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Abstract: Holocene Deepwater Benthic Foraminiferal Biofacies, Northwestern Gulf of Mexico

Megan H. Jones

Cluster analysis of 26 species of benthic foraminifera in 27 core-top samples from water depths between 1538-3850m revealed two groupings with no geographic overlap. Cluster 1 is composed of samples ranging in water depth from 2700-3900m, representing a true abyssal biofacies, whereas cluster 2, made up of samples ranging in water depth from 1500-2300m, reflects a lower bathyal biofacies. The separation of cluster 1 from cluster 2 is based on the highest abundances of three calcareous species, Alabaminella turgidus, Nuttalides decorata and Bolivina lowmani, and several agglutinated species, Glomospira charoides, Karrerulina apicularis, Saccammina sphaerica, Spiroplectella cyclindroides, and Cribrostomoides wiesneri. Overall abundances o these agglutinated species in most samples are <2% but in samples making up cluster 1 their abundances range from 3-12%.

Cluster 2, reflecting the lower bathyal environment, can be divided into three subclusters. Though distinct, the geographic distributions of these subclusters do exhibit some overlap. Subcluster 2a, made up of two samples from 2288 and 2380m of water and both from Orca Basin, is characterized by Osangularia spp. and Gavelinopsis translucens. Subcluster 2b, though containing a few samples from water depths between 1538-1972m, is largely made up of samples from water depths between 2002-2324m. This subcluster is characterized by some of the highest abundances of Hoeglundina elegans; this grouping may reflect a lack of bottom-water corrosiveness, in addition to strictly depth-related factors. Subcluster 2c, made up of samples from water depths between 1584-1919 , is characterized by Bulimina aculeata and Epistominella exigua.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana