Petrogenesis of Ferrar Group rocks
our knowledge regarding the morphology, genesis, classification, and use of Cold Desert soils. This study was supported by National Science Foundation grant DPP 74-20991 to George Denton, Univeristy of Maine. I am grateful to Dr. Denton for his assistance in all phases of the study and for his congenial companionship in the field. Bob Ackert, Tom Davis, Tom Kellogg, Galen Kenoyer, John Pastor, and Noel Potter assisted in the field.
Reference
Denton, G.H., R.L. Armstrong, and M. Stuiver. 1971. The late Cenozoic glacial history of Antarctica. In: Turekian, K.K. (ed.), Late Cenozoic Glacial Ages. Yale University Press, New Haven, Connecticut. 279-306.
Petrogenesis of Ferrar Group rocks PHILIP R. KYLE
Institute of Polar Studies The Ohio State University Columbus, Ohio 43210
Jurassic Ferrar Group rocks are widespread throughout the Transantarctic Mountains, occurring as lava flows
(Kirkpatrick Basalts), dolerite sills and dykes (Ferrar Dolerite), and volcanic breccias and mudflows (Mawson Formation). The large layered gabbroic Dufek intrusion in the northern Pensacola Mountains is presumably correlative with the Ferrar Group (Ford, 1976). Major element analyses of the chilled margins of Ferrar Dolerite sills and dikes indicate three main magma compositions (Gunn, 1966). In order of decreasing MgO and increasing Si0 2 , the types are: olivine tholeiite, hypersthene tholeiite, and pigeonite tholeiite (figure 1). Analyses of Kirkpatrick Basalt flows indicate some have similar major element chemistry to the hypersthene tholeiites and pigeonite tholeiites, while many of the flows from Storm Peak, Beardmore Glacier (Elliott, 1972; Faure et al., 1974) are more evolved (figure 1). Kirkpatrick Basalts from Brimstone Peak, northern Victoria Land (Kyle, unpublished data); Blizzard Peak, central Transantarctic Mountains (Elliot, 1972); and Carapace Nunatak, southern Victoria Land (Gunn, 1962) span the range hypersthene tholeiite to pigeonite tholeiite (figure 1). Electron microprobe analyses of pyroxenes in Kirkpatrick Basalt samples (figure 2) show a well developed crystallization trend. Some of the scatter in the pyroxene compositions is due to metastable crystallization. The crystallization trend is however very similar to that displayed by pyroxenes in the Dufek Intrusion (Himmelberg and Ford, 1976) (figure 2), although the trend in the magnesium-rich pyroxenes from the Kirkpatrick Basalts is more extensive. The basal hidden section of the Dufek Intrusion is estimated to be 1.8 to 3.5 kilometers thick (Behrendt et al., 1974). It is likely that the magnesium-rich pyroxenes in the Kirkpatrick Basalts give a good indication of the pyroxene compositions likely to be encountered at depth in the Dufek Intrusion. Plots of major elements against silica for Kirkpatrick Basalts and chilled margins of Ferrar Dolerite sills (i.e., figure 1) show systematic and regular changes. As Si0 2 in-
12 0(0.7113) N
8
(0.7122)
(0.7094) x (0.7082) —6 (0.7103) 0 (0.7125) a, B
0 Olivine tholeiite sill X Hypersthene tholeiite sills + Pigeonite tholeiite sills * Other dolerite sills and dikes Kirkpatrick Basalt, Brimstone Peak 0 Kirkpatrick Basalt , Storm Peak Kirkpatrick Basalt , Blizzard Peak A Kirkpatrick Basalt , Mount Bumsteod 0 Kirkpatrick Basalt , Carapace Nunatak (0.7113) ( 87 Sri 86 Sr )
4 (0.7113)-_....a (0.7129) 2
0'50
(0.7095)
/ (0.712
I I I 1 I 1 I 52 54 56 58 60 62 64 66 68 Si0 2 (wt. %)
108
Figure 1. MgOlSiO2 variation diagram showing the systematic variation in the chemistry of Kirkpatrick Basalt flows (Elliot, 1970,1972; Faure et al., 1974; Gunn, 1962; Kyle, unpublished data) and representative chilled margins of Ferrar dolerite sills and dikes (Gunn, 1966; Hamilton, 1965). BP and GC represent the basaltic parent and granitic contaminant respectively, which Faure et al. (1974) considered were mixed to give the observed major element chemistry of the Strom Peak lavas. Initial 87Sr!85 Sr ratios (Faure et al., 1972, 1974; Compston et al., 1968) are shown for selected samples. Note the general lack of correlation between ("'Sr/865r) and both 5i02 and MgO for the Ferrar Group as a whole. ANTARCTIC JOURNAL
Di /
m es
\ Hd
0
SIX
.250 C 0
0 0)
En
Fs
Figure 2. Pyroxene crystallization trends in Kirkpatrick Basalts from Storm Peak (crosses) and Brimstone Peak (dots). Solid line represents the compositional trend of pyroxenes in the Dufek Intrusion (Himmelberg and Ford, 1976).
