Alluvial stratigraphic sequences within the Permian
Alluvial stratigraphic sequences within the Permian Transantarctic foreland basin, Beardmore Glacier area, Antarctica JOHN
L. ISBELL
Byrd Polar Research Center
and
Department of Geological Sciences Ohio State University Columbus, Ohio 43210
I.M. MACDONALD
DAVID
British Antarctic Survey Natural Environ,nent Research Council Cambridge CB3 0ET UK
During the austral summer of 1990-1991, we collected data from exposures of the Permian Buckley Formation in the Beardmore Glacier region at Clarkson Peak, Mount Picciotto, Mount Achernar, Mount Bowers, and Willey Point (figure 1). Data consist of detailed vertical logs, maps of lithofacies and sediment-body geometries, and paleocurrent orientations. We took
r
•()
^V* 16 5 0E'L...
L on in C ca Clarkson Cr
Pk.2"
Mt. Miller
A
N
I
"to
wc' i aD o
/
C.PtJ
• Mt. Picciotto o \Painted Cliffs 4°S •Mt. Ropar Mt. Achemar CZ
0 km 30
Lewis Cliffs L-.
1800
840S
'? Mt. Dickerson
9
Barnes Pk
e
tu Area
mt. "j t Donaidsor
LJ\
ANTARCTICA
goow
•V
Mt. Deakin '-I (CKinsey Mt. Bowers Pk.
L
1 650EJ'Mt Mills
I
Figure 1. Location map showing sites with Permian strata visited during the 1990-1991 field season in the Beardmore Glacier area. (km denotes kilometer.) 1991 REVIEW
extensive photo mosaics from helicopter fly-bys at these sites, as well as at Mount Miller, Painted Cliffs, Mount Ropar, Lewis Cliffs, Mount Dickerson, Barnes Peak, Bingley Glacier, Mount Donaldson, Mount Deakin, Kinsey Peak, and Mount Mills. These photos aided in the three-dimensional reconstruction of sedimentary bodies and stratigraphic packages. Rock samples collected for petrographic analysis are stored at the Byrd Polar Research Center and at the British Antarctic Survey. Coal, carbonaceous shale, and samples containing fossil plants were forwarded to E.L. Taylor, T.N. Taylor, and N.R. Cñneo for paleobotanical and palynological analyses. Interpretations made in this paper include data collected during the 1985-1986 field season (Isbell 1990) and data reported by Barrett (1968). Sedimentologic and stratigraphic analyses of the Buckley Formation in the Beardmore Glacier region, support the hypothesis that the Permian strata were deposited within a foreland basin associated with the Gondwanide orogeny. Results suggest that tectonic loading along the paleo-Pacific margin of Antarctica controlled basin formation and sediment deposition. The Buckley Formation in the Beardmore Glacier region, is approximately 750 meters thick and consists of interstratified fluvial sandstone, siltstone, mudstone, and coal. Sandstone in the lower member of the Buckley Formation is quartzo-feldspathic, and upper-member sandstone is volcaniclastic. The Buckley members define two major depositional sequences. Disconformities bound each sequence along the cratonic margin of the basin (figure 2). These disconformities are recognized within measured sections by abrupt upward stratigraphic changes in sandstone composition, facies, and paleocurrent orientations and, at some sites, by well-developed intraformational conglomerates at the base of sandstone bodies. Basinward, these surfaces become conformable and are marked by an abrupt shift in depositional patterns toward the orogenic belt. Using data based on fluvial architecture, the large-scale distribution of sandstone bodies within fine-grained sediments, and their mutual relationship (Allen 1978; Collinson 1986), we identify three major geographically distributed facies patterns within the basin: • a thick succession of overlapping sandstone bodies along the orogenic basin margin, • thick interstratified mudstone and sandstone along the basin axis, and • a thin succession of overlapping sandstone bodies along the cratonic basin margin. Upward within each depositional sequence, the orogenic-margin sandstone expands basinward and the axial mudstone/ sandstone and cratonic-margin sandstone are displaced toward the craton. Facies analysis reveals the occurrence of braided-stream deposits along basin margins. These grade basinward into lowsinuosity, single-channel, and meandering-stream lithofacies. Both braided- and meandering-stream lithofacies occur along the basin axis. Paleocurrent analysis suggests the rivers flowed transversely across basin margins and longitudinally down the topographic basin axis. Upward within each depositional sequence, the position of the longitudinal drainage axis shifted cratonward concurrent with displacement of depositional patterns within the basin. Modeling by Heller, Angevine, and Paola (1988) and Flemings and Jordan (1989, 1990) have produced foreland-basin depositional packages similar to those in the Beardmore Glacier area. Flemings and Jordan (1990) suggested that abrupt shifts in depositional patterns toward the orogenic belt occur during the onset of thrust loading on an elastic lithosphere. Rapid subsi13
CENTRAL TRANSANTARCTIC MOUNTAINS Basin Fill Cratonic Permian-Triassic Disconformity Basin '--.&----Margin Alluvial Stratigraphy "-.. Disconformity
".
