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Victoria University Antarctic Research Expedition Science and Logistics Reports 1979-80: VUWAE 24
SCIENTIFIC ACHIEVEMENTS
SCIENTIFIC ACHIEVEMENTS
Permian coal measures at Mount Fleming and Shapeless Mountain (Alex Pyne)
The Mt. Fleming area was revisited to complete a study of the Weller Coal Measures initiated the previous 1978-79 season. Further outcrops of the coal measures in the "cirque basin" at Mt. Fleming were measured and described in detail. These latest data complete the detailed three dimensional coverage of the outcrops which is required to determine the depositional history of the Weller Coal Measures. The new information has also helped to confirm and refine the interpretation of several features found the previous season.
In southern Victoria Land the alluvial Weller Coal Measures are deposited on the Pyramid Erosion Surface (P.E.S.) overlying the Permian Metschel Tillite. Barrett and Kyle (1975) has already shown from evidence at Mt. Fleming that the "time gap" represented by the Pyramid Erosion Surface is small. Work this year has shown that a pod comprising tillite interbedded with carbonaceous shale (Plate IX) is stratigraphically equivalent to a thin laterally extensive sandstone bed containing dispersed clasts and carbonaceous material. These three lithologies are considered facies of the Metschel Tillite. In some places the pyramid Erosion Surface has formed on the sandstone bed. In others, however, sandstone of the Metshcel Tillite appears to grade into the lowest shale lenses of the Weller Goal Measures.
At Mt. Fleming the Metschel Tillite facies are interpreted to have been deposited in glacial and proglacial environments. Small fluctuations of the ice front incorporated vegetation growing around the ice margin. The basal Weller Coal Measures were deposited immediately after the final ice retreat in a periglacial climate. The lithofacies association suggests deposition from a meandering stream system and this will be checked from analysis of the paleocurrent measurements taken from the coal measures. This will show more precisely the directions of current flow and the sinuosity of the depositing river. The paleocurrent directions from the outcrops at Mt. Fleming also will be compared with the directions from Shapeless Mt. 20 km away where the coal measures are very similar.
Three thin calcareous beds (av 100 mm) previously described by Barrett & Webb (1973) and Bradshaw (in press) were traced over a large area of Mt. Fleming this season. The trace of the outcrop delineates an area of about 10 square kilometres. Three very similar calcareous beds were also found in the same stratigraphic position at Shapeless Mtn. about 20 km away. It is inferred that the depositional environment in which these beds accumulated coexisted at both localities and that the environment was laterally continuous over 20 km.
Bradshaw (in press) has found analcime zeolite associated with the upper calcareous bed at Mt. Fleming and interpreted the analcime to have formed from evaporation. This season symmetrical ripple marks (Plate X) were found in the same bed (Bradshaws main horizon) and indicate subaqueous accumulation.
By determining whether the ripples are wave or current formed it is hoped to define precisely the depositional environment.
A point of interest last season was the finding of paleosols at Mt. Bastion and Mt. Fleming that appeared to have formed under cool temperate conditions in the Permian. This season similar paleosols were found higher in the sequence in the upper part of the Feather Conglomerate at Horseshoe Mtn. A comparison of the paleosols shows that both have a well-developed gammate structure in the greenish clay-rich upper horizon and an iron accumulation zone in the lower clay-deficient horizon.
The paleosols are interpreted to have formed under similar climates yet the nature of the flood plans on which they developed were quite different.
References
Barrett, P.J. and Kyle, R.A. 1975. The Early Permian Glacial Beds of South Victoria Land and the Darwin Mountains, Antarctica. In Gondwana Geology, Campbell, K.S.W. ed. A.K.U. Press, p. 333-346.
page 35
Barrett, P.J. and Webb, P.M., 1973. Stratigraphic Sections of the Beacon Supergroup. (Devonian and Older (?) to Jurassic) in South Victoria Land. No.2. Pub. of VUW Geol. Dept.
