Agoult, Gara Sbaa hill (Barbe collection) (Cretaceous of Morocco)

Where: Er Rachida, Morocco (30.5° N, 4.8° W: paleocoordinates 17.8° N, 4.8° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Akrabou Formation, Late/Upper Cenomanian (99.6 - 93.5 Ma)

• There are no calcareous fossils in the Gara Sbaa Lagerstätte and, consequently, it has proved difficult to establish the precise age of the deposit. The underlying Kem Kem beds, in this region resting on folded Palaeozoic strata, has been dated as Albian or Cenomanian on account of its vertebrate remains. However, over most of the outcrop the vertebrate-bearing part of the Kem Kem beds is overlain by a series of variegated mudstones, thin sandstones and evaporites for which there is no age determination. These mudstones pass up into marls and shelly limestones and, at Gara Sbaa, into the fossiliferous laminated limestone described here. The marls and shelly limestones yield abundant examples of Ilymatogyra cf. africana, a bivalve that usually indicates a mid to early Late Cenomanian age (Ettachfini and Andreu, 2004; Dhondt and Jaillard, 2005). In the Goulmima region of southern Morocco laterally equivalent carbonates of the Akrabou Formation have been dated as Late Cenomanian to Turonian on account of their marine benthic and planktonic foraminiferan assemblages (Ettachfini and Andreu, 2004). It is highly likely that the Gara Sbaa Lagerstätte is of Late Cenomanian or Early Turonian age but because there are no strata overlying the laminites, a minimum age cannot be determined at this locality.

•Previously under Gara Sbaa member of the Akrabou Formation, but the Gara Sbaa unit is now considered a Formation, and is older than the Akrabou Formation (see Ibrahim et al. 2020)

• group of beds-level stratigraphic resolution

Environment/lithology: lagoonal or restricted shallow subtidal; lithified, dolomitic lime mudstone

• The fossil assemblage of Agoult, consisting of both marine and terrestrial organisms, indicates that these laminated carbonates were deposited in a shallow marine coastal environment, most likely a quiet muddy lagoon sheltered from the ocean by a reef.
• The fossil-bearing parts of the Gara Sbaa laminites are restricted to a few horizons within the finely laminated dolomitised limestone with laminae of just 1e2 mm in thickness. In the middle to upper part of the unit the laminae are planar with few interruptions, but toward the base some bedding planes exhibit ripple marks with wave lengths of w50 mm

Size class: macrofossils

Preservation: adpression, soft parts

Collection methods: surface (in situ)

• Repository: private collection of Gérard Barbe, available for study through University of Montpellier

Primary reference: R. Vullo, G. Guinot, and G. Barbe. 2016. The first articulated specimen of the Cretaceous mackerel shark Haimirichia amonensis gen. nov. (Haimirichiidae fam. nov.) reveals a novel ecomorphological adaptation within the Lamniformes (Elasmobranchii). Journal of Systematic Palaeontology 14:1003-1024 [M. Clapham/M. Clapham]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 213630: authorized by Matthew Clapham, entered by Matthew Clapham on 06.09.2020

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
Chondrichthyes
 Lamniformes - Haimirichiidae
Haimirichia amonensis
Haimirichia amonensis Cappetta and Case 1975 mackerel shark