GeolCarp_Vol60_No5_381

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA, OCTOBER 2009, 60, 5, 381—396 doi: 10.2478/v10096-009-0028-x

Biostratigraphy of the Cretaceous/Tertiary boundary in the

Sirwan Valley (Sulaimani Region, Kurdistan, NE Iraq)

KHALID MAHMOOD SHARBAZHERI

, IMAD MAHMOOD GHAFOR

and QAHTAN AHMAD MUHAMMED

1,2

Department of Geology, College of Science, University of Sulaimani, Kurdistan, Iraq; drimadgh@yahoo.co.uk

Kirkuk Technical College, Kirkuk, Iraq; qahtaniraqi@yahoo.com

(Manuscript received September 18, 2008; accepted in revised form March 26, 2009)

Abstract: The Cretaceous/Tertiary (K/T) boundary sequence, which crops out in the studied area is located within the
High Folded Zone, in the Sirwan Valley, northeastern Iraq. These units mainly consist of flysch and flysch-type succes-
sions of thick clastic beds of Tanjero/Kolosh Formations. A detailed lithostratigraphic study is achieved on the outcrop-
ping uppermost part of the Upper Cretaceous successions (upper part of Tanjero Formation) and the lowermost part of
the Kolosh Formation. On the basis of the identified planktonic foraminiferal assemblages, five biozones are recorded
from the uppermost part of Tanjero Formation and four biozones from the lower part of the Kolosh Formation (Lower
Paleocene) in the Sirwan section. The biostratigraphic correlations based on planktonic foraminiferal zonations showed
a comparison between the biostratigraphic zones established in this study and other equivalents of the commonly used
planktonic zonal scheme around the Cretaceous/Tertiary boundary in and outside Iraq.

Key words: Cretaceous/Tertiary boundary, Iraq, Kurdistan region, Sulaimani, biostratigraphy.

Introduction

The Tanjero, Kolosh and Red Bed Series basin, as a part of
the Neotethys, was strongly deformed by the Alpine orogeny
during its activity continuing from Jurassic to Miocene when
a huge thickness of sediments was accumulated (Buday &
Jassim 1987). The Jurassic to Miocene successions are gen-
erally well exposed in different localities and different types
of stratigraphic units in Zagros mountain regions such as the
Balambo, Qulqula, Qamchuqa, Aqra-Bekhme, Kometan,
Shiranish and Tanjero Formations, in addition to the Kolosh,
Gercus Formations and Red Bed Series. The basins of these
units have a complicated history of development and tecton-
ics, this history was demonstrated by different characteristics
of these stratigraphic units.

This study deals with the biostratigraphy of Cretaceous/

Tertiary boundary sequences in the Sulaimani, Kurdistan re-
gion, NE Iraq, depending on planktonic foraminifers through
Late Maastrichtian and Early Paleocene. Lithologically it is
concerned with the Tanjero and Kolosh Formations, in the
studied area.

The studied area is located on the southern boundary (in

front) of the Zagros Thrust Belt, which developed from the
basin fill of the Neotethys and collision of the Iranian and
Arabian plates (Buday 1980). Structurally the studied area is
located within two different zones. The outcrops of the Sir-
wan Valley section (Halabja area) are located in the Imbri-
cated Zone as divided by Buday & Jassim (1987), (Fig. 1).

Tanjero Formation. According to Dunnington (1952) in

Bellen et al. (1959), the Tanjero Formation is first defined and
described under this name from the selected type section in
the Sirwan Valley, 2 km to the south of Kani Karweshkan vil-
lage, near Halabja town (Fig. 1) and on the right bank of the

Sirwan  river  (upstream  of  the  Dialla  river).  The  type  section
comprises two divisions; the lower division represents pelagic
marl, and occasional beds of argillaceous limestone with silt-
stone beds in the upper part (Bellen et al. 1959), whereas, the
upper division comprises silty marl, sandstone, conglomerate,
and  sandy  or  silty  organic  detrital  limestone  interfingering
with  the  Aqra  Limestone  Formation.  The  sandstone  is  com-
posed of chert and green igneous and metamorphic rocks. The
conglomerates contain pebbles of Mesozoic limestones, dolo-
mites,  recrystallized  limestones  and  radiolarian  chert.  The
thickness of the formation is highly variable, with a maximum
thickness  of  about  2000  meters  between  Rowandus  and
Chwarta (Jassim & Goff 2006).

The Tanjero Formation extends into Southeast Iran where

it was referred to as the Maastrichtian flysch by Kent et al.
(1952) in Jassim & Goff (2006), and is described as chert
conglomerate by James & Wynd (1965). In Turkey, the Cre-
taceous parts of the Garmav Formation are equivalent to the
Tanjero Formation (Buday 1980).

Abdel-Kireem (1986a) suggested removal of the word

“clastic”  from  the  name  of  the  formation  and  to  place  its
lower part within the Shiranish Formation, during their study
of the formation within the stratigraphy of the Upper Creta-
ceous and Lower Tertiary of Sulaimani, Dokan region. Ab-
del-Kireem  (1986b)  subdivided  the  formation  into  three
units  according  to  the  microfacies  and  lithofacies  during
their  study  of  planktonic  foraminifers  and  stratigraphy  of
Tanjero Formation.

Karim (2004, 2006) and Karim & Surdashy (2005a,b,

2006) investigated the basin analysis, paleocurrent, tectonic
history and sequence stratigraphy of the Tanjero Formation.
They indicated an unconformity in the lower part of Tanjero
Formation which was represented by about 500 m of boulder

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SHARBAZHERI, GHAFOR and MUHAMMED

and gravel conglomerate. They mentioned that this conglom-
erate was deposited during sea-level fall (lowstand system
tract). According to Sharbazheri (2007) the duration of this
conglomerate unit in the Chwarta area were estimated to be
1.23 Myr.

Kolosh Formation. The formation was first described by

Dunnington (1952, in Bellen et al. 1959) at Kolosh village,
north of Koy Sinjaq in the High Folded Zone: Ditmar et al.
(1971) also mentioned the occurrence of the upper part of the
Sinjar Formation in the type locality. The formation consists
of shale and sandstones composed of green rock, chert, and
radiolarite.

