Fig. 1. Regional stratigraphy of South Victoria Land, Antarctica, and location of Allan Hills study area. The oldest strata exposed in Allan Hills are the Weller Coal Measures. Deposits of the Mawson Formation represent early phases of eruption in the Ferrar large igneous province, and underlie subsequently emplaced Kirkpatrick flood basaltic lavas.

Fig. 2. Map of Watters Peak area. Mawson m₁ includes deposits of a debris avalanche, and a contact zone along which country rock is progressively fragmented. Mawson m₂ is typical heterolithic volcaniclastic material that makes up most of the Mawson Formation throughout the Transantarctic Mountains. Dashed lines ‘A’ and ‘B’ are lines of sections shown in Fig. 3.

Fig. 3. Lithofacies logs A and B show transition from in situ country rock through m₁ along section lines in Fig. 2. M2 denotes transitional Mawson m₂ at the top of logs A and B.

Fig. 4. The size of blocks decreases with distance from in situ Feather Conglomerate, which is a sandstone at this site, along section line B (Fig. 2) in m_1a [and one site, open symbol below, in band of m1b, see Fig. 2]. The decrease appears to be exponential, with the R value indicating that block size is 94.77% negatively correlated with distance through the transition zone (block size decreases as distance from contact increases), with departures from the trend reflecting other factors such as variations in rock characteristics. Distances were measured away from the well-defined contact between m_1a and m₂.

Fig. 5. Mawson m_1a unmixed deposits formed by fragmentation of Victoria Group sedimentary rocks. Deposits range from broken country rock with injected sand derived from the host, to fragments with minor rotation and deformation (A), to rotated fragments with significant self-derived matrix (B); country rock fragments with thin carbonaceous laminae (C) are rotated and recompacted with little inter-block matrix.

Fig. 6. (A) Equal area stereonet of dip direction & magnitude for small blocks (< 1 m; n = 93) from 159 40′ 45″E, 76 43′ 19″S, near the base of section B (Fig. 2) in Mawson m_1a. Mean dip is 17° to 178° (almost due south). We concur with Reubi et al. (in press) in interpreting this fabric as indicative of northward shear along the base of the moving avalanche. (B) Rose diagram showing strike of large blocks (> 1 m; n = 15; 159 40′ 45″E, 76 43′ 37″S) at a site 500 m farther south in Mawson m_1a. Note that these blocks have northerly strikes and a westward dip, implying avalanche flow at this site was in a more easterly direction, perhaps in response to paleotopography.

Fig. 7. Cracked feldspar grains and deformed micas in m_1a matrix (A) are all derived from adjoining blocks of Feather sandstone. Fragments of coal {c}, siltstone, and quartz sand matrix in (B) are derived from different units, and this mixture is typical of m_1b. The matrix of m₂ (C) characteristically contains a volcanic component (v) in a fragment mix otherwise similar to m_1b and including coal (c) and quartz grains (q).

Fig. 8. Broken but monomict sandstone of m_1a is overlain by blocky, chaotic rocks of m_1b, separated here by a “raft” of brownish structureless sand (outlined). Field of view is  15 m wide, and view is to the north.

Fig. 9. A chaotic mixture of blocks (A) of different Victoria Group sedimentary rocks in a gravelly-sand grade matrix (B) is typical of Mawson m_1b. Field of view in (A) is approximately 15 m wide. Rare basaltic fragments are present as blocks locally in m_1b (C).

Fig. 10. Ternary plot comparing the composition of samples from m_1b to samples from the Beacon Supergroup. Results are derived from point counting of thin sections (Table 2). Feldspar grains replaced by clay minerals have been added to the actual feldspar count to lessen the effect of diagenetic alteration of the rocks. ‘Echo’ group of m_1b samples were collected by Bornholdt, 2001.

Fig. 11. Coal breccia in m_1b has formed where coal beds were fragmented but the fragments only weakly, or not at all, dispersed among fragments from enclosing sandstones.

