The Buried Wansleben Salt Lake Chernozem in Central Germany: Age, Development and Properties

INTRODUCTION

Former Wansleben Salt Lake is located in Central Germany, 20 km west of Halle/Saale, in the middle of a vast loess area (Fig.1). The length of the lake was 6 km, its maximum width 2 km, its total area nearly 9 km2 and its mean depth 7 m (Seyfert, 1919). Because occasional floodings in nearby copper mines were supposedly connected with the lake's existence, the lake was reclaimed in 1896. Since then the lake's bed has been used agriculturally.


Figure 1: Map of the soil regions in Germany (according to Federal Bureau of Geosciences and Natural Resources) and the location of Wansleben Salt Lake

The origin of the lake, as well as its elevated Na+, Mg++, SO4- - and Cl - concentrations, are attributed to Permian salt formations in the underground (see Fig.2). The former lake is also located in the middle of the largest contiguous Chernozem region in Germany. Chernozems in Central Germany are considered to be relicts that developed during an early stage of the Holocene (Boreal, see Table 1).

In the course of a regional soil survey in the sixties, a buried soil profile was discovered in the former Wansleben Salt Lake, below a calcareous lake sediment of 0.5 m thickness (Altermann and Mania, 1968). In 1995 this buried soil profile was described in detail and sampled, and the samples were analyzed. Figure 3 shows the soil profile (with German horizon designations, according to AG Boden, 1994). Tables 2a and 2b contain the profile description (according to Soil Survey Division Staff, 1993) and Table 3 gives the results of the analysis, in the format of Soil Survey Staff (1975). Additionally to samples taken for standard physical and chemical analysis, the IIAb1 and IIAb2 horizons (see Fig.3) were sampled for 14C-analysis.


Table 1: Classification of the Late Glacial and Postglacial Aera in Central Europe: Chernozems in Central Germany are presumably of Boreal age (Schachtschabel et al., 1992).

Geological Classification Period (approximately) Climate Botanical and Prehistoric Classification
Subantlantic 600 BC - Present Present temperate-humid climate (oceanic) Fagus sp., Quercus sp., Picea sp., Clearing during Iron Age and Present
Subboreal 2500 - 600 BC Warm, some dry periods (continental) Mixed forest of Quercus sp. with Fagus sp. and Picea sp., Bronze Age
Atlantic 5500 - 2500 BC Warm, humid (oceanic) Mixed forest of Quercus sp., Clearing since begin of Neolithic
Boreal 6800 - 5500 BC Warm, arid (continental) Forests of Betula sp. and Pinus sp. with maximum of Corrynus sp.
Preboreal 8500 - 6800 BC Cool (continental) Forests of Pinus sp. and Betula sp. Begin of Mesolithic
Younger Dryas 9000 - 8500 BC Cold Park tundra with Betula sp. End of Palaeolithic
Alleröd 9800 - 9000 BC Temporarily warmer Sparse forest with Betula sp. and Pinus sp.
Older Dryas 10300 - 9800 BC Cold Tundra
Bölling 10800 - 10300 BC Moderately warm Park tundra with Betula sp.
Oldest Dryas 14000 - 10800 BC Cold (arctic) Tundra
End of Weichselian Pleniglaciation (Pommeranian)


Figure 2: Geology and origin of the Wansleben Salt Lake Area (subsurface leaching of Permian evaporites)



Table 2a: Description of the Wansleben Salt Lake soil profile, together with climatic data from Halle/Saale.

Classification:      Palaeosol (Chernozem) below a Lithic Haplustoll.
Location:            In former Wansleben Salt Lake ("Salziger See"), 0.3 km 
		     north of the road between the villages of Wansleben and 
		     Amsdorf, just outside of Wansleben (Topographic Map 4536; 
		     R=4481740.0, H=5703660.0; 20 km west of Halle/Saale in 
		     the State of Sachsen-Anhalt).
Physiographic pos.:  On the bottom of the former lake (depressional).
Topography:          Nearly level.
Drainage:            Upper soil is well drained; lower soil is apparently 
		     affected by artesian water.
Vegetation:          Field is in agricultural use.
Parent material:     Marly lake deposit overlying loess of Wisconsin age over 
		     glacial till of Illinois age. Lake deposit (Holocene) is 
		     a medium textured sediment derived from surrounding 
		     mesozoic formations, with some fine gravel and shells of 
		     molluscs. The loess ist medium to fine textured and the 
		     glacial till is irregularly alternating loamy, sandy or 
		     clayey, with some medium sized pebbles. The upper seven 
		     horizons all contain gypsum.
Sampled by:          G. Machulla, 
		     H. Ringe, 
                     R.R. van der Ploeg, 
		     M. Volkmann, 
		     Sept.13th, 1995.
Soil No.:            A 674 (Altermann notation).

Table 2b: Description of the Wansleben Salt Lake soil profile.