Bellen et al. (1959) described the following units from

the Kolosh type locality from the top to the base: 1—144 m
of limestone and marl with Miscellanea miscella, ostracods
and  miliolids;  2—30 m  of  limestone  with  Dictyokathina
simplex Smout, Lokhartia sp., valvulinids, miliolids, ostra-
cods;  3—113.5 m  of  limestone  and  shales,  red  shales  and
sandstone  with  the  same  fossils  but  without  Dictyokathina
simplex Smout; 4—6 m of limestone with Saudia labyrinthia,
miliolids and rotalids; 5—410 m of blue shale and green sand.

According to Ditmar et al. (1971), the following fossils

were distinguished in the type locality: Ammodiscus incertus,
Globorotalia angulata, Globigerina bulloides, Gyroidina sol-
danii,  Loxostoma  applinae,  Nodosaria  zippei,  Nuttalides
truempyi,  Pseudovalvulineria  sp.,  Teredolites  sp.,  Ovulites
morelleti,  O.  cf.  elongate,  Trinocladus  perplexus,  Griph-
oporella arabica, Funcoporella diplopora, Cymoporella sp.

Toward the west, the formation comprises mudstone, silt-

stone, and argillaceous limestone beds of distal lithological

character in subsurface sections at the Chamchamal, Taq Taq
and Mushorah region (Jassim & Goff 2006).

The biostratigraphy of the Kolosh Formation was studied

by Kassab (1972, 1974, 1975b, 1976a,b, 1978) and Kassab
et al. (1986) at the type locality and other locations in the
north and northeast of Iraq. They recognized the planktonic
foraminiferal zones of earliest Middle Paleocene, represent-
ed by Globorotalia uncinata Partial Range Zone.

Review on the Upper Cretaceous—Lower Tertiary

contact in Iraq

The Upper Cretaceous and Lower Tertiary sedimentary

rocks in Iraq have been the subject of numerous stratigraphic
and paleontological investigations. Such sediments are well
developed in both surface and subsurface sections at north-
ern and northeastern Iraq.

The Upper Cretaceous and Lower Tertiary boundary is

marked by one of the most dramatic extinctions of different
groups of organism; especially the planktonic foraminifers,
the recognition of the major paleoclimatic change during the
Late Maastrichtian has focused new attention on global cli-
mate changes and their effect on marine organisms.

In particular the last half million years of the Maastrichtian

is increasingly recognized as a time of rapid and extreme cli-
matic changes characterized by maximum cooling at about
65.5 Ma, followed by (3—4 °C) greenhouse warming and the
major Deccan volcanic activity between 65.4 and 65.2 Ma
(Li & Keller 1998a; Keller 2001).

Fig. 1. Location map of the studied area (from Sissakian et al. 2000).

383

BIOSTRATIGRAPHY OF THE CRETACEOUS/TERTIARY BOUNDARY (KURDISTAN, NE IRAQ)

Al-Shaibani et al. (1986) during their stratigraphic analy-

sis of the Tertiary/Cretaceous contact in the Dokan area,
(North Iraq), they placed the contact in Zone P3 (Middle
Thanetian), based on overlapping of the range of Globorota-
lia (T.) trinidadensis Bolli (1957), and Subbotina velascoen-
sis Cushman, 1925 and other species.

During their study of the biostratigraphy of the upper part of

the Kolosh Formation from Sartaq-Bamo in northeastern Iraq,
Ghafor  &  Karim  (1999)  recognized  the  Globorotalia  velas-
coensis Zone of Late Paleocene age. Dunnington (1955, 1957)
recorded the indication of a great gap in the stratigraphic col-
umn,  in  his  biostratigraphic  studies  about  the  nature  of  the
Cretaceous/Tertiary contact in Dohuk, Aqra and northern Iraq,
indicated by the period of great regression of the ocean during
the Late Maastrichtian and Early Paleocene time followed by
uplifting of the area due to the tectonic orogeny, consequently
this  region  underwent  the  process  of  erosion  and  a  period  of
non  deposition.  This  phenomenon  is  applied  for  almost  the
greater part of Iraq, exactly in the region of the northern and
northeastern  part.  Al-Omari  (1970)  during  his  study  on  fora-
minifers  of  Mesozoic  and  Cenozoic  at  wells  Butmah-9  and
Ainzala-16, -17 from the northwestern part of Iraq, confirmed
that the Aaliji Formation overlies the Shiranish Formation un-

conformably. Other biostratigraphic studies carried out in Iraq
and especially in the studied area are summarized in (Fig. 2).

The Sirwan type section is located at the Sirwan Valley, on

the right bank of the Sirwan river (upstream of Diyala river),
2 km to the south of Kani Karweshkan village, near Halabja
town at latitude (35°07’26.7”) and longitude (45°

52’34.7”).

Most of the lower part of the type section for the Tanjero
Formation was covered with water by the Darbandekhan
Dam (Fig. 1).

All samples were collected from the studied section in the

field after removing the surface contaminated soil and trying
to obtain fresh and unweathered materials. Samples were
collected at interval ranging between 20—50 cm at or near the
Cretaceous/Tertiary contact and at interval of 50 cm to 3 m
away from the contact.

The aim of this study includes the complete high resolu-

tion  biostratigraphic  zonation  of  the  section,  regional  bios-
tratigraphic  correlation  of  the  studied  section  correlation
with other similar sequences, ascertaining the age of the se-
quence, by using the new zonal scheme and the age of plank-
tonic  foraminiferal  datum  events  with  correlative  and
relative  methods,  identifying  the  nature  of  the  contact  be-
tween Late Maastrichtian and Early Paleocene.

Fig. 2. Correlation of the previous biostratigraphic zonation. Cretaceous/Tertiary boundary in the studied region and different localities of
Iraq.

385

BIOSTRATIGRAPHY OF THE CRETACEOUS/TERTIARY BOUNDARY (KURDISTAN, NE IRAQ)

green  marl,  occasionally  intervened  by  thin  marly  limestone
layers  and  sandstone.  Three  conglomerate  beds  can  be  ob-
served in the lower part of  the Kolosh Formation, with thick-
nesses  of  3.0 m,  10.0 m  and  13 m,  respectively  (Fig. 5).  The
distribution of foraminiferal content was recorded from twen-
ty samples ranging from sample 185 to sample 205 taken from
the first 14 m of the Kolosh Formation. These samples lacked
foraminifers, but contained reworked radiolarians from the un-
derlying Tanjero Formation and rare reworked planktonic for-
aminifers from the Tanjero Formation. The Kolosh Formation
was overlain by the Sinjar Formation gradually in the studied
sections  and  marked  by  the  regular  change  from  fine  clastic
sediment  of  the  Kolosh  Formation  to  non  clastic  limestone
beds of the Sinjar Formation.

