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).

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.

Colors are for the moist soil unless otherwise indicated.

• 0 - 25 cm.    Dark gray (10YR 4/1) sandy loam; coarse blocky and coarse 
  	      to very coarse granular structure; many fine and very fine roots; 
  	      slightly fine gravelly; mollusc shells; abrupt smooth boundary.

• 25 - 40 cm.   Dark grayish brown (10YR 4/2) sandy loam; very thick platy 
  	      and coarse blocky structure; few very fine to fine nonmatrix 
  	      pores; few fine roots; slightly fine gravelly; mollusc shells; 
  	      clear wavy boundary.

• 40 - 50 cm.   Very dark gray (10YR 3/1) silt loam; very coarse blocky 
  	      structure; few very fine to fine nonmatrix pores; common tubular 
  	      pores; many fine roots; very fine gravelly; with bands of fine 
  	      gravel and sand; shells of molluscs; clear wavy boundary.

• 50 - 75 cm.   Black (10YR 2/1) silt loam; very coarse blocky structure; 
  	      few very fine to fine nonmatrix pores; common tubular pores; 
  	      common fine roots; in the upper part of the horizon some mycelial 
  	      carbonate is observed; diffuse boundary.

• 75 - 90 cm.   Black (10YR 2/1) silt loam; very thick platy and coarse blocky 
  	      structure; common very fine to fine and medium to coarse non-
  	      matrix pores; common tubular pores and few krotovinas; common 
  	      fine roots; irregular diffuse boundary; common large crystals of 
  	      gypsum.

• 90 - 110 cm.  Very dark gray (10YR 3/1) silt loam; structureless; common 
  	      very fine to fine and few fine nonmatrix pores; few tubular 
  	      pores and common krotovinas; few fine roots; diffuse boundary.

• 110 - 140 cm. Grayish brown (10YR 5/2) silt loam with common yellowish brown 
  	      and gray distinct mottles; structureless; few very fine to fine 
  	      nonmatrix pores; very few fine roots; clear smooth boundary.

• 140 - 200 cm. Brown (7.5YR 5/4) sandy loam with common yellowish brown 
  	      distinct mottles; subangular fine to medium blocky structure; 
  	      slightly medium gravelly. 

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

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

• AG Boden. 1994. Bodenkundliche Kartieranleitung. 4ed. E. Schweizerbart Publ. Co., Stuttgart (Germany).
• Altermann, M. and D. Mania. 1968. Zur Datierung von Boeden im mitteldeutschen Trockengebiet mit Hilfe quartaergeologischer und urgeschichtlicher Befunde. Thaer-Archiv 12(7): 539 - 557
• Schachtschabel, P. et al. 1992. Lehrbuch der Bodenkunde. 13 ed. Enke Publishing Co., Stuttgart.
• Seyfert, B. 1919. Anwendung der Theorie der Grundwasserbewegung auf die Draenage. Der Kulturtechniker 22: 44 - 52.
• Soil Survey Division Staff. 1993. Soil Survey Manual. USDA Handbook No.18. Superintendent of Documents, US Government Printing Office, Washington, DC 20402.
• Soil Survey Staff. 1975. Soil Taxonomy. Agricultural Handbook No.436. Superintendent of Documents, US Government Printing Office, Washington, DC 20402.

Letzte Änderung am 03. Februar 1998