LIEZ been metamorphosed to the greenschist facies. The 2470 I60E U BASE CAMP \? MT BOWERS ROCKS EXAMINED Wyatt Formation, which overlies the LaGorce 170\ E PLUNKET MT .O(LEY 2646 \\ POINT Formation, is composed of pyroclastic rock of 0 10 20 MILES MT WILD SCALE rhyodacitic composition; in the area of Scott MT KINISEY \) 3118 Glacier, the formation varies in metamorphic grade in a south to north direction from unaltered pyro- RANFURLY POINT elastics to rocks of the biotite zone. The Leverett M^LIN ,tEMPEST PEAK Formation, which contains a Middle Cambrian trilo- 2808^ 3412 bite fauna, overlies the older rocks with angular un- conformity and has been metamorphosed to the zeo- lite facies. As with the Wyatt Formation, the metamorphic grade of the Leverett Formation seems IT LU CLOIJOMAKER £ )ç (. 2681 LJ to increase in a northerly direction. These meta- AI morphic rocks are intruded by a series of granitic PATRI 2712( V6 MACKE plutons of various ages. The Beacon rocks are composed at the base of a tillite that grades upward into a shale-siltstone-sand- stone sequence; these strata are disconformably overlain by coal measures. Pyroclastic detritus first LLJ C LAYTONJ appears in the basal conglomerate of the coal meas- KY FIN CD ures and culminates in dacitic tuffs and ash falls in 1604 the upper part of the formation. The Beacon rocks MT E below the coal measures were derived from a granitic and high-grade metamorphic source area; during deposition of the coal measures, volcanic detritus Figure 1. A rea in vestigated h Ohio State University party. obliterated sediments from this crystalline source. The Beacon rocks have been metamorphosed to the zeolite facies by the Jurassic diabase sills. Lau- montite, heulandite, prehnite, and albitized plagio- clase, minerals characteristic of the zeolite facies, are widely distributed in the Beacon rocks. — MACKELLARFM j PAGODA_FM.r. Geology of the Beardmore Glacier Area ALEXAMDRA FM.I PETER J. BARRETT, DAVID H. ELLIOT, and JOHN F. LINDSAY lhat, hI J. F. Lind.\1I) Figure 2. Southeast face of Mount Miller. Most of the lower Institute of Polar Studies 1000 in of Beacon rocks in the area investigated are ex- Ohio State University posed here. During the 1966-1967 field season, a four-man party from Ohio State Universitys Institute of Polar Studies carried out a geological investigation of the Queen Alexandra Range (Fig. 1). The rocks examined have been described in gen- eral terms by Grindley (1963). In ascending strati- graphic order (Fig. 2), they are orthoquartzites of the Alexandra Formation (Devonian), the Pagoda Formation (most of which is of glacial origin), dark shales of the Mackellar Formation, and the Buckley Coal Measures (Permian). These beds are overlain #di F by a thin orthoquartzite unit, a thick mudstone and fine sandstone unit containing channel sandstones, (P/iota by P. J. Barrett) Figure 3. View along nest ridge of Mount Falla, showing and the Falla Formation (Triassic), a more or less the youngest Beacon rocks in the area studied and the cyclic sandstone-shale sequence. Above the Falla overlying volcanic rocks. 110 ANTARCTIC JOURNAL Formation there are up to 250 m of pyroclastic part of the postglacial Beacon sequence, the regional beds, which are capped by the Kirkpatrick Basalts paleocurrent direction is to the south and southeast. (Jurassic) (Fig. 3). The whole sequence has been The upper contact of the Buckley Coal Measures intruded by Jurassic dolerite sills. was observed only in the central part of the Queen The Alexandra Formation, which noncon- Alexandra Range, where a 125-rn-thick, massive, formably overlies basement phyllites in the range, burrowed orthoquartzite disconformably overlies the consists mainly of well-sorted orthoquartzite. A rela- coal measures. The orthoquartzite is conformably tively complete section on Hampton Ridge, which is overlain by a sequence of at least 600 m of greenish to the north of Mount Mackellar, is more than 365 mudstone and fine sandstone, with many channel m thick. At a few localities, notably at Mount sandstone units up to 20 rn thick. The upper part of Miller, some thin units of dark shale and grey-to- the unit contains parts of fossilized plants, including black limestone occur. Observations of crossbeds in- longitudinally ribbed sterns (Neocalamites), some dicate that paleocurrents flowed in directions rang- logs as long as 20 m that have well-preserved ing from northeast through southeast to southwest, growth rings, and zones up to I m thick containing though most were in a southeasterly direction. The root impressions. Several stumps, still in place and lower contact of the formation, which was seen at associated with the logs, as well as elements of the only one locality, appeared quite sharp and Un- Dicroidium flora (Triassic), were found at the weathered. mouth of the Prebble Glacier. These beds are over- The Pagoda Formation, which disconformably lain