Figure 3: Photograph of the Wansleben Salt Lake soil profile; designations are according to AG Boden (1994)



Table 3: Physical, chemical and clay fraction mineralogical data of the Wansleben Salt Lake soil profile

Depth (cm) Horizon Size class and particle diameter <2mm
Total Sand Silt
Sand (2-0.063) Silt (0.063-
0.002)
Clay (<0.002) Coarse (2-0.6) Medium (0.6-0.2) Fine (0.2-
0.06)
(0.06-
0.02)
(0.02-
0.006)
(0.006-
0.002)
0-25 Ap 48.4 44.4 7.2 13.5 16.2 18.7 23.3 15.0 6.1
25-40 C1 50.2 43.0 6.8 15.0 17.2 18.0 22.6 14.1 6.3
40-50 C2 15.5 76.7 7.8 1.9 4.4 9.2 44.4 24.3 8.1
50-75 IIAb1 6.3 78.4 15.3 0.8 1.8 3.7 39.8 27.2 11.4
75-90 IIAb2 4.6 74.0 21.4 0.3 1.2 3.1 36.9 27.0 10.1
90-110 IIAbg 4.0 69.0 27.0 0.1 0.6 3.3 36.2 23.0 9.8
110-140 Cg 13.1 72.0 14.9 0.3 2.6 10.1 48.3 18.5 5.2
140-200 III Cg 55.6 28.4 16.0 6.3 22.3 26.9 12.9 8.6 6.9
Depth (cm) Org. Carbon Pct. Nitrog. Pct. C/N Carbonate as CaCO3 Bulk density Water content Hydr. cond. Ksat
m/d
pH
<2mm
Pct.
Ovendry
g/cc
1/3-bar
Pct.
15-bar
Pct.
1/3- to 15-bar
cm/cm
H2O CaCl2
0-25 2.2 0.1 18.3 37.7 1.24 23.9 8.8 15.1 0.50 7.6 7.4
25-40 2.4 0.1 19.9 37.1 1.31 17.7 7.2 10.5 0.63 7.6 7.5
40-50 1.3 0.0 13.2 23.7 1.12 30.8 17.2 13.6 >1.00 7.7 7.5
50-75 1.8 0.1 14.1 0.0 1.29 33.7 25.3 8.4 >1.00 4.7 4.3
75-90 1.6 0.1 13.3 0.0 1.44 27.6 24.4 3.2 >1.00 6.3 6.2
90-110 0.6 0.0 13.3 23.1 1.48 35.0 28.1 6.9 >1.00 8.0 7.8
110-140 13.2 1.56 29.9 19.6 10.3 >1.00 8.4 8.0
140-200 7.0 8.8 8.0
Depth (cm) Extractable bases Sum of bases Ext.acidity Cation exch. capacity Base saturation
Ca Mg Na K Sum of cations Sum of cations
Pct.
0-25 21.5 0.7 0.1 22.3 0.0 22.3 100
25-40 23.6 1.5 0.2 25.3 0.8 26.1 95
40-50 21.4 2.8 0.1 0.2 24.5 0.0 24.5 100
50-75 8.1 2.3 0.4 0.1 10.9 14.5 25.4 27
75-90 15.1 3.9 0.6 0.2 19.8 9.8 29.6 59
90-110 17.4 3.7 0.5 0.1 21.7 0.0 21.7 100
110-140 9.4 2.7 0.5 0.1 12.7 0.0 12.7 100
140-200 6.8 2.7 0.8 0.2 10.5 0.0 10.5 100
Depth (cm) a) Clay fraction mineralogy a) Mineral Code:
VR = vermiculite
KK = kaolinit
MI = mica
QZ = quartz
X-ray
b)
0-25
25-40
40-50 MI4, VR+++, KK2, QZ2
50-75 MI4, VR+++, KK2, QZ2 b) Approximate weight fractions:
4 = one-third to half
2 = one-twentieth to one-fifth
+++ = strong (X-ray)
75-90
90-110
110-140 MI4, VR+++, KK2, QZ2
140-200


INTERPRETATION

The buried soil below former Wansleben Salt Lake resembles the Chernozem of the surrounding upland in many aspects. Additionally, the 14C-analysis provided for the IIAb1-horizon an age of 2355 years (±60) and for the IIAb2-horizon 4120 years (±105). Hence, it is likely that both soils developed simultaneously and that both are of Boreal age. Consequently, Wansleben Salt Lake must be Postboreal age, but, in view of the 14C-data, at least 2355 years old. In one respect however, both soils differ considerably. Whereas the A-horizon of the upland Chernozems around Wansleben shows pH-values near 7.0, the pH-value of the A-horizon of the buried profile is below 5.0 (see Table 3). To explain this low pH-value, the following hypothesis is postulated.

The Holocene climate in the Wansleben area was predominantly warm and dry. Even today the mean annual amount of precipitation is less than 500 mm. Consequently, soils hardly have been leached and in most soils gypsum has accumulated. In the IIAb2-horizon of the buried Chernozem even 1-cm large gypsum crystals can be found, but they are lacking in the IIAb1-horizon. It is likely that after the lake's bottom became flooded (2500 years or more ago), anaerobic conditions and low redox values developed in the A-horizon of the flooded Chernozem. Under such conditions sulfates became reduced and sulfides were built. These sulfides existed until the lake was reclaimed at the end of the last century. Since then oxidative weathering of the sulfides may have lead to the low pH-value that presently is observed. Additional research is needed to check this hypothesis.


LITERATURE



Letzte Änderung am 03. Februar 1998