[dinosaur] Dinosaur trackways from Colorado Cretaceous coastal environment + Early Triassic polar flora recovery

Ben Creisler
[email protected]

Some new dino-related papers:


Nora Noffke, James Hagadorn & Sam Bartlett (2019)
Microbial structures and dinosaur trackways from a Cretaceous coastal
environment (Dakota Group, Colorado, U.S.A.).
Journal of Sedimentary Research 89 (11): 1096-1108
DOI: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.2110_jsr.2019.57&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=af3vVTWa16KnOoPYojfIwquyqStbi_2iO3GctS9llHE&s=4v9hSj78pzKhD-DoMXUGp5AxjhJGpjekgLCLty15YIc&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__pubs.geoscienceworld.org_sepm_jsedres_article-2Dabstract_89_11_1096_575262_Microbial-2Dstructures-2Dand-2Ddinosaur-2Dtrackways-2Dfrom-2Da&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=af3vVTWa16KnOoPYojfIwquyqStbi_2iO3GctS9llHE&s=WqN2y96yWr4bJ6QRX1bBllp_mHVF-3MKGQ9Ju22IRqg&e= 


Microbially induced sedimentary structures may help preserve unique
glimpses of ancient shoreline habitats, but are little known from Mesozoic
epicontinental settings. To help fill this knowledge gap, we describe a
diverse suite of microbial structures from the Upper Cretaceous "J"
Sandstone (South Platte Formation, Dakota Group) that are spectacularly
exposed at Dinosaur Ridge in Morrison, Colorado, USA. Structures include
"tattered" bed surfaces and ferruginous sand chips in supratidal flat
facies. A large over-flip structure is preserved in a channel locally known
as Crocodile Creek. In upper-intertidal facies, multidirectional ripple
marks occur. Perhaps the most well-known microbial structures are exposed
on extensive bedding surfaces known as "Slimy Beach," where lower
supratidal-flat facies are dominated by decimeter-scale erosional remnants
and pockets. Morphologies and superposition of the structures allows
identification of three generations of erosional pockets. Generation A of
these erosional pockets exhibit size similarities to ornithomimid,
sauropod, and ornithopod dinosaur tracks from adjacent bedding planes,
raising the question of whether initial disturbance of the mat-bound
surface could have been from track making. Generation B erosional pockets
are older and record continuous erosion of the initial pockets until they
were eventually overgrown and sealed by microbial mats. Generation C
pockets are the oldest ones, exposing wide areas of barren sediment that
could not be overgrown by microbial mats anymore. In concert, the microbial
structures point to seasonally variable meteorological conditions along the
coastline of the Western Interior Seaway and indicate that the "Slimy
Beach" bedding plane represents a multi-year record of dinosaur locomotion.

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Michael R. Rampino (2019)
Relationship between impact-crater size and severity of related extinction
episodes.
Earth-Science Reviews  102990 (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.earscirev.2019.102990&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=af3vVTWa16KnOoPYojfIwquyqStbi_2iO3GctS9llHE&s=wvHRIXMEYyl3bbAsi2AU0ROn_tg3kyLU7Pkr85sfscI&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_abs_pii_S0012825219303939&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=af3vVTWa16KnOoPYojfIwquyqStbi_2iO3GctS9llHE&s=M0da83GbON1FYxtS-CS8_IWSKcYZHEiaK1qZ5twNxvM&e= 


How large must an extraterrestrial impact be to cause a peak episode of
increased extinctions of life? Impact energies ≥ 3 × 107 Mt TNT (associated
with terrestrial impact craters with final diameters ≥ 100 km) seem to be
required to generate significant widespread climatic effects from
sub-micron dust and soot in the atmosphere, leading to a distinct
extinction episode (≥ 15% extinction of marine genera). Impacts creating
craters smaller than ~100 km in final diameter (in the 106 to 107 Mt TNT
range) are capable of mostly regional destruction, with minimal impact on
global climate or biota. These results are supported by the fact that the
ages of the four known ≥ 100-km diameter craters of the last 260 My
(Popigai, Chicxulub, Morokweng, and Manicouagan) are all correlative with
times of documented extinction episodes, whereas smaller craters are not.
The largest crater, the 180–km diameter Chicxulub crater (a ~108 Mt TNT
event) is associated with the more severe "major" mass-extinction event (≥
45% extinction of genera) at the end of the Cretaceous.

