Magnetic susceptibility as a versatile investigation tool in different ... outcrops, quarries, exploration wells. Sediments: lake and marine bottom sediments ...
Magnetic susceptibility as a versatile investigation tool in different geocontexts: from Palaeozoic rocks to Recent sediments. An overview of three case studies Sorin - Corneliu RĂDAN
and
Silviu RĂDAN
National Institute of ResearchNational Institute of ResearchDevelopment for Geology, Geophysics, Development for Marine Geology Geochemistry and Remote Sensing and Geo-ecology (GeoEcoMar), 23-25 D. Onciul St., RO-024053 (Geological Institute of Romania) 1 Caransebeş St., RO-012271 Bucharest, Romania Bucharest, Romania
III II II
II III
I
3 CASE-STUDIES
I
Poiana Rusca Mountains:
Time: between ca 380 Ma and Recent Space: from Southern Carpathians to Danube and Devonian from Dacian Basin to Danube Delta and Black Sea epimetamorphic schists Rocks (epimetamorphic, pyrometamorphic and sedimentary): outcrops, quarries, exploration wells II Sediments: lake and marine bottom sediments Dacian Basin: 23
Pliocene lignite-clay sequences; Pleistocene porcellanites and clinkers III
I III
45
II
45
Danube Delta Razelm-Sinoie Lagoonal Complex Black Sea: Recent (Modern) lake and marine sediments
23
FIRST CASE-STUDY: MAGNETIC SUSCEPTIBILITY OF THE DEVONIAN EPIMETAMORPHIC SCHISTS FROM THE IAZURI – VLADEASA AREA (POIANA RUSCA MOUNTAINS – SOUTHERN CARPATHIANS)
http://ro.wikipedia.org/ wiki/Mun%C8%9Bii_ Poiana_Rusc%C4%83
(Physical map of Romania, adapted from Jipa & Olariu, 2009)
-
1’ IV
F 73 F 74
F 54 F 56
I
F 76
F 60
8
2
6
9
3
7
10 11
0
F 75 F 61
F 58
5
4
III II
1
200 m
F 78 F 77
F 62
F 81
1
F 64
F 80
3
Iazuri v.
2 I’ II’
F 70
F 66
F 65 F 82
F 68
III’ IV’
F 85
F 83 F 84
F 86
F 88 F 89
3’
2’
GEOLOGICAL SKETCH OF THE STUDIED AREA, ALIGNEMENTS OF THE MAGNETIC SUSCEPTIBILITY PROFILES AND SECTIONS, LOCATION OF THE OUTCROPS FOR TAKING ORIENTED SAMPLES
1 – sericite-chlorite-quartz schist complex (Gh2; Upper Devonian); 2 – main horizon (tuffogenous) of the tuffogenous greenschist complex (Gh1; Middle Devonian); 3 - basal horizon (terrigenous) of the tuffogenous greenschist complex (Gh1; Middle Devonian); 1, 2, 3 – Ghelar Series; 4 – Govajdia Series (Lower Devonian); 5 – boundary lines of the metamorphic units; 6 – fault; 7 – syncline axis; 8 – exploration well; 9 – cross section location; 10 – longitudinal section location; 11 – outcrop for taking oriented samples. Note: Geological sketch and location of profiles, after Refec (1976).
The iron mineralization: disseminated ore (dominantly), stratiform and lenticular ore (subordinately), enclosed within tuffogenous greenschists (basic metatuffs and metatuffites) to a lesser extent, within the terrigenous metamorphic rocks. This points out the volcano-sedimentary origin of metamorphosed Fe-rich deposits. The prevailing ore minerals are the magnetite, hematite oligiste with subsidiary chalcopyrite, pyrite and ilmenite. -
1’ IV
F 73 F 74
F 54 F 56
I
F 76
F 60
8
6
9
3
7
10 11
0
F 75 F 61
F 58
5
2
4
III II
1
200 m
F 78 F 77
F 62
F 81
1
F 64
F 80
3
Iazuri v.
2 I’ II’
F 70
F 66
F 65 F 82
F 68
III’ IV’
F 85
F 83 F 84
F 86
F 88 F 89
3’
2’
the and, the and
MAGNETIC SUSCEPTIBILITY VERTICAL VARIATION IN THE “CROSS SECTION” 1 – 1’ SW
F75
F 61
F 62
NE
F 76
F 76
n = 1453
4π10-3 [SI] F75
n = 1182
4π10-3 [SI] F 61
n = 1345
4π10-3 [SI] F 62
n = 1463
0
4π10 [SI] -3
0 0
96
84 4π10-4 [SI] 0
72 4π10-4 [SI]
4π10 [SI] -4
1 – soil with elements of altered schists; 2 – altered zone; 3 – sericite-chlorite-quartz schist complex; 4 – basic metatuffites metatuffs (upper level, lower level); 5 – basic metatuffs metatuffites (middle level); 6 – schists with terrigenous character; 4, 5, 6 – tuffogenous greenschist complex (Gh1; Middle Devonian); 4, 5 – main horizon (tuffogenous); 6 – basal horizon (terrigenous); 7 – exploration well; 8 – petrographic facies limits; 9 – fault; 10 – magnetic susceptibility diagram; 11 – “Fe” variation diagram; 12 – “magnetic fraction” variation diagram. Note: Geology and the “Fe” and “magnetic fraction” diagrams, according to Refec, 1976.
108 4π10-4 [SI]
1
7
10
2
8
11
3
9
12
4
0
75 m
5 6
A
MAGNETIC SUSCEPTIBILITY VERTICAL VARIATION IN THE “CROSS SECTION” 1 – 1’
f (%)
f (%)
f (%) f (%)
Maximum k value : 560004π10-6 [SI]
F 76
n = 1453
k 4π10-3 [SI] F75
n = 1182
k F 61
F 62
n = 1345
k
4π10-3 [SI]
4π10-3 [SI]
n = 1463
k
4π10-3 [SI]
B
MAGNETIC SUSCEPTIBILITY VERTICAL VARIATION IN THE “CROSS SECTION” 2 – 2’ W
F 68
F 66
F F 82
E
F 83
0
0
0 0
k
844π10-4 [SI]
96
96 k 4π10-4 [SI]
k
4π10-4 [SI] 1
7
10
2
8
11
3
9
12
4 5 6
96 k -4 4π10 [SI] 0
75 m
1 – soil with elements of altered schists; 2 – altered zone; 3 – sericite-chlorite-quartz schist complex; 4 – basic metatuffites metatuffs (upper level, lower level); 5 – basic metatuffs metatuffites (middle level); 6 – schists with terrigenous character; 4, 5, 6 – tuffogenous greenschist complex (Gh1; Middle Devonian); 4, 5 – main horizon (tuffogenous); 6 – basal horizon (terrigenous); 7 – exploration well; 8 – petrographic facies limits; 9 – fault; 10 - magnetic susceptibility diagram; 11 – “Fe” variation diagram; 12 – “magnetic fraction” variation diagram. Note: Geology and the “Fe” and “magnetic fraction” diagrams, according to Refec, 1976.