Biostratigraphy

The comprehensive studies of planktonic foraminiferal bios-

tratigraphy during the last five decades have proved to be more
useful and more accurate among the large number of micropale-
ontological branches, especially than benthonic (Fig. 6).

The comprehensive and motif plan in this work was de-

duced from the planktonic foraminiferal zonation and corre-
lation  for  the  sediments  in  tropical/subtropical  regions,
based on the works of Berggren & Miller (1988), Li & Keller
(1998a,b),  Liu  &  Olsson  (1992),  Berggren  et  al.  (1995),
Berggren & Norris (1997), Olsson et al. (2000), Arenillas et
al.  (2000a),  Elnady  &  Shahin  (2001),  Abramovich  et  al.
(2002),    Samir  (2002),  Keller  (2002,  2004),  Abramovich  &

Fig. 4. Schematic geologic cross-section of the studied section (Sirwan Valley).

Fig. 5. Image showing the Cretaceous/Tertiary contact Tanjero—Kolosh Formations, Sirwan Valley section and three ridge forming con-
glomerate beds at the lower part of Kolosh Formation.

387

BIOSTRATIGRAPHY OF THE CRETACEOUS/TERTIARY BOUNDARY (KURDISTAN, NE IRAQ)

Keller (2003), Obaidalla (2005), Smit (2005), and Sharba-
zheri (2007). Fortunately, this zonation has proved satisfac-
tory, with successful results achieved in different localities
around the world.

Li & Keller (1998a) subdivided the Maastrichtian zonal

scheme into eight Cretaceous Foraminiferal (CF) zones la-
belled CF8 to CF1 from the base to the top; this new biozo-
nation

provides

accurate

and

significantly

higher

biostratigraphic  resolution  than  previous  zonal  schemes.
They calibrated their ranges to the paleomagnetic time scale
in  the  DSDP  Site  525A,  and  on  Tunisian  sections  (Li  &
Keller  1998b),  their  age  estimations  were  also  correlated
with magnetochron ages by Berggren et al. (1995), and con-
sequently the criteria for age estimation and determination of
rate of sedimentation can be proved easily through biostrati-
graphic correlation and datum event comparison.

The biostratigraphic correlation of the studied section is

based  on  planktonic  foraminiferal  zonations,  which  show  a
comparison  between  the  biostratigraphic  zones  established
in  this  study  with  other  equivalents  of  the  commonly  used
planktonic zonal scheme around the Cretaceous/Tertiary (K/T)
boundary in and outside Iraq (Fig. 7).

The foraminiferal occurrence shows evidence of three di-

luted  intervals  of  foraminiferal  survivorship  in  the  studied
upper  part  of  the  Tanjero  Formation,  and  the  fourth  one  at
the base of the Paleocene just after the extinction catastrophe
of organisms at the uppermost part of the Maastrichtian. The
Upper Maastrichtian—Lower Paleocene interval in general at-
tracted particular attention because the foraminifers are rela-
tively moderate and mostly well preserved. It is important to
mention that the conventional index species Abathomphalus
mayaroensis of Late Maastrichtian is very rarely found and it
is  frequently  absent  in  shallow  continental  shelf  sections  in
all studied regions which may be due to paleoenvironmental
conditions  of  the  deeper  and  more  basinal  oceanic  environ-
ment around low latitudes restrictions of the species (Canudo
et al. 1991), and in high latitudes disappear prior to the K/T
boundary  (Blow  1979).  Therefore  the  A.  mayaroensis  Bio-
zone  is  geographically  and  ecologically  restricted.  In  such
cases  it  is  better  to  replace  the  A.  mayaroensis  Biozone  by
other biozones to avoid any ambiguous and vague situation
about the first appearance and last extinction datum event.

For the Paleogene subdivisions, the zonal scheme has pre-

viously been developed in two widely separated geographi-
cal areas: the eastern hemisphere (Caucasus Mountains, e.g.
Subbotina 1953, Krasheninikov 1969 in Samir 2002), and in
the western hemisphere (Trinidad, e.g. Bolli 1957a,b in
Samir 2002).

A discussion of all subsequent modifications of the origi-

nal  zonal  scheme  proposed  by  Bolli  (1966),  Blow  (1979),
Berggren & Miller (1988), Berggren et al. (1995), Berggren
&  Norris  (1997),  Olsson  et  al.  (2000)  with  other  authors
mentioned in (Fig. 7) forms the basis of the Paleocene zonal
scheme  for  this  study,  which  shows  a  comparison  between
this zonal scheme and earlier developed schemes. It is worth
remembering that the original, genetic radiation, phylogenet-
ic  reconstruction  of  relationships  and  geological  ranges  of
Paleocene  planktonic  foraminifers  were  established  by  Liu
& Olsson (1992) and Olsson et al. (2000). Their work forms

the basis for the work of the working group on the Atlas of
Paleocene Planktonic Foraminifera by Olsson et al. (2000).
The biozones from the lower part to the upper part of the sec-
tion are as follows (Fig. 6).

Pseudotextularia intermedia

Interval Zone (CF5): The

Pseudotextularia  intermedia  Zone  (CF5)  is  defined  by  the
LAD  of  the  Globotruncana  linneiana  (d’Orbigny)  at  the
base  and  the  FAD  of  Racemiguembelina  fructicosa  (Egger)
at the top. Nederbragt (1990) originally introduced this bio-
zone  as  the  interval  from  the  FAD  of  Planoglobulina  acer-
vulinoides  at  the  base  to  the  FAD  Racemiguembelina
fructicosa  at  the  top.  In  the  present  study,  the  definition  is
constrained according to Li & Keller (1998a,b).

