Progress report on the Middle Jurassic ammonite zones of Kachchh, W. India
Krishna, Jai; Westermann, Gerd E. G.
published: Mar 15, 1985
ArtNo. ESP026001401006, Price: 29.00 €
Intensive recent work on the classic as well as new Middle Jurassic outcrops in Kachchh (Cutch) has greatly improved precision and correlation of ammonoid zones and enlarged the stratigraphic record. (?) Leptosphinctes and Clydoniceras document (?) Upper Bajocian and late Middle-Upper Bathonian. Two Macrocephalitinae zones of Spath are tentatively upheld: ((1) Macrocephalites triangularis zone, now placed in ? Upper Bathonian rather than basal Callovian and geographically extended to Madagascar, and (2) M. dimerus zone, basal Callovian. They are follwed by the tentative new zones of (3) M. semilaevis ?, middle Lower Callovian, and (4) Subkossmatia opis, latest Lower Callovian. For the Middle Callovian, we retain Spath's informal designation (5) "Anceps Beds", while in the Upper Callovian, the (6) Athleta Standard Zone (and Lamberti Standard Zone) can now be distinguished. Kachchh remains the principal source for East-Tethyan ammonoid biostratigraphy of the Middle and Upper Jurassic and deserves much additional field and laboratory work. This is a progress report of our own ongoing work.