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TitleOn a grain of sand - a microhabitat for the opportunistic agglutinated foraminifera Hemisphaerammina apta n. sp., from the early Eocene Arctic Ocean
AuthorMcNeil, D H; Neville, L A
SourceJournal of Micropalaeontology vol. 37, issue 1, 2018 p. 295-303, https://doi.org/10.5194/jm-37-295-2018
Year2018
Alt SeriesEarth Sciences Sector, Contribution Series 20160362
PublisherThe Geological Society
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
NTS107C; 107F; 107G; 117D; 117E; 117H
AreaArctic Ocean; Beaufort Sea
Lat/Long WENS-140.0000 -132.0000 72.0000 69.0000
Subjectspaleontology; marine geology; Eocene; micropaleontology; microfossils; fossil assemblages; continental margins; continental shelf; marine sediments; detritus; quartz; cherts; paleoenvironment; fossil descriptions; fossil morphology; hydrologic environment; storms; sediment transport; sediment reworking; Natsek N-56 Well; Foraminifera; Hemisphaerammina apta n. sp.; Paleocene-Eocene Thermal Maximum; Taglu Sequence; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous
Illustrationsphotomicrographs; location maps; tables; biostratigraphic charts; lithologic sections
ProgramWestern Arctic Sverdrup Basin, GEM2: Geo-mapping for Energy and Minerals
AbstractHemisphaerammina apta n. sp. is an attached monothalamous agglutinated foraminifera discovered in shelf sediments of the early Eocene Arctic Ocean. It is a simple yet distinctive component of the endemic agglutinated foraminiferal assemblage that colonized the Arctic Ocean after the microfaunal turnover caused by the Paleocene-Eocene Thermal Maximum. Associated foraminifera are characterized by a high percentage of monothalamous species (up to 60 %) and are entirely agglutinated indicating a brackish (mesohaline) early Eocene Arctic Ocean. Hemisphaerammina apta occurs exclusively as individuals attached to fine detrital grains (0.2 to 1.8 mm) of sediment. It is a small species (0.06 to 0.2mm in diameter), fine-grained, with a low hemispherical profile, no floor across the attachment area, no substantive marginal flange, no internal structures, and no aperture. Lacking an aperture, it apparently propagated and fed through minute (micrometre-sized) interstitial pores in the test wall. Attachment surfaces vary from concave to convex and rough to smooth. Grains for attachment are diverse in shape and type but are predominantly of quartz and chert. The presence of H. apta in the early Eocene was an opportunistic response to an environment with an active hydrological system (storm events). Attachment to grains of sand would provide a more stable base on a sea floor winnowed by storm-generated currents. Active transport is indicated by the relative abundance of reworked foraminifera mixed with in situ species. Contemporaneous reworking and colonization by H. apta is suggested by its attachment to a reworked specimen of Cretaceous foraminifera.
Summary(Plain Language Summary, not published)
The early Eocene Arctic (~50 million years ago) was a special time in earth history when CO2 levels were abnormally high and the arctic climate unusually warm ¿ comparable to today¿s southern USA. The early Eocene rocks of the Arctic are also hydrocarbon rich and may be an important future resource for Canada. Our current research is multi-disciplinary involving analyses of petroleum source rocks, geochemistry, seismo-stratigraphy, and micropaleontology. This present paper focuses on one, newly discovered and newly named, microfossil species. This microorganism survived by being attached to fine grains of sand in the ancient ocean. It did so because of the warm, wet, storm-prone climate of the early Eocene. This species is important from an environmental and evolutionary perspective. It emerged after a CO2 caused mass extinction and opportunistically colonized the Arctic when CO2 levels averaged 500 ppm. Today¿s CO2 levels are moving above 400 ppm.
GEOSCAN ID299752