Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ... Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
150 ADVANCES IN PALAEOICHTHYOLOGY This work is important to clarify the Wood Bay Formation subdivision. It is presently different for geologists, using the stratigraphic units, and palaeontologists who use the biostratigraphic units. Brief history A Wood Bay Formation stratigraphy was first proposed by Føyn and Heintz (1943). They divided the formation into three divisions (Kapp Kjeldsen, Lykta, and Stjørdalen) mainly based on the differing suites of pteraspidiforms. Friend (1961) confirmed these divisions for the Woodfjord area. He tried to characterise them from a geological point of view based on colour, grain size, and alternations of beds. However, he replaced the Lykta name by Keltiefjellet. At the same time Friend proposed another geological scale for the Dicksonfjord-Austfjord region where he described two different units: the Austfjord Sandstone and Dicksonfjord Sandstone (Friend 1961, p. 90-92). Friend et al. (1966) pointed out that the previous geological considerations for the Woodfjord area were unsatisfactory. They came back to the concept of faunal divisions, redefining them on the basis of their content of pteraspidiforms and placoderms. They also revised the lithostratigraphic units from the Dicksonfjord-Austfjord area and renamed them as members (Friend et al. 1966, p. 61). Finally, they proposed possible stratigraphic correlations between the Woodfjord and Austfjord-Dicksonfjord regions, without any faunal considerations. The last revision of the biostratigraphy of the Wood Bay Formation was done by Goujet (1984). He enhanced it with the introduction of a new basal faunal division, the Sigurdfjellet, characterised by its peculiar but at that time undescribed faunal content. Since the first subdivision of the Wood Bay Formation by Føyn and Heintz (1943), the ranges of the pteraspidiforms have been used as data for differentiation of the divisions. This choice is dictated by their abundance in terms of specimens and their easy recognition in the field outcrops (Føyn and Heintz 1943; Heintz 1962, 1967). Moreover their diversity is sufficient to characterise the divisions with successions of the different species (Pernegre 2002, 2003, and unpublished revision of the genus Gigantaspis). The other known fauna possess less value for such a work due to the high diversity of forms, as for e.g. the osteostracans: 16 genera with 40 described species (Janvier 1985). Moreover, each taxon is only represented by a restricted number of specimens (often one specimen only), so it is impossible to establish precise range extensions. The placoderms are well represented (Heintz 1929; Goujet 1973, 1984) in terms of occurrence and specimens available, but many forms remain undescribed and others should be redescribed. At the same time, no global biostratigraphic works have been done with the placoderms. Therefore, our biostratigraphic correlations are mainly based, as for preceding authors, on the pteraspidiform associations.
V. Pernegre, V. Dupret. Biostratigraphic correlations within Wood Bay Formation 151 Evidence for correlation in the Wood Bay Formation Woodfjord area (Sigurdfjellet, Kapp Kjeldsen, Keltiefjellet, and Stjørdalen faunal divisions) The major part of the material collected in 1969 comes from the Woodfjord area (Fig. 1). The four faunal divisions were described in this region and are used by paleontologists (Føyn and Heintz 1943; Goujet 1984). With information taken from recent works (Goujet 1984; Janvier 1985; Blieck et al. 1987; Pernegre 2002, 2003, 2004, and still unpublished data), we can now accurately correlate the field localities after identification of their faunal content. By using their identified fauna (pteraspidiforms, placoderms and osteostracans), we can classify the field localities noted as BIV, BII, Bi, BJ and A 11 (Fig. 1) into the Sigurdfjellet faunal division. The BIV locality is the richest collected