creases, Ti0 2 , 2FeO (total Fe as FeO), Na 2 0, K2 0 1 and P2 0 5 also increase, while Al 2 03 , MgO, and CaO decrease. The major element chemistry of the Ferrar Group rocks as a whole suggests a genetic relationship and is compatible with a model of evolution by fractional crystallization processes. The decreasing Al2 03 and CaO suggest feldspar fractionation, while the decrease of MgO and CaO indicate fractionation of pyroxene. To test such a model a number of least square mass balance calculations (Bryan et al., 1970; Wright, 1974) have been developed using ideal and microprobe analyses of phenocryst phases found in Kirkpatrick Basalt lavas (Kyle, unpublished data) and cumulate mineral phases in the Dufek Intrusion (Himmelberg and Ford, 1976). Preliminary calculations indicate that removal of 17 percent plagioclase (An80 ), 14 percent augite (Ca 36 Mg44 Fe20 ) and 8 percent lowCa pyroxene (Ca 8 M957 Fe35 ) from hypersthene tholeiite (average of five analyses of chilled margins, Gunn, 1966) will leave a 61 percent residual of pigeonite tholeiite (average of four chilled margins, Gunn, 1966). Kirkpatrick Basalts from Storm Peak have been described by Elliot (1972) and Faure et al. (1974). The latter paper suggested that variations in the major element chemistry were due to contamination of between 20 and 40 percent salic material. However, the major and trace element chemistry can also be explained by fractional crystallization processes. A mass balance model calculated using the chemistry of mineral phases analysed in the Storm Peak lavas suggests that flow 10 (sample 27.28) on removing 17 percent plagioclase (An 70 ), 5 percent low-calcium pyroxene (Cag Mg64 Fe27 ) and 11 percent augite (Ca 37 Mg49 Fe 14 ) will give a 67 percent residual of flow 6 (sample 27.17). Using published partition coefficients (Paster et al., 1974; Sun et al., 1974) and the above mass balance model solution it is possible to determine if the trace element data, particularly the rare earch elements (REE) also agree with the model. Using the measured REE content of sample 27.28, the calculated REE content for sample 27.17 shows good agreement (within the analytical errors involved) with that measured (figure 3.). The above models and calculations strongly support a differentiation model for all Ferrar Group rocks. The contamination model proposed by Faure et al. (1974) for Kirkpatrick Basalt lavas at Storm Peak is considered unlikeOctober 1977
E 0
Cl)
101 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb I I I
I I I
I
I
Figure 3. Chondrite normalized rare earth element (REE) abundances in Kirkpatrick Basalt lava samples form Storm Peak. See text for discussion of calculated values for sample 27.17.
