Foraminiferal distribution across the Cretaceous/Tertiary transition on ...
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Figure 2. Magnetic anomaly chart of the northern Weddell Basin including the Powell Basin from aerosurvey and shipboard data. Magnetic anomaly identifications are illustrated by dashed lines, and the estimated position of a fossil trench is shown by the heavy black line with teeth showing the direction of underthrusting. In the upper right of the figure, some of the high-altitude data over the Bransfield Strait are visible.
Foraminiferal distribution across the Cretaceous/Tertiary transition on Seymour Island, Antarctic Peninsula B.T. HUBER Department of Geology and Mineralogy
and
Institute of Polar Studies Ohio State University Columbus, Ohio 43210
The Cretaceous/Tertiary (KIT) transition on Seymour Island has been recognized primarily by the last appearance of ammonities (Macellari and Zinsmeister 1983; Macellari 1985, 1986) and by evidence from several other fossil groups (Huber, Har1986 REVIEW
wood, and Webb 1983; Askin 1984; Zinmeister and Macellari 1983). It occurs within the upper Lopez de Bertodano Formation, about 45 meters below the base of the overlying Sobral Formation, at the level of a stratigraphically continuous glauconite bed (figures 1 and 2). Prior to the 1985 Seymour Island field season, no definite Tertiary foraminifera were recovered from samples above the "KIT glauconite bed" (Huber 1985). This report discusses the first record of diagnostic Danian (early Paleocene) foraminifera from Antarctica and the foraminiferal species turnover at the KIT boundary on Seymour Island. The abrupt extinction of planktonic foraminifera at the KIT boundary has been known for many years (e.g., Berggren 1962; Luterbacher and Premolj Silva 1964). In the North American Gulf Coast region, only 1 of 36 foraminiferal species from the latest Cretaceous Abathomphalus mayorensis zone apparently survived the KIT boundary event (Pessagno 1967). It is hypothesized that all Paleocene planktonic species evolved from this single surviving species (Smit 1982). 71
Figure 1. Geologic map of Seymour Island showing the location of samples which yielded latest Cretaceous and Early Tertiary foraminifera and the location of the Cretaceous/Tertiary (KIT) glauconite bed. ("FM" denotes "formation.")
1240
1220 810
0 0 1200
C 0 C B 0
-540 539
5
1180
Dissolution interval 1160 535
C S 1120-- 0 U S S S
I
i*4
1100
1080 Lehilfid bivalves
EJ Burrows Sandy slitetone
2 13 J Calcareous co*cr.ti.ns ED Otauconits
Figure 2. Stratigraphic section and scanning electron micrographs showing the distribution of samples and planktonic foraminifera across the Cretaceous/Tertiary transition and the dissolution interval. 1. Heterohe!ixglobulosa(Ehrenberg); 2. Globigerinelloides mu!tispinatus (Lalicker); 3. Hedbergella monmouthensis (Olsson); 4. Globotruncanella sp.; 5. Globlastica daubjergensis (Brönn imann). ("Fm" denotes "formation.")
