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Marine Geology 227

Geochemistry and sedimentology of shelf and upper slope sediments

of the south-central Black Sea

Muhammet Duman a,*, Sukriye Duman a, Timothy W. Lyons b, Mert AvcV a,

Erol Izdar c, Erkan Demirkurt a

a Institute of Marine Science and Technology, Dokuz Eylul University, Haydar Aliyev BulvarV, No. 10, InciraltV -Izmir, 35340, Turkeyb Department of Earth Sciences, University of California, Riverside, CA, USA

c Piri Reis Foundation for Maritime and Marine Resources, Research, Development and Education, PK 49 Izmir, 35210, Turkey

Received 11 May 2004; received in revised form 31 August 2005; accepted 22 November 2005

Abstract

Eighty-five surface samples from oxic, suboxic and anoxic sites of the south-central Black Sea shelf consist predominantly of

clayey silts and silty clays, reflecting the moderate-to-high energy, wave-dominated hydrological regime. Grain size data and net

sediment transport patterns suggest that the western part of this shelf is an area of east-directed active sediment transport. With the,

exception of localized nearshore zones, the eastern shelf is by contrast an area of major sediment deposition. The sediment transport

vectors are correlated with patterns of surface water circulation and storm-generated longshore currents.

The sources of the shelf sediments are indicated by the total concentrations of 30 major, minor and trace elements in 59 surface

samples. Factor analysis shows that 99.1% of the total variance can be explained by five factors. Factor 1 (As, Cu, Cr, Fe, Pb and

Zn) reflects anthropogenic pollution by the Etibank copper mine. Factor 2 (mainly total organic carbon and S) is linked to anoxia/

redox as saline conditions. Factor 3 (mainly Al, Si) represents aluminosilicates whereas Factor 4 (sand and silt abundance, total

carbonate, Ca and Sr) represents the carbonate component. Factor 5 (Fe, Mn, P, Cr, Ni and V) tracks primary detrital delivery with

strong overprints by redox-dependent, biogeochemical reactions within the anoxic sediments and the oxic/suboxic bottom waters.

The combined data suggest that the sediments on the south-central Black Sea shelf were largely derived from the North

Anatolian Mountains and supplied to the shoreline by a network of small rivers.

D 2005 Elsevier B.V. All rights reserved.

Keywords: Black Sea; shelf; sedimentology; geochemistry

1. Introduction

Along the northern and northwestern Black Sea, the

continental shelves are wide (40–120 km), reflecting a

large sedimentary influx through several major rivers,

including the Danube, Dniester, Dnieper, Don and Bug.

Shelves are notably narrower (5–40 km) in the western,

0025-3227/$ - see front matter D 2005 Elsevier B.V. All rights rese

doi:10.1016/j.margeo.2005.11.009

* Corresponding author.

E-mail addresses: muhammed.duman@deu.edu.tr (M. Duman),

timothy.lyons@ucr.edu (T.W. Lyons), e.izdar@pirireis.org.tr (E. Izdar)

.

rved.

southern and eastern portions of the basin, and only a few

small rivers drain into Black Sea from the south, such as

the KVzVlVrmak, YesilVrmak and Sakarya. The shelf-slope

break occurs between 110 and 150 m water depth, and

generally steep (5–98) slopes lead to the floor of the

Black Sea basin at N2200 m. The slope face is dissected

by numerous submarine canyons and gullies, locally

feeding large submarine fans along the slope apron

(Fig. 1).

Two major cyclonic and several mesoscale anticy-

clonic eddies control the surface water circulation in the

(2006) 51–65

Fig. 1. Location map showing the bathymetry of the Black Sea (from International Bathymetric Charts of the Mediterranean) and the Straits of

Bosphorus and Dardanelles. Isobaths are in metres. Inset is the study area, illustrated in Fig. 2.

M. Duman et al. / Marine Geology 227 (2006) 51–6552

Black Sea (Ozsoy and Unluata, 1997). The b75-km-

wide, counter-clockwise rotating peripheral bRim Cur-

rentQ separates the large basinal cyclonic gyres from the

anticyclonic coastal eddies. This current flows eastward

along the Anatolian coast with velocities of 20–40 cm

s�1 and dominates the surface circulation across the

narrow continental shelves (Ozsoy and Unluata, 1997).

Three distinct water masses occur in the Black Sea

basin: (1) the brackish (17.0–18.5x) Black Sea surface

water mass occupying the upper 50–150 m depth and

showing seasonal temperature variability, (2) the colder

(6.5–8.0 8C) and higher salinity (20.5–21.0x) interme-

diate water mass situated between 75 and 200 m depths,

and (3) the slightly warmer (N8.5 8C) and more saline

(N21.0x) Mediterranean water mass occupying basinal

depths below ~200 m (Ozsoy and Unluata, 1997). In the

study area, a permanent halocline, at 100–110 m water

depth, separates the oxygen-rich surface waters from the

oxygen-poor to anoxic-sulfide basinal waters. Thus, the

shelf region from the shoreline to the shelf-break is

situated beneath the oxygenated surface water mass. A

narrow shore-parallel transitional zone extends from the

100 m to ~200 m isobaths and is characterized by sub-

oxic bottom waters ([O2]b5 AM), whereas the upper

slope below the 200 m isobath is overlain by the anoxic

water mass.

Numerous studies have explored the depositional

history, paleoceanography and geochemistry of the

deep basinal sediments in the Black Sea (Calvert and

Karlin, 1991; Lyons, 1997; Wijsman et al., 2001,

Wilkin and Arthur, 2001). However, except for a

small number of localized studies (Lyons et al., 1993;

Anderson et al., 1994), surprisingly little is known

about the sedimentology of the shallow shelves along

the southern Black Sea, north of the Anatolian coast.

This paper presents the contemporary sedimentary pro-

cesses along the south-central Black Sea and delineates

the sources of these surficial sediments.

2. Material and methods

The sediment samples used in this study were collect-

ed using a grab sampler and the Research Vessel K. Piri

Reis of the Institute of Marine Science and Technology,

Izmir, during cruises in 1994–1996 (Fig. 2). This sam-

pler typically recovers sediments from the upper 10–15

cm of the sea bed and often preserves the stratigraphy

moderately well. At each station, the top of the grab

sampler was carefully opened and only the uppermost

5 cm of the sediment was removed into a plastic bag. Of

the 85 surface sediment samples collected, 13 samples

were recovered beneath anoxic bottom waters, 21 sam-

ples were retrieved beneath suboxic bottom waters,

while the remaining 51 samples were recovered beneath

oxic bottom waters. Four additional sediment samples

were collected from the bed of the Zarbana River, im-

mediately downstream from the Etibank copper mine.

