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

E. Lukševičs, I. Zupiņš. Sedimentology, fauna, and taphonomy of Pav āri
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Naum., Leiotriletes immanus Isch., Dictyotriletes sp. have been identified by M.
Stanichnikova from clayey interbeds (Savvaitova 1977). V. Talimaa has reported remains
of following vertebrate taxa from the Nīgrande Member in the territory of Lithuania:
Chelyophorus sp., Panderichthys sp., Rhizodontidae gen. indet., Osteolepis? sp.,
Onychodus sp., Dipterus? sp., Palaeoniscidae gen. indet. in the lower part of the member;
Bothriolepis sp., Acanthodei gen. indet., Sarcopterygii gen. indet., Panderichthys sp.,
Holoptychius sp. in the upper part (Žeiba and Savvaitova 1981). In this case the
identification of some taxa also causes doubt, as identifiable remains of the genus
Panderichthys so far have been recorded only from the Givetian – Frasnian interval in
the deposits of the Gauja, Lode, Amata, and Dubniki Formations, while the genus
Osteolepis is known mainly from the Middle Devonian.
The eroded surface of the clay and clayey-silty rocks of the Nīgrande Member is
overlaid by the yellowish grey fine-grained sandstone and sand of the Pavāri Member.
In most of the distribution area sand and sandstones consist of quartz with admixture of
feldspars, and in some places contain great amount of mica. In some levels sandstone is
well cemented by dolomite. The content of fine-grained sand increases in the sections
towards the northern part of distribution area (boreholes 27, 1-Priekule, 15-Sab-
Nākotne); towards the north-western margin the amount of the medium sized grains
also increases. The facies of the upper part of the Pavāri Member is more variable,
being composed of thin beds of clay, clayey siltstone, dolomite marl and feldsparquartzitic
micaceous sand. The total thickness of the section is 16-21 meters. Sand and
sandstones of the Pavāri Member contain a rich assemblage of fishes and tetrapods, the
full content of which is described further below.
Sandstones of the upper Varkaļi Member overlie the eroded surface of the Pavāri
Member. The lower part of the Varkaļi Member is composed of light greenish-grey
very fine and fine-grained feldspar-quartz sands and weakly cemented sandstones,
frequently containing large amounts of mica. Parallel cross-bedding is characteristic
for the sandstones. In some beds, smooth horizontal bedding is accentuated by the
distribution of muscovite scales, fish bones and their fragments, and clay pebbles. The
lower part of the Varkaļi Member crops out on the right bank of the Venta River near
the former Ketleri hamlet. The conglomerate in the fine grained sandstones of the lower
part of this member is formed of well rounded blue-grey pebbles of microcrystalline
dolomite marl of usually small, but sometimes quite large (up to 5 – 7 cm) size, dolomite
marl interlayers and vertebrate remains. Mainly small remains of fishes and tetrapods
as well as rounded and abraded fragments of larger bones are to be found in sandy
rocks. During several excavations organized by D. Obruchev (1957), L. Lyarskaya
(1970, 1973) and E. Lukševičs (1984, 1988) rather rich material of fossil vertebrates
has been collected at the locality: fragments of the trunk armour and disarticulated
bones of the head shield of placoderm Bothriolepis ciecere, acanthodian spines, scales
of “Devononchus” ketleriensis Gross un “D.“ tenuispinus (Gross), as well as scales of
at least yet another acanthodian, scales and rare disarticulated bones of the head of the
sarcopterygians Holoptychius cf. nobilissimus, Ventalepis ketleriensis Schultze,
Glyptopomus? bystrowi (Gross), Cryptolepis grossi Vorobyeva, Platycephalichthys sp.,
parasphenoideum of a lungfish Orlovichthys cf. limnatis Krupina, remains of tetrapods
Ventastega curonica Ahlberg, Lukševičs et Lebedev and Tetrapoda gen. indet. (Ahlberg
et al. 1994). Comparison of the vertebrate assemblages from Ketleri and Pavāri sites