72
In most regions, benthic foraminiferal species extinctions are much less drastic in comparison to the planktonics. Percentage extinctions of latest Cretaceous Trinidad foraminifera are only 9 percent for agglutinated species and 22 percent for calcareous benthic species (Webb 1973). Extinctions are higher among coeval Deep Sea Drilling Project (DSDP) site 208 (Lord Howe Rise, Southwest Pacific) foraminifera. Webb (1973) reports 73 percent extinction of agglutinated species and 52 percent for calcareous benthic species. He suggested that the greater faunal turnover at the Lord Howe Rise site may have been because of more extreme climatic fluctuations in higher latitude regions. Foraminiferal distributions on Seymour Island show that most of the 126 benthic species and 15 planktonic species appear within the lower 300 meters of the Lopez de Bertodano Formation. These generally have scattered occurrences throughout the remaining 850 meters of the Cretaceous section. Therefore, it appears as though no major biotic changes took place within the Campanian-Maastrichtian portion of the sequence, attesting to long-term environmental stability. The faunal turnover within 4 meters below the KIT glauconite bed, on the other hand, is quite dramatic. Foraminiferal species terminations at this level are 71 percent for agglutinated, 64 percent for calcareous benthic, and 100 percent for planktonic species. Benthic survivors of the extinction event include a few simple agglutinated forms as well as several long-ranging, cosmopolitan calcareous benthic species. The highest stratigraphic occurrence of Maastrichtian planktonic foraminifera on Seymour Island is in sample numbers 411, 526, and 535, located within 4 meters below the KIT glauconite bed (figure 2), in the upper Lopez de Bertodano Formation. These samples yielded the planktonic species Heterolielix globulosa (Ehrenberg), Globigerinello ides mu/f ispinatus (Lalicker), Hedbergella monmouthensis (Olsson), and Globotruncane/la? sp., in addition to diverse Cretaceous benthic assemblages. Just above the glauconite is a sequence, referred to as the "Dissolution interval," in which foraminifera are poorly represented (figure 2). Of 41 samples collected from this interval, 20 were completely barren of foraminifera and 21 yielded poorly preserved agglutinated assemblages. Other calcareous microfossils (e.g., ostracodes, juvenile molluscs, echinoid spines, calcispheres, and calcarous nannoplankton) are absent from the dissolution interval. Foraminifera diagnostic of the Danian wre recovered from sea cliff sample number 539, collected 1 meter below the Lopez de Bertodano/Sobral Formation contact, and sample numbers 540 and 515, from the lower Sobral Formation (figures 1 and 2). The planktonic species Globastica dauhjergensis (Brönnimann), which is widely recognized as a Danian index fossil (e.g., see Troelsen 1957; Berggren 1962; Hansen 1970), was found in all three of these samples. This taxon is considered as a descendant of an early Danian species, which has not yet been found on Seymour Island. Other specimens making their first stratigraphic appearance above the KIT glauconite bed include forms known elsewhere in Upper Cretaceous/Lower Tertiary deposits and several new or indeterminant species. The calcareous benthic Buliminella n. sp., which makes its first appearance in sample number 539, is conspicuously abundant in all of the Danian samples, dominating up to 82 percent of the foraminiferal assemblages. Agglutinated taxa are very rare above the KIT glauconite bed, contrary to their consistent, moderately abundant representation in the Cretaceous assemblages. This transition, from high to low species equitability, indicates a change from predominantly stable to stressed environmental conditions. It coincides with a sigANTARCTIC JOURNAL
nificant negative excursion in the isotopic carbon-13 isotopic signal and a negative excursion in the isotopic oxygen-18 isotopic signal among several of the Danian benthic taxa (Barrera personal communication). Similar isotopic shifts in isotopic carbon-13 and isotopic oxygen-18 occur at numerous other KIT boundary sites and have been interpreted as representing decreased oceanic productivity and increased marine temperatures, respectively (Perch-Nielson, McKenzie, and He (1982). This study was supported by National Science Foundation grants DPP 82-14174A01 to P.N. Webb and DPP 82-13985A01 to W.J. Zinsmeister and D.H. Elliot. References Askin, R.A. 1984. Palynological investigations of the James Ross Island basin and Robertson Island, Antarctic Peninsula. Antarctic Journal of the U.S., 19(5), 6-7. Barrera, E. 1986. Personal communication. Berggren, W.A. 1962. Some planktonic foraminifera from the Maestrichtian and type Danian stages of southern Scandinavia. Contributions in Geology, 9, 1-106. Hansen, H.J. 1970. Biometric studies on the stratigraphic evolution of Globoconusa daubjergensis (BrOnnimann). Bulletin of the Geological Society of Denmark, 19, 341-360. Huber, B.T. 1985. The location of the Cretaceous/Tertiary boundary on Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 20(5), 46-48. Huber, B.T. 1986. Foraminiferal evidence for a terminal Cretaceous oceanic event. Geological Society of America, Abstract with Programs,
18(4), 309-310. Huber, B.T., D.M. Harwood, and P.N. Webb. 1983. Upper Cretaceous
Palynomorphs and depositional environment for upper Campanian sediments on Seymour Island, Antarctica R. ASKIN
Geology Department Colorado School of Mines Golden, Colorado 80401
Seymour Island, northeastern Antarctic Peninsula, provides an area for effective study of palynomorph assemblages and their value as indicators of Cretaceous and Tertiary paleoenvironments. Paleoenvironmental interpretations can be based on a wealth of evidence from other fossil groups, coupled with sedimentological analyses. The interpretations may also be compared with previous palynological studies from other parts of the world. The essentially unconsolidated Campanian through Eocene Seymour Island sediments are well exposed and yield a plethora of fossils of many different floral and faunal 1986 REVIEW
microfossil biostratigraphy of Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 18(5), 72-74.