All samples were stored in plastic bags in a freezer until

they were dried in the laboratory at 40 8C. The grain-sizedistribution was determined in 85 marine samples using

standard sieve and hydrometer techniques. Samples

were dried above 40 8C and finely ground in a mortar

Fig. 2. (A) Index map of the study area showing the bathymetry and small rivers draining the central North Anatolian Mountains. Isobaths are in

metres. (B) The locations of the surface sediment samples used in this study. S, .=samples with grain size, total organic carbon and total

carbonate and XRF data, .=samples with grain size, total organic carbon and total carbonate data only. Also shown is the geographical distribution

of the oxic, suboxic and anoxic bottom water masses (unpublished data, Institute of Marine Sciences and Technology).

M. Duman et al. / Marine Geology 227 (2006) 51–65 53

for determinations of carbonate and organic carbon con-

tents. Total organic carbon (TOC) was measured using a

modified Walkley-Black method (Gaudette et al., 1974),

which is based on the exothermic heating and oxidation

of organic matter with potassium dichromate and con-

centrated sulphuric acid, followed by back-titration with

ferrous ammonium sulphate using phenyl-amine as an

indicator. The carbonate content was determined using a

gasometric method, which is a modified dScheiblerTgasometer system (Muller, 1967). This method is based

on the volumetric determination of CO2 released by

acidification of the dry sample with 10% HCl solution.

The precision of the analytical methods, estimated using

standard and replicate samples, is F0.5% for total car-

bonate and F0.25% for total organic carbon.

Total sedimentary concentrations of Al, As, Ba, Ca,

Ce, Cl, Cr, Cu, Fe, Ga, K,Mg,Mn, Na, Nb, Ni, P, Pb, Rb,

S, Sc, Si, Sr, Th, Ti, U, V, Y, Zn and Zr were determined

in 59 samples using X-ray fluorescence (XRF) spectrom-

etry. For these analyses, sediments were dried and pow-

dered, and 4 g of powder was mixed with 0.7 g of

phenolic resin binder. After homogenization, pellets

were prepared in a press and baked for 15 min at

200 8C. The analyses were carried out at Memorial

University, Newfoundland, using an ARL 8420+ se-

quential wavelength-dispersive XRF spectrometer with

a Rh end-window X-ray tube and a LiF200 crystal

specially treated for enhanced heavy element sensitivity.

For energies N7.471 keV (20–508 2Q), a scintillation

detector was used with power settings at 75 kV and

M. Duman et al. / Marine Geology 227 (2006) 51–6554

40 mA. For energies b6.398 keV (50–1508 2Q), a flow-

proportional detector was used with power settings at

30 kV and 100 mA. Scan times were 4–6 s for the most

abundant elements, 20 s for the trace elements and 100 s

for Rb, Y and Nb. The intensities were then matrix

corrected using Compton correction for elements with

emission energies greater than Fe and using the La

Chance-Traill algorithm for elements with emission en-

ergies less than and including Fe.

Sediment transport vectors were determined using the

technique developed by Gao and Collins (1992), where

the grain-size trends within a grid of surface samples are

transformed into a residual pattern representing net sed-

iment transport pathways. Several methods using the

grain-size parameters of bottom sediments to establish

their transport directions have been employed over the

last three decades, including those of Gao and Collins

(1992), Chang et al. (2001) and LeRoux et al. (2002). All

Fig. 3. Top: Ternary diagram shows the grain size distribution in the south-

(.) Western shelf=offshore region between Cape Kerempe and Catalzeytin,

Ince. Bottom: Cumulative frequency curves of selected samples from the w

of these methods are based upon the same premise,

namely that sedimentary processes produce changes in

the grain-size parameters (size, sorting and skewness) in

the direction of transport, so that these trends have been

widely used to determine sediment dispersal patterns in

bays and shelf areas (Pedreros et al., 1996; Liu et al.,

2002; Duman et al., 2004).

3. Results

3.1. Grain size distribution

The grain size data, classified using the nomenclature

of Shepard (1954), show that the surface sediments in the

south-central Black Sea shelf and upper slope consist

predominantly of clayey silts and to a lesser extent silty

clays (Fig. 3). The cumulative frequency curves show

that these sediments are generally unimodal (Fig. 3). The

central Black Sea shelf. Sediment nomenclature after Shepard (1954).

and (o) eastern shelf=offshore region between Catalzeytin and Cape

estern and eastern shelf regions.

M. Duman et al. / Marine Geology 227 (2006) 51–65 55

sand content varies from 2% to 14%, and sand is largely

composed of terrigenous siliciclastic grains, but several

samples include varying quantities of mainly carbo-

nate biogenic remains of pelecypods, gastropods and

bivalves. The sand content is highest along the western

segment of the shelf between Cape Kerempe and the

town of Inebolu, but small isolated zones of high sand

content of N10% also occur on the eastern shelf (Fig. 4).

The shoreline along the Black Sea coast of northern

Turkey is composed mainly of coarse sand and gravel,

which quickly fines offshore to sands and silts, reflecting

the high-energy wave dominated nearshore zone. There

is a strong reciprocal relationship between the silt con-

tent and the water depth, with the highest silt abundance

of N70% occurring along the nearshore zone and grad-

ually decreasing seaward to b60%. Silt content is 40–

60% in the western shelf region but increases slightly to

60–72% toward the eastern shelf (Fig. 4). Because the

sand content is generally low, the silt and clay abun-

dances display a reciprocal relationship in the study area.

Clay content is lowest (b20%) along the nearshore zone

but gradually increases seaward, reaching 35–40% near

the shelf edge (Fig. 4). The average size varies between

6.0A and 8.5A on the south-central Black Sea shelf and

upper slope, with an average in the medium-fine silt

range at 7.0A. The surface sediments in the study area

are very poorly sorted, with r1 values ranging between

1.9 and 2.7. Sorting improves with increasing silt content

in the eastern shelf region but deteriorates with increas-

ing sand content in western shelf (Fig. 4).

