Microfossil and geochemical records reveal high-productivity paleoenvironments in the Cretaceous Western Interior Seaway during Oceanic Anoxic Event 2
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作者:
Bryant, Raquel
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Univ Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Texas A&M Univ, Dept Geol & Geophys, 611 Ross St, College Stn, TX 77843 USAUniv Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Bryant, Raquel
[1
,5
]
Leckie, R. Mark
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Univ Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Texas A&M Univ, Dept Geol & Geophys, 611 Ross St, College Stn, TX 77843 USAUniv Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Leckie, R. Mark
[1
,5
]
Bralower, Timothy J.
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Penn State Univ, Dept Geosci, 502 Deike Bldg, University Pk, PA 16802 USAUniv Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Bralower, Timothy J.
[2
]
Jones, Matthew M.
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Smithsonian Inst, Dept Paleobiol, Natl Museum Nat Hist, Washington, DC USAUniv Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Jones, Matthew M.
[3
]
Sageman, Bradley B.
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Northwestern Univ, Dept Earth & Planetary Sci, 2145 Sheridan Rd, Evanston, IL 60208 USAUniv Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
Sageman, Bradley B.
[4
]
机构:
[1] Univ Massachusetts, Dept Geosci, 611 North Pleast St, Amherst, MA 01003 USA
[2] Penn State Univ, Dept Geosci, 502 Deike Bldg, University Pk, PA 16802 USA
[3] Smithsonian Inst, Dept Paleobiol, Natl Museum Nat Hist, Washington, DC USA
[4] Northwestern Univ, Dept Earth & Planetary Sci, 2145 Sheridan Rd, Evanston, IL 60208 USA
[5] Texas A&M Univ, Dept Geol & Geophys, 611 Ross St, College Stn, TX 77843 USA
Oceanic Anoxic Event 2 (OAE2; similar to 94.5 Ma) occurred in the latest Cenomanian and represents a perturbation to the global carbon cycle. The event is geochemically recorded in shales and limestones of the Western Interior Basin of North America and is additionally marked by foraminiferal bio-events (e.g., turnovers, extinctions). These bio-events are attributed to changing paleoceanographic conditions and circulation patterns in the Western Interior Seaway related to the onset of OAE2. Here we investigate the paleoenvironment near the southwestern edge of the seaway during OAE2 by integrating microfossil and geochemical records from the lower beds of the Tokay Tongue (Mancos Shale) at Carthage, New Mexico, USA. We demonstrate that this locality represents an expanded section of OAE2 based on temporal constraints from carbon isotope chemostratigraphy and the occurrence of regional marker ash-fall deposits (bentonites), limestones and other carbonate-rich beds. Prior to the onset of OAE2, a unique assemblage of benthic foraminiferal morphologies suggests the presence of a distinct water mass in the southwestern part of the seaway compared to coeval neritic and distal sites. Microfossil assemblages record the Benthonic Zone, a typical OAE2 bio-event, with some distinctions. The event is still identifiable and thereby useful in marking the earliest stages of OAE2. Early in OAE2, calcareous nannofossil and foraminiferal assemblages indicate intervals of high productivity. The dominance of biserial planktic foraminifera (Planoheterohelix spp.) suggests the development of photic zone euxinia with intensification of OAE2. During OAE2, epifaunal trochospiral benthic foraminifera (Gavelinella dakotaensis) suggest intervals of improved conditions related to food availability and seafloor ventilation. Later, as increased surface water productivity and subsequent food availability prevailed at the seafloor through the end of the OAE2 interval, benthic foraminifera were abundant and assemblages were dominated by infaunal, low oxygen tolerant species (Neobulimina albertensis), suggesting prevailing dysoxia. We attribute differences in the expression of bio-events and foraminiferal community composition at Carthage to the influence of freshwater runoff from the western margin that drove high-productivity conditions throughout OAE2.
机构:
Smithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
Chiba Univ, Fac Sci, Dept Earth Sci, Chiba 2638522, Japan
Res Inst Humanity & Nat, Kyoto 6038047, Japan
Pusan Natl Univ, Div Earth Environm Syst, Coastal Environm Syst Sch BK21, Pusan 609735, South KoreaSmithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
Ando, Atsushi
Huber, Brian T.
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Smithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USASmithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
Huber, Brian T.
MacLeod, Kenneth G.
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Univ Missouri, Dept Geol Sci, Columbia, MO 65211 USASmithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
机构:
Smithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
Chiba Univ, Fac Sci, Dept Earth Sci, Chiba 2638522, Japan
Res Inst Humanity & Nat, Kyoto 6038047, Japan
Pusan Natl Univ, Div Earth Environm Syst, Coastal Environm Syst Sch BK21, Pusan 609735, South KoreaSmithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
Ando, Atsushi
Huber, Brian T.
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机构:
Smithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USASmithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA
Huber, Brian T.
MacLeod, Kenneth G.
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机构:
Univ Missouri, Dept Geol Sci, Columbia, MO 65211 USASmithsonian Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20013 USA