National Science Review,
Journal Year:
2023,
Volume and Issue:
11(1)
Published: Dec. 18, 2023
The
Late
Ordovician
Mass
Extinction
was
the
earliest
of
'big'
five
extinction
events
and
to
affect
trajectory
metazoan
life.
Two
phases
have
been
identified
near
start
Hirnantian
period
in
middle.
It
a
massive
taxonomic
extinction,
weak
phylogenetic
relatively
benign
ecological
extinction.
A
rapid
cooling,
triggering
major
ice
age
that
reduced
temperature
surface
waters,
prompted
drop
sea
level
some
100
m
introduced
toxic
bottom
waters
onto
shelves.
These
symptoms
more
fundamental
planetary
processes
associated
with
range
factors
an
underlying
driver
as
volcanicity.
Volcanic
eruptions,
other
products,
may
extended
back
time
at
least
Sandbian
early
Katian,
suggesting
extinctions
were
protracted
influential
than
hitherto
documented.
Abstract
Expanded
ocean
anoxia
and
global
cooling
have
been
invoked
as
major
causal
mechanisms
for
the
Late
Ordovician
mass
extinction,
but
factors
underpinning
extinction
remain
unresolved.
Here,
we
document
two
intervals
of
particularly
intense
phosphorus
recycling
in
marine
rocks
deposited
across
a
bathymetric
transect
Yangtze
Shelf
Sea.
The
first
occurred
during
initial
phase
and,
coincident
with
cooling,
drove
development
euxinia
on
shelf.
second
re-established
shelf
after
peak
glaciation,
leading
to
extinction.
Integration
these
data
into
biogeochemical
model
indicates
that
would
doubled
long-term
burial
rate
organic
carbon,
driving
~4°C
cooling.
Thus,
through
its
impact
both
spread
extensive
redox-promoted
was
critical
factor
Earth’s
catastrophic
loss
animal
life.
Earth-Science Reviews,
Journal Year:
2021,
Volume and Issue:
220, P. 103748 - 103748
Published: July 24, 2021
The
Late
Ordovician
Mass
Extinction
wiped
out
85%
of
animal
species
in
two
phases
(LOME1
and
LOME2).The
kill
mechanisms
for
the
extinction
are
debated,
but
deteriorating
climate
expansion
marine
anoxia
appear
to
have
been
important
factors.Nevertheless,
spatial
extent
intensity
its
temporal
relationship
with
extinctions
not
well
understood.Here,
we
review
existing
global
paleoredox
proxy
data
based
on
molybdenum
(Mo)
uranium
(U)
isotopes
from
four
paleocontinents
combined
new
Mo
isotope
Dob's
Linn,
Scotland.Individually,
these
sedimentary
records
demonstrate
significant
redox
fluctuations,
our
coupled
dynamic
oceanic
mass
balance
model
evolution
U
cycles
reveals
that
globally
expansive
ocean
is
best
constrained
by
δ
238
carbonates
Anticosti
Island
record
during
LOME2.In
addition,
consider
periodic
sulfidic
developing
well-ventilated
parts
shallow
oceans
(e.g.
warmer
periods
greater
solar
insolation)
produced
temporarily
high
seawater
98
values
LOME1
accordance
trends
observed
records.In
this
view,
oxygen
loss
had
a
causal
role
both
Ordovician.
AGU Advances,
Journal Year:
2022,
Volume and Issue:
3(1)
Published: Jan. 10, 2022
Abstract
The
Ordovician
(Hirnantian;
445
Ma)
hosts
the
second
most
severe
mass
extinction
in
Earth
history,
coinciding
with
Gondwanan
glaciation
and
increased
geochemical
evidence
for
marine
anoxia.
It
remains
unclear
whether
cooling,
expanded
oxygen
deficiency,
or
a
combination
drove
Late
Mass
Extinction
(LOME).
Here,
we
present
combined
iodine
sulfur
isotope
data
from
three
globally
distributed
carbonate
successions
to
constrain
changes
local
global
redox
conditions.
Iodine
records
suggest
locally
anoxic
conditions
were
potentially
pervasive
on
shallow
shelves,
while
isotopes
reduction
euxinic
(anoxic
sulfidic)
Katian
sulfate‐sulfur
show
large
negative
excursion
that
initiated
during
elevated
sea
level
continued
through
peak
Hirnantian
glaciation.
Geochemical
box
modeling
suggests
of
decreasing
pyrite
burial
increasing
weathering
are
required
drive
observed
suggesting
∼3%
decrease
seafloor
euxinia
Ordovician.
datasets
provide
further
this
trend
was
followed
by
increases
which
coincided
eustatic
sea‐level
rise
subsequent
deglaciation
late
Hirnantian.
A
persistence
shelf
anoxia
against
backdrop
waning
then
waxing
linked
two
LOME
pulses.
These
results
place
important
constraints
throughout
non‐sulfidic
shelfal
anoxia—along
glacioeustatic
climatic
cooling—were
environmental
stressors
worsened
fauna,
resulting
second‐largest
history
only
example
an
icehouse
climate.
Geological Society London Special Publications,
Journal Year:
2022,
Volume and Issue:
532(1), P. 267 - 315
Published: Nov. 2, 2022
Abstract
The
Ordovician
of
Scandinavia
(i.e.
Denmark,
Norway
and
Sweden)
has
been
investigated
for
over
two
centuries
and,
through
time,
various
chronostratigraphic
schemes
have
introduced,
facilitating
regional
correlation.
However,
a
modern
chronostratigraphy
never
proposed.
Here,
we
delineate
ten
stages
the
Scandinavia,
comprising,
in
ascending
order,
Slemmestadian,
Ottenbyan,
Billingenian,
Volkhovian,
Kundan,
Segerstadian,
Dalbyan,
Moldåan,
Jerrestadian
Tommarpian.
We
propose
to
discontinue
use
term
Hunnebergian
Regional
Stage
despite
its
Scandinavian
origin;
this
interval
is
included
new
Ottenbyan
Stage.
base
each
stage,
as
(re)defined
here,
selected
coincide
with
appearance
characteristic
fossil
taxon
delimited
at
top
by
overlying
stage.
stage
boundaries
generally
or
approximate
significant
changes
depositional
environment
that
are
recognizable
across
from
carbonate
platform
foreland
basin.
Local
efficacy
primary
criterion
recognition
rather
than
approximating
global
East
Baltic
boundaries.
It
proposed
abolish
Baltoscandian
series
subseries,
correlation
sufficiently
precise
make
these
higher
rank
redundant.