Fig. 4. (Top) Relationships between sand and silt abundances, sorting (rdistribution maps of sand, silt and clay abundances and sorting (r1) in the

3.2. Chemical composition of sediments and elemental

associations

The geochemical data in this study consist of the

bulk sediment concentrations of 30 elements as well as

the TOC and total carbonate concentrations in 59

samples. Preliminary evaluation of these data suggests

that the surface sediments in the south-central Black

Sea shelf are probably derived from a number of

petrologically complex sources and that mixing of

distinct sources must have occurred during sediment

transport. Present-day redox conditions at and below

the seabed also appear to provide a significant chem-

ical signature. Therefore, this large and complex data

set does not allow an immediate and unambiguous

interpretation of the elemental associations and the

potential sources of sediments. Factor analysis is a

powerful statistical technique, which delineates simple

patterns distributed among complex data by evaluating

the structure of the variance–covariance matrix and

extracting a small number of hypothetical variables

(R-mode) or samples (Q-mode), referred to as

bfactorsQ (Klovan and Imbrie, 1971). The extracted

factors account for a percentage of the total variance

in the data set and represent the relationships among a

large number of interrelated variables (R-mode) and

samples (Q-mode).

Normalization of the elemental concentrations to

textural and/or mineralogical characteristics improves

the sensitivity in comparisons of elemental concentra-

1) and mean grain size and skewness (SK1) and (Bottom) regional

south-central Black Sea shelf surface sediments.

M. Duman et al. / Marine Geology 227 (2006) 51–6556

tions, providing a first-order account of elemental

enrichments in sediments. For example, the grain-size

dependence of heavy metal concentrations in sediments

is well documented where most heavy metals can be

absorbed by and/or preferentially adsorb onto the sur-

faces of clays, thus enriching the finer size fraction with

these elements. In order to eliminate elemental differ-

ences that are attributable entirely to variations in grain

size, the geochemical data of the surface samples have

been normalized to the weight percentage of clay in

these samples. The data are also normalized to alumi-

num, because the element/Al ratios minimize potential

spurious enrichments or depletions due to variations in

the aluminosilicate content (e.g. CaCO3 dilution) and

instead highlight only those elemental relationships

caused by environmental factors (e.g. anoxia, anthro-

pogenic input, etc.).

Fig. 5. Results of R-mode factor analysis, showing the elemental composit

variance in the south-central Black Sea data. Factor loadings greater than 0

Factors 1–5 are statistically significant, whereas the straight line created by

Both Q- and R-mode factor analyses were per-

formed on (i) the raw geochemical data and (ii) the

clay-normalized and Al-normalized geochemical data

from the south-central Black Sea shelf. The results for

both are very similar. The factor analysis results for the

raw data show that five factors account for a total of

99.1% of the total variance (Fig. 5). The remaining

0.9% of the variance cannot be explained by factor

analysis and is assumed to be random. Factor 1

accounts for 30.2% of the total variance and shows

very high factor loadings on As and statistically signif-

icant loadings (N0.3; Klovan and Imbrie, 1971) on Cu,

Fe, Mn, Pb and Zn. Factor 2 accounts for 23.6% of the

total variance and shows very high negative loadings

on total organic carbon and sulfur and statistically

significant negative loadings on Cl, Mg, Na and Rb.

This factor also shows statistically significant positive

ion of the four primary factors which account for 99.1% of the total

.3 are considered statistically significant (Klovan and Imbrie, 1971).

factors 6–32 is assumed to represent random variance (bottom right).

M. Duman et al. / Marine Geology 227 (2006) 51–65 57

loadings on Mn and U as redox sensitive elements

(Fig. 5). Factor 3 accounts for 21.9% of the total

variance and shows strong loadings on sand percentage

and Al and Si content and statistically significant load-

ings on Ga, K, Nb, Th, Ti, U, Y and Zr (Fig. 5). Factor

4 accounts for 14.5% of the total variance and shows

high factor loadings on sand and silt abundances, total

carbonate content, Ca, Ce and Sr and significant load-

ings on Ba and Sc (Fig. 5). Factor 5 accounts for 8.9%

of the total variance and shows very high factor

loadings on Fe, Mn and P and statistically significant

loadings on Cr, Ni and V (Fig. 5).

Fig. 6 shows the geographical distribution of the

normalized components of each factor. Factor 1

shows its highest loadings along the western nearshore

zone of the south-central Black Sea shelf, notably

decreasing toward the eastern shelf as well as the

shelf edge (Fig. 6). This distribution trend suggests

that sediments dominated by factor 1 are mainly sup-

plied locally from the small rivers and creeks entering

the Black Sea east of Cape Kerempe, particularly the

Fig. 6. Geographical distribution of the normalized varimax factor compon

variance. Also shown are the correlations between the five varimax factors

Zarbana River. The lowest loadings of factor 1 occur

along the upper slope region beneath anoxic and sulfi-

dic bottom waters. Factor 2 is the dominant factor in

upper slope sediments, seaward of the shelf edge

(Fig. 6). Factor 2 loadings are lowest along the shallow

oxic regions of the shelf but show a sharp increase at

the shelf edge, with highest loadings occurring in the

upper slope (Fig. 6). This geographic trend shows a

remarkable correlation (TOC and S enrichments) with

suboxic, transitional bottom waters between the fully

anoxic and fully oxic regimes. A small zone of high

loadings on factor 2 occurs immediately north of the

mouth of the Zarbana River. Factor 3 has its highest

loadings along the western shelf region, between Cape

Kerempe and Inebolu, and shows a distinct decreasing

trend eastward along the shelf, as well as northward

across the western shelf (Fig. 6). A large zone of

moderate to high loadings on factor 3 occurs between

Catalzeytin and Cape Ince. Factor 4 is generally low in

samples from the western shelf region and then shows

three isolated zones of relatively high loadings imme-

ents (Q-mode) of the five factors accounting for 99.1% of the total

(bottom right).

M. Duman et al. / Marine Geology 227 (2006) 51–6558

diately landward of the shelf edge toward the east (Fig.

6). Another zone of high loadings of factor 4 is found

along the nearshore zone between AyancVk and Cape

Ince (Fig. 6). Factor 5 exhibits its highest loadings

along the eastern shelf between Catalzeytin and Cape

Ince and shows a sharp decrease in its contribution both

westward along the shelf, as well as northward across the

shelf (Fig. 6).

The correlation coefficient matrix of the extracted

factors indicates that factor 1 has strong negative and

positive relationships with factors 2 and 3, respectfully,

but shows little relationship with factors 4 and 5

(Fig. 6). Factor 2 displays variable but strong relation-

ships with all factors. Factor 3 has strong correlation

with factor 1 but weak to moderate relationships with

factors 4 and 5 (Fig. 6). Factor 4 has a moderate

negative relationship with factor 2 but displays weak

to moderate inverse correlation with factor 3 and weak

positive correlations with factors 1 and 5. Factor 5

shows moderate positive and negative correlations

with factors 3 and 2, respectively, but exhibits weak

relationships with factors 1 and 4 (Fig. 6).

