Aalenian (Jurassic) to Berriasian (Cretaceous) chronostratigraphic zonation and guide ammonites of the Central Andes (Argentina, Chile, Peru)

Horacio Parent

Abstract


In the Central Andes there are developed two marine basins with an extensive Jurassic record: the Neuquén (or Central Andean) Basin and the Tarapacá Basin. Their Jurassic and Lower Cretaceous ammonite successions have been studied extensively for more than 150 years, producing detailed chronostratigraphic scales based on ammonite zones and biohorizons. The ammonite faunas include Andean lineages, and cosmopolitan, Tethyan, Caribbean, North American, and Indo-Madagascan elements. This paper presents the results of a revision of the zonation of the interval Aalenian-Berriasian. Before presenting the results, this paper emphasizes the distinction between, and the convenient nomenclature for, biozones, zones, standard zones, and biohorizons.
The scissum Hz. (new) is introduced in the lower (-most?) Manflasensis Zone (Aalenian). The Rotundum Subzone (new) with base at the cf.-leptus Hz., is introduced for the upper part of the Rotundum Zone (Bajocian). The Gulisanoi Zone (Bathonian) is standardized by designation of the cf.-aspidoides Hz. (new) as its base. The Chacaymelehuensis Zone (new) with base at the “prahecquense” Hz. (new) is introduced for the Callovian. The Cubanensis Zone (Oxfordian) is introduced to replace nominally, or to rename, the inconveniently named “Passendorferia” Zone. The Tarapacaense Zone (Oxfordian) is standardized by designation of the tarapacaense Hz. (new) as its base. The Tithonian Malarguensis Zone (formerly subzone) is here emended and standardized by designation of the malarguensis Hz. as its base; this zone replaces the unviable Mendozanus Zone. The Zitteli Zone is standardized by designation of the widely recorded perlaevis Hz. as its base. The Fascipartita Subzone (Internispinosum Zone) is standardized by designation of the internispinosum-beta Hz. (new) as its base. The Alternans Zone is standardized by designation of the vetustum Hz. as its base, and the Koeneni Zone (uppermost Tithonian) by designation of the striolatus Hz. as its base.

Keywords


Neuquén Basin, Tarapacá Basin, chronostratigraphy, zonation, biohorizons, Ammonoidea (Cephalopoda), Aalenian to Berriasian

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