Luterbacher, H.P., and I. Premoli Silva. 1964. Biostratigraphy of the Cretaceous-Tertiary boundary in the Central Appenines Rivista Italiana di Paleontologia e Stratigrafia, 70, 67-88. (In Italian) Macellari, C. E. 1985. The Cretaceous-Tertiary boundary in the Antarctic Peninsula and southern South America. Memorias, Sexto Congreso Latinoamericano de Geologia, 267-278. (In Spanish) Macellari, G.E. 1986. Late Campanian-Maastrichtian ammonite fauna from Seymour Island (Antarctic Peninsula). Journal of Paleontology, Memoir, 18, 1-55. Macellari, CE., and W.J. Zinsmeister. 1983. Sedimentology and macropaleontology of the Upper Cretaceous to Paleocene sequence of Seymour Island. Antarctic Journal of the U.S., 18(5), 69-71. Perch-Nielsen, K., J . McKenzie, and Q. He. 1982. Biostratigraphy and isotope stratigraphy and the "catastrophic" extinction of calcareous nannoplankton at the Cretaceous/Tertiary boundary. Geological Society of America Special Paper, 190, 353-371. Pessagno, E.A., Jr. 1967. Upper Cretaceous planktonic foraminifera from the western Gulf Coastal Plain. Palaeontographica Americana, 5(37), 245-445. Smit, J. 1982. Extinction and evolution of planktonic foraminifera after a major impact at the Cretaceous/Tertiary boundary. Geological Society of America Special Paper, 190, 329-352. Troelsen, J.C. 1957. Some planktonic foraminifera of the type Danian and their stratigraphic importance. Bulletin of the U.S. National Museum, 215, 125-132. Webb, P.N. 1973. Upper Cretaceous-Paleocene foraminifera from Site 208 (Lord Howe Rise, Tasman Sea), DSDP Leg 21. In R.E. Burns, J. Andrews, et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, 21, 541-573. Zinsmeister, W.J., and C. Macellari. 1983. Changes in the macrofossil faunas at the end of the Cretaceous on Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 18(5), 68-69.
groups. Palynomorphs, both marine and nonmarine in origin, are particularly abundant throughout the succession. The following comments on the upper Campanian part of the section exemplify some aspects of this study. Fossil and sedimentological evidence suggests a nearshore marine, low-energy depositional environment for upper Campanian sediments on Seymour Island. Beds dated as upper Campanian by calcareous nannofossils, foraminifera, ammonites and other molluscs, etc., (Huber, Harwood, and Webb 1983; Huber in preparation; Macellari 1984, 1986) and by palynomorphs (Askin 1985, in preparation) comprise the oldest sediments cropping out on Seymour Island. They are assigned to part of the Lopez de Bertodano Formation and contain a high proportion of mud and silt, particularly in massive mudstone units best developed toward the south coast (Macellari in preparation). Upper Campanian Seymour Island sediments are subdivided into six lithologic units ("Rotularia units," Macellari in preparation). The low-diversity invertebrate macrofauna is dominated by the annelid Rotularia, which apparently favored muddy substrates (Macellari 1984). In his discussion of sedimentological data and environmental/ecological preferences of the macrofauna, Macellari (in preparation) concludes that units 1 through 6 were deposited in very shallow marine, low-energy, delta/ estuary-influenced environments, with possible intermittent brackish conditions. 73
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Figure 2. Magnetic anomaly chart of the northern Weddell Basin including the Powell Basin from aerosurvey and shipboard data. Magnetic anomaly identifications are illustrated by dashed lines, and the estimated position of a fossil trench is shown by the heavy black line with teeth showing the direction of underthrusting. In the upper right of the figure, some of the high-altitude data over the Bransfield Strait are visible.
