• The rich ammonite assemblages and lithology of this section has

•made it possible to assess the water depth during deposition.

•During the early Albian, palaeodepth varied between 0 and 50 m,

•and conditions changed from calm coastal shallow water to mobile

•shallow water beyond bars and sand bars. During the middle

•Albian, depth increased to 50e100 m, and in the late Albian to

•100e150 m (Baraboshkin and Nikulshin, 2006).

•Numerous pieces of drift wood, inclusive of large fragments of

•trunks (up to 2 m in length; at Chekovo-1), indicate deposition of

•the levels studied relatively close to the coast. The shallow-water

•conditions are confirmed by examples of burrows of the Skolithos

•type, which suggest a high-energy setting close to shore.

• Clay-sandy layer with numerous phosphorite concretions

•(Fig. 3DeF), enclosed in a sandy “shell”; this is the so-called

•phosphorite horizon, varying in thickness between 10 and

•30 cm. Nodule size varies between 5 and 25 cm; nodule shape

•varies from small and shapeless to large and loaf-shaped. The

•

•nodules contain the following fossils: ammonite shells (Arc-

•thoplites bogoslowski, A. gerassimovi, A. sp. and others), bivalves

•

•(Cyprina, Modiolus, Pectinoida and others); small gastropods,

•

•rare echinoid tests (Nucleolites sp.) and stalk fragments of cri-

•noids, as well as serpulids and decapod crustacean carapaces.

•

•The last-named are occasionally complete, but more often

•fragmentary. Wood is sometimes found in various states of

•preservation (Fig. 3G), as well as conglomeratic lenses with

•concretions. The conglomerate comprises numerous yellow and

•black quartz pebbles ranging in size from 0.5 to 2 cm.

•

•3) A unit of green-grey glauconitic quartz, bioturbated cross-

•bedded sands around 40 cm in thickness.