[dinosaur] Morrison Formation chronostratigraphic framework + calcium before and across K-Pg extinction

Ben Creisler
[email protected]

New papers:


Susannah C.R. Maidment & Adrian Muxworthy (2019)
A chronostratigraphic framework for the Upper Jurassic Morrison Formation,
western U.S.A.
Journal of Sedimentary Research 89 (10): 1017-1038.
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.2110_jsr.2019.54&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ykTGxsZVgkZ1wolXUu8Knbjog3UbR3bFFymdWeT7ViA&s=mnTGE8mzggxBtTs6xRbmUH27YICLmhUfj5TuLjsHDtI&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__pubs.geoscienceworld.org_sepm_jsedres_article-2Dabstract_89_10_1017_574611_A-2Dchronostratigraphic-2Dframework-2Dfor-2Dthe-2DUpper-3FredirectedFrom-3Dfulltext&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ykTGxsZVgkZ1wolXUu8Knbjog3UbR3bFFymdWeT7ViA&s=uTC9U78luHtyVdZMsCUAWFwucqt-9LAckcc9yjmotFE&e= 


The fluvial, overbank, and lacustrine deposits of the Upper Jurassic
Morrison Formation of the Western Interior, U.S.A. have been intensively
studied due to their diverse and well-preserved dinosaurian fauna, and the
presence of economic quantities of uranium and vanadium ores. The formation
crops out over 12 degrees of latitude and 1.2 million km2, and is an
excellent case study for the examination of paleoecology, community
structure, and evolutionary dynamics at a time in Earth's history when the
climate was significantly warmer than today. However, paleoecological
studies have been hampered by lack of correlation across the formation.
Assuming a primarily tectonic control on fluvial architecture, we propose
the first chronostratigraphic framework of the formation, which is based on
sequence stratigraphy, magnetostratigraphy, and radiometric dating. The
formation can be divided into three sequences each represented by a period
of degradation followed by aggradation. This chronostratigraphic framework
indicates that the formation youngs to the north, and was deposited over
about 7 million years during the late Kimmeridgian and Tithonian. This
framework provides a foundation for future sedimentological, stratigraphic,
and paleobiological studies of the iconic dinosaurian fauna known from the
Morrison.

==================

Free pdf:

Benjamin J. Linzmeier, Andrew D. Jacobson, Bradley B. Sageman, Matthew T.
Hurtgen, Meagan E. Ankney, Sierra V. Petersen, Thomas S. Tobin, Gabriella
D. Kitch & Jiuyuan Wang (2019)
Calcium isotope evidence for environmental variability before and across
the Cretaceous-Paleogene mass extinction.
Geology (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1130_G46431.1&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ykTGxsZVgkZ1wolXUu8Knbjog3UbR3bFFymdWeT7ViA&s=FlZmq3RZFOiYVZD9aaVbwgK3Hsha1PdtjqiiD_Ca2GM&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__pubs.geoscienceworld.org_gsa_geology_article_doi_10.1130_G46431.1_574630_Calcium-2Disotope-2Devidence-2Dfor-2Denvironmental&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ykTGxsZVgkZ1wolXUu8Knbjog3UbR3bFFymdWeT7ViA&s=s0joLyTo6UVYfM-kvovwmj4pnU7L-8kaV3m666QcuZY&e= 


Carbon dioxide release during Deccan Traps volcanism and the Chicxulub
impact likely contributed to the Cretaceous-Paleogene (K-Pg) mass
extinction; however, the intensity and duration of CO2 input differed
between the two events. Large and rapid addition of CO2 to seawater causes
transient decreases in pH, [CO32–], and carbonate mineral saturation
states. Compensating mechanisms, such as dissolution of seafloor sediment,
reduced biomineralization, and silicate weathering, mitigate these effects
by increasing the same parameters. The calcium isotope ratios (δ44/40Ca) of
seawater and marine carbonates are hypothesized to respond to these
perturbations through weathering/carbonate deposition flux imbalances
and/or changes in fractionation between carbonate minerals and seawater. We
used a high-precision thermal ionization mass spectrometry method to
measure δ44/40Ca values of aragonitic bivalve and gastropod mollusk shells
from the K-Pg interval of the López de Bertodano Formation on Seymour
Island, Antarctica. Well-preserved shells spanning the late Maastrichtian
(ca. 67 Ma) to early Danian (ca. 65.5 Ma) have δ44/40Ca values ranging from
–1.89‰ to –1.57‰ (seawater [sw]). Shifts in δ44/40Ca inversely correlate
with sedimentological indicators of saturation state. A negative excursion
begins before and continues across the K-Pg boundary. According to a simple
mass-balance model, neither input/output flux imbalances nor change in the
globally integrated bulk carbonate fractionation factor can produce
variations in seawater δ44/40Ca sufficient to explain the measured trends.
The data are consistent with a dynamic molluscan Ca isotope fractionation
factor sensitive to the carbonate geochemistry of seawater. The K-Pg
extinction appears to have occurred during a period of carbonate saturation
state variability caused by Deccan volcanism.

====

<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.avg.com_email-2Dsignature-3Futm-5Fmedium-3Demail-26utm-5Fsource-3Dlink-26utm-5Fcampaign-3Dsig-2Demail-26utm-5Fcontent-3Dwebmail&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ykTGxsZVgkZ1wolXUu8Knbjog3UbR3bFFymdWeT7ViA&s=ENsxrjvZmMgylu2FY8PRGxmVjUZmJ0dmgqPrcIG6hB0&e= >
Virus-free.
www.avg.com
<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.avg.com_email-2Dsignature-3Futm-5Fmedium-3Demail-26utm-5Fsource-3Dlink-26utm-5Fcampaign-3Dsig-2Demail-26utm-5Fcontent-3Dwebmail&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ykTGxsZVgkZ1wolXUu8Knbjog3UbR3bFFymdWeT7ViA&s=ENsxrjvZmMgylu2FY8PRGxmVjUZmJ0dmgqPrcIG6hB0&e= >
<#m_-1293019897561143670_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>