Accession Number:

ADA160612

Title:

Analyses of Extraterrestrial Materials in Terrestrial Sediments,

Descriptive Note:

Corporate Author:

CALIFORNIA UNIV LOS ANGELES DEPT OF GEOLOGY

Personal Author(s):

Report Date:

1983-01-01

Pagination or Media Count:

4.0

Abstract:

Analysis of Cretaceous-Tertiary boundary sediments from Denmark and 2 Pacific sites 465A and GPC-3 have aided in demonstrating that the high concentrations of Ir in this boundary is a global phenomenon. This is consistent with the occurrence of a major accretionary event a this time, one which may have resulted in the massive terminal Cretaceous extinctions. The presence of high Ir concentrations in a mid-Pacific carbonate sequence 465A and abyssal clay GPC-3 indicates that this phenomen is not restricted to shallow continental shelf regions. but occurs in a variety of environments. Relative abundances of the siderophiles Os, Re, Ir, Pt, Ni, Co, Fe, Pd, and Au in the Danish samples are similar to chondritic meteoritic abundances within a factor of 3, relative to Ir and indicate an extraterrestrial source. However, variations in siderophile abundances between sites and even between samples at each site indicate significant fractionation either during accretion, deposition, or disgenetic alteration. These fractionations make it impossible at present to use siderophiles to establish a link between the accreting object and a known meteorite group.

Subject Categories:

  • Astrophysics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE