W.D. Dalziel et al. (Eds.), Initial Reports of the Deep Sea Drilling Project.
Washington, D.C.: U.S. Government Printing Office.
• An Early Permian facies transition from terrestrial to marine toward the orogenic belt. • The existence of two major source areas, the east antarctic craton and calc-alkaline volcanics from a convergent paleo-
EAST ANTARCTIC £ Pensacola Mtns. CRATON /
JAMES W. CoI,uNsoN and JOHN L. ISBELI.
Byrd Polar Research Ccii hr
---------
and
Department of Geology and Mineralogy Ohio State University Columbus, Ohio 43220
New data and interpretations from our 1985-1986 field season in the Beardmore Glacier region lend support to the hypothesis that the Upper Paleozoic/Lower Mesozoic sedimentary sequence is part of a major foreland basin that paralleled the margin of the east antarctic craton. This foreland basin comprises at least four distinct stratigraphic basins (figure 1): Ellsworth Mountains (EM), Central Transantarctic Mountains (cTM), southern Victoria Land (svL), and northern Victoria Land (NvL). The stratigraphy of these basins has been summarized at length by Elliot (1975). Foreland basins are elongated depressions that develop on continental crust, typically near the edge of a craton, inboard of a fold/thrust belt. Lines of evidence supporting the foreland basin hypothesis include: • The widespread similarity of stratigraphic sequences from antarctic basins suggesting that they are genetically related. • Post-Early Permian to pre-Middle Jurassic folding in the Ellsworth and Pensacola mountains indicating the existence of an orogenic belt. • The thickening of time-equivalent sequences toward the orogenic belt. 1987 REVIEW
-1
EM BASIN lsrth Mtns
7
4' + South Pole
CTML BASIN
Shackle ton Beardmore GI. ROSS ICE SHELF
D Stratigraphic basins 500 igoo Kilometers
NVL
C6 ASIN
Rennick GI.
Figure 1. Location map showing extent of stratigraphic basins. ("EM" denotes "Ellsworth Mountains"; "CTM" denotes "central Transantarctic Mountains"; "SVL" denotes southern Victoria Land"; "NVL" denotes "northern Victoria Land?')
17
Eisma, D., W.G. Mook, and H.A. Das. 1976. Shell characteristics, isotopic composition and trace-element contents of some euryhaline
Ontogenetic morphometrics of some Upper Cretaceous foraminifera from the southern high latitudes BRIAN T. HUBER
Byrd Polar Research Center
and
Department of Geology and Mineralogy Ohio State University Colunibus, Ohio 4321()
Several factors have impeded efforts toward improving the Upper Cretaceous planktonic foraminiferal biostratigraphy of the southern high latitudes: (1) rarity of thermophilic taxa used in the standard zonal schemes, (2) apparently slow evolutionary rates, and (3) high morphologic variability of several indigenous planktonic species. The latter factor has caused considerable taxonomic confusion in studies of Upper Cretaceous globigerine foraminifera from Deep Sea Drilling Project hole 511 (Falkland Plateau) and Seymour Island (Antarctic Peninsula). Specimens from these localities, which were previously classified as Rucoglobiçerina rugosa (Plummer), R. pilula Belford, R. pustulata Bro;dinnimann, R. rotundata Bro;dinnimann, and Hedbergella montnouthensis (Olsson) by Sliter (1976), Krasheninnikov and Basov (1983) and Huber, Harwood, and Webb (1983), show considerable intraspecific morphologic overlap, and they differ significantly from the original type descriptions (Huber in press). The proper taxonomic designation of these morphotypes is important because they dominate the antarctic and Falkland Plateau planktonic foraminiferal assemblages. Their original taxonomic assignments were based only on external characteristics of the foraminiferal shells, without regard to the ontogenetic features preserved within. To achieve taxonomic stability within this group, it became apparent that more detailed morphologic information was needed. New methods were used to observe the developmental ontogeny of the Falkland Plateau and Seymour Island specimens and compare them with topotypes of the species listed. One procedure involves a series of test dissections and observations under the scanning electron microscope using techniques sim1987 REVIEW
molluscs as indicators of salinity.