'.-.-a-"
T
Overlapping Channel Bodies IIsolated Channel Bodies
Orogenic Margin Upper Buckley Member Base of Sequence 2 Lower Buckley Member Base of Sequence I
Figure 2. Diagrammatic interpretation of the Permian basin fill in the Beardmore Glacier area. Cross-section is east-west with the cratonic basin margin located along the present Polar Plateau side of the central Transantarctic Mountains.
dence during thrusting traps coarse-grained sediment next to the orogenic belt (cf. Blair and Bilodeau 1988; Heller et al. 1988; Paola 1988). Later, as subsidence decreases, progradation of a clastic wedge with cratonward displacement of depositional patterns occurs. Combined paleocurrent, lithofacies, and petrologic analyses of the Permian Buckley Formation suggest that tectonic loading controlled the deposition of major fluvial sequences. The sequences suggest that two loading events occurred during the Permian. National Science Foundation grant DPP 89-17413 and the British Antarctic Survey provided financial support for this research. Antarctic Support Associates, Helicopters New Zealand Ltd., U.S. Navy Squadron VXE-6, and the National Science Foundation provided logistic support.
Barrett, P.J. 1968. The post-glacial Permian and Triassic Beacon Rocks in the
Beardmore Glacier area, central Transantarctic Mountains, Antarctica.
(Doctoral thesis, Ohio State University, Columbus, Ohio.) Blair, T.C., and WL. Bilodeau. 1988. Development of tectonic cyclothems in rift, pull-apart, and foreland basins: Sedimentary response to episodic tectonism. Geology, 16, 517-520. Collinson, J.D. 1986. Alluvial sediments. In H.G. Reading (Ed.), Sedimentary environments and facies. Oxford: Blackwell Scientific Publications. Flemings, PB., and T.E. Jordan. 1989. A synthetic stratigraphic model of foreland basin development. Journal of Geophysical Research, 94, 3851-3866. Flemings, PB., and T.E. Jordan. 1990. Stratigraphic modeling of foreland basins: Interpreting thrust deformation and lithosphere rheology. Geology, 18, 430-434. Heller, EL., C.L. Angevine, and C. Paola. 1988. Two-phase stratigraphic model of foreland-basin sequences. Geology, 16, 501-504.
References
Isbell, J.L. 1990. Fluvial sedimentology and basin analyses of the Permian Fairchild and Buckley Formations, Beardmore Glacier region, and the Weller Coal Measures, southern Victoria Land, Antarctica. (Doctoral thesis, Ohio
Allen, J.R.L. 1978. Studies in fluvial sedimentation: An exploratory quantitative model for the architecture of avulsion-controlled alluvial suites. Sedimentary Geology, 21, 129-147
State University, Columbus, Ohio.) Paola, C. 1988. Subsidence and gravel transport in alluvial basins. In K.L. Kleinspehn and C. Paola (Eds.), New perspectives in basin analysis. New York: Springer-Verlag.
