Early Jurassic volcanism was in the southern north Victoria Land portion of the Ferrar Large Igneous Province preceded by multiple phases of shallow‐level intrusions of Ferrar sills into the 300 m thick cover of sedimentary rocks of the Triassic‐Jurassic Victoria Group. Upward protrusions from sills into unconsolidated water‐saturated sandstones triggered phreatomagmatic eruptions, forming discordant diatremes. Associated mafic volcaniclastic subaerial sediments are intercalated in the stratigraphic succession at two levels. Based on palynostratigraphy, their ages are late Pliensbachian and Early Toarcian, respectively. The matrix of the mafic volcaniclastic deposits is enriched in the individual minerals of the presently cemented fluviolacustrine country rocks. Clasts of the metamorphic and granitic basement are absent. The igneous clasts are comagmatic, comprising fragmented sill magma as well as scoriaceous juvenile lava shreds and bombs, some of which form welded deposits. All comagmatic and juvenile clasts, as well as those local pillows and lava flows embedded in the phreatomagmatic deposits, are of low‐Ti andesitic composition (Cr 100 ppm).
Viereck et al. (Sun,) studied this question.