ly for petrogenesis of the Ferrar Group for a number of reasons: (1) All Ferrar Group samples are characterized by high initial strontium ratios which show no correlation with major or trace element chemistry (figure 1). The uniform nature of the initial strontium isotope ratios throughout all Ferrar Group rocks is also extremely difficult to reconcile with assimilation. (2) Partial melts of lower crustal rocks would be feldsparrich; therefore Ferrar Group rocks should show positive europium anomalies. In fact (figure 3 and unpublished data) the rocks have negative europium anomalies consistent with their origin by fractional crystallization of plagioclase from a more basic parent. (3) No xenoliths of granitic rocks have ever been found in Ferrar Group rocks. (4) It is unlikely that any differentiating magma would have sufficient superheat to assimilate relatively large amounts of crustal material (Pankhurst, 1969). (5) The similarity of the mineral crystallization trends in the Storm Peak lavas to those in the Dufek Intrusion strongly suggest crystallization in a fractionating magma. Although the variations in strontium isotope ratios of the Storm Peak basalts show a correlation with silica content, which Faure et al. (1974) attributed to contamination by sialic material, it is felt that the variations in the strontium isotope ratios can be as readily explained by post-eruptional contamination and redistribution of rubidium. Two models are suggested to explain the high strontium isotope ratios in Ferrar Group and Dufek Intrusion samples: (1) Selective contamination similar to that described by Pankhurst (1969) has occurred, or (2) The mantle is heterogeneous, as suggested by Brooks et al. (1976). Ferrar Group rocks are widespread along the Trans. antarctic Mountains, and many have high Si0 2 low MgO contents (suggesting considerable fractionation). Thus, a consequence of the fractional crystallization model is that cumulate rocks resembling those at the Dufek Intrusion are 109
probably widespread. It is also predicted that there should be a complete range in compositions of Ferrar Dolerites (based on analyses of chilled margins) and that their classification into three magma types (Gunn, 1966) may only reflect insufficient sampling. This research was conducted during an Ohio State University postdoctoral fellowship. D.H. Elliot collected the Storm Peak samples during fieldwork supported by National Science Foundation grants GA- 12315 and GV-26652. References Behrendt, J.C., J.R. Henderson, L. Meister, and W.L. Rambo. 1974. Geophysical investigations of the Pensacola Mountains and adjacent glacierized areas of Antarctica. U.S. Geological Survey. Professional Paper, 84428 p. Brooks, C., D.E. James, and S.R. Hart. 1976. Ancient lithosphere: Its role in young continental volcanism. Science, 193: 1086-1094. Bryan, W.B., L.W. Finger, and F. Chayes. 1970. Estimating proportions in petrographic mixing equations by least squares approximation. Science, 163: 672-679. Elliot, D.H. 1972. Major oxide chemistry of the Kirkpatrick Basalts, central Transantarctic Mountains. In: Antarctic Geology and Geophysics, ( Adie, R.J., editor). Oslo, Universitetsforlaget. 413-418.
Coal forming elements in permineralized peat from Mountain Augusta (Queen Alexandra Range) JAMES M. SCHOPF
Department of Geology and Mineralogy The Ohio State University Columbus, Ohio 43210 A deposit of permineralized peat, the first to be reported in the Gondwana area, was discovered in the Permian coal measures on Mount Augusta in the Queen Alexandra Range during the 1969-1970 antarctic field season (Schopf. 1970). The mode of preservation has been described (Schopf. 1971) and is most comparable to the calcareous permineralized peat of Pennsylvanian age known as 'coal balls." The Permian peat can be taken as a sample of the plant material that was altered and entered into the composition of Gondwana coal. The present note presents a brief summary of the nature of the plant remains in the sliced surfaces of the peat specimens that are available. The plant structures include sterns, roots, leaves, the gametophytes of mosses, ovules, sporangia, pollen grains, and fungal hyphae. Of these the best preserved and most numerous are the roots that can be identified as Vertebra na (Schopf, 1965; Gould, 1975). The fact that most of the roots are of a similar type suggests that they represent the dorni110
Faure, G.,J.R. Bowman, D.H. Elliot, and L.M.Jones. 1974. Strontium isotope composition and petrogenesis of the Kirkpatrick Basalt, Queen Alexandra Range. Antarctica. tontributions to Mineralogy and Petrology, 48: 153-169. Ford, A.B. 1976. Stratigraphy of the layered gabbroic Dufek Intrusion, Antarctica. U.S. Geological Survey. Bulletin, 1405-D. 36p. Gunn, B.M. 1962. Differentiation in Ferrar Dolerites, Antarctica. N.Z.Journal of Geology and Geophysics, 5: 820-863. Gunn, B.M. 1966. Modal and element variation in Antarctic tholeiites. Geochimica et Cosmochimica A cta, 30: 881-920. Himmelberg, G.R., and A.B. Ford. 1976. Pyroxenes of the Dufek Intrusion, AntarcticaJournal of Petrology, 17: 219.243. Pankhurst, R.J. 1969. Strontium isotope studies related to petrogenesis in the Caledonian Basic Igneous Province of NE. Scotl and. Journal of Petrology, 10: 115-143. Paster, T.P., D.S. Schauwecker, and L.A. Haskin. 1974. The behaviour of some trace elements during solidification of the Skaergaard layered series. Geochimica et Cosmochimica Acta, 38: 1549-1577. Sun, C-O., R.J. Williams, and S-S..Sun. 1974. Distribution coefficients of Eu and Sr for plagioclase- liquid and clinopyroxene- liquid equilibria in oceanic ridge basalt: an experimental study. Geochimica et Cosmochimica Acta, 38: 1415-1433. Wright. T.L. 1974. Presentation and interpretation of chemical data for igneous rocks. Contributions to Mineralogy and Petrology, 48: 233-248.