4. Discussion

4.1. Sedimentary processes

A recent study across the western Black Sea shelf

showed that thick (20–25 m) blanket of transgressive

sediments was deposited during the post-glacial sea-

level rise (Algan et al., 2002). There are no high-

resolution seismic reflection profiles from the south-

central Black Sea shelf, but a similar sedimentary

history can be envisioned, depositing a thin veneer of

transgressive sediments across the study area. There-

fore, the ages of the surface sediments in the study area

are critical for better understanding of sedimentary

processes and provenance.

Storm deposits on modern continental shelves range

in thickness from N100 cm along the coastal zone to 4–

10 mm in the middle shelf zone below the wave base

for major storms (the shelf mud zone of Johnson and

Baldwin, 1996). Within the transitional zone between

the wave base for major storms (i.e., 100 years) and the

wave base of average storms (i.e., annual), these depos-

its are typically 5–100 mm thick (e.g. Aigner and

Reineck, 1982). There are no direct age measurements

for the surface sediments from the south-central Black

Sea. However, age determinations using 137Cs and

excess 210Pb profiles in box cores from the southwest-

ern Black Sea shelf, north of the Bosphorus, as well as

in Sinop Bay, immediately east of Cape Ince, show that

the sedimentation rates along the southern Black Sea

shelves range from 55 to 110 cm/1000 years (Anderson

et al., 1994). These rates suggest that the samples used

in this study, which are from the upper ~5 cm, were

deposited during the last 45–90 years. These rates

equate to 6–11 cm of sedimentation during the last

100 years. This amount of sedimentation in 100 years

is less than or approximately equal to the depth to

which the storms with this recurrent interval are capable

of reworking. Therefore, the sedimentary succession in

the study area is likely to consist of storm-reworked and

storm-transported deposits, with an active layer or sur-

face veneer that undergoes erosion, transport and depo-

sition in response to the last major storm in the area.

These storm–sediment relationships strongly suggest

that, on longer time scales of N100 years, the shelf

sediments must be in equilibrium with the wave-dom-

inated shelf environment.

The transport vectors identified using the residual

grain-size trends are illustrated in Fig. 7. These results

show that the main sediment transport is largely east-

directed along the southern central Black Sea shelf,

with the strongest transport vectors occurring along

the narrowest western shelf region between Cape Ker-

empe and the town of Inebolu (Fig. 7). The transport

vectors across the shelf region east of Inebolu show a

notable decrease, although they still exhibit an east-

directed net transport. Except for the shelf edge,

where moderate southeast-directed transport vectors

occur, the shallower offshore regions between Inebolu

and Catalzeytin display very small transport vectors,

which are directed east or south-southeast. East of

Catalzeytin the transport vectors become stronger and

distinctly northeast-directed in the nearshore zone, par-

alleling the coastline, but remain relatively weak off-

shore. The shelf region between AyancVk and Cape Ince

is dominated by generally south-and southwest-direct-

ed, moderate to weak transport vectors (Fig. 7).

Comparison between the surface currents in the

Black Sea and the transport vectors calculated using

the residual grain-size trends shows some remarkable

similarities (Fig. 7). The eastern and western cyclonic

gyres of the Black Sea surface circulation system con-

verge along a line situated at ~34 8E longitude; thus,

the shelf and upper slope between Cape Kerempe and

Cape Ince are situated beneath the Peripheral Rim

Current of the western cyclonic gyre, immediately

west of this convergence. The eastern limb of the

western cyclonic gyre forms a narrow east-flowing jet

along the north Anatolian coast, attaining velocities of

50–75 cm s�1 along the shelf between Cape Kerempe

and Inebolu (Fig. 7; Ozsoy and Unluata, 1997). Strong

Fig. 7. (A) Net sediment transport patterns determined using residual grain-size trends in south-central Black Sea (discussed in text). (B) Surface

water circulation in the study area, showing the southeast segment of the Peripheral Rim Current and anticyclonic Sinop gyre (Ozsoy and

Unluata, 1997).

M. Duman et al. / Marine Geology 227 (2006) 51–65 59

transport vectors identified along the western shelf

between Cape Kerempe and Inebolu correlate well

with the eastern limb of the western cyclonic gyre

(Fig. 7). The predominant winds in the study area are

from the north and northwest, which generate strong

east-directed longshore currents along the southern

Black Sea shelf, particularly during winter storms.

Therefore, the east-directed oceanographic current, to-

gether with the similarly-directed storm-generated long-

shore currents, are probably responsible for the

winnowing of surface sediments along the western

shelf region, explaining the observed increase in sand

content. East of Inebolu, the Peripheral Rim Current is

deflected toward the east-northeast and flows along the

shelf edge with considerably weaker velocities (b40 cm

s�1). Along the shelf region east of Inebolu, the trans-

port vectors show a significant decrease, probably

reflecting the deflection of the Peripheral Rim Current,

as well as the noticeable widening of the shelf in this

region. The shelf region south of the 110 m isobath and

between Inebolu and Cape Ince is characterized by the

anticyclonic Sinop gyre (Fig. 7; Ozsoy and Unluata,

1997). Except for a narrow zone east and north of the

town of Catalzeytin, where the northeast-directed trans-

port vectors are moderately strong, the entire eastern

shelf is dominated by very weak transport vectors,

which are primarily south- and southeast-directed.

This trend resembles the geometry of the anticyclonic

Sinop gyre. Along the zone of convergence between the

eastern and western cyclonic gyres of the principal

M. Duman et al. / Marine Geology 227 (2006) 51–6560

Black Sea surface circulation, the surface currents flow

mainly toward the south. However, the samples ana-

lyzed for this study were recovered significantly

below the effect of this surface circulation, which

mainly dominate the upper ~50 m of the water column

(Ozsoy and Unluata, 1997). Thus, the transport vectors

are more likely indicative of water-mass movements

below the permanent chemocline at ~100–110 m. On

the other hand, the sediment can be transported in

suspension in the upper water column and deposited

below the zone of surface circulation. The overall grain

size data and the net sediment transport patterns suggest

that the western shelf region is an area of net east-

directed active sediment transport, whereas, except for

localized nearshore zones, the eastern shelf region is an

area of little sediment transport.

4.2. Sources of sediments

4.2.1. Factor 1: anthropogenic factor

The geographic distributions of the principal ele-

ments associated with Factor 1 (Fig. 8) are remarkably

similar in that the total sedimentary concentrations of

As, Cu, Fe, Pb and Zn and to a lesser extent Mn show

their highest concentrations in the western shelf region,

immediately north of the mouth of the Zarbana River,

and decrease eastward along the nearshore shelf (Fig.

