- Source: Nummulite
A nummulite is a large lenticular fossil, characterised by its numerous coils, subdivided by septa into chambers. They are the shells of the fossil and present-day marine protozoan Nummulites, a type of foraminiferan. Nummulites commonly vary in diameter from 1.3 cm (0.5 inches) to 5 cm (2 inches) and are common in Eocene to Miocene marine rocks, particularly around southwest Asia and the Mediterranean in the area that once constituted the Tethys Ocean, such as Eocene limestones from Egypt or from Pakistan. Fossils up to six inches wide are found in the Middle Eocene rocks of Turkey. They are valuable as index fossils.
The ancient Egyptians used nummulite shells as coins and the pyramids were constructed using limestone that contained nummulites. It is not surprising then that the name Nummulites is a diminutive form of the Latin nummulus 'little coin', a reference to their shape.
In 1913, naturalist Randolph Kirkpatrick published a book, The Nummulosphere: an account of the Organic Origin of so-called Igneous Rocks and Abyssal Red Clays, proposing the unconventional theory that all rocks had been produced through the accumulation of forams such as Nummulites.
Gallery
Use
Because nummulites are fossils very abundant, easy to recognize and lived in certain biozones they are used as guide fossil.
It is worth highlighting that thanks to the appearance of Nummulites tavertetensis in the Shallow Bentic Zone 15 (SBZ 15), it was possible to date the oldest fossil remains of Sirenio in Western Europe found in a new paleontological site, in Santa Brígida, Amer (La Selva, Catalunya, Spain) near an old quarry of stone limestone with nummulites.
References
Further reading
Aigner, Thomas (January 1985). "Biofabrics as Dynamic Indicators in Nummulite Accumulations". Journal of Sedimentary Research. 55 (1): 131–134. doi:10.1306/212F8634-2B24-11D7-8648000102C1865D.
Kopaevich, L.F.; Lygina, E.A.; Nikishin, A.M.; Yakovishina, E.V. (2008). "The Crimean Eocene Nummulite Bank". Moscow University Geology Bulletin. 63 (3): 195–8. Bibcode:2008MUGB...63..195K. doi:10.3103/S0145875208030083. S2CID 129503182.
Racey, Andrew (2001). "A Review of Eocene Nummulite Accumulations: Structure, Formation and Reservoir Potential". Journal of Petroleum Geology. 24 (1): 79–100. Bibcode:2001JPetG..24...79R. doi:10.1111/j.1747-5457.2001.tb00662.x.
Papazzoni, Cesare Andrea (1995). "Nummulite biostratigraphy at the Middle/Upper Eocene boundary in the northern Mediterranean area". Rivista Italiana di Paleontologia e Stratigrafia. 101 (1): 63–80.
Guido, Adriano; Papazzoni, Cesare; Mastandrea, Adelaide; Morsilli, Michele; La Russa, Mauro F.; Tosti, Fabio; Russo, Franco (June 2011). "Automicrite in a 'nummulite bank' from the Monte Saraceno (Southern Italy): evidence for synsedimentary cementation". Sedimentology. 58 (4): 878–889. Bibcode:2011Sedim..58..878G. doi:10.1111/j.1365-3091.2010.01187.x.
