Lower Cambrian melanosclerites and foraminiferal linings from the Lontova Formation, St. Petersburg, Russia

Optical thermal maturity parameters and organic geochemical alteration at low grade diagenesis to anchimetamorphism: A review

“…The earliest melanosclerites have been reported from Lower Cambrian rocks of the East European Platform. They have not yet been found in post-Frasnian strata but as this enigmatic palynomorph group seems to have only limited stratigraphical and palaeoecological potential, they may have been overlooked or negelected (Cashman, 1996;Winchester-Seeto and McIlroy, 2006). Melanosclerites seem to be restricted to marine environments.…”

“…Their biological affinity is still a matter of debate. Melanosclerites have been assigned to algae but in most studies they have been interpreted as larval or early polyp stages of various Medusozoa (Cnidaria) (Cashman, 1992(Cashman, , 1996Winchester-Seeto and McIlroy, 2006). In fact, many melanosclerites show strong resemblance with hydroids and in some samples they occur together with hydrozoan periderms (Cashman, 1996).…”

Melanosclerites from the Wilhelmi Formation (Lower Silurian, north-eastern Illinois, USA)

“…Thus, the data provided herein are particularly valuable, as they are directly integrated with biostratigraphical data from another group (i.e., chitinozoans). In terms of their position within the melanosclerite group, the specimens herein cannot be related directly to those earliest recorded melanosclerites described by Winchester-Seeto and McIlroy (2006) from the Lower Cambrian Lontova Formation of Russia. The specimens that they described were assigned to Semenola, Melanosteus and Melanoclava, which have been recorded from Lower Cambrian to Middle Ordovician strata, and as such do not allow for confident relationships to be inferred with the taxa herein.…”

“…To date, melanosclerites have been recorded from marine sediments and erratic boulders from the Lower Cambrian (Winchester-Seeto and McIlroy 2006) to the Late Devonian (Cashman 1992), although published records and detailed descriptions of melanosclerite taxa remain scarce in relation to other microfossil groups. The material described herein is therefore important in providing further taxonomic and biostratigraphical data for the group.…”

Early Cambrian small carbonaceous fossils (SCFs) from an impact crater in western Finland

“…One region where fossils of this type have been particularly well studied is from the palaeocontinent Baltica. Broadly composed of the East European Craton and the Fennoscandian Shield, Baltica hosts an array of intracratonic Proterozoic to early Palaeozoic siliciclastic sediments that are particularly suited to the preservation of carbonaceous microfossils; a combination of shallow burial depth and relatively quiescent tectonic history has meant that many of these sediments remain thermally immature (Kirsimäe et al 1999;Kirsimäe & Jørgensen 2000;Winchester-Seeto & McIlroy 2006). For this reason, organic-walled microfossils (principally acritarchs) feature heavily in correlation schemes devised for Proterozoic to early Palaeozoic strata across this region (Volkova 1968;Vidal 1981;Moczydłowska & Vidal 1986;Mens et al 1987;Hagenfeldt & Bjerkeus 1991;Jankauskas 2002).…”