8). Similarly, the total sedimentary sulfur shows a zone

of anomalously high concentrations in the same region.

Notable loadings of the chalcophile and siderophile

elements on factor 1 and their strong correlations with

one another, as well as with total sulfur (Table 1), are

interpreted to represent inputs via the weathering and

erosion of a proximal massive sulfide metal deposit.

The rocks along the central North Anatolian Mountains

immediately south of the study area contain large out-

crops of Cretaceous to lower Tertiary volcano-sedimen-

tary rocks, which include economically important

massive sulfide deposits.

Continuous copper mining has taken place from an-

cient Greek times to the present (Dincay et al., 1973). In

recent years the annual production of cupriferous pyrite

mounted to 200,000 tons at an average of 5% (Guner,

1980). The mine(s) are located 20 km south of the mouth

of the Zarbana River and discharges its waste waters into

the river. The mine tailings are also stored within the

drainage basin of the Zarbana River and contribute sig-

nificantly to the pollution carried by the river into the

Black Sea. Four samples collected from the bed of the

Zarbana River, immediately south of the Etibank Kure

mine, contain an average of 2197 ppm Cu, 999 ppm Zn,

275 ppm As, ~17.0% Fe (169824 ppm), ~18.6% S

(186149 ppm), 266 ppm Cr, and 111 ppm Pb, clearly

indicating that these sediments are notably contaminated

with respect to these elements. Therefore, factor 1 is

interpreted as an anthropogenic assemblage, with its

elemental enrichments tied to the effluent from a large

copper mine in the region. Eastward-decreasing trends in

the regional distribution maps of all these elements

reflect the effectiveness of loss through oxidation and

sediment transport associated with the east-directed sur-

face-water circulation, antysclonic Sinop gyre (Fig 7)

and storm-induced longshore currents.

4.2.2. Factor 2: anoxia factor

The regional distribution maps for the individual

constituents of factor 2 are illustrated in Fig. 8. The

distribution of TOC on the south-central Black Sea

shelf shows a distinct regional trend. The TOC values

are generally low across the shallow part of the shelf,

ranging between 0.5% and 0.9%. However, a near-

continuous shore-parallel zone of relatively high TOC

values (0.9–1.1%) occurs between the 40 m and 80 m

isobaths. The TOC values then show a progressive

seaward decrease toward the 100 m isobath, reaching

its lowest values of 0.5–0.6% narrow belt paralleling

the shelf edge. The TOC values subsequently show a

sharp seaward increase from 0.6–0.7% at the shelf edge

to N1.8% on the anoxic upper slope (Fig. 8).

The distribution of total sulfur in the study area shows

two distinct areas of higher values (Fig. 8). Sulfur con-

centrations are generally low (1000–2000 ppm) across

the shelf region between the shoreline and the present-

day shelf-edge but show a remarkable and sharp increase

seaward of the shelf break, exceeding 10,000 ppm in

samples from the upper slope (Fig. 8). An exception to

this trend is a narrow zone of high sulfur concentrations

(N8000 ppm) situated immediately seaward of the mouth

of the Zarbana River, which extends with decreasing S

values eastward along the shelf (Fig. 8). The sharp

increase in total sedimentary sulfur values across the

shelf edge is also documented elsewhere (Lein and Iva-

nov, 1991; Lyons, 1997) and correlates well with the

transition from oxic to anoxic-sulfidic bottom water

masses (Figs. 2, 8). The narrow zone of high sulfur

concentrations off the mouth of the Zarbana River clear-

ly indicates a notable influx of sulfur-bearing sediments

from this river (i.e. factor 1) as linked to the mines. The

massive ore bodies consist almost exclusively of sulfides

(90–100%) with only a minor gangue of quartz or, more

rarely, chlorite. The sulfide minerals chiefly comprise

pyrite. In addition, there are varying amounts of chalco-

pyrite, bornite, covellite, sphalerite, digenite, marcasite,

tennantite, carrollite, and traces of idaite and galena.

Fig. 8. Geographic distribution maps of the major constituents of Factor 1 (As, Cu); Factor 2 (total organic carbon=TOC, sulfur); Factor 3 (Al, Si);

Factor 4 (Ca,Sr) and Factor 5 (Fe, Mn) in the study area.

M. Duman et al. / Marine Geology 227 (2006) 51–65 61

The strong similarities between the regional distri-

bution maps of factor 2 (Fig. 6), total organic carbon

and sulfur (Fig. 8), as well as the anoxic bottom water

masses in the study area (Fig. 2), suggest that factor 2 is

related to organic matter and its associated elemental

enrichments under anoxic bottom water conditions.

Table 1

Correlation coefficient matrix of the inorganic geochemical data from the south-central Black Sea shelf

TOC Al As Ba Ca Ce Cl Cr Cu Fe Ga K Mg Mn Na Nb Ni P Pb Rb S Sc S Sr Th Ti U V Y Zn Zr

TOC 0.99 � 0.03 �0.14 0.13 �0.15 �0.21 0.33 0.22 �0.04 0.04 0.44 0.57 0.50 �0.11 0.25 0.37 0.28 �0.13 0.13 0.59 0.71 �0.13 � .03 �0.09 0.08 0.11 0.05 0.23 �0.07 0.10 �0.14

Al �0.03 0.99 0.11 �0.05 0.05 �0.19 0.04 0.53 �0.18 0.17 �0.20 0.07 0.41 0.18 0.42 0.16 0.45 �0.06 �0.38 �0.07 �0.08 0.07 .98 0.00 0.12 0.52 �0.13 0.19 0.33 �0.31 0.29

As �0.14 0.11 0.99 0.19 0.10 0.06 0.31 0.21 0.33 0.75 �0.04 �0.01 0.00 0.69 0.17 0.00 0.28 0.73 0.37 �0.14 �0.28 0.20 .11 0.20 �0.25 0.04 �0.09 0.37 0.12 0.44 �0.19

Ba 0.13 �0.05 0.19 0.99 0.47 0.20 0.56 0.26 �0.39 0.31 0.18 0.53 0.30 0.48 0.24 0.05 0.51 0.55 0.44 0.50 �0.01 0.09 � .05 0.56 �0.19 0.43 0.07 0.68 0.43 �0.15 �0.31