14
ANTARCTIC JOURNAL
L. ISBELL
Byrd Polar Research Center
and
Department of Geological Sciences Ohio State University Columbus, Ohio 43210
I.M. MACDONALD
DAVID
British Antarctic Survey Natural Environ,nent Research Council Cambridge CB3 0ET UK
During the austral summer of 1990-1991, we collected data from exposures of the Permian Buckley Formation in the Beardmore Glacier region at Clarkson Peak, Mount Picciotto, Mount Achernar, Mount Bowers, and Willey Point (figure 1). Data consist of detailed vertical logs, maps of lithofacies and sediment-body geometries, and paleocurrent orientations. We took
r
•()
^V* 16 5 0E'L...
L on in C ca Clarkson Cr
Pk.2"
Mt. Miller
A
N
I
"to
wc' i aD o
/
C.PtJ
• Mt. Picciotto o \Painted Cliffs 4°S •Mt. Ropar Mt. Achemar CZ
0 km 30
Lewis Cliffs L-.
1800
840S
'? Mt. Dickerson
9
Barnes Pk
e
tu Area
mt. "j t Donaidsor
LJ\
ANTARCTICA
goow
•V
Mt. Deakin '-I (CKinsey Mt. Bowers Pk.
L
1 650EJ'Mt Mills
I
Figure 1. Location map showing sites with Permian strata visited during the 1990-1991 field season in the Beardmore Glacier area. (km denotes kilometer.) 1991 REVIEW
extensive photo mosaics from helicopter fly-bys at these sites, as well as at Mount Miller, Painted Cliffs, Mount Ropar, Lewis Cliffs, Mount Dickerson, Barnes Peak, Bingley Glacier, Mount Donaldson, Mount Deakin, Kinsey Peak, and Mount Mills. These photos aided in the three-dimensional reconstruction of sedimentary bodies and stratigraphic packages. Rock samples collected for petrographic analysis are stored at the Byrd Polar Research Center and at the British Antarctic Survey. Coal, carbonaceous shale, and samples containing fossil plants were forwarded to E.L. Taylor, T.N. Taylor, and N.R. Cñneo for paleobotanical and palynological analyses. Interpretations made in this paper include data collected during the 1985-1986 field season (Isbell 1990) and data reported by Barrett (1968). Sedimentologic and stratigraphic analyses of the Buckley Formation in the Beardmore Glacier region, support the hypothesis that the Permian strata were deposited within a foreland basin associated with the Gondwanide orogeny. Results suggest that tectonic loading along the paleo-Pacific margin of Antarctica controlled basin formation and sediment deposition. The Buckley Formation in the Beardmore Glacier region, is approximately 750 meters thick and consists of interstratified fluvial sandstone, siltstone, mudstone, and coal. Sandstone in the lower member of the Buckley Formation is quartzo-feldspathic, and upper-member sandstone is volcaniclastic. The Buckley members define two major depositional sequences. Disconformities bound each sequence along the cratonic margin of the basin (figure 2). These disconformities are recognized within measured sections by abrupt upward stratigraphic changes in sandstone composition, facies, and paleocurrent orientations and, at some sites, by well-developed intraformational conglomerates at the base of sandstone bodies. Basinward, these surfaces become conformable and are marked by an abrupt shift in depositional patterns toward the orogenic belt. Using data based on fluvial architecture, the large-scale distribution of sandstone bodies within fine-grained sediments, and their mutual relationship (Allen 1978; Collinson 1986), we identify three major geographically distributed facies patterns within the basin: • a thick succession of overlapping sandstone bodies along the orogenic basin margin, • thick interstratified mudstone and sandstone along the basin axis, and • a thin succession of overlapping sandstone bodies along the cratonic basin margin. Upward within each depositional sequence, the orogenic-margin sandstone expands basinward and the axial mudstone/ sandstone and cratonic-margin sandstone are displaced toward the craton. Facies analysis reveals the occurrence of braided-stream deposits along basin margins. These grade basinward into lowsinuosity, single-channel, and meandering-stream lithofacies. Both braided- and meandering-stream lithofacies occur along the basin axis. Paleocurrent analysis suggests the rivers flowed transversely across basin margins and longitudinally down the topographic basin axis. Upward within each depositional sequence, the position of the longitudinal drainage axis shifted cratonward concurrent with displacement of depositional patterns within the basin. Modeling by Heller, Angevine, and Paola (1988) and Flemings and Jordan (1989, 1990) have produced foreland-basin depositional packages similar to those in the Beardmore Glacier area. Flemings and Jordan (1990) suggested that abrupt shifts in depositional patterns toward the orogenic belt occur during the onset of thrust loading on an elastic lithosphere. Rapid subsi13
CENTRAL TRANSANTARCTIC MOUNTAINS Basin Fill Cratonic Permian-Triassic Disconformity Basin '--.&----Margin Alluvial Stratigraphy "-.. Disconformity
".
