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Article: Tithonian and Berriasian ammonites from the Chia Gara Formation in northern Iraq

Publication: Palaeontology
Volume: 35
Part: 3
Publication Date: August 1992
Page(s): 597 655
Author(s): Michael K. Howarth
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How to Cite

HOWARTH, M. K. 1992. Tithonian and Berriasian ammonites from the Chia Gara Formation in northern Iraq. Palaeontology35, 3, 597–655.

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The Chia Gara Formation consists of 125-232 m of thin-bedded limestones, marls and shales in the area between Zalkho and Amadia. Iraqi Kurdistan, north of Mosul. The formation ranges in age from the base of the Tithonian, where it is underlain by formations that contain a few Kimmeridgian ammonites, up to nearly the top of the Berriasian, where it is succeeded by the Garagu Formation, which contains uppermost Berriasian and Valangiman ammonites. The Hybonolum and Darwini Zones at the base of the Tithonian are represented by single specimens of Hybonoticeras and Dorsoplanitoides, then there are the rich, high Lower Tithonian or basal Upper Tithonian ammonites, described previously by Spath, followed by many examples of crushed Substeueroceras and Protancyloceras, and finally by well-preserved topmost Tithonian ammonites of the new genus Chigaroceras, including C. banikense, C. wetzeli and C. planum spp. nov. The base of the Berriasian (and the base of the Cretaceous) is marked by a single Berriasella jacobi. After an unfossiIiferous gap, well-preserved Berriasian ammonites from the Occitanica and Boissieri Zones, especially the Paramimouna Subzone, include many Groebericeras rocardi. G. laevigatum sp. nov., Spiticeras spathi sp. nov, Euthymiceras kurdistanense sp. nov., Dalmasiceras (Elenaella) prorsiradiatum sp. nov., Berriasella (Malbosiceras) malbosi, Thurmanniceras (Erdenella) isare, Tirnovella alpillensis, and Banikoceras involutum gen. el sp. nov. The Kurdistan ammonites are all Tethyan rather than Boreal in affinities, and, as well as being similar to ammonites of the same age in southern Europe and North Africa, there are major similarities with the Tethyan ammonites of Cuba. Mexico and Argentina.
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