Ca �0.15 0.05 0.10 0.47 0.99 0.30 0.31 0.41 �0.22 0.17 �0.16 �0.08 0.26 0.46 0.10 �0.49 0.40 0.29 0.06 �0.10 �0.11 0.43 .05 0.91 �0.29 0.32 0.03 0.47 0.31 �0.25 �0.62

Ce �0.21 �0.19 0.06 0.20 0.30 0.99 �0.12 �0.08 �0.14 0.00 �0.23 �0.08 �0.09 0.10 �0.23 �0.09 0.01 0.20 0.13 �0.04 �0.22 0.09 � .19 0.34 �0.08 �0.01 �0.13 0.15 0.02 �0.13 �0.12

Cl 0.33 0.04 0.31 0.56 0.31 �0.12 0.99 0.40 �0.18 0.42 0.30 0.53 0.54 0.47 0.76 0.02 0.56 0.48 0.30 0.45 0.28 0.07 .04 0.40 �0.41 0.33 0.05 0.58 0.16 0.05 �0.45

Cr 0.22 0.53 0.21 0.26 0.41 �0.08 0.40 0.99 0.04 0.54 0.02 0.30 0.62 0.39 0.39 0.07 0.81 0.16 0.02 0.31 0.14 0.26 .53 0.36 �0.04 0.61 �0.06 0.62 0.37 0.08 �0.26

Cu �0.04 �0.18 0.33 �0.39 �0.22 �0.14 �0.18 0.04 0.99 0.44 �0.06 �0.31 �0.30 0.03 �0.20 �0.03 �0.22 �0.02 0.11 �0.31 0.13 0.08 � .18 �0.25 0.00 �0.34 �0.08 �0.12 �0.10 0.88 0.00

Fe 0.04 0.17 0.75 0.31 0.17 0.00 0.42 0.54 0.44 0.99 0.07 0.25 0.16 0.71 0.19 0.12 0.50 0.66 0.42 0.17 �0.06 0.28 .17 0.25 �0.18 0.34 �0.12 0.59 0.39 0.58 �0.19

Ga 0.44 �0.20 �0.04 0.18 �0.16 �0.23 0.30 0.02 �0.06 0.07 0.99 0.55 0.29 �0.09 0.12 0.34 0.11 0.02 0.25 0.60 0.29 0.03 � .20 �0.06 0.13 0.19 �0.02 0.06 �0.02 0.13 �0.01

K 0.57 0.07 �0.01 0.53 �0.08 �0.08 0.53 0.30 �0.31 0.25 0.55 0.99 0.58 0.08 0.36 0.49 0.49 0.17 0.29 0.88 0.38 �0.08 .07 0.12 0.00 0.59 �0.01 0.53 0.27 �0.04 �0.08

Mg 0.50 0.41 0.00 0.30 0.26 �0.09 0.54 0.62 �0.30 0.16 0.29 0.58 0.99 0.13 0.60 0.13 0.74 0.00 �0.04 0.52 0.54 0.17 .41 0.31 �0.12 0.49 �0.10 0.48 0.13 �0.22 �0.33

Mn �0.11 0.18 0.69 0.48 0.46 0.10 0.47 0.39 0.03 0.71 �0.09 0.08 0.13 0.99 0.27 �0.11 0.49 0.78 0.43 �0.03 �0.21 0.27 .18 0.53 �0.38 0.29 0.05 0.54 0.36 0.20 �0.35

Na 0.25 0.42 0.17 0.24 0.10 �0.23 0.76 0.39 �0.20 0.19 0.12 0.36 0.60 0.27 0.99 0.07 0.49 0.21 0.00 0.23 0.28 �0.04 .42 0.17 �0.32 0.32 0.05 0.40 0.07 �0.09 �0.17

Nb 0.37 0.16 0.00 0.05 �0.49 �0.09 0.02 0.07 �0.03 0.12 0.34 0.49 0.13 �0.11 0.07 0.99 0.06 �0.05 0.13 0.53 0.21 �0.28 .16 �0.42 0.33 0.31 0.03 �0.01 0.25 0.08 0.55

Ni 0.28 0.45 0.28 0.51 0.40 0.01 0.56 0.81 �0.22 0.50 0.11 0.49 0.74 0.49 0.49 0.06 0.99 0.32 0.11 0.47 0.16 0.21 .45 0.43 �0.11 0.58 �0.08 0.75 0.39 �0.07 �0.37

P �0.13 �0.06 0.73 0.55 0.29 0.20 0.48 0.16 �0.02 0.66 0.02 0.17 0.00 0.78 0.21 �0.05 0.32 0.99 0.60 0.07 �0.33 0.24 � .06 0.44 �0.38 0.18 0.07 0.52 0.20 0.24 �0.27

Pb 0.13 �0.38 0.37 0.44 0.06 0.13 0.30 0.02 0.11 0.42 0.25 0.29 �0.04 0.43 0.00 0.13 0.11 0.60 0.99 0.31 �0.01 �0.03 � .38 0.22 �0.17 0.01 0.19 0.34 0.11 0.42 �0.27

Rb 0.59 �0.07 �0.14 0.50 �0.10 �0.04 0.45 0.31 �0.31 0.17 0.60 0.88 0.52 �0.03 0.23 0.53 0.47 0.07 0.31 0.99 0.39 �0.12 � .07 0.01 0.11 0.46 0.05 0.44 0.28 �0.04 �0.02

S 0.71 �0.08 �0.28 �0.01 �0.11 �0.22 0.28 0.14 0.13 �0.06 0.29 0.38 0.54 �0.21 0.28 0.21 0.16 �0.33 �0.01 0.39 0.99 �0.09 � .08 �0.12 0.00 �0.06 �0.05 0.03 �0.12 0.14 �0.17

Sc �0.13 0.07 0.20 0.09 0.43 0.09 0.07 0.26 0.08 0.28 0.03 �0.08 0.17 0.27 �0.04 �0.28 0.21 0.24 �0.03 �0.12 �0.09 0.99 .07 0.40 �0.08 0.21 �0.13 0.26 0.00 0.10 �0.24

Si �0.03 0.98 0.11 �0.05 0.05 �0.19 0.04 0.53 �0.18 0.17 �0.20 0.07 0.41 0.18 0.42 0.16 0.45 �0.06 �0.38 �0.07 �0.08 0.07 .99 0.00 0.12 0.52 �0.13 0.19 0.33 �0.31 0.29

Sr �0.09 0.00 0.20 0.56 0.91 0.34 0.40 0.36 �0.25 0.25 �0.06 0.12 0.31 0.53 0.17 �0.42 0.43 0.44 0.22 0.01 �0.12 0.40 .00 0.99 �0.35 0.41 0.00 0.58 0.27 �0.17 �0.67