The recorded planktonic foraminiferal assemblages in this

biozone are represented by well diversified forms of  Hetero-
helix  navarroensis  (Loeblich),  H.  globulosa  (Ehrenberg),  H.
striata  (Ehrenberg),  H.  punctulata  (Cushman),  H.  nauttalli
(Voorwijk), H. reussi (Cushman), H. pulchra (Brotzen), Lae-
viheterohelix  glabrans  (Cushman)  (Fig. 8c),  Planoglobulina
acervulinoides  (Egger),  Rugoglobigerina  hexacamerata
(Bronnimann),  R.  macrocephala  (Bronnimann),  Gansserina
gansseri (Reuss), G. wiedenmayeri (Gandolfi), Globotruncan-
ita stuarti (de Lapparent), G. stuartiformis (Dalbez), G. conica
White, G. pettersi Gandolfi, G. angulata Tilev, Globotrunca-
na aegyptiaca Nakkady, Glt. orientalis El-Naggar, Glt. falsos-
tuarti  Sigal,  Glt.  dupeublei  Caron  et  al.  (Fig. 8e),  Glt.
lapparenti Boli, Glt. arca (Cushman), Glt. bulloides Vohgler,
Glt. rosetta Carsey, Glt. insignis (Gandolfi), Contusotruncana
contusa (Cushman), C. fornicata Plummer, Rugotruncana cir-
cumnodifer  (Gandolfi), R. subcircumnodifer  (Gandolfi),  Glo-
bigerinelloides  volutes  (White),  G.  prairehillensis  Pessagno,
G. bolli Pessango, Pseudotextularia elegans (Rzehak), P. de-
formis (Kikoine), P. intermedia (De Klasz), Racemifructicosa
(Egger),  R.  poweli  Smith  &  Pessagno,  Pseudoguembelina
costulata  (Cushman)  (Fig. 8a,b),  P.  excolata  (Cushman)
(Fig. 8c), Hedbergella monmouthensis (Olsson), H. holmde-
lensis Olsson, Abathomphalus mayaroensis (Bolli) (Fig. 8f—g),
Archaeoglobigerina blowi Pessagno, A. cretacea (d’Orbigny),
Gublerina cuvillieri Kikoine, Gumbelitria cretacea Cushman,
G. dammula (Voloshina).

Due to high similarities of foraminiferal occurrence, the

present  Zone  (CF5)  is  equivalent  to  that  of  Li  &  Keller
(1998a,b), Abramovich et al. (2002), Samir (2002). It is most
likely  equivalent  to  the  upper  part  of  the  Gansserina  gans-
seri  Zone  recorded  in  the  North  and  Northeast  of  Iraq  and
different regions of the world by Robaszynski et al. (1984),
Caron (1985), D’Hont & Keller (1991), Al-Mutwali (1996),
Hammoudi (2000), Al-Mutwali & Al-Jubouri (2005), Obaid-
alla (2005) and it is equivalent to the upper part of the  Glt.
contusa  Zone  of  Abawi  et  al.  (1982),  and  Abdel-Kireem
(1986), and the  Glt. contusa, R. fructicosa Zone of Premoli
Silva & Sliter (1995, 1999) from Italy, Abdel-Kireem & Samir
(1995)  from  Egypt.  The  Pseudotextularia  intermedia  Zone
spans about 0.73 Myr (69.06—68.33 Ma), its absolute age, based
on  magnetochron  ages,  is  estimated  of  about  730  ky/19 m,
providing a moderate rate of deposition (38.5 ky/meter). Age:
late Early Maastrichtian.

Note: it is important to mention that only the upper part of

the Pseudotextularia intermedia Zone was recorded from the

390

SHARBAZHERI, GHAFOR and MUHAMMED

studied section and its lower limit was not studied. This bio-
zone is represented by moderate diversity of planktonic fora-
miniferal assemblage with 42 species in the studied area.

Racemiguembelina fructicosa

Interval Zone (CF4): Race-

miguembelina fructicosa Zone (CF4) was introduced by Li &
Keller  (1998a,b)  as  a  biostratigraphic  interval  between  the
FAD of Racemiguembelina fructicosa (Egger) at the base and
the  FAD  of  Pseudoguembelina  hariaensis  at  the  top.  The
FAD  of  Racemiguembelina  fructicosa  (Egger)  in  the  studied
section is recorded from the uppermost part of the reddish to
pale brown unit and covers the basal part of the Tanjero For-
mation  (sample  no. 38)  to  the  FAD  of  Pseudoguembelina
hariaensis Nederbragt within the Tanjero Formation (sample
no. 58).

It is important to mention that the zonal scheme of Creta-

ceous foraminifers (CF) proposed by Li & Keller (1998a,b),
which  replaces  the  Abathomphalus  mayaroensis  Zone  with
four zones (R. fructicosa Zone, P. hariaensis Zone, P. palpe-
bra  Zone,  P.  hantkeninoides  Zone),  provides  a  much  im-
proved  age  estimate  for  the  Late  Maastrichtian.  The  total
range  of  the  A.  mayaroensis  Zone  characterized  the  Late
Maastrichtian in low latitude regions as well as the Tethyan
paleogeographic  realm.  However  it  has  been  found  that  A.
mayaroensis  is  very  rare  or  absent  in  high  latitude  regions
(Blow 1979) and in the present section also, consequently it
is more accurate to use the new zonal scheme.

Most of the workers in the zonal scheme placed the Race-

miguembelina  fructicosa  Zone  in  the  early  Late  Maastrich-
tian  (Keller  et  al.  1995  from  Tunisia;  Li  &  Keller  1998a,b,
Abramovich  et  al.  2002  at  DSDP  Site  525A;  Samir  2002,

and Obaidalla 2005 from Egypt). As defined above, the
present Biozone CF4 is correlatable with the lower part of
the A. mayaroensis of Abawi et al. (1982) and Abdel-Kireem
(1986a), Premoli Silva & Sliter (1995, 1999) from Italy.

The age of this biozone, estimated by Li & Keller (1998a), is

appropriate for the time span between 68.33 Ma and 66.83 Ma,
providing a high sedimentary rate of about 13.5 ky/m in the
Sirwan area, and a high sedimentary rate of about 18 ky/m in
the Qulka section Dokan area. Age: early Late Maastrichtian.

