White Limestone Fm

Greigert, 1950. [NOTE: In Mali & Niger. Note that it would be appropriate to rename this Formation with an appellation that does not necessarily reflect its color or content; a unique name that perhaps relates to a geographical point where it is most striking or where it was first described would be recommended.]

References: Greigert, 1950, 1966; Fabre et al., 1983; El Hamet, 1987; Dikouma, 1990; Moody & Sutcliffe, 1991; Kogbe, 1991; Meister et al., 1992; Moumouni et al., 2019; Laouali-Idi, 2021.

Synonym: "Série des Calcaires Blancs". Equivalent(s): Together with the Ibeceten Fm (“Séries sénoniennes”), it is laterally equivalent to the Doutchin-Zana Formation in the Dakoro and Ader Doutchi regions (El Hamet, 1987).

The Formation often begins with 4 to 5 meters of limestone with siliceous veins. It continues with a very monotonous alternation of white limestones and argillites or variegated marls, with some glauconitic levels. This thick Formation would translate to rhythmic sedimentation characterize by important subsidence. Compact white limestone slab, sometimes in lenticular beds, alternating with marls. In the area west of Abalak, this unit is marked by a prominent topographic feature, where mottled purple-green siltstones are capped by a marly gray limestone, which is overlain by a massive, chert veined, white, recrystallized limestone. 150-300 m thick.

Very poor in fossils. Greigert (1966) cites among the few fossils present: gastropods (Strombus and Tylostoma), echinoids and oysters. Coilopoceras inflatum (a compressed, involute, lenticular ammonite from the Cretaceous (Albian to Turonian), with a narrow venter and raggedy ammonite suture) has also been found.

Marine; Final episode of the T2 transgression