'.-.-a-"
T
Overlapping Channel Bodies IIsolated Channel Bodies
Orogenic Margin Upper Buckley Member Base of Sequence 2 Lower Buckley Member Base of Sequence I
Figure 2. Diagrammatic interpretation of the Permian basin fill in the Beardmore Glacier area. Cross-section is east-west with the cratonic basin margin located along the present Polar Plateau side of the central Transantarctic Mountains.
dence during thrusting traps coarse-grained sediment next to the orogenic belt (cf. Blair and Bilodeau 1988; Heller et al. 1988; Paola 1988). Later, as subsidence decreases, progradation of a clastic wedge with cratonward displacement of depositional patterns occurs. Combined paleocurrent, lithofacies, and petrologic analyses of the Permian Buckley Formation suggest that tectonic loading controlled the deposition of major fluvial sequences. The sequences suggest that two loading events occurred during the Permian. National Science Foundation grant DPP 89-17413 and the British Antarctic Survey provided financial support for this research. Antarctic Support Associates, Helicopters New Zealand Ltd., U.S. Navy Squadron VXE-6, and the National Science Foundation provided logistic support.
Barrett, P.J. 1968. The post-glacial Permian and Triassic Beacon Rocks in the
Beardmore Glacier area, central Transantarctic Mountains, Antarctica.
(Doctoral thesis, Ohio State University, Columbus, Ohio.) Blair, T.C., and WL. Bilodeau. 1988. Development of tectonic cyclothems in rift, pull-apart, and foreland basins: Sedimentary response to episodic tectonism. Geology, 16, 517-520. Collinson, J.D. 1986. Alluvial sediments. In H.G. Reading (Ed.), Sedimentary environments and facies. Oxford: Blackwell Scientific Publications. Flemings, PB., and T.E. Jordan. 1989. A synthetic stratigraphic model of foreland basin development. Journal of Geophysical Research, 94, 3851-3866. Flemings, PB., and T.E. Jordan. 1990. Stratigraphic modeling of foreland basins: Interpreting thrust deformation and lithosphere rheology. Geology, 18, 430-434. Heller, EL., C.L. Angevine, and C. Paola. 1988. Two-phase stratigraphic model of foreland-basin sequences. Geology, 16, 501-504.
References
Isbell, J.L. 1990. Fluvial sedimentology and basin analyses of the Permian Fairchild and Buckley Formations, Beardmore Glacier region, and the Weller Coal Measures, southern Victoria Land, Antarctica. (Doctoral thesis, Ohio
Allen, J.R.L. 1978. Studies in fluvial sedimentation: An exploratory quantitative model for the architecture of avulsion-controlled alluvial suites. Sedimentary Geology, 21, 129-147
State University, Columbus, Ohio.) Paola, C. 1988. Subsidence and gravel transport in alluvial basins. In K.L. Kleinspehn and C. Paola (Eds.), New perspectives in basin analysis. New York: Springer-Verlag.
14
ANTARCTIC JOURNAL