-
1’ IV
F 73 F 74
F 54 F 56
I
F 76
F 60
8
2
6
9
3
7
10 11
0
F 75 F 61
F 58
5
4
III II
1
200 m
F 78 F 77
F 62
F 81
1
F 64
F 80
3
Iazuri v.
2 I’ II’
F 70
F 66
F 65 F 82
F 68
III’ IV’
F 85
F 83 F 84
F 86
F 88 F 89
3’
2’
VERTICAL SECTION RELATED TO THE MAGNETIC SUSCEPTIBILITY VARIATION ALONG TWO “LONGITUDINAL GEOLOGICAL SECTIONS” W 0
Intersection
100m
Intersection
SE/N
F 78
F 75
Maximum k value contour:
F 81
SE/N
ESE/NW Intersection
I – I’
100m
F 64 F 60
F 66
F 62
2 3 4
5
1
5
2 3 4
6
S/E
F 56
1
F 89
8
7
W
Intersection
F 58 F 54
tS3-3’
F 86
tS2-2’ & tS3-3’
tS1-1’
0
Intersection
Minimum k value 25004π10E-06 [SI] contour:
125004π10E-06 [SI] 100004π10E-06 [SI]
WSW
F 84
F 83
SW
S/NE
tS2-2’
tS1-1’
F 74
F 73
IV – IV’
ESE/NW
E/WNW
8
6 7
(Geological sections, according to Gheorghiu & Lefter, 1975)
F 68 F 70
VERTICAL SECTION RELATED TO THE MAGNETIC SUSCEPTIBILITY VARIATION ALONG A “LONGITUDINAL GEOLOGICAL SECTION” III –III’ SE/N Intersection
Intersection
S/NE
Intersection
tS 2-2’
tS 1-1’
F 80
F 77
tS 3-3’
F 85
F F 82
F 88
F 75
Maximum k value contour:
175004π10E-06 [SI]
1
5
2
6
3 4
7
8
0
100m
Minimum k value contour: 25004π10E-06 [SI]
(Geological sections, according to Gheorghiu & Lefter, 1975)
SW
Magnetic susceptibility map (hachure version) I ezuţi V.
Magnetic susceptibility map (hachure version)
a b 0
200 m
I ezuţi V.
a b c 0
d e f 200 m
Iazuri V. I azuri V.
Aredei V.
at the level of the sericite-chlorite-quartz schists (Upper Devonian) a – k values lower than 5004π10E-06 [SI]; b – (500 – 1000) 4π10E-06 [SI] average k values, based on all cores measured for each exploration well
Aredei V.
Magnetic susceptibility map (k contour version)
at the level of the tuffogenous greenschists b (Middle Devonian) 200 m a
I ezuţi V.
0
I azuri V.
Aredei V.
a – (500 – 1000) b – (1000 – 1500) c – (1500 – 2500) d – (2500 – 3500) e – (3500 – 4500) f – (4500 – 5500) 4π10E-06 [SI]
Magnetic susceptibility map at the LOWER level of the main tuffogenous horizon of the Gh1 complex (Middle Devonian)
0
200 m
Legend: a – exploration well;
b–k
contour; the values must be multiplied by 4π10E-3 [SI]
Magnetic susceptibility map at the MIDDLE level of the main tuffogenous horizon of the Gh1 complex (Middle Devonian)
0
200 m
Legend: a – exploration well;
b–k
contour; the values must be multiplied by 4π10E-3 [SI]
Magnetic susceptibility map at the UPPER level of the main tuffogenous horizon of the Gh1 complex (Middle Devonian)
0
200 m
Legend: a – exploration well;
b – k contour (the values must be multiplied by 4π10E-3 SI)
Magnetic susceptibility map for the WHOLE main tuffogenous horizon of the Gh1 complex (Middle Devonian)
0
200
Legend:
a – exploration well;
b – k contour; the values must be multiplied by 4π10E-3 [SI]
SUPPLY PALAEODIRECTIONS OF THE VOLCANOGENIC MATERIAL AND ASSOCIATED IRON MINERALS INFERRED FROM MAGNETIC SUSCEPTIBILITY DATA A - lower level CB
A D
D CA C
I ezuţi V.
A
0
D D
Iazuri V.
C
B
A
C D B
C
B B
Aredei V.
D
D A
200 m
of the main tuffogenous horizon of the Gh1 Complex (Middle Devonian); B - middle level ; C - upper level ; D - whole main
tuffogenous horizon Legend: a – exploration well; b – well-marked palaeodirections; c – weakmarked palaeodirections
( Z ) MAGNETIC MAP OF THE EASTERN ZONE OF THE IAZURI – POIANA RUSCA SYNCLINE
1600
Z (nT)
I 0
Iazuri v.
- 1000
3 2
1
1 – basal horizon (terrigenous) of the tuffogenous greenschist complex (TGSC) (Gh1- Middle Devonian) 2 – main horizon (tuffogenous) of the TGSC with magnetite (Gh1 Middle Devonian); 3 – sericite-chlorite-quartz schist complex (Gh2 - Upper Devonian);
Vladeasa Hill
0
I’
1
2
200 m
3
(Compilation after Cristescu, 1952, in Botezatu et al., 1976)
Legend: 1 – boundary line of the basic tuffogenous schist horizon with magnetite; 2 – syncline axis; 3 – profile location
MIDDLE level
UPPER level ( Z) MAGNETIC MAP I 0
Iazuri v.
0
200 m
Vladeasa Hill
0
P = 1.1553 F = 1.0932
I’
CB
LOWER level
A D
1
2
3
L = 1.0559 E = 1.0354
D CA C
I ezuţi V.
A
0
D D 0
200 m
WHOLE MAIN HORIZON 0
200 m
Iazuri V.
C
B
A
C D B
C
B B
D A
D
Aredei V.
SUPPLY PALAEODIRECTION MAP
The areal distribution patterns of the magnetic susceptibility allow the identification of several supply palaeodirections of the volcanogenic material and of the genetically associated iron minerals. The vectors are plotted on the maps from the high value to the lower value areas in the way of the lowermost gradients (corresponding to a gradual decrease of the volcanogenic supplies). The areal distribution patterns show a marked and constant tendency of diminuation of susceptibility values from the external to the inner part of the Iazuri-Vladeasa perisyncline area, controlled, of course, by the magnetic minerals contents.
The vectors obtained in this way are more or less superposed for all the magnetic susceptibility maps and form four main groups. The magnetic susceptibility maps show a continuous decrease of the magnetic susceptibility values from North to South and from East to West. These evidences suggest a continuity in time and space of the tuffogenous supplies, from submarine volcanoes located to the East and North-East of the iron-bearing area.
This suggests a simultaneous impoverishment of the mineralization, which is controlled by the scarcity of the tuffogenous material; This tendency is constant for the three productive horizons and for the whole main tuffogenous horizon; The augmented Fe contents seem to be determined by the proximity of some important submarine volcanoes (Mureşan, 1973); The existence of a submarine volcanic activity in the vicinity of the the Iazuri - Vlădeasa area, pointed out by petrographical methods (Mureşan, 1973), acquires a geophysical support, yielded by the magnetic susceptibility data.
II II
II III
I
THE SECOND CASE-STUDY: MAGNETIC PROPERTIES OF THE PLIOCENE COAL BEARING FORMATIONS FROM THE WESTERN DACIAN BASIN (WDB), SOUTHWESTERN ROMANIA STUDY AREA LOCATION Western Carpathians
Alps
R O M A N I A
Apuseni Mountains
R O M A N I A Southern Carpathians
Western Dacian Basin
Western Dacian Basin
DACIAN BASIN
STUDY AREA (Compilation after Jipa, 2006)
MAGNETIC ANOMALY PRODUCED BY A LAYER OF PORCELANITES, ACCOMPANYING A PLIOCENE COAL SEAM, FIRSTLY DETECTED IN THE WESTERN DACIAN BASIN (Rădan, S.C. 1969, in Roşca, Vl., Rădan, S.C., Rădan, S., 1973) ΔZa map (regional measuremnts)
Map of the maximum thickness of the coal bed “X” (Ticleanu & Andreescu, 1988) Matasari
Matasari
Matasari – Runcurel zone Motru – Jilt area ΔZ profiles (detailed measurements)
Matasari
Comparative ΔZ profiles: measured vs. theoretical
regional magnetic measurements detailed measurements
UPPER PLIOCENE LIGNITE– CLAY SEQUENCES: a fragment spanning over 2 Ma of geomagnetic field history retrieved and fixed in the magnetochronological coordinates of the geological time PORCELANITE-LIKE CLAYS
(occurred at the level of the coal seam XIII) PORCELANITES, CLNKERS
PORCELANITES Radan & Radan, 1998
(Van Vugt, 2000)
Porcelanite-like clays, porcelanites and clinkers occurred at the level of the coal seam X
(after Snel et al., 2006)
certain coals with availability for spontaneous ignition/autocombustion, present inside of the lignite-clay doublets post–depositional thermal perturbations
“new rocks” formed:
“baked clays”, sometimes “melted”/”fused” clays, hardened red clays and sands with brick-like appearance (PORCELANITES); slaggy or vitreous texture with marked vesicularity and dark colour (CLINKERS) (see the “Dictionary of geological terms”, Anchor Press, 1976);
PORCELANITES and CLINKERS immediate consequences: essential changes of the magnetic recording medium (m.r.m.) (a paleogeomagnetic framework modified in comparison with the initial context, i.e. prior to the intervention of the thermal perturbations).
Microsequences and oriented monolith-blocks (cut at 2 - 5 levels), taken out from the Pliocene lignite – clay sequences; The transition from the “old” /”initial state” of the m.r.m. (“fresh” clays – the main constituent elements) to a “subsequent”/ ”new state” (“thermally-affected” clays: porcelanite-like clays, porcelanites and clinkers)
A ROCK MAGNETIC ANOMALY PRODUCED BY A PORCELANITE-LIKE CLAY DETECTED IN THE SOUTH JILT LIGNITE QUARRY (WESTERN DACIC BASIN) JILT QUARRY XIII
JL 66
JL 66A,B
k
NRM
A B C
Q
237.3
NRM intensities and k,
JL 66A
B A
BA
67.6
PORCELANITE - LIKE CLAYS
H
232.5 1223.
H
L, F, P, E values higher than for the “original”/”fresh” clays)
H
baking temperature:
JL 66B
higher than 250-400°C, but lower than 800-850°C H (mA/m)
L XIII
JL 66 A B C
PORCELANITE - LIKE CLAYS
(x4π x10E-06) [SI]
F
P
E
q
V
F = 1.19 – 1.32 P = 1.20 – 1.33 q and V: undisturbed sediments JL 66C
CLAYS
F = 1.002 – 1.01 P = 1.002 – 1.01
JILT QUARRY XIII
JL66 JL65
JL 41 – JL 66
AMS
distribution of the k1,k2,k3 directions: typical for a primary depositional magnetic fabric (with a few slight deviations)
NRM
strongly dominant reversed polarities
JL 62 – JL 65
AMS
typical distribution of the k1,k2,k3 directions
NRM
JL 65
negative polarities only
JL 66A,B,C
AMS
some slight deviations of the k1,k2,k3 directions
NRM
positive and negative polarities
XII
JL66: pink clay (porcelanitelike clay)
the all clay samples collected between the coal beds XII-XIII (the pink clay included)
4 samples (clays) collected just below the monolith-block JL66
3 sub-samples A,B,C cut from the monolithblock JL66 (a pink clay)
LUPOAIA QUARRY AMS
T
f(%)
T
f(%)
T F P
T
L L
P
F
L F
f(%)
P
P' f(%) F
F
T
L F
f(%)
T
f(%)
L L F
P'
P
P
L F
f(%)
P
L F
f(%)
T
f(%)
F
P
P
T
P
P
L L
P' f(%) F P
F
f(%)
T L L
f(%)
T P
P P
f(%)
P' f(%) F P f(%)
T T
P' f(%)
L L F
“FRESH”/ORIGINAL CLAYS
AMS
L F
L L F
P'
f(%)
F
P
P f(%)
P
L F
LUPOAIA BOREHOLE 11 AMS
minimum susceptibility
JILT QUARRY L L L
F F
L
T
f(%) f(%)
P
P' f(%)
L F L
L L
P
f(%)
P
FF P P
P
f(%)
T
F F
T
AMS
L F T
P
P
(QUARRIES)
P
P'
f(%)
L
ROVINARI AREA
AMS F F P P
P'
L F
f(%) f(%)
P'
P L F
(Western Dacic Basin)
(Primary) depositional/sedimentary fabric: the minimum axes placed in a vertical or near vertical direction and the maximum and intermediate axes randomly oriented in a (quasi)horizontal plane;
maximum susceptibility intermediate susceptibility
AMS
MAGNETIC FABRIC OF THE COAL BEARING FORMATIONS
