Cretaceous stratigraphy of Seymour Island, East ...
Cretaceous stratigraphy of Seymour Island, East Antarctic Peninsula CARLOS MACELLARI and BRIAN
Four profiles were measured on Seymour Island in areas of little tectonic disturbance, previously selected by photointerpretation (figure 1). A total of 250 samples were systematically collected within these profiles at approximately 10meter intervals. Good weather and invaluable support from the helicopter pilots and the crew of the USCGC Glacier made it possible to visit and measure profiles on Snow Hill, Vega, and James Ross Islands in addition to the planned activities on Seymour Island. We hope these observations and samples will provide valuable information regarding the correlation of different Cretaceous outcrops within the James Ross Island area. They may be particularly helpful in establishing a detailed correlation between the Seymour and Snow Hill Island sequences. The oldest unit exposed on the island is the Lopez de Bertodano Formation of Campanian (Howarth 1966; Olivero 1981) to possibly Maestrichtian (Spath 1953) age (figure 2). The maximum measured thickness was encountered in profile 1(1,190 meters). Several minor units were recognized on the basis of lithology, degree of cementation, and fossil content; many of these were laterally continuous throughout the island. In general, the predominant lithology is composed of monotonous, gray, friable, sandy siltstones. Sporadic intercalations of calcareous, indurated fine-grained sandstones occur within the sandy siltstone units, resulting in a more positive relief. Rounded to irregular concretions and concretionary horizons are found throughout the sequence. With the exception of the lower 300 meters of the section, fossils are extremely abundant and very well preserved. Different and laterally persistent mac-
T. HUBER
Institute of Polar Studies Ohio State University Columbus, Ohio 43210
The Cretaceous stratigraphy of Seymour Island (Isla Vicecomodoro Marambio in Argentine literature) has been described by Andersson (1906) and more recently by several authors (Elliot et al. 1975, Rinaldi 1982, and Rinaldi et al. 1972, among others). However, no detailed sedimentological or stratigraphic account of these sediments has yet been published. As one of the programs on the Seymour Island Expedition, we undertook a comprehensive survey of the Cretaceous portion of the island. The objectives of this study were to provide the first detailed sedimentological description and a detailed geologic map of the Upper Cretaceous section, as well as to collect microand macropaleontological samples in order to refine the present zonation of the sequence. Correlation with other faunas from the Southern Hemisphere will then be attempted, primarily on the basis of the foraminiferal and molluscan specimens.
/
BOOMAN POINT o I 2KM -1
FOSSIL BAY CAPE LAMB
LOPEZ de BERTODANO BAY
Du
Teim
b
I
>>^
MEASURED SECTIONS RINALDI j 01. SECTION
PENGUIN
ARSEN OVE
tQ .-...
I
PENGUIN BAY
QUATER NARY J .:. Q :. 1 GLACIAL DEPOSITS
NT
TERTIARY Ji Telmi LAMESETA FM. CRETACEOUS
SOBRAL FM.
III kb I LOPEZ de BERTODANO FM.
Figure 1. Simplified geologic map of Seymour Island showing location of measured sections (after Rinaldi et al. 1978).
68
ANTARCTIC JOURNAL
S 400
200
Iv
ii N
L _
1000
'LU - 0M.
E]Sob1 Fm Lopez de Bertodano Fm.
Figure 2. General correlation between sections measured on Seymour Island.
rofaunal assemblages were recognized, including numerous ammonites, bivalves, gastropods, echinoderms, corals, and sporadic fossil wood. Large benthic foraminifera were recog-
nized in the field within the unconsolidated strata, where faunal diversity appeared to be quite low. Preliminary observations indicate that the foraminiferal population is more abundant in the lower three-quarters of the Upper Cretaceous sequence. The Sobral Formation, which may be Maestrichtian to Paleocene in age, overlies the Lopez de Bertodano Formation in an apparently concordant fashion. It consists of up to 265 meters of somewhat coarser and more glauconitic silty sandstone, grading into fine-grained sandstones. Rounded concretions and concretionary horizons are frequent. Some beds are laterally continuous, but generally this formation shows a more pronounced lateral variation than the previous unit. The base of the Sobral Formation is a laterally continuous, 15-20-meter thick, dark brown, well-laminated to flaser-bedded silty mudstone which displays local channels. This moderately resistant bed produces a conspicuous positive break an the topography (figure 3). A continuous, well-cemented, large-scale trough crossbedded glauconitic sandstone appears at approximately 180 meters from the base of the Sobral. Above this, the sequence becomes more sandy, glauconitic, and occasionally yellowstained, with increasingly abundant concretions and fossil wood. All of these characteristics indicate that this may be an independent unit lithologically similar to the Cross Valley Formation (Elliot et al. 1975). Fossils found in the Sobral Formation
Figure 3. Oblique aerial photograph showing the major units recognized in the Cretaceous of Seymour Island, and the unconformable contact Sobral Formation; Ksu = upper unit of the Sobral with the Tertiary La Meseta Formation: KIb = Lopez de Bertodano Formation; Ks = undifferentiated Quaternary deposits. (Photograph by W. J. Zinsmeister) Formation; TeIm = La Meseta Formation; 0 =
1982 REVIEW
69
include bivalves, gastropods, echinoderm spines, and abundant wood. This work was supported by National Science Foundation grant DPP 80-20096.