Pseudoguembelina hariaensis

Interval Zone (CF3): The

Pseudoguembelina  hariaensis  Zone  was  defined  by  Li  &
Keller (1998a) as a partial range of the nominate species be-
tween  the  FAD  of  Pseudoguembelina  hariaensis  Nederbragt
and  the  LAD  of  Gansserina  gansseri  (Bolli).  In  the  studied
area this zone also marked by the FAD of the nominate spe-
cies to the last occurrence of Gansserina gansseri (Bolli). The
interval  of  this  zone  is  30  meters  in  the  Sirwan  section
(Fig. 7). This zone shows reliable abundance of Pseudoguem-
belina  hariaensis  Nederbragt  and  other  assemblages’  plank-
tonic  foraminifers  which  totally  resembles  that  of  the
underlying  Racemiguembelina  fructicosa  Zone  (CF4),  in  the
Gali section with the following planktonic foraminifers of 50
species like: Heterohelix navarroensis Loeblich, H. globulosa
(Ehrenberg),  H.  striata  (Ehrenberg),  H.  punctulata  (Cush-
man),  H.  nauttalli  (Voorwijk),  Laeviheterohelix  glabrans
(Cushman), Planoglobulina carseyae (Plummer), P. acervuli-
noides (Egger), Rugoglobigerina rugosa  (Plummer) (Fig. 9d-e),
R.  scotti  (Bronnimann),  R.  hexacamerata  Bronnimann,  R.
macrocephala Bronnimann, R. pennyi Bronnimann, R. reiche-
li  Bronnimann,  R.  rotundata  Bronnimann,  Gansserina  gans-

Fig. 9. a – Globotruncanella pschadae (Keller), Tanjero Formation, Late Maastrichtian, Sirwan. Specimen from P. hariaensis Zone.
b – Globotruncanella petaloidea (Gandolfi), Tanjero Formation, Late Maastrichtian, Sirwan. Specimen from P. hariaensis Zone. c – Plum-
merita hantkeninoides (Bronnimann), Tanjero Formation, Late Maastrichtian, Sirwan. Specimen from Plummerita hantkeninoides Zone.
d—e – Rugoglobigerina rugosa (Plummer), Tanjero Formation, Late Maastrichtian, Sirwan. Specimen from P. hariaensis Zone. f – Hedber-
gella monmouthensis (Olsson), Tanjero Formation, Late Maastrichtian, Sirwan. Specimen from Plummerita hantkeninoides Zone. g – Pseudot-
extularia intermedia (De Klasz), Tanjero Formation, Late Maastrichtian, Sirwan. Specimen from P. hariaensis Zone.

391

BIOSTRATIGRAPHY OF THE CRETACEOUS/TERTIARY BOUNDARY (KURDISTAN, NE IRAQ)

seri (Reuss), Globotruncanita stuartiformis Dalbez, G. conica
White, G. pettersi Gandolfi, G. angulata Tilev, Globotrunca-
na falsostuarti Sigal, Glt. dupeublie Caron et al., Glt. lappar-
enti  Bolli,  Contusotruncana  contusa  (Cushman),  C.  plicata
White, C. walfischensis Todd, C. sp. (nov. sp.?), Rugotrunca-
na circumnodifer (Gandolfi), R. subcircumnodifer (Gandolfi),
Globotruncanella petaloidea (Gandolfi) (Fig. 9b), G. pschadae
(Keller) (Fig. 9a), Globigerinelloides volutes  (White), G. prai-
riehillensis  Pessango,  Pseudotextularia  elegans  (Rzehak),  P.
deformis (Kikoine), P. intermedia (De Klasz) (Fig. 9g), Racem-
iguembelina  fructicosa  (Egger),  Pseudoguembelina  costulata
(Cushman),  P.  palpebra,  P.  excolata  (Cushman),  Hedbergella
monmouthensis  (Olsson)  (Fig. 9f),  H.  holmdelensis  Olsson,
Abathomphalus  mayaroensis  (Bolli),  Kuglerina  rotundata
(Bronnimann),  Costellagerina  cf.  bulbosa  Belford,  Gublerina
cuvillieri  Kikoine,  Gumbelitria  cretacea  Cushman.  As  de-
fined above, the present Biozone CF3 is correlatable with the
zone  recorded  by  Li  &  Keller  (1998a,b),  Abramovich  &
Keller (2003) in DSDP Site 525A, Abramovich et al. (2002)
from  Madagascar,  Keller  et  al.  (1995)  from  Tunisia,  Keller
(2004)  from  Eastern  Tethys,  Samir  (2002),  Keller  (2002),
Obaidalla  (2005)  from  Egypt,  Sharbazheri  (2007)  from  NE
Iraq.  It  is  correlated  with  the  middle  part  of  the  Aba-
thomphalus  mayaroensis  Zone  recorded  in  the  Northeast  of
Iraq by Abawi et al. (1982) and Abdel-Kireem (1986a); in Italy
by Premoli Silva & Sliter (1995, 1999) and Premoli Silva et
al. (1998);  in Egypt by Abdel-Kireem & Samir (1995).

The age of this biozone, estimated by Li & Keller (1998a),

corresponds to the middle Late Maastrichtian, with the time
span between 66.83 Ma and 65.45 Ma, based on magneto-
chron ages, providing a low to moderate rate of sedimentation
(46 ky/m) in the Sirwan Valley. Age: middle Late Maastrichtian.

Pseudoguembelina palpebra

Interval Zone (CF2): This

zone is defined as the interval between the LAD of Gansseri-
na gansseri at the base and the FAD of Plummerita hantken-
inoides at the top. Li & Keller (1998a,b) introduced this zone
from DSDP Site 525A and Tunisia. The recorded planktonic
assemblage of this zone is characterized by the same number
50  species  diversity  as  the  underlying  Pseudoguembelina
hariaensis Zone, and marked by the extinction of Heterohe-
lix  punctulatus  (Cushman),  Gansserina  gansseri,  Globiger-
inelloides  volutes  (White),  and  Laeviheterohelix  glabrans
(Cushman), in the upper part of the zone. Besides, the plank-
tonic  foraminiferal  species  enduring  from  the  underlying
biozones, some species, including Globotruncana falsoscal-
carata  Kerdany  &  Abdelsalam,  Globotruncanella  sp.  and
Trinitella  scotti  Bronnimann,  have  their  first  appearance  in
this  zone.  The  Pseudoguembelina  palpebra  Interval  Zone
(CF2)  in  the  Sirwan  Valley  displays  spans  25 m  (Fig. 7),
biostratigraphically represented by a decrease in the number
of species from 49 to 38 and there is no distinctive appear-
ance of new species in this zone. The planktonic foraminifer-
al  assemblages  of  this  zone  in  the  Sirwan  section  are
represented by Heterohelix navarroensis Loeblich, H. globu-
losa  (Ehrenberg),  Laeviheterohelix  glabrans  (Cushman),
Planoglobulina carseyae (Plummer), P. acervulinoides (Eg-
ger), Rugoglobigerina rugosa (Plummer), R. scotti (Bronni-
mann),  R.  hexacamerata  Bronnimann,  R.  macrocephala
Bronnimann, R. pennyi Bronnimann, R. reicheli Bronnimann,

