An event bed with abundant Skolithos burrows from the late Pridoli (Silurian) of Saaremaa (Estonia)

Abstract

Abundant Skolithos burrows are here described from a possible regressive event bed at Ohesaare cliff (Pridoli), Saaremaa, Estonia. The vertical, cylindrical burrows are identified as Skolithos rather than Trypanites because they intercept and bypass rather than cut bioclasts in the limestone matrix. The absence of encrustation on the upper bedding surface also is evidence that these traces are soft-sediment burrows rather than hardground borings. We interpret this intensive bioturbation by Skolithos-producing organisms as an indicator of a shallow water paleoenvironment with high hydrodynamic energy.Key Words: Trace fossils; Skolithos; shallow shelf; late Silurian; Baltica. Résumé : Un banc remarquable par ses skolithes dans le Pridoli supérieur (Silurien) de Saaremaa (Estonie).-D'abondants terriers de type Skolithos sont décrits dans une strate remarquable, bathydécroissante, identifiée dans la falaise de Ohesaare (Pridoli) à Saaremaa (Estonie). Ces terriers cylindriques et verticaux sont attribués à Skolithos plutôt qu'à Trypanites, car quand ils rencontrent de gros bioclastes dans la matrice calcaire du banc ils ont pris l'option de les contourner plutôt que de les traverser. L'absence d'encroûtement à la surface sommitale du banc est une preuve supplémentaire que ces traces correspondent à des terriers dans un sédiment meuble plutôt qu'à des perforations dans un fond durci. Nous interprétons cette intense bioturbation par les organismes produisant des skolithes comme une des caractéristiques d'un paléoenvironnement de faible bathymétrie à hydrodynamisme élevé.

Encrustation and bioerosion on late Sheinwoodian (Wenlock, Silurian) stromatoporoids from Saaremaa, Estonia

“…Similarly, a taxonomic polarity of epibionts has been reported from the reef stromatoporoids from the Ludlow of Gotland (SEGARS & LIDDELL, 1988). Anticalyptraea has previously been reported from cryptic surfaces under the late Silurian hardground from Ohesaare, Saaremaa (VINN & WILSON, 2010a). Cryptic surfaces in the Silurian were similar to the Ordovician, being mostly populated by the bryozoans, and cornulitids may also have been locally important (KERSHAW, 1980;TAYLOR & WIL-SON, 2003).…”

“…Encrustation patterns and bioerosion is relatively well known for western Baltica, especially for Gotland, Sweden (KERSHAW, 1980;NIELD, 1984;BEUCK et al, 2008). However, little published data on sclerobionts are available from the Silurian of eastern Baltica (KALJO, 1970;VINN & WILSON, 2010a, 2010b.…”

Shell repair in Anticalyptraea (Tentaculita) in the late Silurian (Pridoli) of Baltica

“…Thus, the vesicular shell structure of Anticalyptraea could be a protective morphology. In addition to thick vesicular walls, Anticalyptraea has reported to have some preference for the cryptic surfaces when associated with the hardgrounds in Pridoli of Saaremaa that can indicate predation pressure (VINN & WILSON, 2010b). The latest known Anticalyptraea-like fossils belong to Streptindytes (Middle Devonian to Carboniferous), which lived embedded in the host coral skeleton.…”

“…It belongs to encrusting tentaculitoid tubeworms and is closely related to cornulitids, microconchids and tentaculitids (VINN & ISAKAR, 2007;VINN, 2010). Anticalyptraea occurs as an encruster on various shelly fossils, such as brachiopods, stromatoporids, corals, but also on hardgrounds (VINN & WILSON, 2010b). The aims of this paper are: 1) to describe in detail the shell repairs in the encrusting tentaculitoid tubeworm Anticalyptraea for the first time; 2) to assess how often Anticalyptraea was attacked by predators in the late Silurian; 3) to describe shell repair mechanisms in Anticalyptraea; 4) to find correlations between shell repair rate and size of Anticalyptraea specimens; and 5) to discuss possible antipredatory adaptations in Anticalyptraea morphology and behavior.…”

Rare earth elements (REEs) in vertebrate microremains from the upper Pridoli Ohesaare beds of Saaremaa Island, Estonia: geochemical clues to palaeoenvironment c

“…Diverse and rich benthic fauna and intense bioturbations in the Ohesaare section indicate shallow nearshore environments. The presence of such trace fossils as Cruziana and Skolithos has led to interpretations that this part of the basin presumably had high hydrodynamic energy (Vinn & Wilson 2013;Vinn 2014). In this work we present results of the first REE analyses from fish microremains of this important early vertebrate site and the first quantitative interpretations of the REE data record as a proxy to palaeoredox conditions and palaeoenvironment.…”