Cambrian, Ordovician and Silurian pedostratigraphy and global events in Australia

COMMENT: MARINE INFLUENCE IN THE UPPER ORDOVICIAN JUNIATA FORMATION (POTTERS MILLS, PENNSYLVANIA): IMPLICATIONS FOR THE HISTORY OF LIFE ON LAND: PALAIOS, v. 25, no. 8, p. 527-539, 2010

“…Differences between the Potters Mills burrows and those of snake millipedes (Julida) are confirmed by well-illustrated recent studies of julid burrows (Hembree, 2009). Euthycarcinoid body fossils and tracks in Cambrian and Ordovician intertidal and fluvial facies have been a surprising recent discovery, but these creatures were more likely amphibious than burrowing (Retallack, 2009a(Retallack, , 2009bCollette et al, 2010). Davies et al (2010, p. 535-536) err in assuming that non-repichnial trace fossils older than Silurian and that early Paleozoic calcareous paleosols are ''anomalous.''…”

“…Davies et al (2010, p. 535-536) err in assuming that non-repichnial trace fossils older than Silurian and that early Paleozoic calcareous paleosols are ''anomalous.'' I have found calcareous paleosols at five other localities in Pennsylvania (Retallack, 1985), and 867 paleosols in earliest Cambrian to latest Ordovician fluvial sequences of Australia (Retallack, 2008(Retallack, , 2009a(Retallack, , 2009b. Diverse lacustrine and fluvial Cambrian and Ordovician non-repichnial trace fossil assemblages have been described by Trewin andMcNamara (1994), Mikuláš (1995), and Retallack (2008Retallack ( , 2009a.…”

“…Only eight ichnogenera are known from the Juniata Formation (cf. Diplichnites, Circulichnus, Helminthopsis?, Palaeophycus, Planolites, Scolicia?, Scoyenia, Skolithos: Retallack, 1985Retallack, , 2001Diecchio and Hall, 1998;Davies et al, 2010) and comparable forms are found elsewhere in Cambrian-Ordovician fluvial and lacustrine rocks (Trewin and McNamara, 1994;Mikuláš, 1995;Retallack, 2008Retallack, , 2009aRetallack, , 2009b. The Juniata Formation has not yet yielded such traces as Rusophycus or Chondrites, common among at least 22 ichnogenera in Ordovician (Katian) marine rocks around Cincinnati, Ohio, United States (Osgood, 1970).…”

“…Diverse lacustrine and fluvial Cambrian and Ordovician non-repichnial trace fossil assemblages have been described by Trewin andMcNamara (1994), Mikuláš (1995), and Retallack (2008Retallack ( , 2009a. Because of revised age, the Tumblagooda Sandstone of Western Australia now has the oldest reported backfilled burrows in calcareous paleosols (''Beaconites'' of Trewin and McNamara, 1994, at 704 m and 756 m, or 461 Ma and 458 Ma, in the age model of Retallack, 2009b), which is early Sandbian (earliest Late Ordovician), and thus predates the Katian or Hirnantian burrows from Potters Mills. Early Silurian backfilled burrows (''Taenidium'') from the Grampians in Victoria, Australia (Retallack, 2009a), now connect Ordovician records with late Silurian (Retallack, 1985) and Devonian backfilled burrows in paleosols (Gordon, 1988;Retallack and Huang, 2010, figs.…”

“…The evidence of paleosols formed in part by their trace fossils is critical to the issue, and remains unfalsified. Terrestrial ecosystems of the Cambrian and Ordovician remain poorly known, but their presumed millipedes, euthycarcinoids, and liverworts have become apparent to many investigators (Johnson et al, 1994;Trewin and McNamara, 1994;Strother, 2000Strother, , 2004Retallack, 2008Retallack, , 2009aRetallack, , 2009bCollette et al, 2010). These trace and body fossils deserve more attention, not less.…”