A strongly foliated (oblate) fabric; The deposition has taken place on a horizontal surface, in a quiet sedimentary environment (similar results: e.g. Krijgsman, 1996)
JILT QUARRY JL 27 – JL 31
JL 27 – JL 31 JL 67 – JL 69
JL 70 – JL 73
AMS
AMS
NRM
X
NRM
for a depositional/primary magnetic fabric NRM: reversed polarities JL67, JL68: clays JL 67 – JL 69 from coal interbeds JL69 – PORCELANITE-LYKE CLAY
NRM
AMS: some deviations of the k1, k2, k3 directions, provided by JL 69; a very low anisotropy degree (P=1.005-1.008); some isotropic specimens were measured
JL 69
IX
JL 31/1
JL 31/2
NRM: JL 69 - reversed polarities,
JL 69
Gy
Cl 700°C
H H Gy
Gy
(original/”fresh”; thermally unaffected)
AMS: typical characteristics
AMS
XI
JL69 JL68 JL67
CLAYS
Gy
Gy
P
with the declination deviated by 90°; JL67, JL68 – negative and positive polarities JL 70 – JL 73
PORCELANITES 500°C AMS: a slight deviation of the JL 31/3 JL 70 foliation plane related to the horizontal H H one and of the k3 axes related to the Cl P original stratification pole; 300°C NRM: normal polarities baking temperature: higher for JL 70 than for JL 69; lower than 750°C
Cl
PARALLEL ANALYSIS OF THE NRM AND AMS BEHAVIOUR DURING THE THERMAL DEMAGNETISATION PROCESS AMS
JL 62/5
NRM
AMS
JL 73/1
JL 70, JL 71, JL 72, JL 73
PORCELANITES
Laboratory-induced thermochemical reaction concerning a naturally thermally affected clay possible magnetite - produced on the expense of the hematite (identified by XRD in the porcelanite JL 70 ) - and subsequent (partial) oxidation, with k decreasing
JL 70/6
JL 27/4
JL 27, JL 31, JL 62
“FRESH”/ORIGINAL CLAYS
NRM
JL 72/5
JL 31/5
JILT QUARRY
(cf. Dekkers, 1988, Dekkers & Linssen, 1989, Tarling & Hrouda, 1993)
NRM
JL 70/3
JL 71/4
k
JL 73/1
AMS
JL 72/5 E
JL 70/6 JL 27/4 P V
JL 31/5 F
JL 62/5 q
L
Normal polarity of the Characteristic Remanent Magnetisation (ChRM)
JL 72/1
LUPOAIA LIGNITE QUARRY (Eastern area; porcelanite quarry) LP 210, LP211, LP213
NRM: normal polarity maximum intensity: 7050 mA/m MAGNETIC SUSCEPTIBILITY: maximum k value: 24554π10-6 [SI]
NRM
lower NRM intensity and k values (than for LP 211 and LP 213), but neoformation minerals are present H
PORCELANITES
Sample
NRM (mA/m)
k 4πx10-6 [SI]
LP 210
333.3
22.8
LP 211
4669.9
754.6
LP 210
H
H Cr
H Cr
LP 213 4659.7 1627.2 Baking temperature: higher than for the porcelanites collected in the southern Lupoaia quarry (LP 202-208), but lower than for the clinkers and porcelanites LP 200, LP 220, LP 240
CLAYS f(%)
f(%)
NRM
Q1 100%
PORCELANITE-LIKE CLAYS AND PORCELANITES f(%)
NRM
NRM
f(%)
(mA/m)
(mA/m)
LP 209
LP 67-69
(mA/m)
NRM 209
LP 210, LP211, LP213
X-XI
LP 202 - LP205
NRM
Reversed polarity
All the NRM intensity (In) values higher than the maximum In measured for clays, reaching 7209.8 mA/m NRM
X-XI
Normal polarity
69
68
67
f(%) f(%)
k
k x 4πx10E-06 [SI]
f(%)
k
f(%)
k k
x 4πx10E-06 [SI]
x 4πx10E-06 [SI] x 4πx10E-06 [SI]
Most k values between 10x4πx10E-06 – 20x4πx10E-06 [SI]
Frequent k values between 2004 10E-06 – 15004 10E-06 [SI], reaching 12812x4πx10E-06 [SI]
MAGNETIC PROFILES
LUPOAIA AREA (ROMANIA)
BH 7
NEW ZEALAND
ΔT
VII 490nT
500-800nT
BH 6 BH 6 VIII
600nT
V
BH 7
V
BH 7
I 500–1000nT
VI VI
1880nT
730nT
BH 6
IX
LP 200 LP 220 LP 240
BH 11
ΔT
800-1300nT
IX 1485nT
700nT
ΔT
1400nT
900nT
BH 6
III
1700nT 920nT
(Lindqvist et al., 1985)
USA II 500nT 500nT 150nT
IV 370nT “magnetic IV
1125nT
noise” drilling equipment
I
LP 201-LP 205
LP 210 – LP 213
(Hasbrouck & Hadsell, 1976)
THERMALLY NOT-DISTURBED M.R.M. (“original” m.r.m./“initial” state):
“original”/”fresh” clays (non-affected by heating) mineralogical support: clay minerals (illite, smectite, kaolinite, chlorite); non-clay minerals (angular quartz and quartzite grains, feldspars/ plagioclases, calcite, dolomite). rock magnetic signal: low amplitude initial magnetic susceptibility (kin): values between 10410E-06 - 20410E-06 [SI], rarely exceeding 75410E-06 [SI]; magnetic foliation (F) and anisotropy degree (P): most frequent values are between 1.03 – 1.05; magnetic fabric: (primary) depositional / sedimentary fabric; a strongly foliated (oblate) fabric; natural remanent magnetisation (NRM) intensity (In): low and very low intensity values, mostly lower than 1mA/m, rarely exceeding 30 mA/m; NRM directions for the samples taken at a similar level with that of the porcelanites (e.g. coal bed X): usually associated with a reversed polarity;
palaeomagnetic signal: DRM; geomagnetic field polarity record within Pliocene/Romanian, assigned to the Gilbert Chron, namely to the lower part of the C2Ar Subchron (ATNTS 2004; 4.187 – 3.596 Ma).
