Shallow-Marine Carbonates - Trace Fossils as Indicators of Sedimentary Environments - page 695

the Oslo region in Norway. Everywhere it is recognizable by G. oelandicus pits
usually filled with glauconite grains.
4.1.2 Lowstand Systems Tract, Upper Part of the Dikari
Limestone (BII a )
The upper part of the Dikari Limestone consists of 10 distinctive beds ( Figs. 2
and 3 ). The Butina Bed is the most remarkable one, comprising 1-5 cm of rela-
tively soft red marlstone with thin Thalassinoides forming a network typical for
the Central Baltoscandian Confacies belt. This bed is the best marker and may be
interpreted as a short-term invasion of relatively deep-water conditions. The
Dikari are predominantly of gray bioclastic packstone or grainstone with numer-
ous scattered glauconite grains. Distinctive hardground surfaces, emphasized by
yellow goethite impregnation, are abundant at some levels (e.g., the Krasny,
Zhelty, Nadzhelty, and Konoplasty beds). Some of these surfaces are pitted with
Balanoglossites and, more rarely, Trypanites . These beds usually consist of four
to eight elementary layers, each 3-4.5 cm thick. Most of the layers are distinctly
graded. Brachiopods, echinoderms, bryozoans, ostracods, and trilobites are the
main fossils. The uppermost bed of the Dikari Limestone (Butok) has a distinctive
hardground non-depositional surface at the top, marked by an extensive yellow
impregnation down to 2 cm. It is penetrated by shallow vertical borings attributed
to Trypanites ( Fig. 6 C) and a complex Balanoglossites ichnofabric augmented by
the weathering/dissolution of the surface prior to its hardening ( Fig. 6 D-F). The
hardground is interpreted as a transgressive surface. Other ichnogenera of this
unit include Thalassinoides , Bergaueria ,and Palaeophycus .
4.1.3 Transgressive Systems Tract, Zheltiaki Limestone (BII b )
The Zheltiaki Limestone differs from the underlying rocks of the Dikari Lime-
stone in having more argillaceous material within the carbonate rock, the
appearance of numerous clay layers, and the variegated, mostly red and yellow,
color of the rocks. Glauconite is rare or absent. The faunal assemblages recov-
ered from interbeds of clay are dominated by brachiopods, ostracods, and echi-
noderms, whereas those from the limestone beds are rather different and contain
many trilobites. These differences can be explained by the tempestite origin of
the limestone beds. The yellow and red colors of the rocks and the smaller grain
size in comparison with the underlying and overlying strata point to a relatively
deep-water origin. The Zheltiaki Limestone is subdivided into seven informal
lithostratigraphic units ( Fig. 2 ). The units bear rich ichnocomplexes dominated
by Thalassinoides and Chondrites ( Fig. 6 G). Washed-out surface trace fossils
are rare (e.g., Rusophycus ; Dronov et al., 2002 ).
4.1.4 Highstand Systems Tract, Frizy Limestone (BII g )
The Frizy Limestone consists of intercalations of greenish gray bioclastic
limestone and bluish gray clay, both containing scattered glauconite grains.
It can be subdivided into seven informal lithostratigraphical units ( Fig. 2 ).