. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. TRACE FOSSILS OF THE SARDINIA BAY FORMATION 15 DIPLOCRA TERION Description Spreiten demarcated by pyrite-rich laminae, indicating the former position of a U-tube, were found in a loose boulder of quartzite (Fig. 6). ,The exact strati- graphic position of this fragment has not been fixed but is probably close to the interval 30-60 m (see Fig. 2). Irregular U-tubes up to 2 cm in diameter, with the limbs of the tube up to 7 cm apart, occur 48 m from the base of the Sardinia Bay Formation. Spreiten can b
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. TRACE FOSSILS OF THE SARDINIA BAY FORMATION 15 DIPLOCRA TERION Description Spreiten demarcated by pyrite-rich laminae, indicating the former position of a U-tube, were found in a loose boulder of quartzite (Fig. 6). ,The exact strati- graphic position of this fragment has not been fixed but is probably close to the interval 30-60 m (see Fig. 2). Irregular U-tubes up to 2 cm in diameter, with the limbs of the tube up to 7 cm apart, occur 48 m from the base of the Sardinia Bay Formation. Spreiten can be discerned between the limbs of one U-tube (Fig. 7).. Fig. 6. Spreiten demarcating the former positions of U-tubes indicating upward migration of U-shaped burrows, probably Diplocraterion. Tracing from a loose boulder. Interpretation Figure 6 shows a typical example of Diplocraterion in which upward migration of the U-shaped burrow has occurred in response to sedimentation. The U-tubes themselves are not represented, possibly because of erosional truncation following sedimentation (cf. Goldring 1964, in Hantzschel 1975: W30). The irregular U-tubes shown in Figure 7 are less convincing examples of the ichnogenus. Diplocraterion is thought to be the dwelling trace of a suspension-feeding organism living in a high wave energy environment, and is known from strata of Cambrian to Cretaceous age (Hantszchel 1975: W62). Description Millimetre-thin straight or gently-meandering sand-filled tubes, perpendicu- lar to the bedding, occur in sandstones of the Upper Sardinia Bay Formation (see Fig. 2). Tube cross-sections are oval to roughly circular. The tubes are gen- erally crowded to the extent that the internal lamination of the host bed is virtually destroyed (Fig. 8). Individual tubes appear to penetrate whole beds of up to 60 cm in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and a
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
