M. Harting

Spherule deposits in Cretaceous-Tertiary boundary sediments in Belize and Guatemala

Large spheroid deposits at Albion Island and Armenia in northern and central Belize and the spherule deposits of southern Belize and eastern Guatemala have the same glass origin based on the presence of almost pure Cheto smectite derived from alteration of impact glass from the Chicxulub impact on Yucatan, Mexico. The same origin has also been determined for altered glass spherules in Mexico, Haiti and the Caribbean. However, the spherule layers have variable ages as a result of erosion and redeposition, with an early Danian (Parvularugoglobigerina eugubina) zone Pla(1) age in southern Belize, Guatemala, Haiti, southern Mexico and the Caribbean, and a pre-K–T (Plummerita hantkeninoides) zone CF1 age of 65.27 ± 0.03 Ma in NE Mexico. A pre-K–T age for the Chicxulub impact has now also been determined from the new Yaxcopoil 1 core drilled in the impact crater. These data show that Chicxulub was not the K–T impact that caused the end-Cretaceous mass extinction, but an earlier impact event. A multiple impact hypothesis, volcanism and climate change appears the likely scenario for the end-Cretaceous mass extinction.

Late Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): mineralogy, trace and platinum group elements, biostratigraphy and faunal turnovers

The late Maastrichtian to early Danian at Mishor Rotem, Israel, was examined based on geochemistry, bulk rock and clay mineralogies, biostratigraphy and lithology. This section contains four red clay layers of suspect impact or volcanic origin interbedded in chalk and marly chalks. PGE anomalies indicate that only the K/T boundary red layer has an Ir dominated PGE anomaly indicative of an impact source. The late Maastrichtian red clays have Pd dominated PGE anomalies which coincide with increased trace elements of terrigenous and volcanogenic origins. Deccan or Syrian-Turkey arc volcanism is the likely source of volcanism in these clay layers. Glauconite, goethite and translucent amber spherules are present in the clay layers, but the Si-rich spherules reported by Rosenfeld et al. [l989] could not be confirmed. The absence of Cheto smectite indicates that no altered impact glass has been present. The red layers represent condensed sedimentation on topographic highs during sea level highstands. In the Negev area, during the late Maastrichtian, the climate ranged from seasonally wet to more arid conditions during zones CF3 and CF2, with more humid wet conditions in the latest Maastrichtian zone CF1 and in the early Danian, probably linked to greenhouse conditions. Planktic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids. Times of intensified stress are indicated by the disaster opportunist Guembelitria blooms, which can be correlated to central Egypt and also to Indian Ocean localities associated with mantle plume volcanism. Marine plankton thus support the mineralogical and geochemical observations of volcanic influx and reveal the detrimental biotic effects of intense volcanism.