Petroleum Science,
Journal Year:
2024,
Volume and Issue:
unknown
Published: May 1, 2024
Nitrogen
isotope
compositions
(δ15N)
of
sedimentary
rocks
are
usually
used
to
reconstruct
the
paleoenvironment
and
nitrogen
(N)
biogeochemical
cycle.
The
δ15N
values
crude
oils
inherit
characteristics
relevant
source
can
well
reflect
information
hydrocarbon-forming
organisms
environment
in
ancient
water
column.
However,
studies
on
limited
due
low
N
content.
In
this
study,
a
new
efficient
method
is
applied
marine
from
Bashituo
(BST)
Halahatang
(HLHT)
areas
Tarim
Basin
obtain
nitrogenous
components
(i.e.,
nonhydrocarbons
asphaltenes)
for
achievement
concentration.
carbon
isotopes
these
biomarkers
were
measured.
asphaltenes
(δ15NAsp)
significantly
heavier
than
those
(δ15NNSOs)
oils,
which
attributed
potential
directional
transfer
kinetic
fractionation
during
thermal
evolution
organic
matters
(OM).
δ15NAsp
have
significant
correlations
with
OM
origin
associated
parameters
weak
environmental
parameters,
suggesting
that
difference
mainly
resulted
biological
rather
redox
conditions.
δ15NNSOs
closer
relationship
condition
characteristics,
indicating
they
good
response
paleoenvironmental
variation
column,
not
completely
overprinted
by
origin.
Different
conditions
give
rise
distinct
cycles,
resulting
various
values.
Anammox
occurs
column
Early
Cambrian
dominated
physically
stratified
fractionation,
relatively
BST
area.
Middle–Late
Ordovician
period,
suboxic
zone
leads
an
insignificant
positive
bias
caused
partial
denitrification
HLHT
oils.
evaluation
fractions
enables
more
comprehensive
reconstruction
cycle
oceans.
Scientific Reports,
Journal Year:
2022,
Volume and Issue:
12(1)
Published: Aug. 1, 2022
Abstract
The
Ordovician–Silurian
transition
was
a
critical
period
in
geological
history,
during
which
profound
changes
climatic,
biotic,
and
oceanic
conditions
occurred.
To
explore
the
provenance,
palaeoclimate,
palaeoredox
Sichuan
Basin
Late
Ordovician–early
Silurian
interval,
we
conducted
mineralogical,
geochemical,
isotopic
analyses
of
three
formations
(Wufeng,
Guanyinqiao
Longmaxi
formations)
Xindi
No.
2
well.
ternary
bivariate
diagrams
indicate
that
provenance
is
mainly
felsic
igneous
rocks
originated
from
collisional
setting,
presumably
due
to
an
active
continental
margin.
chemical
index
alteration
(CIA)
values
lower
Wufeng
are
relatively
high
(67.48–73.57),
indicating
warm
humid
climate.
In
contrast,
CIA
declined
rapidly
(58.30–64.66)
late
Katian
early
Hirnantian,
had
fluctuating
cold
dry
climate
interrupted
by
transient
indices
(Mo
concentrations
Mo
auth
/U
,
U/Th,
V/Cr,
Ni/Co,
V/V
+
Ni
values)
two
cycles
water
column
euxinia.
first
cycle
occurred
Formation
deposition,
with
bottom
waters
evolving
oxic-suboxic
suboxic-anoxic.
Most
samples
show
low
redox-sensitive
trace
element
Formation,
pointing
conditions.
second
cycle,
transitioned
oxic
euxinic
Our
δ
13
C
org
data
comparable
previously
reported
records
exhibit
strong
correlation
between
Hirnantian
carbon
excursion
(HICE),
change,
redox
We
suggest
variations
related
elements:
(1)
increased
photosynthetic
activity
under
conditions,
(2)
carbonate
weathering
exposed
glacio-eustatic
sea-
level.
addition,
might
more
shelf-proximal
setting
well
deposition.
effectively
constrain
timing
Ordovician
mass
extinction
(LOME)
evolution
temporal
climatic
ocean
suggesting
apparent
stratigraphic
coincidence
fluctuations
two-phase
extinctions,
implies
causal
relationship.
LOME
systematically
driven
combination
cooler
glacial
temperatures,
sea-level
fluctuations,
anoxic
caused
pulses
Yangtze
shelf
sea.
