acritarch

[′ak·rə‚tark]

(paleontology)

A unicellular microfossil of unknown or uncertain biological origin that occurs abundantly in strata from the Precambrian and Paleozoic.

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References in periodicals archive ?

1990; Mens & Pirrus 1997) and possibly to the Asteridium tornatum-Comasphaeridium velvetum acritarch Zone (Moczydlowska 1991).

Early Cambrian tubular fossils of the genus Onuphionella from Estonia/Perekonna Onuphionella torujad kivistised Eesti Alam-Kambriumist

9b), and acritarch assemblages restrict the age of the Lumsden Dam Formation to the early to middle Tremadocian (White et al.

Stratigraphy, provenance, and tectonic setting of the Lumsden Dam and Bluestone Quarry formations (Lower Ordovician), Halifax Group, Nova Scotia, Canada

As an acritarch assemblage typical of the Agnostus pisiformis Zone has not been recorded in the Petseri Formation (Paalits 1992; Mens et al.

Ediacaran and Cambrian stratigraphy in Estonia: an updated review/Ediacara ja Kambriumi stratigrafia Eestis: ajakohastatud ulevaade

Environmental control in the distribution of acritarchs in the Lontova Stage of Estonia.

Trace fossils Didymaulichnus cf. tirasensis and Monomorphichnus isp. from the Estonian Lower Cambrian, with a discussion on the early Cambrian ichnocoenoses of Baltica/Ihniidid Didymaulichnus cf. tirasensis ja Monomorphichnus isp. Eesti alamkambriumis ja Baltika urgmandri varakambriumi voimalik Ihnokooslus

Acritarchs in Cambrian and Ordovician rocks of Nova Scotia and New Brunswick, Canada: new constraints on correlation and palaeogeography.

Hypothesized Cambrian medusae from Saint John, New Brunswick, reinterpreted as sedimentary structures

A metacarbonate bed near the top of the group yielded Middle Cambrian, Acado-Baltic trilobite fragments (Pratt and Waldron 1991), and graptolites and acritarchs in the upper part of the overlying Halifax Group indicate an Early Ordovician age (Cumming 1985; White et al.

Stratigraphy of the Lower Paleozoic Goldenville and Halifax groups in southwestern Nova Scotia

Acritarch excystment and surface ultrastructure with descriptions of some Ordovician taxa.

Discovery of the messaoudensis-trifidum acritarch assemblage (upper Tremadocian-lower Floian, Lower Ordovician) in the subsurface of Morocco

The age of the Kotlin sandstone is rather loosely constrained (< 570 Ma), whereas the Lontova Formation is represented by the sub-trilobitic acritarch assemblage of Asteridium tornatum-C.

Provenance shift in Cambrian mid-Baltica: detrital zircon chronology of Ediacaran-Cambrian sandstones in Estonia

It is worthy of note that the acritarch assemblages discovered in the studied succession include besides the typical Siberian taxa several representatives of different Ordovician microphytoplankton 'provinces' (Servais et al.

New data on acritarchs from the Upper Ordovician of the Tungus basin, Siberian Platform

and the acritarch assemblage found from two levels in the Maekalda section near the centre of Tallinn (15 km west of the Ulgase section) allow tentative correlation of the Ulgase Formation in Tallinn and its environs with the Olenus trilobite Biozone (Mens et al.

Phosphatized organic nanostructures in the Cambrian Linguloid brachiopod Ungula inornata (Mickwitz)/Fosfatiseerunud orgaanilised nanostruktuurid Kambriumi brahhiopoodil Ungula inornata (Mickwitz)

The only published source on the Ordovician sequence in the vicinity of Shahrud is a paper by Ghavidel Syooki (2006), where he reported for the first time on the presence of Tremadocian deposits north of the Kalat-e Molla village and subdivided the Cambrian (Furongian)-Ordovician sequence into six acritarch assemblage zones.

Early Ordovician (Tremadocian) brachiopods from the Eastern Alborz Mountains, Iran/Vara-Ordoviitsiumi (Tremadoci) brahhiopoodid Ida-Alborzi magedest Iraanist

He and other paleontologists have suspected for some time that a fraction of the known acritarch species represent predecessors of modern dinoflagellates.