nant plants of the peat forming vegetation. Fungal remains variously represented in all kinds of peaty plant material are indicative of degradation. Some small spheroidal fruiting structures have been observed, and the sporadic abundance of fungal vegetative hyphae is more common than in Pennsylvanian age coal balls. Peaty material. Early in the course of these studies two distinctly different types of organic preservation, colored brown and black, were noticed that are not attributable to kinds of plants, to mineralization, recrystallization, or weathering. In many instances the contrast between "black" and "brown" organic matter is similar to that in Pennsylvania coal balls where brown organic matter (humified) usually preponderates and the larger black organic fragments are easily recognized as representing the ingredient of coal known as fusain or as fusinite. In coal petrography, the coarser tissue fragments of black-opaqueorganic matter are generally assigned to Fusinite, the finer textured opaque matter to micrinite, and a material intermediate between the brown and the black to semfusinite. All three together, since they share the same properties, may be grouped as inertinite. The change leading to this difference in organic preservation occurred very early in diagenesis, prior to mineralization. Many of the permineralized blocks from Mount August contain a preponderance of the black organic material. Its occurrence in Permian peat serves additionally to confirm one of the peculiarities in petrographic composition of Gondwana coals, many of which show high concentrations of inertinite (Mackowsky, 1975). The contrast between brown and black organic matter in the permineralized Mount Augusta peat is sufficiently prominent that peels prepared from etched surfaces, acANTARCTIC JOURNAL
Reference
Denton, G.H., R.L. Armstrong, and M. Stuiver. 1971. The late Cenozoic glacial history of Antarctica. In: Turekian, K.K. (ed.), Late Cenozoic Glacial Ages. Yale University Press, New Haven, Connecticut. 279-306.
Petrogenesis of Ferrar Group rocks PHILIP R. KYLE
Institute of Polar Studies The Ohio State University Columbus, Ohio 43210
Jurassic Ferrar Group rocks are widespread throughout the Transantarctic Mountains, occurring as lava flows
(Kirkpatrick Basalts), dolerite sills and dykes (Ferrar Dolerite), and volcanic breccias and mudflows (Mawson Formation). The large layered gabbroic Dufek intrusion in the northern Pensacola Mountains is presumably correlative with the Ferrar Group (Ford, 1976). Major element analyses of the chilled margins of Ferrar Dolerite sills and dikes indicate three main magma compositions (Gunn, 1966). In order of decreasing MgO and increasing Si0 2 , the types are: olivine tholeiite, hypersthene tholeiite, and pigeonite tholeiite (figure 1). Analyses of Kirkpatrick Basalt flows indicate some have similar major element chemistry to the hypersthene tholeiites and pigeonite tholeiites, while many of the flows from Storm Peak, Beardmore Glacier (Elliott, 1972; Faure et al., 1974) are more evolved (figure 1). Kirkpatrick Basalts from Brimstone Peak, northern Victoria Land (Kyle, unpublished data); Blizzard Peak, central Transantarctic Mountains (Elliot, 1972); and Carapace Nunatak, southern Victoria Land (Gunn, 1962) span the range hypersthene tholeiite to pigeonite tholeiite (figure 1). Electron microprobe analyses of pyroxenes in Kirkpatrick Basalt samples (figure 2) show a well developed crystallization trend. Some of the scatter in the pyroxene compositions is due to metastable crystallization. The crystallization trend is however very similar to that displayed by pyroxenes in the Dufek Intrusion (Himmelberg and Ford, 1976) (figure 2), although the trend in the magnesium-rich pyroxenes from the Kirkpatrick Basalts is more extensive. The basal hidden section of the Dufek Intrusion is estimated to be 1.8 to 3.5 kilometers thick (Behrendt et al., 1974). It is likely that the magnesium-rich pyroxenes in the Kirkpatrick Basalts give a good indication of the pyroxene compositions likely to be encountered at depth in the Dufek Intrusion. Plots of major elements against silica for Kirkpatrick Basalts and chilled margins of Ferrar Dolerite sills (i.e., figure 1) show systematic and regular changes. As Si0 2 in-
