The
Triassic
-
Jurassic
boundary
is
marked
by
one
of
the
‘big
five’
mass
extinctions
of
the
Phanerozoic.
This
boundary
event
was
accompanied
by
several
carbon
cycle
pert
urbations,
potentially
induced
by
the
opening
of
the
Central
Atlantic
and
associated
volcanism,
and
accompanied
by
an
ocean
acidification
event.
Continuous
carbonate
successions
covering
this
interval
of
environmental
change
are
however
rare.
Here
data
fro
m
a
shallow
-
marine
equatorial
mixed
carbonate
-
siliciclastic
succession
is
presented,
that
was
studied
on
a
regional
scale.
Four
sections
that
are
48
km
apart
were
examined
on
the
Musandam
Peninsula
(United
Arab
Emirates
and
Sultanate
of
Oman).
The
system
w
as
analysed
for
its
sedimentology,
vertical
and
lateral
facies
changes,
and
stable
carbon
and
oxygen
isotopes.
Strontium
isotope
analysis
was
used
to
determine
the
position
of
the
Triassic
-
Jurassic
boundary
horizon.
The
studied
ramp
experienced
an
episode
of
demise
during
the
Late
Triassic,
followed
by
a
restricted
microbialite
dominated
ramp,
containing
large
amounts
of
siliciclastic
facies.
During
the
Latest
Triassic
the
diverse
carbonate
factory
revived
and
flourished
across
the
Triassic
-
Jurassic
boundar
y.
No
clear
evidence
for
a
biocalcification
crisis
or
an
ocean
acidification
event
across
the
Triassic
-
Jurassic
boundary
is
visible.
Lateral
facies
heterogeneities
can
be
observed
across
the
studied
interval,
attributed
to
hydrodynamic
activity,
including
tropical
storms,
crossing
the
extensive
shelf
area.
Although
evidence
for
synsedimentary
tectonic
activity
is
present,
the
vertical
stacking
pattern
is
largely
controlled
by
changes
in
relative
sea
level.
The
refined
chronostratigraphy
accompanied
by
the
d
etailed
environment
of
deposition
analysis
allows
for
a
refinement
of
the
regional
palaeogeography.
The
neritic
equatorial
carbonate
ramp
has
archived
a
negative
carbon
isotope
excursion
preceding
the
Triassic
-
Jurassic
boundary
that
has
also
been
reported
from
other
study
sites.
The
lack
of
evidence
for
a
biocalcification
crisis
across
the
equatorial
Triassic
-
Jurassic
boundary
indicates
that
the
Tethys
did
not
experience
a
distinct
global
acidification
event.