THERMALLY DISTURBED M.R.M. (“subsequent” state):
“baked clays”, sometimes “melted”/”fused” clays (porcelanites and clinkers, generated by natural spontaneous burning of lignite seams): mineralogical support: thermo-mineralogically affected rocks; modified mineral assemblages or even newly formed [hematite, cristobalite, trydimite, mullite, spinel, cordierite, magnetite (?)], correlated with the increasing temperature, in successive stages, from slight baking to more or less total fusion; rock magnetic signal: changed, considerably increased intensity initial magnetic susceptibility (kin): values between 200410E-06 - 1500410E-06 [SI], sometimes reaching 12800410E-06 [SI];
enhancement of several magnetic anisotropy parameters: e.g. F and P record values between 1.10 – 1.20, sometimes in the range 1.30 – 1.40; magnetic fabric: similar characteristics to the “original”/”fresh” clays; the features of the spatial distribution of the principal susceptibilities: generally preserved; remark consistent with Perarnau & Tarling (1985), concerning the thermal enhancement of magnetic fabric: “irrespective of the mineralogical models, it is clear that the observed fabric can only be a result of mimicking of fabrics that must already exist within the rocks”
natural remanent magnetisation (NRM):
intensity (In): high and very high In values, between 1–7 A/m, occasionally reaching 7.982 A/m; NRM direction: modified, usually, a normal polarity; palaeomagnetic signal: changed, mainly a TRM (normal polarity);
porcelanites situated in the vicinity of the “original”/”fresh” clays: the palaeofield polarity assigned to the Brunhes Chron (ATNTS2004; 0.781 – 0.00 Ma): the autocombustion process of the lignite seams that produced the porcelanites has taken place at a time within the Middle-Upper Pleistocene (supported also by some geological arguments). Some remarks: the ability of porcelanite deposits to produce significant magnetic anomalies, easily to be mapped with portable magnetometers; in Lupoaia quarry, amplitudes up to 1880 nT; the mapped magnetic anomalies show the changes that appeared within the magnetic recording medium represented by the “coal bearing formations”. the magnetic anomalies resulting from the baked clays associated with the burnt coal: of use in coal exploration and exploitation
III
III
THIRD CASE-STUDY: THE USE OF THE MAGNETIC SUSCEPTIBILITY AS AN INVESTIGATION TOOL IN AQUATIC SEDIMENTARY ENVIRONMENTS
Romania Black Sea Danu b e Delta
Romania
Danube River
STUDY AREAS
Danube Delta: Surface: 3510 km2 (in Romania)
Channels/canals: ~ 3500 km
Danube Delta Branches: Chilia (Kilia) Br. 120 km
Lakes: > 450
Razim - Sinoie Lagoonal Complex:
Sulina Br. 63.7 (92) km
Surface: 1015 km2 Main lakes: Razim (Razelm), Golovita, Zmeica, Sinoe Marginal lakes: Agighiol, Babadag, Ceamurlia, Istria, Nuntasi
Black Sea Littoral Zone: Main lakes: Tasaul, Techirghiol, Siutghiol, Mangalia
Northwestern Black Sea:
Sf. Gheorghe Br. 70 (109) km
Northwestern Black Sea
Area under the influence of Ukrainian rivers sediment discharge; Area under the influence of the Danube River sediment discharge; Western Black Sea shelf areas; Shelfbreak and uppermost continental slope zone; Deep sea fan area; Deep sea floor area (Panin et al., 1999)
Black Sea
Fluvial research vessel “Istros”
LOGISTICS, GEOMATERIALS AND METHODS
Grab sampler
Research vessels and sampling equipments Bottom sediment
Radar / GPS / Echosounder equipment
Fluvial vessel “Stuful” Box corer
Grab sampler
Bottom sediment
Gravitational corer
Gravitational corer
Magnetic susceptibility scale (k, MS) used for calibration of bottom sediments (Radan & Radan, Geo-Eco-Marina, 13, p. 61-74, 2007)
Danube Delta Depositional units Fluvial Delta Plain
2 4 1
3 5
1. Mesteru – Fortuna Depression 2. Matita – Merhei Depression 3. Gorgova – Uzlina Depression
Marine Delta Plain 4. Raducu – Raduculet Depression 5. Lumina – Rosu Depression
Meşteru Lake
Meşteru Lake
125
Lungu Lake 125
100 75
Lungu Lake
50 50 75
100
Tataru Lake
75
75
1980
100 125 150
1987
100
a)
Meşteru – Fortuna Depression Depresiunea Mesteru - Fortuna
1980 1980
b)
1987 1987
700 650 600 550 500 450 400 350 300 250 200 150 100 50 0
L. Me ste L. Me ru-V steruV L. Me steruV L. Me steruE
k map (1987 cruise)
L. Lu ngu-S L. Lu ngu-S L. Lu ngu-S
L. Lu ngu-N L. Lu ngu-N L. Lu ngu-N L. Lu ngu-N
k map (1980 cruise)
k (x10E-06) u.SI
(zona vestica)
1987 1980
k values for sediments sampled in the Lungu Lake (northern and c)southern zones) and Mesteru Lake (western and eastern zones) before (i.e., 1980) and after (i.e., 1987) the human intervention in the area (hydrotechnical works)
ce lu
L. Pu r
he Ve c C
No ua
C
C .Visina
ar as u
Ve ch e
.P ap ad ia C
filc ro
a
nng LLuu
Tu lc ea
Mit ch ina
os cin da Ra L.
No ua C Pa C .Dunarea Veche pa d ia
L. Lidinet
L
u cel Pur L .
Martin
L. Rotund
C.C rin jala
a as ire
L. C
C.Razboinita
ce lu
C
S C.
C.
T
Sulina Br.
L.T
C. Olgu ta
Br .
L.T
filc ro
a
u cel Pur L .
Martin C.
C. Olgu ta
L. Lidinet
Magnetic susceptibility of the sediments sampled in Sulina the Br.Lungu, Mesteru and Tataruc)lakes, in the 1980 – 2012 period. b)
Tu lc ea
a)
L. Ma na hu
. .LL.Resvertina . uuL Ma re a Chn g g e n l n i u h . LLu rag D L. Fortuna L. L uru r a t a Taat T
L. Vacaru
Mit ch ina
os cin da Ra L.
Br .
C .Visina
Durnoi L.
L. Vacarel
Sulina Br.
B
L. Lideanca
C. Olgu ta
L. Nisipos
L. Rotund
aN ou a
tea Girla Son
n rti La. n MMartiL. No ua
L. Lideanca L.
B L.
L. i nesti Ba cla ari M
Ve ch e
a as ire
.P ap ad ia
S C.
C .S onte
C. Stipoc
C.Razboinita
i L. etch inti Cut ab
C
L. Vacarel
C. Iacob
L. Pintilie Pintilie L.
oua
ar as u
L. Vacaru
C .Iacob
L. Hontu
aN
C .Visina
a Girla Sonte
L. Rotund
M3 i6la” C 36a n”a Cl a n
.P ap ad ia
ce lu
ara su
Lu ng u L. Pu r
he Ve c
M3 i6la” C 36a n”a Cl a na l
.P ap ad ia C
“M i“la
L. Nisipos
L. Lideanca L.
L. Vacarel
iL etch Cut . Babinti
oua
a)
C. S onte
C. Stipoc
L. Nisipos
C.C rin jala
L. Vacaru
aN
L. Lidinet
C. Mit ch ina
C.
Tu lce aB r.
hin inos c aa ad L.R
a Girla Sonte
C. C .Dunarea Veche Pa pa dia
L. Nisipos
hin inos ca
C.C rin jala
C. Mit c
L. i nesti Bacla a ri M
L.L. ruru tee est M Mes hn. C L. Beliii ilea h g Dra L.L. L. Fortuna aaruru t t a Ta
a ad L.R
No ua
L. Martin
C. S onte
C. Stipoc
C .Iac
29 00' 29 10'
Ve ch e
36 “M ila a filc ro L.T
a filc ro L.T
1980
L. Pintilie
L.L. ruru tee est M Mes hn. C L. Beliii lea i h g Dra L.L. c 4 ) rL.uuFortuna aar t t a TTa II
C.S
a as ire
b)
L. Hontu
L. i nesti Bacla a ri M
Cut
C Pa C .Dunarea Veche pa d ia
Sulina Br.
he
L.C
ce lu
T
L. Beliii
C
1980
L. Pintilie
i L. etch
L. Martin
2929 10'00'
hin ino c aa ad L.R
ta L. v a io rc are Co M
Tu lce aB r.
os cin
g Dra L4.L b ). aaru u t r a T at
C 23%
2929 10'00' C .Iacob
Tu lce aB r.
Br.
a filc ro L.T
Tu lce aB r.
s L. cino da Ra
a ad L.R
hn.
II hilea C
sa ea .Sir
L. Nisipos
s L. cino da Ra
69%
L. Pu r
lca rofi L.T
an
ara su
al
ru L. 23% M IIIeste 77%
a Girla Sonte
Ve c
8%
IV
aN ou a
M3 i6la” C 36a n”a Cl a na l
tchi Cute
Son te
aN ou a
C. Mit c
os cin
Tataru L. (1980) utetchi L.III C.