Globotruncanita stuartiformis Dalbez, G. conica White, Glo-
botruncana aegyptiaca Nakkady, Glt. falsocalcarata Kerdany
& Abdelsalam (Fig. 8g—i), Glt. falsostuarti Sigal, Glt. dupeu-
blie  Caron  et  al.,  Glt.  lapparenti  Bolli,  C.  plicata  White,  C.
walfischensis  Todd,  Rugotruncana  circumnodifer  (Gandolfi),
R. subcircumnodifer (Gandolfi), Globotruncanella petaloidea
(Gandolfi),  G. pschadae  (Keller), Globigerinelloides prairie-
hillensis Pessagno, Pseudotextularia elegans (Rzehak), P. de-
formis  (Kikoine),  Racemiguembelina  fructicosa  (Egger),
Pseudoguembelina hariaensis Nederbragt, P. palpebra, P. ex-
colata  (Cushman),  Hedbergella  monmouthensis  (Olsson),  H.
holmdelensis  Olsson,  Gublerina cuvillieri  Kikoine,  Gumbeli-
tria cretacea Cushman.

As defined above, the present Zone CF2 of the studied

area is equivalent to the same zone of the P. palpebra Zone
of  the  South  Atlantic  DSDP  Site  525A  by  Li  &  Keller
(1998a) and Abramovich et al. (2002); and of Tunisia by Li
& Keller (1998b) and Arenillas et al. (2000); eastern Tethys
by Keller (2004). The present P. palpebra Zone is equivalent
to  the  upper  part  of  Abathomphalus  mayaroensis  Zone  re-
corded from different parts of the world – Premoli Silva &
Sliter (1995, 1999); from Spain: Canudo et al. (1991), Moli-
na et al. (1996); from eastern Mediterranean: Premoli Silva
et  al.  (1998);  from  USA  California:  Maestas  et  al.  (2003);
from  Egypt: Luning et al. (1998), Elnady & Shahin (2001),
Samir (2002), and Obaidalla (2005). The present P. palpebra
Zone  is  equivalent  to  the  upper  part  of  the  Abathomphalus
mayaroensis  Zone  recorded  from  different  localities  in  Iraq
(Kassab  1972,  1974,  1975a,b,  1976a,b,  1979;  Abawi  et  al.
1982; Abdel-Kireem 1986a; Kassab et al. 1986; Al-Mutwali
1996; Hammoudi 2000; Al-Mutwali & Al Juboury 2005).

The age of this biozone, estimated by Li & Keller (1998a),

corresponds to the late Late Maastrichtian, with the time
span between 65.45 Ma and 65.30 Ma, based on magneto-
chron ages, providing a high rate of sedimentation (6 ky/m)
in the Sirwan Valley. Age: late Late Maastrichtian.

Plummerita hantkeninoides

Taxon Range Zone (CF1):

The biostratigraphic interval of this zone is defined by the to-
tal  range  of  the  nominate  taxon  Plummerita  hantkeninoides
(Bronnimann) (Fig. 9c). Pardo et al. (1996) introduced the P.
hantkeninoides Zone for the latest Maastrichtian of Spain. It
marks the uppermost Cretaceous biozone, and its top marks
the  K/P  boundary.  The  upper  limit  of  this  zone  coincides
with the mass extinction of large tropical-subtropical taxa. In
the studied sections, this zone covers the top 25 meters of the
Maastrichtian in the Sirwan area. The characteristic recorded
planktonic  foraminiferal  assemblage  of  this  zone  shows  a
gradual  decrease  in  both  species  and  individual  numbers
from the Pseudoguembelina palpebra Zone to the Plummeri-
ta hantkeninoides Zone from 37 to 29 species in the Sirwan
section.

Heterohelix navarroensis Loeblich, H. globulosa (Ehren-

berg), H. striata (Ehrenberg), Rugoglobigerina rugosa (Plum-
mer), R. scotti (Bronnimann), R. macrocephala Bronnimann,
R.  pennyi  Bronnimann  &  Abdelsalam,  Globotruncana  falso-
stuarti  Sigal,  Glt.  dupeublie  Caron  et  al.,  Contusotruncana
contusa  (Cushman),  C.  plicata  (White),  Globotruncanella
petaloidea  (Gandolfi),  Pseudotextularia  elegans  (Rzehak),
Pseudoguembelina costulata (Cushman), P. hariaensis Neder-

392

SHARBAZHERI, GHAFOR and MUHAMMED

bragt, P. palpebra, P. excolata (Cushman), Hedbergella mon-
mouthensis (Olsson), H. holmdelensis Olsson, Gumbelitria cre-
tacea Cushman, Plummerita hantkeninoides (Bronnimann).

As defined above and based on the associated planktonic

foraminiferal assemblage, the present Plummerita hantkeni-
noides  Total  Range  Zone  (CF1)  is  equivalent  to  the  same
zone recorded from Tunisia by Li & Keller (1998b), Arenil-
las et al. (2000); from Eastern Tethys Israel by Keller (2004);
from  Egypt  by  Keller  (2002),  Samir  (2002)  and  Obaidalla
(2005), Pardo et al. (1996), Keller (1996); and to the upper
part of Zone (CF 1—2) from South Atlantic DSDP Site 525A
by  Li  &  Keller  (1998a);  from  Madagascar  (Abramovich  et
al.  2002);  from  DSDP  Site  525A  by  Abramovich  &  Keller
(2003); from USA by Stinnesbeck et al. (2004). The present
Plummerita hantkeninoides Zone is equivalent to the upper-
most part of the Abathomphalus mayaroensis Zone recorded
from  different  parts  of  the  world:  Spain–  Canudo  et  al.
(1991), Smit (2005), Chacon & Martin-Chivelet (2005); Ita-
ly – Premoli Silva & Sliter (1995, 1999); eastern Mediterra-
nean – Premoli Silva et al. (1998);  India –Govindan et al.
(1996);  USA,  California – Maestas  et  al.  (2003);  south
USA – Martinez  (1989),  Luning  et  al.  (1998).  It  is  also
equivalent to the Plummerita reicheli Zone of Elnady & Sha-
hin  (2001),  and  Shahin  (1992)  from  Egypt.  The  present
Plummerita hantkeninoides Zone is equivalent to the Kassa-
biana falsocalcarata Zone recorded from Shalki village and
the Sirwan Valley by Kassab (1976b), Kassab et al. (1986),
Ghafor (1988 – Tel Hajar no 1 well).