Fig. 12. Graph of vitrinite reflectance results. The higher the reflectance value the higher the rank of coal. It is seen that the vent value and that for the Mawson m2 are higher than those of Mawson m1, Weller Coal Measures and Lashly Formation. The trend lines are those of the standards only. The samples were added to this line so their reflectance could be determined (x-axis). Mawson m2 and vent values from Hood Hills (2004). The Weller Coal Measures and Lashly Formation samples on the lower trend line were collected by J. Prebble during the 2001/2002 Antarctic field season.

Fig. 13. Graph of determined vitrinite reflectance and C/H atomic ratios for coal samples from within the Mawson Formation (values for m₂ and vent from Hood Hills, 2004), Weller Coal Measures and Lashly Formation. Weller Coal Measures and Lashly Formation samples were collected by J. Prebble during the 2001/2002 Antarctic field season.

Fig. 14. Graph of determined vitrinite reflectance and C/O atomic ratios for coal samples from within the Mawson Formation (values for m₂ and vent from Hood Hills, 2004), Weller Coal Measures and Lashly Formation. Weller Coal Measures and Lashly Formation samples were collected by J. Prebble during the 2001/2002 Antarctic field season.

Fig. 15. Graph of C/O and C/H atomic ratios for coal samples from within the Mawson Formation, (Mawson m₂ and vent values from Hood Hills, 2004), Weller Coal Measures and Lashly Formation. These element concentrations can be used as a proxy for the rank of the coal.

Fig. 16. Mawson m₂ contains abundant juvenile basaltic fragments, of various shapes and vesicularity, in both matrix and block fractions (A). The highly attenuated fragments in (B) are inferred to indicate that the clasts were still hot and ductile at the time they were deposited at this site.

Field grid-counts are presented as clast-type percentages for clasts greater than 1 cm, plus percent sandy matrix Counts were made along section A

Abbreviations: matrix material under 1 cm in size. Larger clasts are of pebbly-coarse sandstone (includes rare conglomerate); fragments of medium sandstone; fine sandstone (includes rare mudrock); coal (also includes carbonaceous sandstone and mudrock); and glassy basaltic juvenile clasts.

Point counting results based on 300 points per sample (Gazzi–Dickinson method), for the Mt Watters field area

Formation abbreviations are: LFC — Lower Feather Conglomerate; UFC — Upper Feather Conglomerate; Lash — Lashly Formation; m1a — Mawson Formation, subunit 1a; m1b — Mawson Formation, subunit 1b. Replaced Feldspar (clay): is feldspar crystals that have been replaced by clay minerals. All values are given as percentages. A point count of 300 grains provides accuracy to within ± 2.5%. Repeated point counts for Beacon and m1a samples were compared and an average internal error of ± 1.48% was calculated. ‘Echo’ samples were collected by Bornholdt, during the 2000/2001 Antarctic field season. Due to rounding, not all totals are 100%.

Vitrinite reflectance results, showing the determined reflectance and the apparent rank (North,1985) of the coals

Formation abbreviations — WCM — Weller Coal Measures; Lashly — Lashly Formation; Mawson m_1b and m₂;Vent — sample from small vent complex within Mawson m₂. Results from Mawson m₂ and Vent are from Hood Hills (2004). Samples with ‘AH’ prefix were collected by J. Prebble during the 2001/2002 field season.

Carbon, hydrogen, nitrogen, oxygen, and sulfur analyses of coal samples from the Weller Coal Measures and the Mawson Formation

Precision of results is ± 0.3%, and the detection level is 0.1%. Impurities, such as siliciclastic dust and zeolite veinlets, are reflected by totals < 100%. Mawson m₂ and Vent values from Hood Hills, 2004. Samples with ‘AH’ prefix were collected by J. Prebble during the 2001/2002 field season. The ultimate analysis for each sample was carried out using a Carlo Erba Elemental Analyser EA 1108, by an analyst in the Chemistry Department Microanalytical Laboratory, University of Otago, New Zealand.