Green Spherules as Indicators of the Cretaceous/Tertiary Boundary in Deep Sea Drilling Project Hole 603B

Abstract

Dark green spherules occur in the lower part of a turbidite in Section 603B-22-3, at the 70 cm level. In all probability these spherules originally consisted of massive glass, but now appear to have become completely altered into smectite. The presence of numerous microscopic fissures in the spherules probably mediated in the alteration process.Judging by the presence of similar spherules at the Cretaceous/Tertiary (K/T) boundary in DSDP Hole 390B, the green spherules are thought to represent diagenetically altered impact ejecta from one large or several smaller extraterrestrial objects at the end of the Cretaceous. The presence of anomalously high concentrations of Ni, Co, and As higher up in the turbidite are in agreement with an expected enrichment of these elements in the K/T boundary clay. However, precise Ir analyses are necessary in order to confirm this.

A dual-layer Chicxulub ejecta sequence with shocked carbonates from the Cretaceous–Paleogene (K–Pg) boundary, Demerara Rise, western Atlantic

“…The marine K-Pg sites in the western Atlantic, were in part affected by turbiditic reworking, though -due to the lack of high-resolution analysis on a mm-to sub-mm scale -a distinct stratification of the K-Pg spherule deposit may have been overlooked (e.g., Klaver et al, 1987;Norris et al, 1999;Smit, 1999;Martínez-Ruiz et al, 2002). However, the Bass River ODP Leg 174AX K-Pg site includes a 6-cm thick, graded spherule layer with shocked quartz in its uppermost centimeter (Olsson et al, 1997).…”

Experimental evidence for the global acidification of surface ocean at the Cretaceous–Palaeogene boundary: the biogenic calcite-poor spherule layers

“…3(a)) abruptly separates the uppermost Maastrichtian glauconitic clay from the glauconitic clay of the early Danian. The smectitic spherules at Bass River are also similar to those from Blake Nose and from other locations on the northern American margin such as Hatteras Rise (Klaver et al 1987;Haggerty et al 1986;Olsson et al 1997;Martı´nez-Ruiz et al 2001b. According to Olsson et al (1997), spherical impressions of spherules at the top of the late Maastrichtian indicate nearly immediate deposition of ejecta fallout.…”

“…3(a)). Geochemical studies indicate that the spherules are composed primarily of smectite and that they were transported by a turbidite (Klaver et al 1987). They are structurally and geochemically similar to the smectitic spherules at Blake Nose (Martı´nez-Ruiz et al 2001a,b, 2002, ranging in diameter from 0.5-1.0 mm (Klaver et al 1987;Bohor & Betterton 1989;Haggerty et al 1986;Olsson et al 1997).…”

Spherules associated with the cretaceous–paleogene boundary in Poland

“…3B) similarly as noted by Izett et al (1991) in Haitian spherules. Klaver et al (1986) reported spherules completely altered to smectite from a few boreholes in the North Atlantic. An impact origin for smectite spherules was confirmed by Sigurdsson et al (1991) and Bohor and Glass (1995).…”

“…In contrast, K-Pg spherules are generally smooth although their surfaces may show sculpturing (Bohor and Betterton 1990;Sigurdsson et al 1991) and altered phases. Small, regular, internal cavities were probably originally gas bubbles (Klaver et al 1986) or microspherules (Glass and Simonson 2013;Text- fig 3B). All of the Lechówka spherules seen appear to be spherical.…”