12 0(0.7113) N
8
(0.7122)
(0.7094) x (0.7082) —6 (0.7103) 0 (0.7125) a, B
0 Olivine tholeiite sill X Hypersthene tholeiite sills + Pigeonite tholeiite sills * Other dolerite sills and dikes Kirkpatrick Basalt, Brimstone Peak 0 Kirkpatrick Basalt , Storm Peak Kirkpatrick Basalt , Blizzard Peak A Kirkpatrick Basalt , Mount Bumsteod 0 Kirkpatrick Basalt , Carapace Nunatak (0.7113) ( 87 Sri 86 Sr )
4 (0.7113)-_....a (0.7129) 2
0'50
(0.7095)
/ (0.712
I I I 1 I 1 I 52 54 56 58 60 62 64 66 68 Si0 2 (wt. %)
108
Figure 1. MgOlSiO2 variation diagram showing the systematic variation in the chemistry of Kirkpatrick Basalt flows (Elliot, 1970,1972; Faure et al., 1974; Gunn, 1962; Kyle, unpublished data) and representative chilled margins of Ferrar dolerite sills and dikes (Gunn, 1966; Hamilton, 1965). BP and GC represent the basaltic parent and granitic contaminant respectively, which Faure et al. (1974) considered were mixed to give the observed major element chemistry of the Strom Peak lavas. Initial 87Sr!85 Sr ratios (Faure et al., 1972, 1974; Compston et al., 1968) are shown for selected samples. Note the general lack of correlation between ("'Sr/865r) and both 5i02 and MgO for the Ferrar Group as a whole. ANTARCTIC JOURNAL
Di /
m es
\ Hd
0
SIX
.250 C 0
0 0)
En
Fs
Figure 2. Pyroxene crystallization trends in Kirkpatrick Basalts from Storm Peak (crosses) and Brimstone Peak (dots). Solid line represents the compositional trend of pyroxenes in the Dufek Intrusion (Himmelberg and Ford, 1976).
creases, Ti0 2 , 2FeO (total Fe as FeO), Na 2 0, K2 0 1 and P2 0 5 also increase, while Al 2 03 , MgO, and CaO decrease. The major element chemistry of the Ferrar Group rocks as a whole suggests a genetic relationship and is compatible with a model of evolution by fractional crystallization processes. The decreasing Al2 03 and CaO suggest feldspar fractionation, while the decrease of MgO and CaO indicate fractionation of pyroxene. To test such a model a number of least square mass balance calculations (Bryan et al., 1970; Wright, 1974) have been developed using ideal and microprobe analyses of phenocryst phases found in Kirkpatrick Basalt lavas (Kyle, unpublished data) and cumulate mineral phases in the Dufek Intrusion (Himmelberg and Ford, 1976). Preliminary calculations indicate that removal of 17 percent plagioclase (An80 ), 14 percent augite (Ca 36 Mg44 Fe20 ) and 8 percent lowCa pyroxene (Ca 8 M957 Fe35 ) from hypersthene tholeiite (average of five analyses of chilled margins, Gunn, 1966) will leave a 61 percent residual of pigeonite tholeiite (average of four chilled margins, Gunn, 1966). Kirkpatrick Basalts from Storm Peak have been described by Elliot (1972) and Faure et al. (1974). The latter paper suggested that variations in the major element chemistry were due to contamination of between 20 and 40 percent salic material. However, the major and trace element chemistry can also be explained by fractional crystallization processes. A mass balance model calculated using the chemistry of mineral phases analysed in the Storm Peak lavas suggests that flow 10 (sample 27.28) on removing 17 percent plagioclase (An 70 ), 5 percent low-calcium pyroxene (Cag Mg64 Fe27 ) and 11 percent augite (Ca 37 Mg49 Fe 14 ) will give a 67 percent residual of flow 6 (sample 27.17). Using published partition coefficients (Paster et al., 1974; Sun et al., 1974) and the above mass balance model solution it is possible to determine if the trace element data, particularly the rare earch elements (REE) also agree with the model. Using the measured REE content of sample 27.28, the calculated REE content for sample 27.17 shows good agreement (within the analytical errors involved) with that measured (figure 3.). The above models and calculations strongly support a differentiation model for all Ferrar Group rocks. The contamination model proposed by Faure et al. (1974) for Kirkpatrick Basalt lavas at Storm Peak is considered unlikeOctober 1977
E 0
Cl)
101 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb I I I
I I I
I
I
Figure 3. Chondrite normalized rare earth element (REE) abundances in Kirkpatrick Basalt lava samples form Storm Peak. See text for discussion of calculated values for sample 27.17.