The age of this biozone, estimated by Li & Keller (1998a),

corresponds to the latest Late Maastrichtian, with the time
span between 65.30 Ma and 65.00 Ma, based on magneto-
chron ages, providing a high rate of sedimentation (12 ky/m)
in the studied area. Age: Late Maastrichtian.

P0 & P

αα

αα: In the present study, the earliest Paleocene P0

Guembelitria cretacea Zone, and Parvularugoglobigerina
eugubina Zone was not recorded completely or continuously
in the Sirwan section.

The Cretaceous/Tertiary boundary is located at the base of

3  meters  of  pale  grey  to  yellowish,  weathered  friable  con-
glomerate. This conglomerate and the overlying 12 meters of
dark  grey  organic  rich  shale  alternating  with  marl,  marly
limestone  and  thin  layers  of  siltstone,  sandstone,  are  barren
of  foraminifers.  As  mentioned  previously,  the  sedimentary
succession  of  the  studied  sections  in  the  Sirwan  Valley
shows  evidence  of  three  diluted  intervals  of  foraminiferal
survivorship in the studied upper part of the Tanjero Forma-
tion, and the fourth one at the base of the Paleocene just after
the  extinction  catastrophe  of  organisms  in  the  uppermost
part of the Maastrichtian.

The age of this interval, estimated on the basis of the mag-

netic  polarity and  datum events by Olsson et al. (2000) and
Keller (2002, 2004), implies the time span between 65.00 Ma,
marked by last appearance of Plummerita hantkeninoides, and
64.90  Ma,  marked  by  last  occurrence  of  Parvularugoglobi-
gerina  eugubina  (Fig.  10e—g),  considered  the  magnetochron
ages of 100 ky, providing  a high rate of deposition (6.5 ky/m)
in the Sirwan section (Fig. 7).

No sedimentological evidence of an erosional surface,

condensed section or mineralogical record, trace fossils or

hard  ground  was  observed  beside  these  significant  points.
The  great  lithological  similarity  between  the  Tanjero  and
overlying Kolosh Formations means that no one can observe
or  distinguish  the  contact  line  of  the  K/T  boundary  in  the
field. As there is no sign of the presence of an unconformity,
we  propose  that  this  interval  may  be  equivalent  to  both  the
P0  &  P

α (G. cretacea—P. eugubina Zone). In addition to

these categories, the sedimentation rate of deposition imme-
diately  around  the  Cretaceous/Tertiary  boundary  recorded
high to very high rates of sedimentation which reveal contin-
uous  uninterrupted  sedimentary  sequences.  Otherwise  the
significant  amount  of  conglomerate  beds  within  the  studied
upper part of the Tanjero Formation represented by 7 repeat-
ed beds of 0.5 to 2 meters thickness and three conglomerate
beds within the lower part of the Kolosh Formation. This re-
veals the intraformational conglomerate beds of limited lat-
eral  extensions  (Figs. 4,  5),  which  could  be  attributed  to
either  its  extremely  short  duration,  or  its  restriction  to  near
shore,  or  diluted  in  foraminiferal  survivorship  rather  than
open ocean environments as outlined by Berggren & Norris
(1997).

(P1a) Parvularugoglobigerina eugubina—Subbotina trilo-

culinoides

Interval Subzone: Definition: Biostratigraphic in-

terval  between  the  LAD  of  Parvularugoglobigerina
eugubina  and  the  FAD  of  Subbotina  triloculinoides  (Plum-
mer)  (Fig. 10a—d),    (P1a;  defined  in  Berggren  et  al.  1995);
emendation  of  the  Parasubbotina  pseudobulloides  Subzone
(P1a) in Berggren & Miller (1988). In the present study, the
P1a  Subzone  attains  a  thickness  of  35 m.  The  associated
planktonic foraminiferal assemblage is represented by com-
plete  occurrences  of  the  following  species  in  the  Sirwan
area:  Parvularugoglobigerina  alabamensis  (Liu  &  Olsson),
Rectoguembelina  cretacea  Cushman,  Woodringina  clyton-
ensis  (Loeblich  &  Tappan),  W.  hornerstownensis  (Olsson),
Chiloguembelina  morsei  (Kline),  Ch.  midwayensis  (Cush-
man),  Globoconusa  daubjergensis  (Bronnimann),  Para-
subbotina  pseudobulloides  (Plummer),  Subbotina  trivalis
(Subbotina),  Globanomalina  archeocompressa  (Blow),  G.
planocompressa (Shutskaya), Eoglobigerina edita (Subboti-
na), E. eobulloides Morozova, E. simplicissima Blow, Prae-
murica  taurica  (Morozova),  P.  pseudoinconstans  (Blow),
Guembelitria  cretacea  Cushman.  Guembelitria  cretacea
Cushman is represented in the lower part, while Woodringi-
na  clytonensis  (Loeblich  &  Tappan),  and  Globoconusa
daubjergensis  (Bronnimann)  extend  into  the  middle  part  of
this  biozone.  The  faunal  similarities  suggest  that  the  com-
bined P1a Subzones of the studied sections could be equiva-
lent  to  the  lower  part  of  the  Morozovella  pseudobulloides
Zone  of  Bolli  (1966),  Caron  (1985),  P1a  Subzone  of  Blow
(1979); Elnady & Shahin (2001) from Egypt; Arenillas et al.
(2000)– Tunisia. The present subzones are correlatable with
P1a Subzones of Berggren & Miller (1988); Samir (2002) in
Egypt; the P1b of Keller (1988) and Keller et al. (1995) in Tu-
nisia;  the  P.  pseudobulloides  of  Obaidalla  (2005)  in  Egypt;
and  also  it  is  equivalent  to  the  P1a  of  Berggren  &  Norris
(1997), Berggren et al. (1995), Keller (2002, 2004), Abramov-
ich et al. (2002), Olsson (2000); and Smit (2005) in SE Spain.

