MP9: Chapter 17: Recent Overprinting of CretaceousPaleogene Thalassinoides Framework
by L.A. Wiest and I.V. Buynevich.
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This chapter is from GAC's Miscellaneous Publication 9: "Ichnology: Papers from Ichnia III" editted by Dr. Duncan McIlroy. To purchase the entire book on disc, please see the Miscellaneous Publications section of our bookstore at http://www.gac.ca/publications/view_pub.php?id=262.
Overprinting of marine ichnofossils by morphologically similar recent continental traces is reported in unconsolidated Cretaceous‒Paleogene successions of southern New Jersey, USA. Within the glauconitic sand-dominated Hornerstown Formation, Thalassinoides isp. burrow framework contains traces of modern burrowing bees and wasps that penetrate the outcrop up to 1 m. The modern insect traces exhibit occasional branching and are unlined. Insect burrow diameters (7‒25 mm) are within the range of Thalassinoides traces (4‒31 mm), therefore, neither size nor gross morphology can be used to distinguish between these widely diachronous, and unrelated, trace fossils. However, the presence of backfill menisci and a beige clay-rich burrow halo (suggestive of bio-irrigation) help distinguish the thalassinidean origin, whereas the highly oxidized fill and the presence of a terminal brooding chamber are diagnostic of the modern insect burrows.
Geological Association of Canada
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