The percent species extinctions show a significant linear relationship with
final crater diameter and impact energy. The very large Chicxulub impact
lies close to the predicted curve of percent extinction versus
impact-crater diameter (and energy), but the low-angle of impact, an
unusual composition of the target area (with thick sediments rich in
carbonates, sulfates and organic material), and a large excavated transient
crater, may have led to the generation of unusually large amounts of CO2,
widely distributed dust, soot and sulfate aerosols, and a uniquely severe
impact-related environmental disaster. Chicxulub may thus be the only
large-body impact associated with a "major" mass extinction in the
Phanerozoic. Target sensitivity may apply to large impacts into ocean crust
having only a thin cover of organic-poor and carbonate-poor pelagic
sediments, and thus even large oceanic impacts (which are still unknown)
may not produce enough dust, soot and aerosols to cause environmental
crises leading to global extinction peaks above background levels.


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Chris Mays, Vivi Vajda, Tracy D. Frank, Christopher R. Fielding, Robert S.
Nicoll, Allen P. Tevyaw & Stephen McLoughlin (2019)
Refined Permian−Triassic floristic timeline reveals early collapse and
delayed recovery of south polar terrestrial ecosystems.
Geological Society of America  Bulletin (advance online publication)
DOI: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1130_B35355.1&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=af3vVTWa16KnOoPYojfIwquyqStbi_2iO3GctS9llHE&s=gsMGMvFQ0At-lhjj1IlCe37DBRi52iYMvEj5z-x4IvI&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__pubs.geoscienceworld.org_gsa_gsabulletin_article-2Dabstract_doi_10.1130_B35355.1_575264_Refined-2DPermian-2DTriassic-2Dfloristic-2Dtimeline&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=af3vVTWa16KnOoPYojfIwquyqStbi_2iO3GctS9llHE&s=vnwYVgSo9hUXu7Qt9hyY599PM-0zcvkiE1rOWAhWL1s&e= 


The collapse of late Permian (Lopingian) Gondwanan floras, characterized by
the extinction of glossopterid gymnosperms, heralded the end of one of the
most enduring and extensive biomes in Earth’s history. The Sydney Basin,
Australia, hosts a near-continuous, age-constrained succession of high
southern paleolatitude (~65−75°S) terrestrial strata spanning the
end-Permian extinction (EPE) interval. Sedimentological, stable carbon
isotopic, palynological, and macrofloral data were collected from two cored
coal-exploration wells and correlated. Six palynostratigraphic zones,
supported by ordination analyses, were identified within the uppermost
Permian to Lower Triassic succession, corresponding to discrete vegetation
stages before, during, and after the EPE interval. Collapse of the
glossopterid biome marked the onset of the terrestrial EPE and may have
significantly predated the marine mass extinctions and conodont-defined
Permian−Triassic Boundary. Apart from extinction of the dominant Permian
plant taxa, the EPE was characterized by a reduction in primary
productivity, and the immediate aftermath was marked by high abundances of
opportunistic fungi, algae, and ferns. This transition is coeval with the
onset of a gradual global decrease in δ13Corg and the primary extrusive
phase of Siberian Traps Large Igneous Province magmatism. The dominant
gymnosperm groups of the Gondwanan Mesozoic (peltasperms, conifers, and
corystosperms) all appeared soon after the collapse but remained rare
throughout the immediate post-EPE succession. Faltering recovery was due to
a succession of rapid and severe climatic stressors until at least the late
Early Triassic. Immediately prior to the Smithian−Spathian boundary (ca.
249 Ma), indices of increased weathering, thick redbeds, and abundant
pleuromeian lycophytes likely signify marked climate change and
intensification of the Gondwanan monsoon climate system. This is the first
record of the Smithian−Spathian floral overturn event in high southern
latitudes.

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