Bradshaw, M.A., in press. Occurrence and origin of an analcimolite from the Permian Weller Coal Measures of Antarctica. N.Z. J. G.G.
Triassic studies at Horseshoe Mountain (Barry Walker)
Five days were spent at Horseshoe Mountain, near Mt. Fleming, where geological mapping and sampling was carried out. The strata cropping out are the Feather Conglomerate (Late Permian-Early Triassic) and tile Lashly Formation (Mid-Late Triassic). (Plate XI)
The Feather Conglomerate is a corase to very coarse poorly sorted quartzose sandstone with large scale trough cross-bedding. The upper part is represented by a series of "fining-upward" cycles of medium, moderately well-sorted sandstone (Fleming Member - McKelvey et al., 1970).
The Lashly Formation is a sequence of sandstone and carbonaceous mudstone and has been divided into four members (Barrett et al., 1972); Members A, B and C appear to be complete at Horseshoe Mountain with member D occurring within the top 15 meters of the summit.
The Lashly Formation also crops out at the summit of Mount Fleming where 20–30 meters of member A is represented. Reconnaissance and a small amount of sampling of the Lashly Formation at Shapeless Mountain was all that time and weather conditions permitted. Several of the key stratigraphic horizons found at Horseshoe Mountain could be recognised at Shapeless Mountain, including the thin blue-grey muds-bone beds containing white rootlets and the silicified tree horizon.
Detailed petrological studies will be made of the sandstone samples from Horseshoe Mountain to determine mineralogical changes that may occur throughout this Triassic sequence. The relationship between sandstone texture and sedimentary structures will also be studies.
References
Barrett, P.J.; Grindley, G.W.; Webb, P.N., 1972. The Beacon Supergroup of East Antarctica. In Adie, R.J. (ed.), Antarctic Geology and Geophyics, Pp. 319-332.
McKelvey, B.C.; Webb, P.N.; Gorton, M.P.; Kohn, B.P., 1970. Stratigraphy of the Beacon Supergroup between the Olympus & Boomerang Ranges, Victoria Land, Antarctica. Nature 225, 1126-8.
Pre-Pleistocene lodgement tills in the Coombs Hills - Odell Glacier region (Barry McKelvey)
The Coombs area was visited this season to locate and examine remnants of pre-Pleistocene lodgement tills. A study of these deposits was started in 1977/78 by VUWAE 22 and this season's work was a continuation of that programme.
A major find this season was the uncovering of a fossil striated pavement at over 2800 m on Mt. Brooke. This is at least 800 m above the present ice level. This pavement, in conjunction with other evidence from Mt. Feather (Brady and McKelvey 1979) strongly suggests the East Antarctic Ice sheet in Southern Victoria Land predated the Victoria Orogeny. In other words, the mountains are being pushed up through the ice-sheet. The ice-flow direction shown by the pavement is in very close agreement with that determined from the Cenozoic tillite described from Mt. Feather.
The pre-Pleistocene tillite examined at the northeastern end of the Coombs Hills was previously considered to be a Plateau derived remnant of the so-called Sirius Tillite (Mayewski 1975). However, when taking into account the composition of the till stones and comparing these with the geological composition of the Coombs Hills it appears the till can only have been derived from a local neve field in the Convoy Range region, that was drained by an earlier phase of the then expanded Curreen Glacier.
Further Palaeontological and mineralogical investigations of the Cenozoic till are planned.
References
Brady, H.; McKelvey, B.C., 1979. The interpretation of a Tertiary tillite at Mt. Feather, Southern Victoria Land, Antarctica. Journal of Glaciology, 22, 36, pp. 189-193.
Mayewski, P.A., 1975. Glacial geology and late Cenozoic history of the Transantarctic Mountains, Antarctica. Ohio State University, Institute of Polar Studies, Report No. 56.
