Smit, Jan et al. (1997): Preliminary iridium analysis from a graded spherule layer at the K/T boundary and late Eocene ejecta from ODP sites 1049, 1052, 1053, Blake Nose, Florida

Leg/Site/Hole:
ODP 171B
ODP 171A 1049
ODP 171B 1052
ODP 171B 1053
Identifier:
1998-066636
georefid

Creator:
Smit, Jan
Vrije University Amsterdam, Department of Sedimentary Geology, Amsterdam, Netherlands
author

Rocchia, Robert
CEA-CNRS, France
author

Robin, Eric
author

Identification:
Preliminary iridium analysis from a graded spherule layer at the K/T boundary and late Eocene ejecta from ODP sites 1049, 1052, 1053, Blake Nose, Florida
1997
In: Anonymous, Geological Society of America, 1997 annual meeting
Geological Society of America (GSA), Boulder, CO, United States
29
6
141
ODP Site 1049 recovered a complete Cretaceous-Tertiary (K/T) boundary. From bottom to top: 1) Slumped A. mayaroensis Zone ooze. 2) A 17 cm thick graded layer consisting of green spherules. The spherule layer contains also Maastrichtian foraminifers and is presumably re-deposited. A few lime-clasts occur, similar to non-melted limestone ejecta clasts from the Gulf of Mexico. 3) A 1 mm thick diagenetic orange layer with small spherules, capping the green spherule layer 4) A 3 cm thick bioturbated dark ooze of P0 Zone age, grading into 5) A light gray ooze with abundant "G"fringa, "G"eugubina, "G"minutula, of P1a Zone age. Burrows filled with this ooze extend downwards into the underlying dark marl. Iridium analyses of 1049b show an increase in Ir concentration from <0.06 ppb at the base of the spherule layer towards about 1 ppb in the top of the ejecta layer. The orange layer(3) represents a minimum in the Ir distribution (0.3 ppb). In the basal Tertiary dark ooze (4) Ir concentrations decrease from 1.3 ppb to <0.05 ppb within 3 cm. This Ir-profile is consistent with ejecta layers of the Western Interior, the Gulf coast and Beloc. The K/T ejecta layers at ODP site 1049 show a little disturbed sequence of impact ejecta and biotic events at the K/T boundary, in contrast to the ejecta layers in the Gulf of Mexico that are disturbed by tsunami's. The strong foraminiferal changes at the K/T boundary are strictly coincident with the emplacement of the ejecta layer, and do not postdate the ejecta layer. Hole 1053 contains an expanded highly siliceous sequence across the North American and Pacific tektite and microkrystite strewn fields. The foraminiferal changes and microprobe analyses of the ejecta layers are compared with the K/T boundary events.
English
Coverage:Geographic coordinates:
North:30.3000
West:-77.0000East: -76.0000
South:29.3000

Stratigraphy; Geochemistry of rocks, soils, and sediments; Atlantic Ocean; Blake Nose; Blake Plateau; Cenozoic; clastic sediments; clasts; Cretaceous; diagenesis; ejecta; Eocene; Foraminifera; Gulf of Mexico; Invertebrata; iridium; K-T boundary; Leg 171; Leg 171B; lower Paleocene; Mesozoic; metals; North Atlantic; Ocean Drilling Program; ODP Site 1049; ODP Site 1052; ODP Site 1053; ooze; Paleocene; Paleogene; platinum group; Protista; sediments; spherules; stratigraphic boundary; Tertiary; Upper Cretaceous; upper Eocene;

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