References Andersson, J. C. 1906. on the geology of Graham Land. Bulletin of the Geological Institute of the University of Upsala, 7, 19-71. Elliot, D. H., Rinaldi, C. A., Zinsmeister, W. J., Trautman, T. A., Bryant, W. B., and del Valle, R. 1975. Geological investigations on Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 10(4),182-186.
Howarth, M. K. 1966. Ammonites from the Upper Cretaceous of the James Ross Island Group. Bulletin of the British Antarctic Survey, 10,
55-69. Olivero, E. G. 1981. Esquema de zonaciOn de ammonites del Cretácico Superior del Grupo de Islas James Ross, Antártida. VIII Congresso Geologico Argentino, San Luis, September 20-27, 1981. Acta, 311, 897-907. Rinaldi, C. A. 1982. The Upper Cretaceous in the James Ross Island Group. In C. Craddock(Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Rinaldi, C. A., Massabie, A., Morelli, J., Rosenman, H. L., and del Valle, R. 1978. GeologIa de la Isla Vicecomodoro Marambio. Contribuciones del instituto Antdrtico Argentino, 217, 1-37. Spath, L. F. 1953. The Upper Cretaceous cephalopod fauna of Graham Land. Falkland Islands Dependencies Survey, Scientific Reports, 3, 1-60.
Palynological investigations of Campanian to lower Oligocene sediments on Seymour Island, Antarctic Peninsula -; ROSEMARY
A.
A
ASKIN
B
Geology Department Colorado School of Mines Golden, Colorado 80401 R. F1\11lY F1I:MIN;
Department of Geological Sciences University of Colorado Boulder, Colorado 80309
/
C
Palynomorphs have been recovered from all of the first prepa rations of samples collected during the February-March 1982 expedition to Seymour Island. In all, 363 samples were collected, mainly from Seymour Island but also from Snow Hill Island (provided by B. Huber), Cape Lamb on Vega Island, The Naze on northeastern James Ross Island, and Cape Melville on King George Island. The stratigraphy of Seymour Island is summarized by Macellari and Huber (Antarctic Journal, this issue; Campanian to ? Paleocene, Lopez de Bertodano and Sobral Formations) and by Zinsmeister and DeVries (Antarctic Journal, this issue; ? Paleocene to lower Oligocene, Seymour Island Group). Apart from cemented resistant sandstone beds and concretions, most of the sedimentary sequence on Seymour Island is unconsolidated. Fine-grained sediments (mud and silt) are abundant in places particularly in the Sobral Formation. Much of the finegrained sediment is carbonaceous and highly suitable for palynological sampling. The best continuously exposed section of predominantly fine-grained sediment crops out in the central part of Seymour Island. This approximately 300-meter-thick section includes the Sobral Formation and is believed to include the Cretaceous70
4. 1 E
F
5Opm
Photomicrographs of fossil pollen from Seymour Island (bar is equivalent to 50 micrometers). A, M!crocachryidites antarcticus Cookson; B, Phyllocladidites mawsoniiCookson; C, Nothofagidites fleming!! (Couper) Potonie; D, Proteacidites parvus Cookson; E, Haloragacid!tes harris!! (Couper) Harris; F, Tricolpates sp. A, B, D, and E occur in the Sobral Formation and throughout the Seymour Island Group; C occurs in the Seymour Island Group; and F occurs In the Sobral Formation and the Cross Valley Formation. ANTARCTIC JOURNAL
Four profiles were measured on Seymour Island in areas of little tectonic disturbance, previously selected by photointerpretation (figure 1). A total of 250 samples were systematically collected within these profiles at approximately 10meter intervals. Good weather and invaluable support from the helicopter pilots and the crew of the USCGC Glacier made it possible to visit and measure profiles on Snow Hill, Vega, and James Ross Islands in addition to the planned activities on Seymour Island. We hope these observations and samples will provide valuable information regarding the correlation of different Cretaceous outcrops within the James Ross Island area. They may be particularly helpful in establishing a detailed correlation between the Seymour and Snow Hill Island sequences. The oldest unit exposed on the island is the Lopez de Bertodano Formation of Campanian (Howarth 1966; Olivero 1981) to possibly Maestrichtian (Spath 1953) age (figure 2). The maximum measured thickness was encountered in profile 1(1,190 meters). Several minor units were recognized on the basis of lithology, degree of cementation, and fossil content; many of these were laterally continuous throughout the island. In general, the predominant lithology is composed of monotonous, gray, friable, sandy siltstones. Sporadic intercalations of calcareous, indurated fine-grained sandstones occur within the sandy siltstone units, resulting in a more positive relief. Rounded to irregular concretions and concretionary horizons are found throughout the sequence. With the exception of the lower 300 meters of the section, fossils are extremely abundant and very well preserved. Different and laterally persistent mac-
T. HUBER
Institute of Polar Studies Ohio State University Columbus, Ohio 43210
The Cretaceous stratigraphy of Seymour Island (Isla Vicecomodoro Marambio in Argentine literature) has been described by Andersson (1906) and more recently by several authors (Elliot et al. 1975, Rinaldi 1982, and Rinaldi et al. 1972, among others). However, no detailed sedimentological or stratigraphic account of these sediments has yet been published. As one of the programs on the Seymour Island Expedition, we undertook a comprehensive survey of the Cretaceous portion of the island. The objectives of this study were to provide the first detailed sedimentological description and a detailed geologic map of the Upper Cretaceous section, as well as to collect microand macropaleontological samples in order to refine the present zonation of the sequence. Correlation with other faunas from the Southern Hemisphere will then be attempted, primarily on the basis of the foraminiferal and molluscan specimens.
/
BOOMAN POINT o I 2KM -1
FOSSIL BAY CAPE LAMB
LOPEZ de BERTODANO BAY
Du
Teim
b
I
>>^
MEASURED SECTIONS RINALDI j 01. SECTION
PENGUIN
ARSEN OVE
tQ .-...
I
PENGUIN BAY
QUATER NARY J .:. Q :. 1 GLACIAL DEPOSITS
NT
TERTIARY Ji Telmi LAMESETA FM. CRETACEOUS
SOBRAL FM.
III kb I LOPEZ de BERTODANO FM.
Figure 1. Simplified geologic map of Seymour Island showing location of measured sections (after Rinaldi et al. 1978).
68
ANTARCTIC JOURNAL
S 400
200
Iv
ii N
L _
1000
'LU - 0M.
E]Sob1 Fm Lopez de Bertodano Fm.
Figure 2. General correlation between sections measured on Seymour Island.
rofaunal assemblages were recognized, including numerous ammonites, bivalves, gastropods, echinoderms, corals, and sporadic fossil wood. Large benthic foraminifera were recog-
nized in the field within the unconsolidated strata, where faunal diversity appeared to be quite low. Preliminary observations indicate that the foraminiferal population is more abundant in the lower three-quarters of the Upper Cretaceous sequence. The Sobral Formation, which may be Maestrichtian to Paleocene in age, overlies the Lopez de Bertodano Formation in an apparently concordant fashion. It consists of up to 265 meters of somewhat coarser and more glauconitic silty sandstone, grading into fine-grained sandstones. Rounded concretions and concretionary horizons are frequent. Some beds are laterally continuous, but generally this formation shows a more pronounced lateral variation than the previous unit. The base of the Sobral Formation is a laterally continuous, 15-20-meter thick, dark brown, well-laminated to flaser-bedded silty mudstone which displays local channels. This moderately resistant bed produces a conspicuous positive break an the topography (figure 3). A continuous, well-cemented, large-scale trough crossbedded glauconitic sandstone appears at approximately 180 meters from the base of the Sobral. Above this, the sequence becomes more sandy, glauconitic, and occasionally yellowstained, with increasingly abundant concretions and fossil wood. All of these characteristics indicate that this may be an independent unit lithologically similar to the Cross Valley Formation (Elliot et al. 1975). Fossils found in the Sobral Formation
Figure 3. Oblique aerial photograph showing the major units recognized in the Cretaceous of Seymour Island, and the unconformable contact Sobral Formation; Ksu = upper unit of the Sobral with the Tertiary La Meseta Formation: KIb = Lopez de Bertodano Formation; Ks = undifferentiated Quaternary deposits. (Photograph by W. J. Zinsmeister) Formation; TeIm = La Meseta Formation; 0 =
1982 REVIEW
69
include bivalves, gastropods, echinoderm spines, and abundant wood. This work was supported by National Science Foundation grant DPP 80-20096.