Sampling basement rocks for fission track investigations (Barry McKelvey)
Granitic basement rocks were sampled in the Bull Pass - Lake Vida region to use for fission track investigation. The samples arrived in Melbourne at the end of February where processing of the material by Dr A. Gleadow of the Particle Tracking Laboratory, University of Melbourne was immediately commenced. The fission track technique will be employed to decipher the uplift history of the Transantarctic Mountains (i.e. the Victoria Orogeny) by determining the time when the basement reached a certain level in the earth's crust.
Investigation of moraines in the Pearse Valley (Ian Wright)
Moraine lobes which flank the Pearse Valley slopes of the Kukri Kills were mapped in detail. The lobes average 250 to 300 metres in length with faces approximately 25 metres high and have wind-blown hollows giving the surface hummocky relief. Surface clasts show no evidence of imbrication or elongation.
These lobes are interpreted to result from at least two phases of alpine glaciation. Detailed mapping revealed that one lobe contains features possibly formed by delayed retreat during the second phase. This could possibly be interpreted as a third alpine glacial phase.
The alpine moraines can be distinguished from Robinson's (1978) "early Taylor" moraines present in the Pearse Valley by mineralogical composition. The "early Taylor" moraines contain plutonic clasts, specifically K-feldspar granites, which are absent from the alpine moraines.
Formation of patterned ground on the alpine moraine surfaces indicates they are ice-cored and Robinson (pers. comm.) has found matrix ice within the moraines. The shape of the moraines suggests plastic deformation of the matrix ice is presently occurring.
Further investigation in the Pearse Valley is needed to relate the chrono-stratigraphy and ice-flow directions of the "Taylor" glacial expansions to the alpine glacial phases, and also to the fluctuations in levels of Lakes House and Joyce.
Marine seismic surveying in McMurdo Sound (B.A. Sissons)
The present survey was intended to extend marine seismic coverage to: i) the western side of McMurdo Sound, in order to examine the nature of any faulting or other structures in the boundary zone between the Trans Antarctic Mountains and the Ross Sea: ii) to examine the continuity of the basin structure to the north side of Ross Island; iii) to extend seismic coverage northwards to link with previous work at Terra Nova Bay; iv) to obtain reconnaissance results around Beaufort and Franklin Islands and also across the sould into Granite Harbour. With the limited time available it was not possible to achieve many of our objectives. However, a moderate amount of good data was obtained in this year's survey, which will form a good basis for future work intended in this region.
Seismic operations commenced at 0530 UT, 7 February, and continued until 0600, 11 February, except for a seven hour break on 8 February to return to McMurdo station. Several piston cores were also taken by the Project S207 team during the survey, some of which coincided with downtimes of K-12 seismic system. K-12's larger compressor was damaged due to oil pressure failure before the start of surveying, and they were therefore obliged to use their backup airgun system and smaller compressor throughout the survey. This meant that maintenance downtime was much greater than would otherwise have been the case. However, the K-12 backup system in general operated reliably.
Standard operation procedure was as follows: three siesmic arrays and a magnetometer fish were trailed astern of the fantail, while the airgun was launched and towed from the portside fantail winch. The signal from one array was filtered and fed to the K-12 EPC recorder to give an immediate analog display of the seismic coverage, while a second array was fed without filtering into a FM tape recorder for later processing and playback. The third array was also directly recorded to provide a trigger signal corresponding to gun fire instant. The magnetic field was recorded in analog form on two chart recorders. Three disposable sonobuoys were launched to obtain seismic refraction data. Two worked well, and one transmitted data which can probably be reprocessed to give a usable record. A continuous PDR watch was also maintained by members of the S207 project team and the marine science technicians during seismic operations.
