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Title: Variations in the neodymium and strontium isotopic composition and REE content of molluscan shells from the Cretaceous Western Interior seaway

Rare earth element concentrations, [epsilon][sub ND](T) values, and strontium isotopic compositions of mollusc shells were used to trace variations in the neodymium and strontium isotopic composition of the epicontinental Late Cretaceous Western Interior seaway of North America. Rare earth element patterns are different in aragonite and calcite produced by the molluscs endemic to the seaway, indicating that either mineralogical control or possibly scavenging by organic films associated with the different phases of biogenic carbonate resulted in differential partitioning of the REEs from seawater during shell formation. The biogenic carbonate also may contain REEs associated with Fe-flocs trapped in the shells during growth, but these flocs cannot result in different REE patterns of aragonite and calcite produced by the molluscs. The neodymium isotopic composition of the Western Interior seaway is inferred to have varied 13 [epsilon]-units over 20 My as a result of incursions of seawater from the Arctic Ocean and Gulf of Mexico, river influx from tectonically active terranes, benthic diagenetic fluxes, and volcanic ash falls. Ash from a variety of volcanic centers in western North America was significant in producing rapid and marked changes in [sup 143]Nd/[sup 144]Nd ratios of the seaway, and abrupt regional variations in neodymium isotopicmore » composition of the seaway make the construction of an accurate neodymium isotope evolution curve difficult for this basin. Strontium isotopic compositions of the mollusc shells indicate the [sup 87]Sr/[sup 86]Sr ratio of the Western Interior seaway was generally similar to contemporaneous oceans, although, periodically, the basin had strontium isotopic compositions distinct from contemporaneous seawater. 58 refs., 7 figs., 3 tabs.« less
Authors:
;  [1]
  1. (Univ. of Saskatchewan, Saskatoon (Canada))
Publication Date:
OSTI Identifier:
5412536
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; (United States); Journal Volume: 57:16
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; MOLLUSCS; ISOTOPE RATIO; NEODYMIUM; SEAS; PALEONTOLOGY; SHELLS; STRONTIUM; ARAGONITE; ARCTIC OCEAN; CALCITE; CRETACEOUS PERIOD; GULF OF MEXICO; IRIDIUM; NEODYMIUM 143; NEODYMIUM 144; NORTH AMERICA; STRONTIUM 86; STRONTIUM 87; THORIUM; URANIUM; ACTINIDES; ALKALINE EARTH ISOTOPES; ALKALINE EARTH METALS; ALPHA DECAY RADIOISOTOPES; ANIMALS; AQUATIC ORGANISMS; ATLANTIC OCEAN; BETA DECAY RADIOISOTOPES; CARBONATE MINERALS; CARIBBEAN SEA; ELECTRON CAPTURE RADIOISOTOPES; ELEMENTS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; GEOLOGIC AGES; HOURS LIVING RADIOISOTOPES; INTERMEDIATE MASS NUCLEI; INVERTEBRATES; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; MESOZOIC ERA; METALS; MINERALS; NEODYMIUM ISOTOPES; NUCLEI; PLATINUM METALS; RADIOISOTOPES; RARE EARTH NUCLEI; RARE EARTHS; STABLE ISOTOPES; STRONTIUM ISOTOPES; SURFACE WATERS; TRANSITION ELEMENTS; YEARS LIVING RADIOISOTOPES 540310* -- Environment, Aquatic-- Basic Studies-- (1990-)