Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...

More documents

Recommendations

Info

ACTA UNIVERSITATIS LATVIENSIS, 2004, Vol. 679, pp. 120-147 Silurian acanthodian succession of the Lužni-4 borehole (Latvia) JUOZAS VALIUKEVIČIUS Juozas Valiukevičius, Institute of Geology and Geography, T. Ševcenkos 13, 03223 Vilnius, Lithuania; valiukevicius@geo.lt Acanthodians of the Lužni-4 borehole core include about 50 species and other dermal element forms distributed in the late Ludlow to the topmost Pridoli. Eleven acanthodian associations are obtained classified as the intervals (=intervals of partial ranges) of index species. Ranges of taxa which characterize the local and regional stratigraphical units are given, and most valuable species are distinguished. The earliest occurrence of Nostolepis gracilis in the Baltic region is reported from the late Ludlow, a lower stratigraphic level than previously recognized. Some taxa, such as Nostolepis latvica sp. nov., N. alifera sp. nov., N. cf. linleyensis, Rohonilepis breviornatus, Arenaceacanthus arcuatacanalis, Fecundosquama basiglobosa, Poracanthodes marssae sp. nov., have biozonal utility, and Nostolepis linleyensis, Gomphonchus mediocostatus, Monospina erecta, Poracanthodes spp., are significant for wide interregional correlations. The short-ranging topmost Pridolian acanthodian associations of the Lužni-4 lack some taxa characteristic of the deepest water Jura Formation as compared to southwestern Lithuania, perhaps indicating a shortened geological profile in this basin part. Key words: Acanthodii, Climatiiformes, Ischnacanthiformes, histology, associations, biostratigraphy. Introduction The Lužni-4 borehole is on the shore of the Baltic Sea, in the northwestern part of the Kurzeme peninsula (west Latvia). The Silurian portion of the core has been used as a reference to characterise Latvian stratigraphical units and the palaeogeographical development of this part of the basin. I direct readers to publications of 1974-1987 (Gailite and Ulst 1974; Ulst 1974; Gailite 1978; Ulst and Gailite 1986; Gailite, Ulst and Yakovleva 1987; Karatajute-Talimaa 1978) for the geological and facies characteristics of this section and of the whole Kurzeme area, and for distribution of different faunal groups including ostracodes, brachiopods, conodonts and vertebrates. The acanthodian-bearing stratigraphic sequence studied here embraces the late Ludlow (Ventspils Formation) and Pridoli (Minija and Targale formations). The geological profile is composed of biomorphic and detrital limestones (the main part of Ventspils Fm.), clayey marls with interlayers of detrital limestones (Šilale Beds of the Minija Fm.), clayey marls (Varniai Beds of the Minija Fm.), dominant nodular biomorphic limestones (Venzava Beds), marls (Garzde Beds) and dolomitized limestones and dolomitic marls (Lužni Beds) of the Targale Formation. The sediments were mostly accumulated in the near shore zone of the shallow shelf. This environment was replaced by a lagoonal one during the latest Pridoli, with deposition of the Lužni Beds in the gradual transition from Silurian to Devonian.
J. Valiukevičius. Silurian acanthodians from Lūžņi-4 121 The first microvertebrate report of the Lužni-4 core was provided by Gailite and Ulst (1974) based mainly on thelodont identifications by V.Karatajute-Talimaa. In the Pagegiai Formation (of the old nomenclature, embracing modern Mituva and Ventspils formations), Thelodus laevis Thelodont Zone (TZ) was distinguished; Th. sculptilis TZ in the lower part of the Minija Fm.; and Th. parvidens TZ in the upper Minija and the principal part of the Targale Formation (until the depth of 195 m). Two following facts obtained from this core are of great interest in discussing the completeness of the Silurian profile in the basin, and in tracing the Silurian/Devonian boundary. These are the discovery of the Katoporodus lithuanicus TZ (195-176.6 m), a short-ranging topmost unit of the Silurian Vertebrate Standard Scheme (Karatajute-Talimaa 2000; Märss 2000), and the earlier entry into the sequence of Turinia pagei, which first occurs here about 4.6 m below the traditional Silurian/Devonian boundary drawn at the base of the red dolomitic marls. Both facts demonstrate the developmental peculiarities of this part of the basin, which became more isolated and lagoonal, but with the complete occurrence of index fossils which mark the Silurian/Devonian boundary beds with no stratigraphic gap. Acanthodians of the Lužni-4 collection were reported in the publications of 1974, with only short biostratigraphical comments (Karatajute-Talimaa 1978). Only the widest spread, commonly known taxa were recognized - Nostolepis striata Pander, N. gracilis Gross, Gomphonchus sandelensis (Pander), G. hoppei (Gross) and representatives of Poracanthodes. The present study extends the list to about 50 taxa or skeletal elements of an animal (teeth, spines) which attribution to distinct taxa is uncertain (Table). The collection is housed at the museum of the Institute of Geology and Geography (abbreviated LIGG) in Vilnius and is numbered 25-A. Systematic palaeontology Class ACANTHODII Berg, 1922 Order CLIMATIIFORMES Berg, 1940 Family CLIMATIIDAE Berg, 1940 Genus Nostolepis Pander, 1856 Type species. Nostolepis striata Pander, 1856; Upper Silurian, Pridoli, Ohesaare Regional Stage. Ohesaare Cliff, Saaremaa, Estonia. Nostolepis alifera sp. nov. Fig. 1A-L, 2 A-D Etymology. Alifer (Latin) - winged, referring to the lateral crown slopes on scale crowns. Holotype. LIGG 25-A-2550, flank scale (Fig. 1 F). Type horizon. Garzde Beds of the Targale Formation, Pridoli, Upper Silurian. Range. Type horizon only. Material. About 2500 scales.
Page 1 and 2:
LATVIJAS UNIVERSITĀTES RAKSTI 679.
Page 3 and 4:
LATVIJAS UNIVERSITĀTES RAKSTI 679.
Page 5 and 6:
Contents Ervīns Lukševičs and Ģ
Page 7 and 8:
ACTA UNIVERSITATIS LATVIENSIS, 2004
Page 9 and 10:
Ervīns Lukševičs, Ģirts Stinkul
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Olga Afanassieva. Microrelief on th
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
D.K. Elliott, E. Mark-Kurik, E.B. D
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
C.G.Miller, T. Marss, H. Blom. New
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
ACTA UNIVERSITATIS LATVIENSIS, 2004
Page 59 and 60:
H.-P. Schultze, T. Marss. Revisitin
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70: H.-P. Schultze, T. Marss. Revisitin
Page 79 and 80: ACTA UNIVERSITATIS LATVIENSIS, 2004
Page 81 and 82: O.A. Lebedev. A new tetrapod from R
Page 99 and 100: ACTA UNIVERSITATIS LATVIENSIS, 2004
Page 101 and 102: E. Lukševičs, I. Zupiņš. Sedime
Page 119: E. Lukševičs, I. Zupiņš. Sedime
Page 123 and 124: J. Valiukevičius. Silurian acantho
Page 149 and 150: V. Pernegre, V. Dupret. Biostratigr
Page 159 and 160: Ž. Žigaite. New telodont from Tuv
show all

Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?