Page 166 - Carbonate Facies in Geologic History

Major Facies and Paleotectonic Patterns in Europe 153

Bioclastic layer -~,..--.:'

Lagoonal limestone
..

Fig. V -6. Diagrammatic cross sections of Waul sort ian banks showing growth of layers of lime
mudstone with inclined beds of stromatactoid structure and bioclastic debris parallel with the
inclination. Vertical thickness usually only a few meters. From Lees (1961, Fig. 5)

Major Facies and Paleotectonic Patterns in Europe

1. The Waulsortian developed in clear, open marine water: The massive Waulsor-
tian micritic facies lies some distance off from any land mass, and is a type of shelf
margin facies. Land masses, which were mainly isolated blocks standing as islands
in the shelf, contributed some terrigenous sediments to the shelves but this sedi-
ment did not reach the Waulsortian areas.
2. The basinalfacies, termed Culm, consists of shale, sandstone, and calcareous
mudstone: The terrigenous sediments were apparently derived from somewhere in
southern Europe and were partly deposited in deep water. The bedding is flysch-
like.
3. The shelf facies behind the Waulsortian mounds are highly varied: These
shelves generally contain strata deposited in conditions of open circulation. Black
(but not organic) peloidal and laminated limestone of shelf lagoonal facies is
present in Belgium. The shelf above the Craven fault in England (Great Scar
Limestone in Fig. V -10) contains crinoidal-bryozoan lime wackestones and thin,
cross-bedded grainstone with shell banks of Gigantoproductus, and some
coral beds. These strata are not very fossiliferous. Shelf strata equivalent to the
highest mounds were influenced by incursion of deltaic clastics from the north of
England and Scotland and form the strikingly cyclic Yoredale beds. In Ireland
some shallow water oolitic and algal limestone was apparently deposited around
islands but tidal flat deposits are rare. Shelves landward of the major Waulsortian
development are spotted with isolated mounds and intermound facies which are
clearly of open marine origin.

4. Evidence exists of structural control of Waulsortianfacies: The Waulsortian
major facies belt subsided rapidly. In Ireland the composite mass is almost
1000 m thick. Basin-prograding growth stages in these massive sheets of strata
may be traced by careful attention to depositional dips, indicated by bedding, and
oriented sparry calcite fillings of void space (stromatactoids) (Figs. V -6, V -7).
Regionally, the Waulsortian facies grades over some distance to the shelf facies