The age of this interval, estimated on the basis of the mag-

netic polarity and datum events by Olsson et al. (2000) and

393

BIOSTRATIGRAPHY OF THE CRETACEOUS/TERTIARY BOUNDARY (KURDISTAN, NE IRAQ)

Keller (2002, 2004), implies the time span between 64.90 Ma,
marked by the last appearance of Parvularugoglobigerina eu-
gubina and 64.50 Ma, marked by the first appearance of Sub-
botina triloculinoides, considered the magnetochron ages,
providing a high rate of deposition (11.5 ky/m) in the Sirwan
section. The estimated age is Early Paleocene (Early Danian).

(P1b) Subbotina triloculinoides—Globanomalina com-

pressa/Praemurica inconstans

Interval Subzone: Defini-

tion:  Biostratigraphic  interval  between  the  FAD  of
Subbotina triloculinoides at the base and the FAD of Globa-
nomalina  compressa  and/or  Praemurica  inconstans  at  the
top. Remarks: Berggren et al. (1995) introduced this subzone
to  emend  the  P1b  (Subbotina  triloculinoides)  Subzone  of
Berggren  &  Miller  (1988).  In  the  studied  section  only  the
lower part of this subzone is studied. It attains a thickness of
15 meters in the Sirwan section. Faunal similarities suggest
that the combined P1b Subzones of the studied section could
be  equivalent  to  the  upper  part  of  the  Morozovella  pseudo-
bulloides  Zone  of  Bolli  (1966)  and  Blow  (1979);  to  Caron
(1985); Elnady & Shahin (2001), Samir (2002) from Egypt;
Arenillas et al. (2000) Tunisia; to the P1c of Keller (1988),
and  Keller  et  al.  (1995)  in  Tunisia;  to  the  S.  triloculinoides
by Obaidalla (2005) in Egypt; and also it is equivalent to the
P1b  of  Berggren  &  Norris  (1997),  Berggren  et  al.  (1995),

Keller (2002, 2004), Abramovich et al. (2002), Olsson (2000);
and Smit (2005) in SE Spain. The age estimation of this inter-
val depending on magnetic polarity and recorded datum
events by Olsson et al. (2000) and Keller (2002, 2004) with
the time span of 64.50 Ma from the first occurrence of Subbot-
ina triloculinoides, to the FAD of Globanomalina compressa
and/or Praemurica inconstans at the top of 63.00 Ma. The ab-
solute ages are estimated on the basis of magnetochron ages.
The estimated age is Early Paleocene (Early Danian).

Conclusions

The biostratigraphic study of the Cretaceous-Tertiary suc-

cession in the studied section from the Sirwan Valley in the
Sulaimani area of the Kurdistan region of northeastern Iraq,
led to the following conclusions:

1 – The detailed study has produced a good description

and high resolution lithological analysis of the well exposed
uppermost Upper Cretaceous and Lower Tertiary succes-
sions incorporated in the upper part of the Tanjero Formation
in the Sirwan Valley.

2 – On the basis of the geological range and relative

abundance of planktonic foraminiferal species, the studied

Fig. 10. a,b,c,d – Subbotina triloculinoides (Plummer); a –side
view;  b,  d – spiral  view;  c – umbilical  view;  Early  Paleocene,
Kolosh Formation, Dokan. Specimen from (P1b) Subbotina triloc-
ulinoides—Globanomalina  compressa/Praemurica  inconstans
Zone.  e,f,g,h,i,j –   Parvularugoglobigerina  eugubina  (Luter-
bacher  &  Premoli  Silva);  e,f   – spiral  view;  g,j – side  view;
h,i – umbilical  view;  Early  Paleocene,  Kolosh  Formation,
Smaquli. Specimen from (P

α) Parvularugoglobigerina eugubina

Zone.

394

SHARBAZHERI, GHAFOR and MUHAMMED

section  along  the  K/T  boundary  has  been  precisely  divided
into  a  number  of  biostratigraphic  zones,  based  on  the  new
zonal  scheme  derived  from  high  resolution  biostratigraphic
studies, which are generally adequate and commonly used in
low and middle latitudes. In addition to this, these biostrati-
graphic  zones  were  correlated  with  their  equivalents  in  and
outside  the  region  and  with  world  wide  standard  biostrati-
graphic zones with the aid of datum events, which show the
age  of  planktonic  foraminiferal  zones.  The  distinguished
biostratigraphic  zones  in  the  Sirwan  section  from  the  base
upwards are as follows:

C1 – Pseudotextularia intermedia Interval Zone (CF5)

(Tanjero Formation), (late Early Maastrichtian).

C2 – Racemiguembelina fructicosa Interval Zone (CF4)

(Tanjero Formation), (Late Maastrichtian).

C3 – Pseudoguembelina hariaensis Zone (CF3) (Tanjero

Formation), (Late Maastrichtian).

C4 – Pseudoguembelina palpebra Interval Zone (CF2)

(Tanjero Formation), (Late Maastrichtian).

C5 – Plummerita hantkeninoides Total Range Zone

(CF1) (Tanjero Formation), (Late Maastrichtian).

C6 – Guembelitria cretacea and Parvularugoglobigerina

eugubina Interval Zone (P0 & P

α), (Kolosh Formation), ear-

liest Paleocene (Danian).

C7 – Parvularugoglobigerina eugubina—Subbotina trilo-

culinoides Interval Zone (P1a), (Kolosh Formation), Early
Paleocene (Early Danian).

C8 – Subbotina triloculinoides—Praemurica inconstans

Interval Zone (P1b), (Kolosh Formation), Early Paleocene
(Danian).

Acknowledgments: Our sincere thanks go to the reviewers
Dr. Ercan Ozcan (Istanbul Technical University) and Dr Ali
Al-Juboury (Mosul University, Iraq) for their very useful
suggestions and corrections of the present paper.

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