Planktic foraminiferal species turnover across deep-sea Aptian/ Albian boundary sections

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doi: 10.2113/gsjfr.41.1.53
Author(s): Huber, Brian T.; Leckie, R. Mark
Author Affiliation(s): Primary:
Smithsonian Institution National Museum of Natural History, Department of Paleobiology, Washington, DC, United States
University of Massachusetts at Amherst, United States
Volume Title: Journal of Foraminiferal Research
Source: Journal of Foraminiferal Research, 41(1), p.53-95. Publisher: Cushman Foundation for Foraminiferal Research, Ithaca, NY, United States. ISSN: 0096-1191 CODEN: JFARAH
Note: In English. 108 refs.; illus., incl. 5 tables, strat. col.
Summary: A major planktic foraminiferal species turnover accompanied by a dramatic reduction in shell size, a fundamental change in shell architecture, and a precipitous drop in the abundance of planktic relative to benthic species occurs across the Aptian/Albian boundary interval (AABI) at globally distributed deep-sea sections. Extinction of the large and distinctive planktic foraminifer Paraticinella eubejaouaensis, used to denote a level at or near the Aptian/ Albian boundary, coincides with the extinctions of relatively long-ranging Aptian species of Hedbergella and Globigerinelloides. At Deep Sea Drilling Project (DSDP) Site 511 (southern South Atlantic), which is the most complete and best preserved of the studied AABI sections, the Aptian assemblage is of low diversity and species are replaced by initially one and then two very small, smooth-surfaced, thin-walled species of Microhedbergella n. gen. The oldest species of this genus, Mi. miniglobularis n. sp., probably descended from Hedbergella praelippa n. sp. and is the nominate taxon for a new lowermost Albian interval zone and is considered ancestral to several small, gradually evolving microperforate species, including Mi. praeplanispira n. sp., Mi. pseudoplanispira n.sp., and Mi. pseudodelrioensis n. sp., which range into the middle and upper Albian. The small hedbergellids that characterize the Mi. miniglobularis Interval Zone at Site 511 have also been identified from samples taken just above the Kilian black shale level in the Vocontian Basin of southeast France. The Albian record at Site 511 reveals a gradual increase in planktic foraminifera shell size and assemblage dominance, as well as the gradual evolution during the middle Albian of species characterized by a finely perforate, pustulose test. Taxa with this shell infrastructure are included in Muricohedbergella n. gen. A new "Ticinella yezoana" Partial Range Zone is erected at Site 511 for correlation of the middle-upper Albian at high latitudes. At Ocean Drilling Program (ODP) Site 1049 (western North Atlantic), which also yields well-preserved foraminifera across the AABI, Aptian species of Hedbergella, Globigerinelloides, and Pseudoguembelitria blakenosensis n. gen., n. sp. are replaced by lower Albian assemblages composed only of two minute species of Microhedbergella. However, this boundary section is considered incomplete because of the absence of the Mi. miniglobularis Zone. A new upper lower Albian Ti. madecassiana Zone is defined at Site 1049 for the interval between the lowest occurrence (LO) of the nominate taxon and the LO of Ti. primula, the nominate species of the middle Albian Ti. primula Zone. The AABI at DSDP Site 545 (eastern North Atlantic) has a major unconformity spanning the uppermost Aptian through the upper Albian. A black shale sequence previously placed in the lower Albian and designated as Oceanic Anoxic Event 1b is now determined to be latest Aptian in age. The AABI at ODP Site 763 (southeast Indian Ocean) is also marked by an unconformity between the upper Aptian Pa. eubejouaensis Zone and the lower Albian Mi. rischi Zone. This site needs further study to resolve whether overlap of species from both zones is the result of downslope reworking or an exception to the pattern of abrupt species turnover observed at the other deep-sea sites. The dramatic changes in planktic foraminiferal assemblages across the AABI suggest major changes in carbonate chemistry, vertical stratification, or productivity in the surface mixed layer occurred during the last 1 myr of the Aptian. Understanding the cause or causes for these changes will require much further investigation.
Year of Publication: 2011
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Albian; Aptian; Assemblages; Atlantic Ocean; Biostratigraphy; Biozones; Blake Nose; Blake Plateau; Cretaceous; DSDP Site 390; DSDP Site 392; DSDP Site 511; DSDP Site 545; Deep Sea Drilling Project; Deep-sea environment; Europe; Exmouth Plateau; Foraminifera; France; Globigerinina; Hedbergella; Hedbergella praelippa; Hedbergellidae; IPOD; Indian Ocean; Invertebrata; Leg 122; Leg 171B; Leg 44; Leg 71; Leg 79; Lower Albian; Lower Cretaceous; Marine environment; Mazagan Plateau; Mesozoic; Microfossils; Microhedbergella; Morphology; New taxa; North Atlantic; ODP Site 1049; ODP Site 763; Ocean Drilling Program; Paleoenvironment; Protista; Pseudoguembelitria blakenosensis; Rotaliporidae; South Atlantic; Stratigraphic boundary; Taxonomy; Upper Aptian; Vocontian Trough; Western Europe
Coordinates: S203512 S203511 E1121232 E1121231
N333951 N333952 W0092152 W0092153
N300832 N300832 W0760644 W0760644
S510017 S510017 W0465818 W0465818
Record ID: 2011012712
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Cushman Foundation for Foraminiferal Research, Reference includes data from GeoScienceWorld, Alexandria, VA, United States

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