by the Falla Formation (upper Falla Formation overlies the Alexandra Formation, is about 120 m of Grindley), which is a cyclic sequence of orange- thick and is composed mainly of massive sandy til- weathering channel sandstone and carbonaceous lite that can be divided into as many as 13 beds. In shale (the latter also contains well-preserved Dicroi- the lower part of the formation, the tillites are inter- dium). In contrast to the paleocurrent directions bedded with lensoidal units of crossbedded channel from the lower Beacon strata, which are southward sandstone, most of which are of limited extent, al- and southeastward, those from the beds above the though near Mount Mackellar one large channel at Buckley Coal Measures are northwestward. least 60 m wide could be traced for almost 8 km. Volcanic rocks are abundant from 335 to 580 m Higher in the formation, particularly near the con- above the base of the Falla Formation on Mount tact with the overlying Mackellar Formation, dark Falla. The lower beds are probably acid to interme- fissile mudstone is dominant. Grooved, soft-sediment diate tuffs. They are overlain by, and apparently pavements and striated boulder pavements were have a gradational contact with, a 60-rn-thick, mas- found at most localities visited. The lower contact of sive, buff, poorly sorted conglomerate that contains the formation at Mount Miller is defined very sharply volcanic and sedimentary pebbles. Samples of this by a deeply grooved surface, with up to 2 m of conglomerate are very similar to those of the Maw- relief, cut in orthoquartzite of the Alexandra Forma- son Tillite of South Victoria Land (Gunn and War- tion. Four other striated surfaces were observed here ren, 1962). Above the sediments of the Falla For- also. Striae with associated "crag and tail" features mation at other localities in the central and south indicate a paleoice flow to the southeast, a direction Queen Alexandra Range there are agglomerates, recorded consistently from outcrops as far apart as tuffaceous sediments, and (locally) poorly sorted 95 km. Paleocurrents, as indicated by crossbeds, conglomerate. flowed mostly to the south and southeast. The only The pyroclastic rocks in this area are overlain by fossils found were plant fragments that occur in a lavas (the Kirkpatrick Basalts), which attain a max- tillite located high in the formation at Mount Mack- imum thickness of 550 m in the Marshall Moun- ellar. tains. The basalt lavas are between 1.5 and 150 m The Mackellar Formation, a predominantly dark thick, and the maximum number measured at any shale unit about 90 m thick, conformably overlies locality was 23, on Mount Falla. Most of the lavas the Pagoda Formation, and is overlain conformably have a thin, vesicular lower contact zone and a by a 120- to I 80-m-thick massive crossbedded sand- much thicker, vesicular upper part, which has been stone (the lower part of Grindleys Buckley Coal baked by the overlying basalt; selvedges, geodes, Measures). The transition zone between this sand- and veins of secondary minerals are not common. stone and the overlying coal measures, which are at The nonvesicular parts of the flows vary between a least 600 m thick, contains discontinuous lenses of very fine grained black basalt and a coarse-grained, well-rounded vein-quartz pebbles. The coal meas- red-weathering rock similar to the underlying intru- ures locally contain abundant Glossopteris leaves. sive dolerite sheets. Fossil wood was found in the Coal seams are not common, although one 10-rn- upper part of several flows. A thin shale unit occurs thick seam was found at Painted Cliffs. In this lower near the top of the section on Blizzard Peak and in a July-August, 1967 111 section to the northwest of that locality. At both southern continents to one another during the Per- localities, well-preserved conchostracans (Lioes- mian appears to be the only satisfactory way to ex- theria) and ostracods were found. At two localities plain the distribution of these fossils. Accordingly, a in the Marshall Mountains, the underlying sediments program was devised to collect conchostracans and are cut by features that are probably volcanic vents. to gather other paleolimnological data from the Dolerite sheets are conspicuous throughout the Ohio Range and to search for conchostracans in the Queen Alexandra Range. Concordant or only slightly Polarstar Formation of the Sentinel Range. transgressive sills as much as 150 in occur Some of the considerations upon which the study in the northern part of the range and at Painted was based and the preliminary results of the field Cliffs, but from the Prebble Glacier southward to work are given in the following paragraphs. Inas- Mount Wild, relationships are more complex. In the much as the discussion has been drawn primarily latter area, there are a few dolerite dikes up to 18 m from field notes, some modification of it may be re- wide.