site of the 1969 French mission and includes Doryaspis arctica, Gigantaspis sp. nov. and Xylaspis prima (pteraspidiforms) in association with Sigaspis lepidophora, Arctaspis sp. (placoderms) and Boreaspis rostrata, B. intermedia, B. ceratops, B. ginsburi, Cephalaspis curta, Norselaspis glacialis, and Axinaspis whitei (osteostracans). The BII samples contain Doryaspis arctica, Gigantaspis sp. nov., Xylaspis prima and Arctaspis sp. Doryaspis arctica, Gigantaspis sp. nov. and Diademaspis sp. are identified in the Bi locality. We only find Gigantaspis sp. nov. in our material from the BJ site and in the A 11 area we only identify Xylaspis prima. The occurrence of these two last species, however, is sufficient to indicate the Sigurdfjellet faunal division (Fig. 2). With the two close BI’ and BI localities (Fig. 1), we can identify the Sigurdfjellet - Kapp Kjeldsen boundary. Doryaspis arctica and Gigantaspis sp. nov. are found in the BI’ samples, two associated species which indicate the Sigurdfjellet faunal division. In the BI samples we identify Gigantaspis isachseni, the characteristic pteraspidiform of the Kapp Kjeldsen division. In conclusion, the Sigurdfjellet – Kapp Kjeldsen boundary is localised somewhere between these two close localities. This implies a quite rapid boundary without important transitional beds and fauna. The characteristic fauna of the Kapp Kjeldsen division is identified in the A 1-4 , BO and BL localities (Fig. 1). Gigantaspis isachseni, Gigantaspis bocki and Doryaspis arctica are found in the A 1-4 and BL samples. The BO material contains Gigantaspis isachseni and Doryaspis arctica in association with Diademaspis poplinae and Meteoraspis moythomasi (osteostracans). Gigantaspis isachseni is considered to be a guide fossil for the Kapp Kjeldsen division (Fig. 2), and its identification alone is sufficient to characterise this division. The Kapp Kjeldsen – Keltiefjellet boundary is exemplified in the Woodfjordalen, between the mounts Vaktaren and Wagner. In this region, many localities have been visited (H 1-3 , BG, BC and BE, C 4 , and BD; Fig. 1). The faunal identifications of the collected samples do not highlight a clear and precise boundary as for the Sigurdfjellet and Kapp Kjeldsen divisions. The fauna suggests a transitional boundary between Kapp Kjeldsen and Keltiefjellet faunal divisions. In the H 1-3 locality we find Gigantaspis isachseni, a huge unidentified Doryaspis sp. 1 (plate dimensions twice those of Doryaspis nathorsti) and another Doryaspis
- Page 99 and 100: ACTA UNIVERSITATIS LATVIENSIS, 2004
- Page 101 and 102: E. Lukševičs, I. Zupiņš. Sedime
- Page 103 and 104: E. Lukševičs, I. Zupiņš. Sedime
- Page 105 and 106: E. Lukševičs, I. Zupiņš. Sedime
- Page 107 and 108: E. Lukševičs, I. Zupiņš. Sedime
- Page 109 and 110: E. Lukševičs, I. Zupiņš. Sedime
- Page 111 and 112: E. Lukševičs, I. Zupiņš. Sedime
- Page 113 and 114: E. Lukševičs, I. Zupiņš. Sedime
- Page 115 and 116: E. Lukševičs, I. Zupiņš. Sedime
- Page 117 and 118: E. Lukševičs, I. Zupiņš. Sedime
- Page 119 and 120: E. Lukševičs, I. Zupiņš. Sedime
- Page 121 and 122: J. Valiukevičius. Silurian acantho
- Page 123 and 124: J. Valiukevičius. Silurian acantho
- Page 125 and 126: J. Valiukevičius. Silurian acantho
- Page 127 and 128: J. Valiukevičius. Silurian acantho
- Page 129 and 130: J. Valiukevičius. Silurian acantho
- Page 131 and 132: J. Valiukevičius. Silurian acantho
- Page 133 and 134: J. Valiukevičius. Silurian acantho
- Page 135 and 136: J. Valiukevičius. Silurian acantho
- Page 137 and 138: J. Valiukevičius. Silurian acantho
- Page 139 and 140: J. Valiukevičius. Silurian acantho
- Page 141 and 142: J. Valiukevičius. Silurian acantho
- Page 143 and 144: J. Valiukevičius. Silurian acantho
- Page 145 and 146: J. Valiukevičius. Silurian acantho
- Page 147 and 148: J. Valiukevičius. Silurian acantho
- Page 149: V. Pernegre, V. Dupret. Biostratigr
- Page 153 and 154: V. Pernegre, V. Dupret. Biostratigr
- Page 155 and 156: V. Pernegre, V. Dupret. Biostratigr