The approximate coordinates of end points of seismic lines, and the positions of sonobuoy drops are listed below. Deviations from straight course and breaks in seismic records along these lines Occurred due to ice conditions, equipment downtime and coring station stops.
| From | To | |
| Line 1 | −77°41′, 165°53′ | −77°46′, 164°50′ |
| Line 2 | −77°46′, 164°47′ | −77°38′, 164°23′ |
| Line 3 | −77°39′, 164°23′ | −77°35′, 165°06′ |
| Line 4 | −77°32′, 164°53′ | −77°36′, 164°13′ |
| Line 5 | −77°36′, 164°17′ | −77°38′, 164°25′ |
| Line 6 | −77°37′, 164°25′ | −77°22′, 166°19′ |
| Line 7 | −77°24′, 166°30′ | −77°30′, 166°3′ |
| Line 8 | −77°32′, 166°6′ | −77°15′, 166°0′ |
| Sonobuoy 1 | −77°21′, 166°7′ | − |
| Line 9 | −77°7′, 167°5′ | −77°19′, 169°18′ |
| Sonobuoy 2 | −77°17′, 167°43′ | − |
| Line 10 | −77°19′, 168°14′ | −77°22′, 167°35′ |
| Line 11 | −77°22′, 167°35′ | −77°12′, 167°53′ |
| Line 12 | −77°12′, 167°53′ | −76°53′, 167°4′ |
| Line 13 | −76°51′, 167°4′ | −76°55′, 163°16′ |
| Line 14 | −76°53′, 163°16′ | −76°7′, 167°1′ |
| Sonobuoy 3 | −76°52′, 163°20′ | − |
A reasonable amount of useful seismic data, and a good bathymetric record were obtained. The Beaufort Island - Granite Harbour leg in particular gave a good seismic record. Gently dipping strata are evident and are truncated at or near the seabed by an unconformity. The unconformity is thought to be the same as that observed elsewhere in McMurdo Sound and the Ross Sea.
Dry Valley gravity survey (B.A. Sissons)
The Dry Valleys gravity survey was designed to compliment the Sea Ice gravity survey made earlier in the season and to fill gaps in the existing data measured by Bull (1962, 1964), Smithson (1971), Stern (1978) and Hicks, Bennett and Wendon (1980). A detailed gravity traverse was completed down Taylor Valley from Northwest Mountain to the sea, with stations at 1 to 3 km intervals. Gravity readings were also made at approximately 10 km spacings in the Lower Ferrar and Blue Valleys and on the Dailey Islands.
Gravity was measured with a Worden gravity meter relative to the Scott Base Gravity Ease for which absolute gravity is 982992.6 mgals Hatherton (1961). Precision of measurement is within 0.3 mgals. Heights of stations were determined barometrically relative to surveyed heights of trig stations and lake surfaces; heights are known to within ± 5 M. Where available the 1:50 000 USGS topographic maps which now cover most of the survey area were used. Terrain corrections for Hamner Zones B to D were estimated in the field and for zones E to M templates were used on the topographic maps. The total error in determination of Bouguer Anomalies is less than 2 mgals.
References
Bull, C. 1960. Gravity Observations in the Wright Valley Area, Victoria Land, Antarctica. N.Z. J. Geol. Geophys. 3: 543-52.
Bull, C., 1962. Gravity Observations in the Koettlitz Glacier Area, Southern victoria Land, Antarctica. N.Z. J. Geol. Geophys. 5: B10-19.
Hatherton, T. 1961. N.Z.D.S.I.R. Bull. 140. 117 p.
Hicks, S.R.; Bennett, O.J.; Wendon, M.J. Gravity Models of the Lower Taylor Valley, Antarctica, in press. N.Z. J. Geol. Geophys.
Stern, T., 1978. Gravity Survey of the Taylor Glacier, Victoria Land, Antarctica. Geology Department, VUW Publ. No.8.
Smithson, S.B., 1972. Gravity Interpretation in the Transantarctic Mountains near McMurdo Sound, Antarctica. Geol. Soc. of Am. Bull. 83: 3437-42.