Th 0.08 0.12 �0.25 �0.19 �0.29 �0.08 �0.41 �0.04 0.00 �0.18 0.13 0.00 �0.12 �0.38 �0.32 0.33 �0.11 �0.38 �0.17 0.11 0.00 �0.08 .12 �0.35 0.99 0.07 0.02 �0.30 0.10 �0.07 0.47

Ti 0.11 0.52 0.04 0.43 0.32 �0.01 0.33 0.61 �0.34 0.34 0.19 0.59 0.49 0.29 0.32 0.31 0.58 0.18 0.01 0.46 �0.06 0.21 .52 0.41 0.07 0.99 0.02 0.55 0.58 �0.25 0.05

U 0.05 �0.13 �0.09 0.07 0.03 �0.13 0.05 �0.06 �0.08 �0.12 �0.02 �0.01 �0.10 0.05 0.05 0.03 �0.08 0.07 0.19 0.05 �0.05 �0.13 � .13 0.00 0.02 0.02 0.99 �0.06 0.25 �0.03 0.07

V 0.23 0.19 0.37 0.68 0.47 0.15 0.58 0.62 �0.12 0.59 0.06 0.53 0.48 0.54 0.40 �0.01 0.75 0.52 0.34 0.44 0.03 0.26 .19 0.58 �0.30 0.55 �0.06 0.99 0.36 0.10 �0.46

Y �0.07 0.33 0.12 0.43 0.31 0.02 0.16 0.37 �0.10 0.39 �0.02 0.27 0.13 0.36 0.07 0.25 0.39 0.20 0.11 0.28 �0.12 0.00 .33 0.27 0.10 0.58 0.25 0.36 0.99 �0.06 0.18

Zn 0.10 �0.31 0.44 �0.15 �0.25 �0.13 0.05 0.08 0.88 0.58 0.13 �0.04 �0.22 0.20 �0.09 0.08 �0.07 0.24 0.42 �0.04 0.14 0.10 � .31 �0.17 �0.07 �0.25 �0.03 0.10 �0.06 0.99 �0.12

Zr �0.14 0.29 �0.19 �0.31 �0.62 �0.12 �0.45 �0.26 0.00 �0.19 �0.01 �0.08 �0.33 �0.35 �0.17 0.55 �0.37 �0.27 �0.27 �0.02 �0.17 �0.24 .29 �0.67 0.47 0.05 0.07 �0.46 0.18 �0.12 0.99

M.Dumanet

al./Marin

eGeology227(2006)51–65

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M. Duman et al. / Marine Geology 227 (2006) 51–65 63

Weaker negative loadings of Al, Si, K, Nb and Yon this

factor suggest that factor 2 inversely tracks aluminosil-

icate abundances as a consequence of clastic dilution

under high rates of deposition.

A strong positive correlation between organic C and

pyrite S has been recognized for a wide variety of

normal (oxically deposited) marine deposits because

pyrite formation in these settings is often limited by

the availability of reactive organic matter. Although

pyrite formation within euxinic environments, which

are characterized by anoxic and sulfidic bottom waters,

is typically limited by the availability of reactive iron

phases, there is a general relationship of high total

organic carbon occurring with high pyrite sulfur within

the deep-basin sediments of the Black Sea (e.g. Calvert

and Karlin, 1991; Lyons, 1997). Bacterial sulphate

reduction, which is fueled by labile organic matter

and concomitant pyrite formation, is believed to be

the primary mechanism by which sulfur is incorporated

into these sediments (e.g. Lyons, 1997). Underlying the

oxygenated surface waters in the Black Sea water col-

umn, bacteria reduce sulphate ions to form dissolved

sulfide species, which build up to concentrations of

~400 AM in the deep bottom waters.

Provided ample reactive organic matter is present,

bacterial sulfate reduction also occurs within pore

water, beneath both oxic and anoxic bottom waters.

Additional sulphate ions diffuse into the sediment

from the overlying seawater, adding to the accumula-

tion of hydrogen sulphide in the sediments. This sulfide

generally reacts with iron-bearing minerals in the sedi-

ments or the water column to form a variety of iron

sulphide minerals, which are eventually converted to

pyrite with time.

Formation of pyrite within the euxinic Black Sea

water column yields pronounced Fe and S enrichments

in the central basin relative to the detrital fluxes from

the basin margin (Wijsman et al., 2001). On the anoxic

basin margin, however, these enrichments and those of

other redox sensitive elements can be swamped by

rapid rates of siliciclastic sedimentation. As a result,

redox sensitive elements, such as Mn and U are not

noticeable components of factor 2, although S contents

remain high relative to the proximal oxic shelf (com-

pare Lyons et al., 1993 and Lyons, 1997).

Comparison between the TOC values and the re-

gional distribution of the bottom water masses shows a

strong positive correlation between increasing TOC and

decreasing dissolved oxygen in bottom waters. Al-

though the deep, central Black Sea is not a site of

anomalous organic C preservation (Arthur et al.,

1994), concentrations do still average in excess of 5

wt.% (Calvert and Karlin, 1991), compared to values 1–

2 wt.% on the oxic shelf (Lyons et al., 1993). On the

anoxic basin margin, however, siliciclastic dilution

yields concentrations averaging ~2 wt.% despite or-

ganic C accumulation rates that are 17 times greater

than those in the central basin (Sageman and Lyons,

2004). This relationship suggests that the first-order

TOC variations in the study area must be controlled

by the interplay between net primary productivity in

the water column and the relative oxidation of the

organic matter under fully oxygenated versus anoxic

bottom water conditions. Concentrations of TOC are

also obviously controlled by clastic dilution and the

extent of organic C preservation as coupled to bulk

sedimentation rate.

The TOC values observed in the study area are

comparable with those reported from the southern

Black Sea but are notably higher than those found

in the Aegean and Eastern Mediterranean. This differ-

ence probably reflects the comparatively high rate of

primary productivity in the Black Sea, which exceeds

250 g C per m2 year�1 (Lein and Ivanov, 1991).

Collectively, the controls outlined above result in

strong factor 2 (organic C and pyrite S) loading in

the study area under anoxic conditions relative to the

oxic shelf, while high siliciclastic sedimentation (dilu-

tion) mutes the metal enrichments that might other-

wise also be expressed in the euxinic basin-margin

setting.

