4.2.4. Hodimont Formation - HOD

Authors:Laloux et al., 1996.

 

Description:  In the type locality, the Hodimont Fm is made up of grey greenish micaceous shales (silstones) occurring in decimetric to metric thick beds, with locally, numerous decimetric limestone nodules containing brachiopods and goniatites.  The Hodimont Fm also contain several (locally, at least 4) levels of oolitic hematite lenticular beds, up to ± 1 m thick, made up of mottled sandy limestones with crinoids, brachiopods and cephalopods.  The lowermost oolitic hematite bed is considered as the base of the formation; the uppermost, as the top.

 

Stratotype: Hodimont, near Verviers.  Reference section : La Grappe street, Dison.

 

Area: Vesdre Nappe, Theux Window.

 

Thickness: 50 to 110 m.

 

Age: Lower Famennian (Fa1a) and base of the Middle Famennian (Fa2a).  The lowermost hematite bed corresponds to a condensation of the 2 Lower Famennian conodont zones (P. triangularis and P. crepida); the uppermost hematite bed, to a condensation of parts of the 2 first conodont biozones of the lowermost Middle Famennian (Palmatolepis rhomboidea and Palmatolepis marginifera marginifera).  The presence of goniatite Cheiloceras in the two upper hematite levels is an important marker for international correlations.