L. Beliii
C
L. Hontu
C
C
sa ea .Sir L.
II
a4)
b3)
Mesteru L. (1980)
III
L. Pintilie
.P ap ad ia
2006
L.
20%
lea ghi Dra . c 2 ) aruuL L. t r a T a ta
. Chn
.P ap ad ia
”C II
a ad L.R
No ua
III
II
M
> 1000 T Tu 675-1000 lce Sulina 575- 675 aB 275 - 575 r. 175- 275 c)75- 175 10 - 75 < 10 C .Iacob 1987-1997 c3) x 10-6 [ SI u.]
“M i“la
60%
Lu ng u
Lungu L. 15% (1980)
10%
III
Vd Vc Vb Va IV III II 29 I 00' k classes
Pa pa d ia
IV
57%
C
10%
20% a3)
50%
85%
Va
Va
”C
20%
Vb
Mesteru L. (1987)
36
10%
b2)
“M ila
Lungu L. (1987)
a2 )
13%
Son te
a Girla Sonte
L. esteru
hi
s L. cino da Ra
20%
37%
C.
C.Razboinita
lca rofi L.T
ce lu
II
II
a as ire
C. Mit c
L. Nisipos
s L. cino da Ra
33%
II
tchi Cute
etc Cut
L. Martin
L. Hontu
L. Hontu
al
a as ire L. C.S
III
27%
L. Beliii
aN ou a
C.S
b)
III
L.
43%
III
IV
. Chn
Tat Sulina Br.
1987-1997
L. Pintilie
ara su
13%
IV
29 00'
c1)
2006
Tataru L. (1993; 1995 - 1997)
Va
31%
19%
45%
L.C
Va
Mesteru L. (1987; 1992-1996)
L. esteru
lea ghi Dra L.L. aaru u t r a T
Son te
a Girla Sonte
c)
L. Pu r
a1)
Lungu L. (1987; 1993; 1995-1997) Vb 7%
a Br. Sul in b1)
an
k (x 10E-06) SI u.
B r.
II
Lu ng u
300
ea
ce lu
36 i la
C.
Tu lc
M
os cin
Tu lce aB r.
III
55%
Fortuna L.
L. Pu r
200
Durnoi
L.C ara su
100
III
Tataru L. (2006)
L.
.
Samples 0
L. Cutetchi
a ad L.R
“M ila
Mesteru - Fortuna Depression (western zone)
IV
226.34 122.8 78.22 107.06 113.90141.74 80.08
36
May 2012 Cruise Lungu L. (2006)
L.C
lca rofi L.T
L. Pu r
C)
an
7%
B)
al
C
tchi Cute
sa ea .Sir L.
L.
II
C.
L.C ar a su
L. Hontu
Pa pa d ia
I
“M i“la
93%
”C
A)
II III
1987-1997
L. Pintilie
L.C ara su
75%
56%
II 44% III IV
2006
No ua
19%
29 00'
Lacul Tataru (mai 2012) 2012) Tataru L. (May
L. C
6%
Mesteru L. (May Lacul Mesteru (mai 2012) 2012)
Pa pa d ia
Lacul Lungu (mai2012) 2012) Lungu L. (May
Dynamic environments :
Confined environments :
lakes located close of the main fluvial influx, with active change of water and sediment supply 29 00'
29 10'
1987 L. . Durnoi
L. stii lane Bac ari M
L. Lideanca L. Babi
na
L. Martin C.Olgut a
L.. Fortuna
taru Ta L..
C. .
Mil a3 6
29 30'
29 20'
1992 - 1999
L. Vacaru
pa dia .P a
L. Beliii
C
Pu rc L.
Lu L ng . u
C.Stipoc
Ve ch e
teru L. . Mes ilea ragh C. D
Son tea Noua
tea Girl a Son
29 30'
29 20'
1978 C .Vi sin a
hi utetc L. C elu
sa
29 30'
29 20'
C.Iacob
C.
ir ea C.S
lakes protected or located far from the main fluvial influx points (more or less stagnant sedimentation environments)
L. Lidinet
Br. Sulina
A)
Matita – Merhei Depression
1992 - 2006
29 30'
29 20'
29 30'
29 20'
2006 C.S u lim an
ca
L. Gorgova
L. ro ste ap Bogd
C)
Mesteru – Fortuna Depression 1979
Tre L. i Oz ere
L. Rotund
C.Sulim anca
Br .T ul ce a
L. Arginti u
MS fingerprints (in lake sediments): intermediate and high intensities (k classes III, IV, V)
C.Pardina Sf isL. tof ca
D)
L. Polu dion ca Sfi L. st of ca
L. Miazaz i
Du na rea
D
un
are
a
ch Ve
e
a)
Tre L. iO ze re
L. ro st e dap Bo g
L. Radacinos
L.La Amia za
L. Raducu
L.Cazanel
ch e
L.Lung
gu un L.L
L.cu Ciulini
L. Serbata
C.E r ac le
ra cl e
L. Radacinos
Ve
L. Matita
L. Babin a
ludio nc a L. Po Lu L.
D un area
Gorgova – Uzlina Depression
L.Lung
L. Radacinoasele
ngu
L. Miazaz i
iaza
B)
L.Merhei
L.cu Ciulini
C.E
Dyn. env.
L. Merhei u Mi c
dac inoas ele
L.Merhei
L. Radacinoasele
L. Matita
L. Babina
L. Merhei u Mi c
L. Uzlina
L.Rosca
C. Ra
L. Serbata
L. Raducu
L. ro ste gdap Bo
L.Cazanel
Ve ch e
C. Lop atn a
Conf. env.
Tre L. iO zere L.La Am
b)
L.Rosca
C. R a da cinoa sele
C. Lo pa tn a
a)
L. Uzlina
L. Isacova
C. Pardina
L. Arginti u
L. Isacova
un D
e ar
he ec aV
b)
MS fingerprints (in lake sediments): low and very low intensities (k classes I, II)
Magnetic susceptibility characterisation of the lake sediments sampled in dynamic (dyn. env.) and confined (conf. env.) deltaic environments. Note: The MS fingerprint intensities are shown by the average k values (based on all the samples which were measured for each lake), and the assigned colours are according to k scale (Radan & Radan, 2007).
O
a)
Lungu Lake Tătaru Lake
10
90 80
O
b)
Uzlina Lake Isacova Lake
10
90
20 80
20
30
70
30
70
40
60 50 40
50
60
30
70
60
70
30
40
50
20
70 80
20
90
10
80
60
30
80
90
50
40
20
M
40
60
50
C
10
90
10
M
90
80
60
70
Fig. 5.1. Litologia sedimentelor recente din Depresiunea Mesteru - Fortuna (Lacurile Lungu si Tataru - iulie 2006) .
c)
O
Puiu Lake Rosu Lake Rosulet Lake
M=Fractiune minerala detritica (cuart, silicati); C=Carbonati (autigeni); O=Material organic. 90 10 Lacul Lungu
80
20
40
50
30
20
O d)
Matita Lake 90
10
80
Lacul Tataru
Poludionca Lake 20
Merhei Lake 30
70 30
70
60 60
40
40
50 50
40
60
30
10
60
50
40
30
20
10
80
10
90
70
70
20
80
80
60
30
70
20
90
50
50
40
M
C
10
C
M
90
90
80
70
60
50
40
30
20
10
C
The lithology of the recent sediments sampled in 10 lakes from four main aquatic depressions in the Danube Delta. Legend (ternary diagrams): M – Detrital mineral fraction (quartz, silicates); C – Carbonates (authigenic); O – Organic matter.