ly for petrogenesis of the Ferrar Group for a number of reasons: (1) All Ferrar Group samples are characterized by high initial strontium ratios which show no correlation with major or trace element chemistry (figure 1). The uniform nature of the initial strontium isotope ratios throughout all Ferrar Group rocks is also extremely difficult to reconcile with assimilation. (2) Partial melts of lower crustal rocks would be feldsparrich; therefore Ferrar Group rocks should show positive europium anomalies. In fact (figure 3 and unpublished data) the rocks have negative europium anomalies consistent with their origin by fractional crystallization of plagioclase from a more basic parent. (3) No xenoliths of granitic rocks have ever been found in Ferrar Group rocks. (4) It is unlikely that any differentiating magma would have sufficient superheat to assimilate relatively large amounts of crustal material (Pankhurst, 1969). (5) The similarity of the mineral crystallization trends in the Storm Peak lavas to those in the Dufek Intrusion strongly suggest crystallization in a fractionating magma. Although the variations in strontium isotope ratios of the Storm Peak basalts show a correlation with silica content, which Faure et al. (1974) attributed to contamination by sialic material, it is felt that the variations in the strontium isotope ratios can be as readily explained by post-eruptional contamination and redistribution of rubidium. Two models are suggested to explain the high strontium isotope ratios in Ferrar Group and Dufek Intrusion samples: (1) Selective contamination similar to that described by Pankhurst (1969) has occurred, or (2) The mantle is heterogeneous, as suggested by Brooks et al. (1976). Ferrar Group rocks are widespread along the Trans. antarctic Mountains, and many have high Si0 2 low MgO contents (suggesting considerable fractionation). Thus, a consequence of the fractional crystallization model is that cumulate rocks resembling those at the Dufek Intrusion are 109
probably widespread. It is also predicted that there should be a complete range in compositions of Ferrar Dolerites (based on analyses of chilled margins) and that their classification into three magma types (Gunn, 1966) may only reflect insufficient sampling. This research was conducted during an Ohio State University postdoctoral fellowship. D.H. Elliot collected the Storm Peak samples during fieldwork supported by National Science Foundation grants GA- 12315 and GV-26652. References Behrendt, J.C., J.R. Henderson, L. Meister, and W.L. Rambo. 1974. Geophysical investigations of the Pensacola Mountains and adjacent glacierized areas of Antarctica. U.S. Geological Survey. Professional Paper, 84428 p. Brooks, C., D.E. James, and S.R. Hart. 1976. Ancient lithosphere: Its role in young continental volcanism. Science, 193: 1086-1094. Bryan, W.B., L.W. Finger, and F. Chayes. 1970. Estimating proportions in petrographic mixing equations by least squares approximation. Science, 163: 672-679. Elliot, D.H. 1972. Major oxide chemistry of the Kirkpatrick Basalts, central Transantarctic Mountains. In: Antarctic Geology and Geophysics, ( Adie, R.J., editor). Oslo, Universitetsforlaget. 413-418.
