Spherules from the Cretaceous/Tertiary boundary clay at Gubbio, Italy: the problem of outcrop contamination

Journal Article · Mon Dec 01 00:00:00 EST 1986 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1986)14<1024:SFTCBC>2.0.CO;2· OSTI ID:5717494

Montanari, A

Surficial outcrop contamination has occurred in some well-known stratigraphic sections of carbonate rocks in the northern Apennines. A critical case involves several contaminated clay partings, including the Cretaceous/Tertiary boundary clay in the classic Bottaccione section near Gubbio, Italy. These clay layers contain shiny spherules which, in several recent studies, have been said to consist of volcanic glass and have been used to support the hypothesis that the terminal Cretaceous mass extinction was caused by widespread volcanism. Laboratory tests, however, indicate that these shiny spherules are made of HF-insoluble and combustible material and are therefore of recent biological origin. These objects were introduced into the Cretaceous/Tertiary boundary clay and other clay layers from the surrounding soil along with abundant detrital contaminants derived from erosion of the middle Miocene flysch exposed at the head of the Bottaccione Gorge. They are completely different from the altered and flattened microtektitelike spheroids that are found only in the iridium-rich Cretaceous/Tertiary boundary clay and that provide strong evidence for a large impact.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 5717494
• Journal Information: Geology; (United States), Vol. 14:12
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CRETACEOUS PERIOD
BOUNDARY CONDITIONS
GEOLOGIC DEPOSITS
GEOCHEMISTRY
ITALY
TERTIARY PERIOD
CARBONATE ROCKS
CLAYS
CONTAMINATION
ENVIRONMENTAL TRANSPORT
GEOLOGIC HISTORY
LAYERS
CENOZOIC ERA
CHEMISTRY
EUROPE
GEOLOGIC AGES
MASS TRANSFER
MESOZOIC ERA
ROCKS
SEDIMENTARY ROCKS
WESTERN EUROPE
580400* - Geochemistry- (-1989)
580100 - Geology &amp; Hydrology- (-1989)