Hailes Lava Member

From Earthwise
Jump to navigation Jump to search

Hailes Lava Member (HSLA), Carboniferous, Midland Valley of Scotland[edit]

Hailes Lava Member is part of the Garleton Hills Volcanic Formation

Name[edit]

Previously named the Hailes Member (see McAdam and Tulloch, 1985[1]).

Lithology[edit]

The Hailes Lava Member consists of dark grey, feldspar-phyric olivine basalts (‘Markle’ type) with sparse to abundant, large or small feldspar phenocrysts, aphyric basalts and pale purple-grey, platy-jointed mugearites. Thicknesses of flows are up to 17 m. The feldsar-phyric basalts characterise this unit of about six flows.

Stratotype[edit]

The type area is East Lothian (NT 4500 6900 to 6000 8300) around North Berwick, East Linton, the Garleton Hills, and Hailes (see Davies et al., 1986, fig. 10[2]; McAdam and Tulloch, 1985, fig. 17[1]), and in the Spilmersford Borehole (BGS Registration Number NT46NE/73) (NT 4570 6902), which provides a complete section from about 348 to 372 m depth.

Lower and upper boundaries[edit]

The base is conformable or locally unconformable on the East Linton Lava Member (olivine-, clinopyroxene- and sometimes plagioclase-phyric basaltic lavas; basalt and basanite and hawaiite) or locally unconformable on the North Berwick Pyroclastic Member.

The member is overlain by the Bangley Trachytic Member. The contact is conformable and locally unconformable. The change is from olivine basalt and mugearite lavas up into trachytic lavas with trachytic tuff and lapilli-tuff.

Thickness[edit]

Between 0 and 70 m.

Distribution and regional correlation[edit]

East Lothian, outcrop of the Garleton Hills Volcanic Formation around North Berwick, East Linton, Garleton Hills, Hailes and in the subcrop farther west in the BGS Spilmersford Borehole (see above) near Pencaitland, but absent south of Hailes adjacent to the Dunbar–Gifford Fault.

Age[edit]

Early Visean (Chadian to Arundian).

References[edit]

  1. 1.0 1.1 McAdam, A D, and Tulloch, W.1985.Geology of the Haddington district.Memoir of the British Geological Survey, Sheet 33W, part 41 (Scotland)
  2. Davies, A, McAdam, A D, and Cameron, I B.1986.Geology of the Dunbar district.Memoir of the British Geological Survey, Sheet 33E and part of Sheet 41 (Scotland)