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Multiple extinction events at end of Cretaceous?



From: Ben Creisler
bcreisler@gmail.com

An article from New Scientist about evidence for extinctions related
to Deccan volcanism with links to the technical papers:

http://www.newscientist.com/article/dn22137-two-separate-extinctions-brought-end-to-dinosaur-era.html

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G. Keller, T. Adatte, P.K Bhowmick, H. Upadhyay, A. Dave, A.N. Reddy &
B.C. Jaiprakash (2012)
Nature and timing of extinctions in Cretaceous-Tertiary planktic
foraminifera preserved in Deccan intertrappean sediments of the
Krishna–Godavari Basin, India.
Earth and Planetary Science Letters 341–344: 211–221
http://dx.doi.org/10.1016/j.epsl.2012.06.021
http://www.sciencedirect.com/science/article/pii/S0012821X12003056


In C29r below the Cretaceous-Tertiary boundary (KTB) massive Deccan
Trap eruptions in India covered an area the size of France or Texas
and produced the world’s largest and longest lava megaflows 1500 km
across India through the Krishna–Godavari (K–G) Basin into the Bay of
Bengal. Investigation of ten deep wells from the K–G Basin revealed
four lava megaflows separated by sand, silt and shale with the last
megaflow ending at or near the KTB. The biologic response in India was
swift and devastating. During Deccan eruptions prior to the first
megaflow, planktic foraminifera suffered 50% species extinctions.
Survivors suffered another 50% extinctions after the first megaflow
leaving just 7–8 species. No recovery occurred between the next three
megaflows and the mass extinction was complete with the last mega-flow
at or near the KTB. The last phase of Deccan volcanism occurred in the
early Danian C29n with deposition of another four megaflows
accompanied by delayed biotic recovery of marine plankton. Correlative
with these intense volcanic phases, climate changed from
humid/tropical to arid conditions and returned to normal tropical
humidity after the last phase of volcanism. The global climatic and
biotic effects attributable to Deccan volcanism have yet to be fully
investigated. However, preliminary studies from India to Texas reveal
extreme climate changes associated with high-stress environmental
conditions among planktic foraminifera leading to blooms of the
disaster opportunist Guembelitria cretacea during the late
Maastrichtian.

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This paper was already mentioned on the DML in July (now published):
http://dml.cmnh.org/2012Jul/msg00052.html


Thomas S. Tobin, Peter D. Ward, Eric J. Steig, Eduardo B. Olivero,
Isaac A. Hilburn, Ross N. Mitchell, Matthew R. Diamond, Timothy D.
Raub & Joseph L. Kirschvink (2012)
Extinction patterns, delta18 O trends, and magnetostratigraphy from a
southern high-latitude Cretaceous–Paleogene section: Links with Deccan
volcanism.
Palaeogeography, Palaeoclimatology, Palaeoecology 350-352: 180-188
http://dx.doi.org/10.1016/j.palaeo.2012.06.029
http://www.sciencedirect.com/science/article/pii/S0031018212003847

Although abundant evidence now exists for a massive bolide impact
coincident with the Cretaceous–Paleogene (K–Pg) mass extinction event
(~ 65.5 Ma), the relative importance of this impact as an extinction
mechanism is still the subject of debate. On Seymour Island, Antarctic
Peninsula, the López de Bertodano Formation yields one of the most
expanded K–Pg boundary sections known. Using a new chronology from
magnetostratigraphy, and isotopic data from carbonate-secreting
macrofauna, we present a high-resolution, high-latitude
paleotemperature record spanning this time interval. We find two
prominent warming events synchronous with the three main phases of
Deccan Traps flood volcanism, and the onset of the second is
contemporaneous with a local extinction that pre-dates the bolide
impact. What has been termed the K–Pg extinction is potentially the
sum of multiple, independent events, at least at high latitudes.