Palaeogeography, Palaeoclimatology, Palaeoecology, 19, 39-62. Kennett, J.P. 1977. Cenozoic evolution of antarctic glaciation, the cir-
cum-antarctic ocean, and their impact on global paleoceanography.
Journal of Geophysical Research, 82(27), 3843-3859. Panella, C., and C. MacClintock. 1968. Biological and environmental rhythms reflected in molluscan shell growth. Journal of Paleontology, 42(5, part II), 64-80. Tilzer, MM., and Z. Dubinsky. 1987. Effects of temperature and day length on the mass balance of Antarctic phytoplankton. Polar Biology, 7, 35-42. Urey, H.C., H.A. Lowenstam, S. Epstein, and C.R. McKinney. 1951.
Measurement of paleotemperatures and temperatures of Upper Cretaceous of England, Denmark, and the southeastern United States.
Geological Society of America Bulletin, 62, 399.
ilar to those described by Huang (1981). Removal of the ventral chamber walls was achieved through the use of a very finely ground needle mounted on a Sensaur micromanipulator, which enables precisely controlled movement in all three dimensions. Examination of the internal morphology using this method reveals valuable information on the ontogenetic changes in (1) wall surface ornament and porosity, (2) apertural position, (3) chamber size, and (4) number of chambers per whorl (figure 1, items 1, 3, 4, 5, and 6; figure 2, items 1, 3, 4, 5, 6, and 7). High resolution X-radiograph images of planktonic foraminifera were produced by adapting techniques described by Arnold (1982) (figure 1, item 2; figure 2, item 2). Equatorial views of the X-ray 1 x images were analyzed using morphometrics software in conjunction with a Leitz orthoplan microscope, a digitizing tablet, and a microcomputer. The chosen parameters include presence/absence and numerical attributes as well as linear and areal measurements which characterize the ontogenetic morphological changes. Internal morphologic characteristics considered as taxonomically useful include: (1) number of chambers in the penultimate whorl, (2) ontogenetic changes in the cross-sectional chamber area and shape, (3) position of the generating curve, and (4) ratio of the penultimate and antepenultimate chamber areas. The advantage of using this method is that data can be generated rapidly from large foraminiferal populations, and it can easily be analyzed statistically. Results of this study indicate that the upper Campanian! Maastrichtian specimens from the Falkland Plateau and Seymour Island, which were previously included in Hedbergella and Rugoglobigerina, are growth morphovariants of a single, new, high-latitude rugoglobigerinid species whose distribution is probably restricted to the southern high-latitude austral province. Specimens which were previously identified as Hedbergella mon;nouthensis at these high latitudes are now considered as juvenile and kummerform adult forms of the new rugoglobigerinid species. The gerontic morphotypes of this taxon, formerly considered as Rugoglobigerina pilula, R. rugosa, R. pustulata, and R. rotundata, show substantial variability in
maximum test diameter, cross-sectional area ratio of the ultimate and penultimate chambers, and position of the generating curve. They differ from typical species of Rugog!ohigerina in that surface ornamentation is predominantly composed of randomly arranged pustules, with only rare occurrence of mendionally aligned costellae. Kummerform chambers occur in moderate frequency and umbilical cover plates (tegilla) are rare. 15
Figure 1. Scanning electron micrographs and X-ray micrograph (item 2) of an upper Campanian specimen of Rugoglobigerina n. sp. showing ontogenetic changes in its morphology. This specimen bears faintly developed meridional costellae on the adult chamber surface and a tegillum. Note the rapid rate of chamber size increase and smoother wall of the pre-adult chambers. ("mm" denotes "millimeter:')
Figure 2. Scanning electron micrographs and X-ray micrograph (item 2) of an upper Campanian specimen of Rugoglobigerina n. sp. from Deep Sea Drilling Project hole 511 (core 24-5, 69-71 centimeters) from the Falkland Plateau. Note that the ontogenetic development of this form is similar to the specimen shown in figure 1. ("mm" denotes "millimeter:') 16
ANTARCTIC JOURNAL
Examination of the pre-adult morphology of planktonic foraminifera using the methods described above provides additional criteria for understanding their taxonomy and phylogenetic relationships. Although this study was concerned with a single time-slice in the Late Cretaceous, analysis of stratigraphic changes in the ontogenetic morphometry of particular taxonomic groups will certainly improve high-latitude biostratigraphy and provide further insight to paleoceanographic and paleoclimatic evolution. Samples provided by the Deep Sea Drilling Project (East Coast Repository, Lamont-Doherty Geological Observatory) are gratefully acknowledged. This research was partially funded by National Science Foundation grants DPP 85-17625 and Di p 84-20622. Jam grateful to the curators at the Scripps Institution of Oceanography for making the Deep Sea Drilling Project samples available to me. References
Arnold, A.J. 1982. Techniques for biometric analysis of foraminifera. Third North American Paleontological Convention, Proceedings, 1, 13-15.
