The oldest abundant volcanic glass on Earth

The oldest abundant volcanic glass on Earth occurs in a Carboniferous ignimbrite in the region of Port Stephens, NSW. The K‐Ar age of 332 ± 4 Ma on biotite is consistent with the geological relations and establishes a Carboniferous age for the glass. The glassy nature has been established by X‐ray diffraction and electron diffraction.

Although Palaeozoic glass is relatively rare it appears that locally abundant glass occurs in felsic ignimbrite of Permian and Carboniferous age at several places in Australia and Europe.

Apart from a minor occurrence of Precambrian glass in a dyke apophysis there appears to be no well established occurrence of pre‐Carboniferous volcanic glass on Earth.

Key words:

• Carboniferous
• glass
• K‐Ar age determination
• volcanic