4.2.3. Factor 3: aluminosilicate factor

The distribution maps of the major elemental con-

stituents of factor 3 (Al, Si) show that the highest

concentrations of these elements occur along the nar-

row western shelf region between Cape Kerempe and

Inebolu. Secondary, but more restricted zones of mod-

erate to high concentrations are also identified across

the central shelf region seaward of Catalzeytin and

AyancVk (Fig. 8) coincide with Sinop gyre (Fig. 7). In

these maps, there is a clear eastward decreasing trend.

The strong correlations between Al, Si, Ga, K, Nb and

Y (Table 1) suggest that this factor represents the most

common constituents of the marine siliciclastic sedi-

ments, the aluminosilicates.

The distribution map of factor 3 (Fig. 6) shows

positive correlations with the patterns of sorting (Fig.

4), where highest factor loadings occur along the nar-

row western shelf region between Cape Kerempe and

Inebolu, which also corresponds with the strongest

sediment transport vectors (Fig. 7). The high degree

of correlation between factor 3, as well as the distinct

inverse relationship of this factor with factor 2 (Fig. 6)

M. Duman et al. / Marine Geology 227 (2006) 51–6564

and its constituents, further suggest that siliciclastics

dilute the factor 2 components.

4.2.4. Factor 4: carbonate factor

The distribution map of factor 4 is largely patchy,

with highest values mainly concentrated along the east-

ern shelf (Fig. 6). A zone of high concentrations of

factor 4 components (total carbonate, Ca, Sr) occurs

along the shoreline between Cape Ince and Catalzeytin

(Fig. 8). The high degree of correlation between Ca and

Sr (r =0.91; Table 1), sand abundance and total carbon-

ate (r=0.67) suggest that most of the carbonate is

stored in the sand fraction. The absence of major car-

bonate-bearing successions along the North Anatolian

Mountains immediately south of the study area and the

visual identifications of pelecypods and gastropods in

samples where factor 4 exhibits its highest loadings

indicate that this factor mainly represents biogenic

carbonate. Moderate local reciprocal relationships ob-

served between factor 4 and the other 3 factors are

interpreted as the dilution of the siliciclastic shelf sedi-

ments by locally abundant calcareous benthic organ-

isms and coccoliths.

4.2.5. Factor 5: iron-manganese factor

The high degree of correlation between Mn, Fe and

P, and to a lesser extent Cr, Ni and V, in factor 5 (Table

1) is interpreted to result from iron-manganese enrich-

ments. Regional distribution maps of the elemental

constituents of factor 5 show notable similarities, with

highest concentrations of these elements occurring

along the eastern segment of the study area between

Catalzeytin and AyancVk (Fig. 8). Comparison between

these maps and the bottom water masses (Fig. 2) clearly

shows that the highest factor loadings occur beneath

oxidizing bottom waters.

The composition of ferromanganese nodules and

micro nodules considerably differs in similar sedimen-

tation conditions (e.g., at the same station). As the

micro nodules grow in the high bioproductivity regions

of the ocean, their composition gradually approaches

that of macro nodules and the reactive part of associ-

ated sediments, reflecting an increasing influence of

early diagenetic processes. The finest micro nodule

fractions are most affected by diagenesis in the low

productivity regions. The composition of micro nodules

approaches that of the hydrogenetic macro nodules with

an increase of their size. As the micro nodules grow

and, consequently, their surface area increases, the

composition of Fe–Mn oxyhydroxides changes due to

an increasing role of diagenesis or hydrogenetic partic-

ulate flux after the segregation of micro nodules from

the sediment. Evolution of the micro nodule composi-

tion and nodule type depend on the productivity of

surface waters, i.e., the amount of organic matter de-

livered to sediments after its oxidation in the water

column (Dubinin, 2004).

Lyons et al. (1993) described pronounced Mn and

Fe enrichments in oxic sediments as a consequence of

past shoaling of the chemocline, but this is also

expressed in high sulfur contents. There is no rela-

tionship between factor 5 and S abundance. The or-

ganic-poor, suboxic pore waters of the oxic shelf show

signs of subsurface Fe and Mn reduction with the

possibility of enrichments in the surface-most sedi-

ment layers beneath oxic bottom waters (Lyons et

al., 1993). Concerning the relationship between Mn,

Fe and P, we can suggest that P may occur as com-

ponent of organic and terrigenous materials, adsorbate

onto Fe oxides.

5. Conclusions

The surface sediments of the south-central Black

Sea shelf and upper slope are composed of clayey

silts and silty clays. The net transport vectors identi-

fied using residual grain-size trends show that the

main sediment transport is largely eastward along

the southern central Black Sea shelf, with the stron-

gest transport vectors occurring along the narrowest

western shelf region between Cape Kerempe and the

town of Inebolu. These data suggest that the western

portion of the shelf is a region of active sediment

transport.

Factor analysis shows that five factors account for

99.1% of the total variance. Factor 1 has statistically

significant loadings in As, Cu, Fe, Mn, Pb and Zn and

represents anthropogenic contamination of the western

shelf region by mine copper mine discharge. Factor 2

shows loadings in total organic carbon, sulphur and

represents marine sediments deposited under anoxic

bottom water conditions. Factor 3 shows loadings in

Al, Si, Ga, K, Nb, Th, Ti, U, Y and Zr characteristic of

an aluminosilicate-dominated assemblage. Along the

western shelf region, this factor represents a coarser-

grained suite, which is winnowed under strong east-

directed oceanic and longshore currents. Factor 4 shows

loadings in sand and silt abundances, total carbonate,

Ca, and Sr and represents carbonate component. Factor

5 has loadings in Fe, Mn, P, Cr, Ni and V. It is

dominated by Fe, Mn oxyhydroxides accumulating

beneath oxic bottom waters, with the possibility of

metal remobilization and surficial enrichments under

suboxic pore water conditions.

M. Duman et al. / Marine Geology 227 (2006) 51–65 65

Acknowledgments

We thank Prof. Dr. Orhan Uslu, the former Director

of the Institute of Marine Sciences and Technology, for

his continued support and encouragement. We ac-

knowledge research funds from (a) the Scientific and

Technical Research Council of Turkey (TUBITAK)

through the Black Sea Monitoring Projects (Hydro-

Black, ComsBlack 91–93) and (b) the Dokuz Eylul

University Grant No. AIK 0921-94-02-02 to Muham-

met Duman. We thank the officers and crew of the RV

K. Piri Reis for their assistance in data acquisition

during the cruises in 1994–1996. We extend our special

thanks to Ali Aksu of the Department of Earth

Sciences, Memorial University of Newfoundland for

his support in the XRF analyses. The manuscript has

benefited from the insightful and constructive reviews

of Gert J. De Lange, Jack Middelburg and one anony-

mous reader.

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