Evidence from the Beardmore Glacier region for a late Paleozoic/early Mesozoic foreland basin
Huang, C. 1981. Observations on the interior of some late Neogene planktonic foraminifera. Journal of Foraminiferal Research, 1(3), 173-190.
Huber, B.T. In press. Upper Campanian-Paleocene foraminifera from the James Ross Island region (Antarctic Peninsula). In R.M. Feldmann and M.O. Woodburne (Eds.), Geology and Paleontology of Seymour Island, Antarctica. (Geological Society of America, Memoir Series 169.) Huber, B.T., D.M. Harwood, and P.N. Webb. 1983. Upper Cretaceous microfossil biostratigraphy of Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 18(5), 72-74.
Krasheninnikov, V.A., and I.A. Basov. 1983. Stratigraphy of Cretaceous sediments of the Falkland Plateau based on planktonic foraminifers, Deep Sea Drilling Project, Leg 71. In W.J. Ludwig, V.A. Krasheninnikov, et al. (Eds.), Initial Reports of the Deep Sea Drilling Project. Washington, D.C.: U.S. Government Printing Office. Sliter, W.V. 1976. Cretaceous foraminifera from the southwest Atlantic Ocean, Leg 36, Deep Sea Drilling Project. In P.F. Barker, I.W.D. Dalziel et al. (Eds.), Initial Reports of the Deep Sea Drilling Project.
Washington, D.C.: U.S. Government Printing Office.
• An Early Permian facies transition from terrestrial to marine toward the orogenic belt. • The existence of two major source areas, the east antarctic craton and calc-alkaline volcanics from a convergent paleo-
EAST ANTARCTIC £ Pensacola Mtns. CRATON /
JAMES W. CoI,uNsoN and JOHN L. ISBELI.
Byrd Polar Research Ccii hr
---------
and
Department of Geology and Mineralogy Ohio State University Columbus, Ohio 43220
New data and interpretations from our 1985-1986 field season in the Beardmore Glacier region lend support to the hypothesis that the Upper Paleozoic/Lower Mesozoic sedimentary sequence is part of a major foreland basin that paralleled the margin of the east antarctic craton. This foreland basin comprises at least four distinct stratigraphic basins (figure 1): Ellsworth Mountains (EM), Central Transantarctic Mountains (cTM), southern Victoria Land (svL), and northern Victoria Land (NvL). The stratigraphy of these basins has been summarized at length by Elliot (1975). Foreland basins are elongated depressions that develop on continental crust, typically near the edge of a craton, inboard of a fold/thrust belt. Lines of evidence supporting the foreland basin hypothesis include: • The widespread similarity of stratigraphic sequences from antarctic basins suggesting that they are genetically related. • Post-Early Permian to pre-Middle Jurassic folding in the Ellsworth and Pensacola mountains indicating the existence of an orogenic belt. • The thickening of time-equivalent sequences toward the orogenic belt. 1987 REVIEW
-1
EM BASIN lsrth Mtns
7
4' + South Pole
CTML BASIN
Shackle ton Beardmore GI. ROSS ICE SHELF
D Stratigraphic basins 500 igoo Kilometers
NVL
C6 ASIN
Rennick GI.
Figure 1. Location map showing extent of stratigraphic basins. ("EM" denotes "Ellsworth Mountains"; "CTM" denotes "central Transantarctic Mountains"; "SVL" denotes southern Victoria Land"; "NVL" denotes "northern Victoria Land?')
17