Foraminiferal distribution across the Cretaceous/Tertiary transition on Seymour Island, Antarctic Peninsula B.T. HUBER Department of Geology and Mineralogy
and
Institute of Polar Studies Ohio State University Columbus, Ohio 43210
The Cretaceous/Tertiary (KIT) transition on Seymour Island has been recognized primarily by the last appearance of ammonities (Macellari and Zinsmeister 1983; Macellari 1985, 1986) and by evidence from several other fossil groups (Huber, Har1986 REVIEW
wood, and Webb 1983; Askin 1984; Zinmeister and Macellari 1983). It occurs within the upper Lopez de Bertodano Formation, about 45 meters below the base of the overlying Sobral Formation, at the level of a stratigraphically continuous glauconite bed (figures 1 and 2). Prior to the 1985 Seymour Island field season, no definite Tertiary foraminifera were recovered from samples above the "KIT glauconite bed" (Huber 1985). This report discusses the first record of diagnostic Danian (early Paleocene) foraminifera from Antarctica and the foraminiferal species turnover at the KIT boundary on Seymour Island. The abrupt extinction of planktonic foraminifera at the KIT boundary has been known for many years (e.g., Berggren 1962; Luterbacher and Premolj Silva 1964). In the North American Gulf Coast region, only 1 of 36 foraminiferal species from the latest Cretaceous Abathomphalus mayorensis zone apparently survived the KIT boundary event (Pessagno 1967). It is hypothesized that all Paleocene planktonic species evolved from this single surviving species (Smit 1982). 71
Figure 1. Geologic map of Seymour Island showing the location of samples which yielded latest Cretaceous and Early Tertiary foraminifera and the location of the Cretaceous/Tertiary (KIT) glauconite bed. ("FM" denotes "formation.")
1240
1220 810
0 0 1200
C 0 C B 0
-540 539
5
1180
Dissolution interval 1160 535
C S 1120-- 0 U S S S
I
i*4
1100
1080 Lehilfid bivalves
EJ Burrows Sandy slitetone
2 13 J Calcareous co*cr.ti.ns ED Otauconits
Figure 2. Stratigraphic section and scanning electron micrographs showing the distribution of samples and planktonic foraminifera across the Cretaceous/Tertiary transition and the dissolution interval. 1. Heterohe!ixglobulosa(Ehrenberg); 2. Globigerinelloides mu!tispinatus (Lalicker); 3. Hedbergella monmouthensis (Olsson); 4. Globotruncanella sp.; 5. Globlastica daubjergensis (Brönn imann). ("Fm" denotes "formation.")
