. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. TRACE FOSSILS OF THE SARDINIA BAY FORMATION 21. Fig. 12. Weathered surface of a mudrock unit showing disseminated pyrite now altered to lim- onite (dark nodules) and short, gently curved burrows with rounded ends (arrowed), which resemble Planolites. Note that the burrow fill is almost indistinguishable from the substrate; the burrow margins are revealed only by the effects of differential weathering. mind, however, that ichnofacies models are likely to be less reliable in dealing with ancient sedime
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. TRACE FOSSILS OF THE SARDINIA BAY FORMATION 21. Fig. 12. Weathered surface of a mudrock unit showing disseminated pyrite now altered to lim- onite (dark nodules) and short, gently curved burrows with rounded ends (arrowed), which resemble Planolites. Note that the burrow fill is almost indistinguishable from the substrate; the burrow margins are revealed only by the effects of differential weathering. mind, however, that ichnofacies models are likely to be less reliable in dealing with ancient sedimentary rocks than is the case in younger strata and sediments, where the organisms responsible for producing the traces can be more readily identified and their behaviour more easily correlated with changes in the govern- ing conditions. SKOLITHOS ICHNOFACIES The Skolithos ichnofacies model described by Seilacher (1967) and Frey & Pemberton (1984: 198-199) is typified by the presence of burrows with rein- forced wall linings and a predominance of vertical shafts. Characteristic ichno- genera are Skolithos, Ophiomorpha and Diplocraterion. The wall linings indicate burrowing in soft sediment. Sedimentary structures associated with this ichno- facies include near-horizontal lamination, ripple laminae, trough cross-bedding, and flaser-, wavy- and lenticular-bedding. Biogenic structures are subordinate. The Skolithos ichnofacies is believed to indicate high current and wave energy regimes in shallow marine settings, ranging from shallow shelf and shore face to estuarine and tidal-flat Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original South African Museum. Cape Town : The Museum
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
