The study focuses on occurrences of Ophiomorpha burrows in a transgressive–regressive succession composing the Early Paleocene Firkanten Formation deposited in paralic, prodelta to delta front conditions in the Central Basin of Spitsbergen. The burrows colonize sandstones of the Todalen Member at four sites and belong to two ichnospecies: Ophiomorpha cf. nodosa, forming dominantly vertical shafts; and O. cf. irregulaire, consisting of horizontal sinuous tunnels ending in subconical shafts. Both species are observed in shoreface sandstones deposited as a barrier bar. Lithological features and stratigraphic positions suggest that the trace-makers preferentially colonized high-energy sand environments. Foraminiferal faunas occurring below and above …
Geological Society London Special Publications,
Journal Year:
2021,
Volume and Issue:
514(1), P. 213 - 238
Published: Jan. 1, 2021
Abstract
The
flooding
of
the
Lower
Jurassic
shelf
in
North
Gondwana
Palaeomargin
during
early
Toarcian
occurred
on
a
fragmented
and
irregular
topography
affected
by
differential
subsidence
–
owing
to
activity
listric
faults
along
North–South
Axis
Tunisia
that
favoured
lateral
changes
facies
thickness
at
kilometric
scale.
onset
sedimentation
(Polymorphum
ammonite
Zone,
NJT5c
nannofossil
Subzone)
two
adjacent
sections
was
characterized
deposition
limestones
under
high-energy
conditions.
Châabet
El
Attaris
section
located
depressed
sub-basin,
recorded
restricted
environmental
conditions
water
stagnation
an
oxygen-depleted
sea
bottom.
Therefore,
dark
mudstones
developed,
with
increased
total
organic
carbon
contents
enhanced
accumulation
redox-sensitive
elements.
bearing
gutter
cast
structures
is
related
gravity
flows
probably
linked
storm
activities.
These
processes
remobilization
sediments
seafloor,
as
well
oxygen
input
bottom
waters,
shown
record
trace
fossils
including
Zoophycos
,
Ophiomorpha
secondarily,
Chondrites
Diplocraterion
.
thinly
interbedded
are
locally
rich
thin-shelled
bivalves
re-colonized
after
these
deposits,
subsequently
underwent
mass
mortality
return
Kef
Hassine
upper
part
tilted,
less
subsident
block,
indicated
its
reduced
compared
section;
absence
implies
oxic
Polymorphum
Zone
consists
showing
evidence
conditions,
hardgrounds.
occurrence
(deep-tiers)
some
limestone
beds
minor
erosive
processes.
top
sequence
below
deposits
marly
interval
corresponding
Levisoni
interpreted
hardground
given
high
content
belemnites
Arenicolites
them
boring
eroded
Thalassinoides
This
study
shows
sedimentary
expression
Jenkyns
Event
not
uniform
across
Tunisia,
supporting
importance
local
determining
development
anoxic
