Ordovician chitinozoan zones from Baltoscandia

Nõlvak, Jaak; Grahn, Yngve

doi:10.1016/0034-6667(93)90025-p

Cited by 159 publications

(191 citation statements)

References 17 publications

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“…The Late Ordovician chitinozoan data available from Baltica (Nõlvak 1999, Nõlvak & Grahn 1993 and from eastern Laurentia (Achab 1978(Achab , 1981Soufiane & Achab 2000a) do not allow precise correlation with the chitinozoan assemblages from northern Gondwana. Surprisingly, some ties exist with chitinozoan assemblages from western and northern Laurentia.…”

Section: Chitinozoansmentioning

confidence: 99%

Late Ordovician-earliest Silurian palynomorphs from northern Chad and correlation with contemporaneous deposits of southeastern Libya

Hérissé¹,

Paris²,

Steemans³

2013

Bull. Geosci.

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Well preserved assemblages of cryptospores, chitinozoans, acritarchs, leiospheres, tasmanitids, colonies of Gloeocapsomorpha, scolecodonts and eurypterid fragments from 23 core samples of the Moussegouda core hole in the Erdi Basin, northern Chad, and from two samples from well KW-2 in Kufra Basin, South East Libya are investigated. These palynomorphs were recovered from the southernmost North African marine deposits of Late Ordovician and possibly early Silurian age. The palaeoenvironment evolves from late Hirnantian glacio-marine diamictites to silt-dominated sequences suggesting a marginal marine environment of possibly latest Hirnantian to earliest Rhuddanian age (post-elongata-pre-fragilis chitinozoan assemblages). The recovered palynomorph assemblages are compared and correlated with contemporaneous assemblages recorded in other northern Gondwana localities (Mauritania, Morocco Algeria, Libya, Africa, Saudi Arabia, Jordan), and in South Africa, in order to evaluate possible effects of the ice cap melting on palynomorph assemblages and sedimentation. Our goal is also to improve the regional biostratigraphy across the Ordovician-Silurian boundary. The composition of the recovered palynomorph assemblages, with mixed terrestrial and marine microflora, suggests that the topmost Ordovician or earliest Silurian in northern Chad and southeastern Libya, reflects nearshore conditions, with obvious fresh water influences. The lack of black shale or grey shale in the uppermost Ordovician and of "hot shale" in the lower Silurian in these areas, and their replacement by siltstones, are probably related to an isostatic readjustment that rapidly starved the marine sedimentation in the areas previously overlain by a thick ice cover during the climax of the Hirnantian glaciation. Tasmanites tzadiensis Le Hérissé sp. nov. and Euconochitina moussegoudaensis Paris sp. nov., two new palynomorphs of biostratigraphical interest are described and illustrated.•

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Section: Chitinozoansmentioning

confidence: 99%

Late Ordovician-earliest Silurian palynomorphs from northern Chad and correlation with contemporaneous deposits of southeastern Libya

Hérissé¹,

Paris²,

Steemans³

2013

Bull. Geosci.

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“…In addition, a species listed by Nõlvak & Grahn (1993) as being characteristic for the upper part of the Laufeldochitina stentor Biozone and its E. rhenana Subzone, namely Conochitina tigrina, has been discovered in the Spy Wood Brook section in the same sample as the topmost find of E. ?rhenana. According to Nõlvak (2005), C. tigrina has been found in the upper part of the E. rhenana Subzone in the Mehikoorma core. Nõlvak (2001) also shows the presence of C. tigrina in the topmost part of the L. stentor Biozone of the Valga (10) core, immediately above the E. rhenana Subzone.…”

Section: A1 Eisenackitina Rhenana Subzone?mentioning

confidence: 99%

“…According to Nõlvak (2005), C. tigrina has been found in the upper part of the E. rhenana Subzone in the Mehikoorma core. Nõlvak (2001) also shows the presence of C. tigrina in the topmost part of the L. stentor Biozone of the Valga (10) core, immediately above the E. rhenana Subzone. In short, we consider their coexistence to be quite stable.…”

Section: A1 Eisenackitina Rhenana Subzone?mentioning

confidence: 99%

A modern assessment of Ordovician chitinozoans from the Shelve and Caradoc areas, Shropshire, and their significance for correlation

et al. 2008

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-New chitinozoan data are presented from the classical section along the Onny River in the type Caradoc area, and from the deeper-water sections in the Shelve area, including the former British candidate GSSP for the base of the Upper Ordovician Series. The rich and well-preserved chitinozoan fauna of the Onny River has been a standard for 40 years, but new data revise some of the identifications. The assemblages are now attributed to biozones that are more readily applicable for international correlation. The main part of the section can be interpreted as belonging to the originally Baltoscandian Spinachitina cervicornis Biozone, although this is uncertain in the lower part. Within this biozone, the Fungochitina actonica Subzone has been defined. The Onny Formation at the top of the section is equated with the Acanthochitina latebrosa-Ancyrochitina onniensis Biozone; contrary to earlier reports, Acanthochitina barbata is absent. The Lower Wood Brook and Spy Wood Brook section from the Shelve Inlier yielded a great number of moderately to well-preserved chitinozoans, but a low-diversity assemblage. Their ranges have been neatly positioned against the well-known graptolite stratigraphy in the area. A local Eisenackitina rhenana Biozone? has been recognized, allowing us to suggest some international correlations.

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“…Endemic taxa are useful for paleobiogeographical reconstructions. Biozonations exist for Gondwana [1], north east Laurentia [2] and Baltica [3] during the Ordovician and a global zonation has been proposed for the Silurian [4]. The biological affinities of the Chitinozoa are not known precisely, but most authors do favor the hypothesis of a reproductive stage of Metazoa.…”

Section: Introductionmentioning

confidence: 99%

Classification of Chitinozoa (Llandoverian, Canada) Using Image Analysis

Verrecchia

Grootel

Guillemet³

1996

Microsc. Microanal. Microstruct.

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(Llandoverian, Canada) were studied using image analysis. After digitalization of the objects, shape parameters were calculated. The boundary of each fossil was then traced by a vector centred at the centroid for Fast Fourier Transform (FFT). Results of the two methods were used as variables in a hierarchical cluster analysis in order to group the samples. These results show that Chitinozoa can be significantly classified in terms of taxa using independent shape parameters obtained by image analysis.

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Ordovician chitinozoan zones from Baltoscandia

Cited by 159 publications

References 17 publications

Late Ordovician-earliest Silurian palynomorphs from northern Chad and correlation with contemporaneous deposits of southeastern Libya

Late Ordovician-earliest Silurian palynomorphs from northern Chad and correlation with contemporaneous deposits of southeastern Libya

A modern assessment of Ordovician chitinozoans from the Shelve and Caradoc areas, Shropshire, and their significance for correlation

Classification of Chitinozoa (Llandoverian, Canada) Using Image Analysis

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