Razim (Razelm) – Sinoie Lagoonal Complex 6. Razim Lake; 7. Golovita Lake; 8. Sinoie Lake; 9. Zmeica Lake.
6
Landsat image (1991)
7 9
8
Relative silt contents in the water systems
Magnetic susceptibility maps for two lakes from the lagoonal complex, sampled at both ends of a 30 year period. Note: The scales are not similarly calibrated by coloured intervals.
Lithological components of the sediments sampled in two lakes from the Razim (Razelm) – Sinoie Lagoonal Complex
Razelm – Sinoie Lagoonal Complex (1976 – 2008) lc L. Va
Razelm L. (2003)
ica
Razelm L. (1976)
Va
Va
IV
72%
4% 2%
22%
III
2%
75%
II
12% 11%
IV III II
C. Mustaca
C. Enisa la
a 1)
a 2)
Enisala
Va IV Salcioara
l 17% du in
r is or
Capul Iancina
III
Pe
16%
L. Golovita 1977 1% 20%
II
Gr Periteasca
L. Golovita 2002; 2004 2% 16%
Vb IV III II
Capul Dolosman Jurilovca
63%
Bisericuta
b1)
Ran ec du l Grin
Lunca
b2)
65%
L. Ceam urlia
L. Zmeica 1978 2%
L. Zmeica 2002; 2004 42%
Va III C.2
II
Periboina
Zmeica L. (2008) III
55%
III
II
II
47% Pricop
51%
III
L. Tuzla
43%
53%
c Ch itu
Bl ac k
II
d1 )
0
8
c2)
58% L. Sinoie 2004 4%
du l
IV
Grin d
Va
G rin
L. Sinoe 1977 2% 2%
ul S ace le
c1)
Se a
45% c3)
Sinoie L. (2008) 2% 2%
IV III II
Va IV III II
52% 44%
d2)
53%
43% d3)
16 km
Synoptic model showing the magnetic susceptibility characterization of the recent sediments of the Razim (Razelm) – Sinoie Lagoonal Complex four main lakes, related to three periods: 1976 - 1978 (left; a1, b1, c1, d1); 2002 - 2004 (middle; a2, b2, c2, d2); 2007 - 2008 (right; a3, b3, c3, d3).
k class II: an increasing trend (%) in the direction: Razim
Golovita
Sinoie
Zmeica
1976 – 1978 : R (4 %)
G (16%)
2002 – 2004 : R (2 %)
G (17%)
S (43%) S (44%)
2007 –2008 : R (3 %)
G (14%)
S (53%)
Z (51%) Z (58%) Z (55%)
k classes (IV+V): a decreasing trend (%), in the same direction: Razim
Golovita
Sinoie
Zmeica
1976 – 1978 : R (24 %)
G (21%)
S (4%)
Z (2%)
2002 – 2004 : R (23 %)
G (18%)
S (4%)
Z (0%)
2007 – 2008 : R (34 %)
G (27%)
S (4%)
Z (0%)
Sf. Gheorghe Branch
Model showing the water flowing direction in the Razim – Sinoie Lagoonal Complex (RSLC) :
R
G
S
Z
L. Ra ze
water flow direction in the RSLC: from North southwards
lm
L. Golovita Si n
oi e
a
meic L.
L. Z
Black Sea
water sources (related to the RSLC): from the Danube River (Sf. Gheorghe Branch), mainly through the Dunavat and Dranov Channels
Composite model showing the trends features of the magnetic susceptibility classes which characterize the bottom sediments of the four main lakes from the Razim – Sinoie Lagoonal Complex (based on the synoptic model previously presented). Note: in the lower part of the figure, the water flow direction within the lagoonal complex is indicated, in connection with the main water sources.
Goloviţa
Sinoie Lake (2008) 2% 2%
Va IV III II
b)
Channel 5 Zmeica 172.32 L a k e 29.62 220.47
87.84 105.56 84.40
Channel 2 27.58
43%
53%
32.91 80.79 114.84 46.52
Lupilor sand ridge
61.09
22.19 32.28 37.18
Sinoie 18.53
Lake
Lake
71.72 33.55 78.40 79.70 59.33 50.93 158.03
78.47
68.46 65.43 Săcele 80 44 86.64 Chituc 95 06 sand ridge 106.06 88 50 sand 90 93 94 84 83 55
ridge
a)
k classes
1000 675 1000 575 675 275 575 175 275 75 175 10 75 10 10E-06 SI
c)
72.43 94.54
89.48 78.50 81.89 77.80 41.72 45.33 60.67 44.98 100.7571.37 51.52 42 42 552.69 78.74 69.90 72.17 27 52
Vd Vc Vb Va IV III II I
Black
Sea
CLRS
Delta Dunarii
Lacul Sinoie Marea Neagra
d)
Magnetic susceptibility characterization and lithological classification of the sediments collected from the Sinoie Lake (August 2008). a) chart with the areal distribution of the k values, indicating also the MS classes to which the lake sediments were calibrated [marked by coloured cubes, according to the k scale reproduced in c)]; b) 3-D pie chart with the MS characterization of the bottom sediments [based on the k classes from c)]; c) MS scale; d) ternary diagram showing the lithological classification of the sampled recent sediments.