References Andersson, J. C. 1906. on the geology of Graham Land. Bulletin of the Geological Institute of the University of Upsala, 7, 19-71. Elliot, D. H., Rinaldi, C. A., Zinsmeister, W. J., Trautman, T. A., Bryant, W. B., and del Valle, R. 1975. Geological investigations on Seymour Island, Antarctic Peninsula. Antarctic Journal of the U.S., 10(4),182-186.
Howarth, M. K. 1966. Ammonites from the Upper Cretaceous of the James Ross Island Group. Bulletin of the British Antarctic Survey, 10,
55-69. Olivero, E. G. 1981. Esquema de zonaciOn de ammonites del Cretácico Superior del Grupo de Islas James Ross, Antártida. VIII Congresso Geologico Argentino, San Luis, September 20-27, 1981. Acta, 311, 897-907. Rinaldi, C. A. 1982. The Upper Cretaceous in the James Ross Island Group. In C. Craddock(Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Rinaldi, C. A., Massabie, A., Morelli, J., Rosenman, H. L., and del Valle, R. 1978. GeologIa de la Isla Vicecomodoro Marambio. Contribuciones del instituto Antdrtico Argentino, 217, 1-37. Spath, L. F. 1953. The Upper Cretaceous cephalopod fauna of Graham Land. Falkland Islands Dependencies Survey, Scientific Reports, 3, 1-60.
Palynological investigations of Campanian to lower Oligocene sediments on Seymour Island, Antarctic Peninsula -; ROSEMARY
A.
A
ASKIN
B
Geology Department Colorado School of Mines Golden, Colorado 80401 R. F1\11lY F1I:MIN;
Department of Geological Sciences University of Colorado Boulder, Colorado 80309
/
C
Palynomorphs have been recovered from all of the first prepa rations of samples collected during the February-March 1982 expedition to Seymour Island. In all, 363 samples were collected, mainly from Seymour Island but also from Snow Hill Island (provided by B. Huber), Cape Lamb on Vega Island, The Naze on northeastern James Ross Island, and Cape Melville on King George Island. The stratigraphy of Seymour Island is summarized by Macellari and Huber (Antarctic Journal, this issue; Campanian to ? Paleocene, Lopez de Bertodano and Sobral Formations) and by Zinsmeister and DeVries (Antarctic Journal, this issue; ? Paleocene to lower Oligocene, Seymour Island Group). Apart from cemented resistant sandstone beds and concretions, most of the sedimentary sequence on Seymour Island is unconsolidated. Fine-grained sediments (mud and silt) are abundant in places particularly in the Sobral Formation. Much of the finegrained sediment is carbonaceous and highly suitable for palynological sampling. The best continuously exposed section of predominantly fine-grained sediment crops out in the central part of Seymour Island. This approximately 300-meter-thick section includes the Sobral Formation and is believed to include the Cretaceous70
4. 1 E
F
5Opm
Photomicrographs of fossil pollen from Seymour Island (bar is equivalent to 50 micrometers). A, M!crocachryidites antarcticus Cookson; B, Phyllocladidites mawsoniiCookson; C, Nothofagidites fleming!! (Couper) Potonie; D, Proteacidites parvus Cookson; E, Haloragacid!tes harris!! (Couper) Harris; F, Tricolpates sp. A, B, D, and E occur in the Sobral Formation and throughout the Seymour Island Group; C occurs in the Seymour Island Group; and F occurs In the Sobral Formation and the Cross Valley Formation. ANTARCTIC JOURNAL
