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

104 ADVANCES IN PALAEOICHTHYOLOGY
enabled us to come to the conclusion that two oryctocoenoses most probably originated
from the same palaeobiocoenosis, differing mainly in the character of transportation
and burial conditions (Lukševičs 1992).
No spores or conodonts have been found in the Ketleri Formation, therefore the age
of the formation (corresponding to the expansa conodont zone; Esin et al. 2000) could
be judged only from its position above the Žagare Formation. Dolomite of the Žagare
Formation yeilds conodonts providing the possibility to correlate it with the interval
from marginifera to postera Zones (Esin et al. 2000). The underlying Švete Formation
(in Lithuania; corresponds to the Sniķere and Tērvete formations in Latvia) contains
conodonts of the postera Zone (Middle – Lower styriacus Zone of the previous conodont
zonation; Žeiba and Valiukevičius 1972).
Results
Sedimentology. The detailed studies of the outcrop of the Ketleri Formation on the left
bank of Ciecere River, opposite the former Pavāri hamlet, show a sandstone body with
a total thickness of more than 3 m, most of which is only visible after major excavation
and cleaning of the wall-shaped outcrop. The lithology of the section is shown in Figure
2. Very fine-grained to fine-grained white or light yellow almost unconsolidated quartzose
sandstone dominates the sequence. An erosional surface, interpreted here as a relatively
shallow (about 0,5 m deep) and at least 8 m wide erosional channel, is traced in the
lower part of the section (Fig. 3). Measurements of dip suggest that a stream flowing
from NNE to SSW formed this erosional channel. The same direction is characteristic
for the whole cross-stratified deposits of the Ketleri Formation (Savvaitova 1974). In
accordance with the results from a grain-size analysis (Fig. 4), the erosional channel
was filled by a well-sorted fine-grained sand in the lower part (Fig. 3, layer 6, sample
6A) and more silty moderately sorted material in the upper part (sample 6), showing
fining upward sequence which contains numerous vertebrate remains in the bottom
part of infilling, but no admixture of dispersed clay particles. Vertebrate remains are
unevenly spread in the rocks, mainly forming accumulations in the bottom part of the
sandstone infilling of the erosional channel. Accumulations were found also below a
thin clay layer (number 5 in Fig. 3) underlying the erosional surface.
Large-scale cross-bedding is characteristic for the lower and middle part of the
channel infilling. Small-scale current(?) ripples are also noticed above the cross-stratified
sandstone. Cross-stratified beds are rather thick in the lower part and very thin in the
middle part, usually bearing layers of mica on their surfaces. Measurements of crossstratified
beds show their bipolar orientation (Fig. 5), and their dip azimuth is almost
perpendicular to the axis of the erosional channel. Such orientation is usually explained
by the influence of inter-tidal streams (Reineck and Singh 1980). Laminae of the crossbedded
layers show variable angle of dip, in some places the high angle reaches 37 o .
Deformations of sandstone bedding and intrabasinal conglomerate consisting of clay
pebbles noticed mainly in the left side of the outcrop (along the right edge of the erosional
channel) indicate the role of slump processes in the filling of sides of the channel.
Another erosional surface (below the layer 7, Fig. 3) lies above the filling of the erosional
channel, trapping animal remains. The azimuth and dip angle of the upper channel are