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Victoria University Antarctic Research Expedition Science and Logistics Reports 1979-80: VUWAE 24

Smear Slide Analysis (BW)

page 23

Smear Slide Analysis (BW)

The core was sampled for smear slide analysis at varying intervals depending on lithology.

Cadex was used as a mounting media and after initial problems in its application, proved to be a reasonable substitute for Canada Balsum. The slightly higher refractive index of cadex did not allow differentiation between Ca and Na plagioclase feldspar.

The smear slide analysis proved useful in determining sediment texture (sand: silt: clay ratio), mineralogy of the sand size fraction and nature of the biogenic component.

Three petrographic provinces could be recognised in the cored section:
(1)Clinopyroxene-glass zone, from 9 to 13 metres sub-bottom, derived from McMurdo Volcanics, which are mainly less than 5 million years old
(2)Biotite-hornblende Zone, from 19 metres (s.b.) to base, derived from reworked basement heavy minerals
(3)Rounded quartz grain Zone, from 140 metres (s.b.) to base, containing reworked quartz grains from the Beacon Supergroup.

Micritized carbonate (micarb) often occurs in large quanities, probably derived from the dissolution of foraminifera and other calcareous fossils or from erosion of marble basement rocks in southern Victoria Land. No calcareous nannoplankton were observed in the smear slides. Micarb appeared at 40 metres (s.b.) and occurred consistently to the bottom of the hole.

Coarse-grained, well rounded quartz, with occasional silica overgrowth, characteristic of Beacon Sandstone sediments were found in significant proportions at 130 metres (s.b.).

The smear slide analysis has proved to be useful for a quick and effective determination of mineralogical changes that occurred in the core. It is useful for determining the presence of diatoms and was the basis for detailed sampling for diatoms.

The exclusion of the coarse fraction during slide preparation caused a textural bias which resulted in an apparent increase in the amount of mud-size sediment.