- Page 157 and 158: V. Pernegre, V. Dupret. Biostratigr
- Page 159 and 160: Ž. Žigaite. New telodont from Tuv
- Page 161 and 162: Ž. Žigaite. New telodont from Tuv
- Page 163 and 164: Ž. Žigaite. New telodont from Tuv
- Page 165 and 166: Ž. Žigaite. New telodont from Tuv
150<br />
ADVANCES IN PALAEOICHTHYOLOGY<br />
This work is important to clarify the Wood Bay Formation subdivision. It is presently<br />
different for geologists, using the stratigraphic <strong>un</strong>its, <strong>and</strong> palaeontologists who use the<br />
biostratigraphic <strong>un</strong>its.<br />
Brief history<br />
A Wood Bay Formation stratigraphy was first proposed by Føyn <strong>and</strong> Heintz (1943).<br />
They divided the formation into three divisions (Kapp Kjeldsen, Lykta, <strong>and</strong> Stjørdalen)<br />
mainly based on the differing suites of pteraspidiforms.<br />
Friend (1961) confirmed these divisions for the Woodfjord area. He tried to characterise<br />
them from a geological point of view based on colour, grain size, <strong>and</strong> alternations of beds.<br />
However, he replaced the Lykta name by Keltiefjellet. At the same time Friend proposed another<br />
geological scale for the Dicksonfjord-Austfjord region where he described two different <strong>un</strong>its:<br />
the Austfjord S<strong>and</strong>stone <strong>and</strong> Dicksonfjord S<strong>and</strong>stone (Friend 1961, p. 90-92).<br />
Friend et al. (1966) pointed out that the previous geological considerations for the<br />
Woodfjord area were <strong>un</strong>satisfactory. They came back to the concept of fa<strong>un</strong>al divisions,<br />
redefining them on the basis of their content of pteraspidiforms <strong>and</strong> placoderms. They<br />
also revised the lithostratigraphic <strong>un</strong>its from the Dicksonfjord-Austfjord area <strong>and</strong><br />
renamed them as members (Friend et al. 1966, p. 61). Finally, they proposed possible<br />
stratigraphic correlations between the Woodfjord <strong>and</strong> Austfjord-Dicksonfjord regions,<br />
without any fa<strong>un</strong>al considerations.<br />
The last revision of the biostratigraphy of the Wood Bay Formation was done by Goujet<br />
(1984). He enhanced it with the introduction of a new basal fa<strong>un</strong>al division, the Sigurdfjellet,<br />
characterised by its peculiar but at that time <strong>un</strong>described fa<strong>un</strong>al content.<br />
Since the first subdivision of the Wood Bay Formation by Føyn <strong>and</strong> Heintz (1943),<br />
the ranges of the pteraspidiforms have been used as data for differentiation of the<br />
divisions. This choice is dictated by their ab<strong>un</strong>dance in terms of specimens <strong>and</strong> their<br />
easy recognition in the field outcrops (Føyn <strong>and</strong> Heintz 1943; Heintz 1962, 1967).<br />
Moreover their diversity is sufficient to characterise the divisions with successions of<br />
the different species (Pernegre 2002, 2003, <strong>and</strong> <strong>un</strong>published revision of the genus<br />
Gigantaspis).<br />
The other known fa<strong>un</strong>a possess less value for such a work due to the high diversity of forms,<br />
as for e.g. the osteostracans: 16 genera with 40 described species (Janvier 1985). Moreover,<br />
each taxon is only represented by a restricted number of specimens (often one specimen only),<br />
so it is impossible to establish precise range extensions. The placoderms are well represented<br />
(Heintz 1929; Goujet 1973, 1984) in terms of occurrence <strong>and</strong> specimens available, but many<br />
forms remain <strong>un</strong>described <strong>and</strong> others should be redescribed. At the same time, no global<br />
biostratigraphic works have been done with the placoderms. Therefore, our biostratigraphic<br />
correlations are mainly based, as for preceding authors, on the pteraspidiform associations.
Change language