72
In most regions, benthic foraminiferal species extinctions are much less drastic in comparison to the planktonics. Percentage extinctions of latest Cretaceous Trinidad foraminifera are only 9 percent for agglutinated species and 22 percent for calcareous benthic species (Webb 1973). Extinctions are higher among coeval Deep Sea Drilling Project (DSDP) site 208 (Lord Howe Rise, Southwest Pacific) foraminifera. Webb (1973) reports 73 percent extinction of agglutinated species and 52 percent for calcareous benthic species. He suggested that the greater faunal turnover at the Lord Howe Rise site may have been because of more extreme climatic fluctuations in higher latitude regions. Foraminiferal distributions on Seymour Island show that most of the 126 benthic species and 15 planktonic species appear within the lower 300 meters of the Lopez de Bertodano Formation. These generally have scattered occurrences throughout the remaining 850 meters of the Cretaceous section. Therefore, it appears as though no major biotic changes took place within the Campanian-Maastrichtian portion of the sequence, attesting to long-term environmental stability. The faunal turnover within 4 meters below the KIT glauconite bed, on the other hand, is quite dramatic. Foraminiferal species terminations at this level are 71 percent for agglutinated, 64 percent for calcareous benthic, and 100 percent for planktonic species. Benthic survivors of the extinction event include a few simple agglutinated forms as well as several long-ranging, cosmopolitan calcareous benthic species. The highest stratigraphic occurrence of Maastrichtian planktonic foraminifera on Seymour Island is in sample numbers 411, 526, and 535, located within 4 meters below the KIT glauconite bed (figure 2), in the upper Lopez de Bertodano Formation. These samples yielded the planktonic species Heterolielix globulosa (Ehrenberg), Globigerinello ides mu/f ispinatus (Lalicker), Hedbergella monmouthensis (Olsson), and Globotruncane/la? sp., in addition to diverse Cretaceous benthic assemblages. Just above the glauconite is a sequence, referred to as the "Dissolution interval," in which foraminifera are poorly represented (figure 2). Of 41 samples collected from this interval, 20 were completely barren of foraminifera and 21 yielded poorly preserved agglutinated assemblages. Other calcareous microfossils (e.g., ostracodes, juvenile molluscs, echinoid spines, calcispheres, and calcarous nannoplankton) are absent from the dissolution interval. Foraminifera diagnostic of the Danian wre recovered from sea cliff sample number 539, collected 1 meter below the Lopez de Bertodano/Sobral Formation contact, and sample numbers 540 and 515, from the lower Sobral Formation (figures 1 and 2). The planktonic species Globastica dauhjergensis (Brönnimann), which is widely recognized as a Danian index fossil (e.g., see Troelsen 1957; Berggren 1962; Hansen 1970), was found in all three of these samples. This taxon is considered as a descendant of an early Danian species, which has not yet been found on Seymour Island. Other specimens making their first stratigraphic appearance above the KIT glauconite bed include forms known elsewhere in Upper Cretaceous/Lower Tertiary deposits and several new or indeterminant species. The calcareous benthic Buliminella n. sp., which makes its first appearance in sample number 539, is conspicuously abundant in all of the Danian samples, dominating up to 82 percent of the foraminiferal assemblages. Agglutinated taxa are very rare above the KIT glauconite bed, contrary to their consistent, moderately abundant representation in the Cretaceous assemblages. This transition, from high to low species equitability, indicates a change from predominantly stable to stressed environmental conditions. It coincides with a sigANTARCTIC JOURNAL
nificant negative excursion in the isotopic carbon-13 isotopic signal and a negative excursion in the isotopic oxygen-18 isotopic signal among several of the Danian benthic taxa (Barrera personal communication). Similar isotopic shifts in isotopic carbon-13 and isotopic oxygen-18 occur at numerous other KIT boundary sites and have been interpreted as representing decreased oceanic productivity and increased marine temperatures, respectively (Perch-Nielson, McKenzie, and He (1982). This study was supported by National Science Foundation grants DPP 82-14174A01 to P.N. Webb and DPP 82-13985A01 to W.J. Zinsmeister and D.H. Elliot. References Askin, R.A. 1984. Palynological investigations of the James Ross Island basin and Robertson Island, Antarctic Peninsula. Antarctic Journal of the U.S., 19(5), 6-7. Barrera, E. 1986. Personal communication. Berggren, W.A. 1962. Some planktonic foraminifera from the Maestrichtian and type Danian stages of southern Scandinavia. Contributions in Geology, 9, 1-106. Hansen, H.J. 1970. Biometric studies on the stratigraphic evolution of Globoconusa daubjergensis (BrOnnimann). Bulletin of the Geological Society of Denmark, 19, 341-360. Huber, B.T. 1985. The location of the Cretaceous/Tertiary boundary on Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 20(5), 46-48. Huber, B.T. 1986. Foraminiferal evidence for a terminal Cretaceous oceanic event. Geological Society of America, Abstract with Programs,
18(4), 309-310. Huber, B.T., D.M. Harwood, and P.N. Webb. 1983. Upper Cretaceous
Palynomorphs and depositional environment for upper Campanian sediments on Seymour Island, Antarctica R. ASKIN
Geology Department Colorado School of Mines Golden, Colorado 80401
Seymour Island, northeastern Antarctic Peninsula, provides an area for effective study of palynomorph assemblages and their value as indicators of Cretaceous and Tertiary paleoenvironments. Paleoenvironmental interpretations can be based on a wealth of evidence from other fossil groups, coupled with sedimentological analyses. The interpretations may also be compared with previous palynological studies from other parts of the world. The essentially unconsolidated Campanian through Eocene Seymour Island sediments are well exposed and yield a plethora of fossils of many different floral and faunal 1986 REVIEW
microfossil biostratigraphy of Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 18(5), 72-74.
