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Flora assemblages at the Triassic/Jurassic boundary in Junggar Basin, Xinjiang Northwest China

Deng S.

Volumina Jurassica

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2006

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Vol. 4, no. 1

278-278

EN

The Upper Triassic and Lower Jurassic deposits in Junggar Basin, Xinjiang, Northwest China represent continuous succession and are divided into the Haojiagou Formation, Badaowan Formation and Sangonghe Formation (from base to the top). The Sangonghe Formation is definitely of the Early Jurassic age as based on plant, spore-pollen, conchostracans and bivalves. The ages of the Haojiagou and Badaowan formations are less clear. The Triassic/Jurassic boundary runs somewhere in the uppermost part of the Haojiagou Formation or in the Badaowan Formation as indicated by flora assemblages. Organic carbonaceous isotopic measurement suggests the position of the boundary in question at the base of the Badaowan Formation. The flora of the Haojiagou and the Badaowan Formations may be subdivided into the following assemblages. 1. Danaeopsis fecunda - Cladophlebis ichunensis assemblage. This assemblage is from the lower part of the Haojiagou Formation. It consists of about 20 species, characterized by Danaeopsis fecunda and numerous Cladophlebis. The main species include Danaeopsis fecunda Halle, Todites cf. shensiensis Pan, Cladophlebis ichunensis Sze, Cl. nebbensis (Brongn.) Nathorst, Cl. paralobifolia Sze, Sphenopteris chowkiawanensis Sze, Rireticopteris sp. and Cycadocarpidium sp. It is definitely of the Late Triassic age. 2. Neocalamites - Hausmannia assemblage. This assemblage is from the upper part of the Haojiagou Formation. It is composed of about 10 species with marked dominance of Neocalamites horerensis and Hausmannia xinjiangensis sp. nov. The assemblage is possibly of the Late Triassic age. 3. Todites princeps - Clathropteris elegans, assemblage. This assemblage is from the lower part of the Badaowan Formation, with about 15 species. Todites princes and Clathropteris elegans are dominant in the assemblage. It may be of earliest Early Jurassic age. 4. Coniopteris gaojiatianensis - Cladophlebis denticulata assemblage. This assemblage is abundant and of higher specific diversity. The main elements are: Selaginellites drepanoformis Zheng, Todites williamsoni (Brongniart) Seward, Coniopteris gaojiatianensis Zhang, Cladophlebis denticulata (Brongniart) Fontaine, Cl. gracilis Sze, Cl. hirta Moeller, Cl. cf. shansiensis Sze, Raphaelia diamensis Seward, Ginkgoites sp., Sphenobaiera sp., Czekanowskia rigida Heer, Samaropsis parvula Heer, S. rotundata Heer. It is noticeable that Coniopteris is recorded commonly. The assemblage occurs in the upper part of the Badaowan Formation and is of Early Jurassic age.

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The impact of the River Odra on the phytoplankton composition and biomass in the Pomeranian Bay

Gromisz S., Witek Z., Mackiewicz T.

Oceanologia

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1999

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No. 41 (3)

403-427

EN

The article is based on the analysis of phytoplankton samples collected in the Pomeranian Bay during five cruises in the years 1993, 1996 and 1997. In each season a number of phytoplankton assemblages were formed under the impact of the hydrological and hydrochemical conditions gradually changing along an axis from the outlets of the Szczecin Lagoon towards the open sea. The most distinct assemblages could be described as "river-mouth", "open-Bay"and "open-sea" assemblages. The highest phytoplankton biomass was noted near the mouth of the Swina Strait in the "river-mouth" assemblages, where the concentration of chlorophyll a was 4 to 5 five times higher in comparison with the "open-sea" values. The phytoplankton biomass in the "open-Bay" assemblages was roughly twice as high as that in the 'open-sea' assemblages. Because of the high N:P ratio in the Odra waters, phosphorus was very probably the factor limiting phytoplankton primary production in the Pomeranian Bay during periods of intensified inflow of riverine waters. The species dominating the phytoplankton of the Pomeranian Bay during the present study were found to be the same as those recorded in this region 40 years earlier.

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Calcareous nannoplankton assemblages of the Badenian evaporites in the Carpathian Foredeep

Peryt D.

Biuletyn Państwowego Instytutu Geologicznego

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1999

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nr 387

158--161