bioturbated silty sandstone

bioturbated silty sandstone
This facies is gradational in character with facies
4, with which it shares the common feature of
sharp-based sandstone beds that punctuate a silty
background. Facies 5 differs from facies 4 in four
aspects: (i) thicker, commonly amalgamated, sandstone
beds (1-3 cm thick); (ii) a higher sand content;
(iii) a more diverse, clearly recognisable trace fossil
assemblage; and (iv) a wider range of sedimentary
structures.
Four trace fossils were recognised: Helminthopsis
horizontalis; Planolites; Palaeophycos; and Thalassinoides.
In addition, three sedimentary structures were
noted: (i) exquisitely defined, low-angle inclined, undulatory
stratification (LAIS) of variable estimated
wavelengths (10-50 cm); (ii) wave ripples (wavelength
around 10 cm); and (iii) combined wave and
current ripples (i.e. combined flow ripples).
Interpretation. The trace fossil assemblage….