Coal forming elements in permineralized peat from Mountain Augusta (Queen Alexandra Range) JAMES M. SCHOPF
Department of Geology and Mineralogy The Ohio State University Columbus, Ohio 43210 A deposit of permineralized peat, the first to be reported in the Gondwana area, was discovered in the Permian coal measures on Mount Augusta in the Queen Alexandra Range during the 1969-1970 antarctic field season (Schopf. 1970). The mode of preservation has been described (Schopf. 1971) and is most comparable to the calcareous permineralized peat of Pennsylvanian age known as 'coal balls." The Permian peat can be taken as a sample of the plant material that was altered and entered into the composition of Gondwana coal. The present note presents a brief summary of the nature of the plant remains in the sliced surfaces of the peat specimens that are available. The plant structures include sterns, roots, leaves, the gametophytes of mosses, ovules, sporangia, pollen grains, and fungal hyphae. Of these the best preserved and most numerous are the roots that can be identified as Vertebra na (Schopf, 1965; Gould, 1975). The fact that most of the roots are of a similar type suggests that they represent the dorni110
Faure, G.,J.R. Bowman, D.H. Elliot, and L.M.Jones. 1974. Strontium isotope composition and petrogenesis of the Kirkpatrick Basalt, Queen Alexandra Range. Antarctica. tontributions to Mineralogy and Petrology, 48: 153-169. Ford, A.B. 1976. Stratigraphy of the layered gabbroic Dufek Intrusion, Antarctica. U.S. Geological Survey. Bulletin, 1405-D. 36p. Gunn, B.M. 1962. Differentiation in Ferrar Dolerites, Antarctica. N.Z.Journal of Geology and Geophysics, 5: 820-863. Gunn, B.M. 1966. Modal and element variation in Antarctic tholeiites. Geochimica et Cosmochimica A cta, 30: 881-920. Himmelberg, G.R., and A.B. Ford. 1976. Pyroxenes of the Dufek Intrusion, AntarcticaJournal of Petrology, 17: 219.243. Pankhurst, R.J. 1969. Strontium isotope studies related to petrogenesis in the Caledonian Basic Igneous Province of NE. Scotl and. Journal of Petrology, 10: 115-143. Paster, T.P., D.S. Schauwecker, and L.A. Haskin. 1974. The behaviour of some trace elements during solidification of the Skaergaard layered series. Geochimica et Cosmochimica Acta, 38: 1549-1577. Sun, C-O., R.J. Williams, and S-S..Sun. 1974. Distribution coefficients of Eu and Sr for plagioclase- liquid and clinopyroxene- liquid equilibria in oceanic ridge basalt: an experimental study. Geochimica et Cosmochimica Acta, 38: 1415-1433. Wright. T.L. 1974. Presentation and interpretation of chemical data for igneous rocks. Contributions to Mineralogy and Petrology, 48: 233-248.
nant plants of the peat forming vegetation. Fungal remains variously represented in all kinds of peaty plant material are indicative of degradation. Some small spheroidal fruiting structures have been observed, and the sporadic abundance of fungal vegetative hyphae is more common than in Pennsylvanian age coal balls. Peaty material. Early in the course of these studies two distinctly different types of organic preservation, colored brown and black, were noticed that are not attributable to kinds of plants, to mineralization, recrystallization, or weathering. In many instances the contrast between "black" and "brown" organic matter is similar to that in Pennsylvania coal balls where brown organic matter (humified) usually preponderates and the larger black organic fragments are easily recognized as representing the ingredient of coal known as fusain or as fusinite. In coal petrography, the coarser tissue fragments of black-opaqueorganic matter are generally assigned to Fusinite, the finer textured opaque matter to micrinite, and a material intermediate between the brown and the black to semfusinite. All three together, since they share the same properties, may be grouped as inertinite. The change leading to this difference in organic preservation occurred very early in diagenesis, prior to mineralization. Many of the permineralized blocks from Mount August contain a preponderance of the black organic material. Its occurrence in Permian peat serves additionally to confirm one of the peculiarities in petrographic composition of Gondwana coals, many of which show high concentrations of inertinite (Mackowsky, 1975). The contrast between brown and black organic matter in the permineralized Mount Augusta peat is sufficiently prominent that peels prepared from etched surfaces, acANTARCTIC JOURNAL
