Iirosion of headlands along the southern coast of Victoria results chiefly from the attack of storm waves, and is concentrated above a defined level, marked by certain level shore platforms, whose surfaces are at about high tide level. These platforms are initiated and maintained by storm wave erosion. Their surfaces undergo plahation and lowering, chiefly by the scouring action of waves of translation, but increasingly by water-layer weathering as the platforms age and widen.

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In situ overpressures in sedimentary basins are commonly attributed to disequilibrium compaction or fluid expansion mechanisms, although overpressures in shallow sedimentary sequences may also develop by vertical transfer of pressure from deeper basin levels, for example, via faults. Mafic sill complexes are common features of sedimentary basins at rifted continental margins, often comprising networks of interconnected sills and dikes that facilitate the transfer of magma over considerable vertical distances to shallow basinal depths. Here, we document evidence for deep sills (depths >5 km [>16,000 ft]) hosting permeable, open fracture systems that may have allowed transmission of overpressure from ultradeep basinal (>7 km [>23,000 ft]) levels in the Faroe-Shetland Basin, northeast Atlantic margin. Most notably, well 214/28-1 encountered overpressured, thin (<8 m [<26 ft]), and fractured gas-charged intrusions, which resulted in temporary loss of well control. Although the overpressure could reflect local gas generation related to thermal maturation of Cretaceous shales into which the sills were emplaced, this would require the overpressures to have been sustained for unfeasibly long timescales (>58 m.y.). We instead suggest that transgressive, interconnected sill complexes, such as those penetrated by well 214/28-1, may represent a previously unrecognized mechanism of transferring overpressures (and indeed hydrocarbons) laterally and vertically from deep to shallow levels in sedimentary basins and that they represent a potentially underrecognized hazard to both scientific and petroleum drilling in the vicinity of subsurface igneous complexes.

The Tertiary era in Victoria was marked by two extensive periods of intermittent vulcanicity; one ranging from the Oligocene to the Middle Miocene (Older Volcanic Series), the other from the Pliocene to the Recent (Newer Volcanic Series). The Older Volcanic Series, now greatly eroded, occurs mostly south and east of Melbourne. The Newer Volcanic Series, which has suffered much less erosion, extends north-west and west from Melbourne as a broad plain of about 10,000 square miles in area, and forms the floor of the Great Valley of Victoria. This paper is concerned with lavas of the Newer Volcanic Series lying between longitudes 144° E. and 145° E. (Fig. 1). The Geological Survey of Victoria generously provided facilities for cutting 500 thin sections, and lent to me another 500 slides on my departure for England, besides putting at my disposal maps, literature, and unpublished analyses. Mr. D. E. Thomas, of the Survey, in conjunction with whom the detailed field work was done, generously withdrew from the work. Fifty chemical analyses were prepared in the Geochemistry Department, Imperial College of Science and Technology, London, under Dr. H. F. Harwood. Much helpful criticism was received from Professors Boswell and Brammall, and my thanks are due to Dr. G. W. Tyrrell of Glasgow and Dr. E. S. Hills of Melbourne for reading the manuscript, and to Professor Brammall for seeing the paper through the press. P revious L iterature A bibliography of references to Victorian basalts is provided in Professor Skeats's Presidential Address, on the volcanic