Luterbacher, H.P., and I. Premoli Silva. 1964. Biostratigraphy of the Cretaceous-Tertiary boundary in the Central Appenines Rivista Italiana di Paleontologia e Stratigrafia, 70, 67-88. (In Italian) Macellari, C. E. 1985. The Cretaceous-Tertiary boundary in the Antarctic Peninsula and southern South America. Memorias, Sexto Congreso Latinoamericano de Geologia, 267-278. (In Spanish) Macellari, G.E. 1986. Late Campanian-Maastrichtian ammonite fauna from Seymour Island (Antarctic Peninsula). Journal of Paleontology, Memoir, 18, 1-55. Macellari, CE., and W.J. Zinsmeister. 1983. Sedimentology and macropaleontology of the Upper Cretaceous to Paleocene sequence of Seymour Island. Antarctic Journal of the U.S., 18(5), 69-71. Perch-Nielsen, K., J . McKenzie, and Q. He. 1982. Biostratigraphy and isotope stratigraphy and the "catastrophic" extinction of calcareous nannoplankton at the Cretaceous/Tertiary boundary. Geological Society of America Special Paper, 190, 353-371. Pessagno, E.A., Jr. 1967. Upper Cretaceous planktonic foraminifera from the western Gulf Coastal Plain. Palaeontographica Americana, 5(37), 245-445. Smit, J. 1982. Extinction and evolution of planktonic foraminifera after a major impact at the Cretaceous/Tertiary boundary. Geological Society of America Special Paper, 190, 329-352. Troelsen, J.C. 1957. Some planktonic foraminifera of the type Danian and their stratigraphic importance. Bulletin of the U.S. National Museum, 215, 125-132. Webb, P.N. 1973. Upper Cretaceous-Paleocene foraminifera from Site 208 (Lord Howe Rise, Tasman Sea), DSDP Leg 21. In R.E. Burns, J. Andrews, et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, 21, 541-573. Zinsmeister, W.J., and C. Macellari. 1983. Changes in the macrofossil faunas at the end of the Cretaceous on Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 18(5), 68-69.
groups. Palynomorphs, both marine and nonmarine in origin, are particularly abundant throughout the succession. The following comments on the upper Campanian part of the section exemplify some aspects of this study. Fossil and sedimentological evidence suggests a nearshore marine, low-energy depositional environment for upper Campanian sediments on Seymour Island. Beds dated as upper Campanian by calcareous nannofossils, foraminifera, ammonites and other molluscs, etc., (Huber, Harwood, and Webb 1983; Huber in preparation; Macellari 1984, 1986) and by palynomorphs (Askin 1985, in preparation) comprise the oldest sediments cropping out on Seymour Island. They are assigned to part of the Lopez de Bertodano Formation and contain a high proportion of mud and silt, particularly in massive mudstone units best developed toward the south coast (Macellari in preparation). Upper Campanian Seymour Island sediments are subdivided into six lithologic units ("Rotularia units," Macellari in preparation). The low-diversity invertebrate macrofauna is dominated by the annelid Rotularia, which apparently favored muddy substrates (Macellari 1984). In his discussion of sedimentological data and environmental/ecological preferences of the macrofauna, Macellari (in preparation) concludes that units 1 through 6 were deposited in very shallow marine, low-energy, delta/ estuary-influenced environments, with possible intermittent brackish conditions. 73
