21. CALPIONELLIDS AND THE JURASSIC/CRETACEOUS BOUNDARY AT DEEP SEA DRILLING PROJECT SITE 534, WESTERN NORTH ATLANTIC OCEAN1
Calpionellids occur from Section 534A-87-2 in the lowermost Blake-Bahama Formation down to Section 534A-93-4 in the uppermost Cat Gap Formation. Stratigraphically significant faunas have only been observed between Sections 534A-90-2 and 534A-93-1, indicating calpionellid Zone B (latest Tithonian to...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.494.4470 http://www.deepseadrilling.org/76/volume/dsdp76_21.pdf |
| Summary: | Calpionellids occur from Section 534A-87-2 in the lowermost Blake-Bahama Formation down to Section 534A-93-4 in the uppermost Cat Gap Formation. Stratigraphically significant faunas have only been observed between Sections 534A-90-2 and 534A-93-1, indicating calpionellid Zone B (latest Tithonian to earliest Berriasian) for the interval from Sections 534A-90-2 through 534A-92-2 and Zone A (early late Tithonian) for the interval from Sections 534A-92-6 through 534A-93-1. In southeastern France, the Jurassic/Cretaceous boundary, as defined by ammonites, lies in the middle of Zone B. In Hole 534A, the boundary can be placed in the lower half of Core 90. A strange fact, which cannot yet be explained in a satisfactory manner, is the complete absence of mid-Berriasian through early Valanginian calpionellid associations (Zones C, D, and E), not only at this site, but apparently over most of the western North Atlantic. |
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