O 69.75
Goloviţa
Lake
88.69 125.10
148.72
123.34
24.91
17.58
M
C
d)
55.51
72.32
87.22
60.12
39.25
60.44
Zmeica Lake 34.84
26.64
25.51 86.37
90.03
95.62
Lupilor
105.31
sand ridge 109.75
c) 67.39
Sinoie
a)
Channel 2
Vd Vc Vb Va IV III II I k classes
1000 675 1000 575 675 275 575 175 275 75 175 10 75 10
10E-06 SI
Lake
b)
Magnetic susceptibility characterization and lithological classification of the sediments c) collected from the Zmeica Lake (August 2008). a) chart with the areal distribution of the k values, indicating, also, the MS classes to which the lake sediments were calibrated [marked by coloured cubes, according to the k scale reproduced in c)]; b) 3-D pie chart with the MS characterisation of the bottom sediments [based on the k classes from c)]; c) MS scale; d) ternary diagram showing the lithological classification of the sampled recent sediments. b)
BLACK SEA LITTORAL ZONE
Tasaul Lake
Siutghiol Lake
Techirghiol Lake
Mangalia Lake
I
490.97
422.72
444.85
II
10
III
10 75
IV
75 175
Va
Vb
175 275 575
575 675 675 1000
c)
58.59 467.85
467.10
39.39
156.09
Vc
Vd
k classes
1000
10-6 [SI]
Tasaul Lake
82.15 72.02 46.89
69.22
89.78 104.01
53.47
48.40 37.04 165.60
151.35
76.85
Taşaul Lake 145.56 57.36 214.47
65.05
40 30 0 0
460 4916000
60
MS map k (x 10E-06) SI
500 480 460 440 420 400 380 360 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0
4915000
80
80
4914000
120 80
Ada Isle
4913000
0 16
40 80 60
Taşaul Lake
4912000
100
4911000
60 80
4910000
k [100 10E-06 SI] 4909000 622000
623000
624000
625000
626000
627000
628000
629000
630000
631000
18.41
106.31
78.33 36.88
172.97
d)
a)
140.16 15.13
52.90 x10E-06 [SI]
Black Sea
a) 50.19
30.16
92.93 39.51
33.67
22.83 17.59 60.25 41.74 96.99 61.61
Black Sea
31.38 57.55 97.79
e) e)
b)
Composite magneto-lithological model for the Tasaul Lake recent sediments (sampled during the 2008 Fig. 13 GeoEcoMar cruise). a) chart showing the areal distribution of the k values, indicating, also, the MS classes to which the sediments were calibrated (marked by coloured cubes, according to the k scale); b) MS map with k contours; c) magnetic susceptibility scale ; d) magnetic susceptibility characterisation of the bottom sediments (based on the k classes); e) lithological composition of the recent sediments; f) ternary diagram showing the lithological classification of the recent sediments.
Black Sea Littoral Zone
Black Sea Littoral Zone
Tasaul Lake (2007)
Tasaul Lake (2007)
III
53
0%
IV
34
Va
2 11
25% 50% 75% 100% Magnetic susceptibility a) (k classes)
TOM
Lake sediment
Lake sediment
II
62,7
0%
25%
50%
CAR
SIL
4 33,3
75%
100%
Lithological components (average contents)
b)
Correlation coefficients (n = 47) k vs TOM
k vs CAR
k vs (TOM+CAR)
k vs SIL
- 0.5020
- 0.1649
- 06059
0.6059
c)
Magnetic susceptibility characterization and the lithological composition of the bottom sediments sampled from the Taşaul Lake (Black Sea Littoral Zone). a) 3D bar-chart showing the calibration of the recent sediments to the MS scale; b) 3D bar-chart indicating the contents of the lithological components (i.e., TOM, CAR and SIL) of the bottom sediments; TOM – Total Organic Matter; CAR – Carbonates; SIL – mineral/siliciclastic fraction; c) correlation between magnetic susceptibility and the lithological components.
Vd
Vc Vb Va IV III
1000 675 1000 403.44
61.29
275 575 175 275 75 175
I
10 75 10
k classes
10E-06 SI
II
42.37
575 675
31.84
35.81
46.36
17.21
109.81 43.01
27.55
391.57 46.83 83.73
120.63 571.94
c)
71.76
949.19 151.47 127.28
317.25
S i u t g h 61.98 i o l 52.48 L a k62.43 e
230.72 138.94 132.94
200 311.82
175.47 48.65 94.94 46.20
69.12 18.45
48.84
25.16
k [20010E-06] SI 65.10
5.70
b)
Dunarea
e)
Lacul Siutghiol
150.62
32.51
23.67
19.59
39.03
Black Sea
Marea 21.42 14.29
Neagra 18.56
17.58
d)
Siutghiol Lake (2008) -5.78
16.89 32.60
4% 2% 10% 62%
4%
23.11
f)
a)
18%
Vc Va IV III II I
d)
Composite magneto-lithological model for the Siutghiol Lake recent sediments (sampled during the 2008 GeoEcoMar cruise). a) chart showing the areal distribution of the k values, indicating, also, the MS classes to which the sediments were calibrated (marked by coloured cubes, according to the k scale); b) MS map with k contours; c) magnetic susceptibility scale ; d) magnetic susceptibility characterization of the bottom sediments (based on the k classes); e) lithological composition of the recent sediments; f) ternary diagram showing the lithological classification of the recent sediments.
The magneto-lithological models carried out for four main lakes from the Black Sea Littoral Zone (BSLZ) add up the huge data bank carried out for the aquatic ecosystems from the Danube Delta (DD) and Razim (Razelm) - Sinoie Lagoonal Complex (RSLC). By comparing the results presented in the paper with the data obtained for a series of case-/history studies developed for the DD and RSLC sedimentary environments, some new issues have arisen;
They are particularly connected with the different processes of sedimentation taking place in deltaic lakes (confined or dynamic environments), lagoons (e.g., Sinoie and Siutghiol) or limans (e.g., Tasaul, Techirghiol and Mangalia); As regards the latter, the process of filling up with sediments is controlled by the simultaneous and successive activity of several supplies of sedimentary material. The special geological context of the fluvio-marine liman Tasaul is a good example in this respect;
Moreover, mineralogical and geochemical data for the sediment samples collected from the littoral lakes are needed.
1995 Cruise, Leg 2 R/V “Prof. Vodyanitskiy”
1997 Cruise, Leg 2 R/V “Prof. Vodyanitskiy”
Danube Delta
Danube Delta
Black Sea
k 1.2 10E-06 – 448.110E-06 SI
Black Sea
k - 4.4 10E-06 – 438.310E-06 SI
Magnetic susceptibility maps for recent sediments sampled in the Northwestern Black Sea 1
B l a c k Danube Delta
2
3
4
5
6
S e a
7 8 9
Main sedimentary environments in the northwestern Black Sea area. 1, 2 – Area under the influence of the Ukrainian rivers (Dnieper and Dniester) sediment discharge. 3 – Danube delta front area; 4 – Danube prodelta area; 5 - 6 Western Black Sea shelf area (5 – area under the influence of the Danube originated sediment flux; 6 – sediment starved area); 7 – Shelfbreak and uppermost continental slope zone; 8 – Deep sea fan area; 9 – Deep sea floor area (according to Panin et al., 1999).
The magnetic susceptibility maps carried out for the sediments sampled in the marine area, namely in the Northwestern Black Sea, were correlated with the main sedimentary environments from the fluvial - marine interaction zone. As we have new MS data from the area, based on the cruise carried out in 2010, the comparative analysis of the results obtained in 1995/1997 and 2010 could give some useful information for the evaluation of the environmental status of this very interesting region, particularly related to the area under the influence of the Danube River sediment discharge, but placed in an extended context defined by the Danube River – Danube Delta – Western Black Sea geosystem.
Starting with Palaeozoic epimetamorphic schists, passing then to the Pliocene lignite – clay sequences and Pleistocene porcelanites, and ending with the Recent lake and marine sediments, we hope the overview of 3 case-studies has proved that the magnetic susceptibility is, indeed, a versatile investigation tool, in different geocontexts.
Poiana Rusca Mountains (I) http://ro.wikipedia.org/ wiki/Mun%C8%9Bii_ Poiana_Rusc%C4%83
Thank
Dacic Basin (II)
You ! Danube Delta and … (III)
