1 Introduction ................................................. 9
2 Sequence and objectives of the exploration and methods
employed .................................................... 12
2.1 Chronological order and objectives of the
exploration ............................................ 12
2.2 Seismic reflection and refraction surveys .............. 15
2.3 Surface exploration boreholes .......................... 16
2.3.1 Salt dome exploration boreholes ................. 16
2.3.2 Shaft pilot boreholes ........................... 27
2.3.3 Salt table boreholes ............................ 34
2.4 Underground mapping .................................... 43
2.4.1 Shafts Gorleben 1 and Gorleben 2 ................ 44
2.4.2 Drifts and chambers ............................. 45
2.5 Underground exploration boreholes ...................... 45
2.6 Electromagnetic survey methods ......................... 50
2.6.1 Electromagnetic reflection surveys .............. 50
2.6.2 High-frequency absorption surveys ............... 53
2.7 Mineralogical and geochemical investigations ........... 54
2.7.1 Sample preparation and analysis to determine
the qualitative mineralogical composition ....... 55
2.7.2 Determining the quantitative mineralogical
composition ..................................... 56
2.7.3 Determining the bromide content in the
evaporites ...................................... 57
3 Salt dome exploration results ............................... 59
3.1 Composition, extent and genesis of the cap rock ........ 59
3.1.1 Late Mesozoic to Cenozoic cap rock
development ..................................... 60
3.1.1.1 Quaternary subrosion ................... 64
3.1.1.2 Cretaceous and Tertiary subrosion ...... 71
3.1.2 Middle Mesozoic cap rock formation .............. 73
3.2 Salt table and selective subrosion ..................... 75
3.3 Composition and structure of the salt dome ............. 79
3.3.1 Stratigraphy and petrography .................... 79
3.3.1.1 Stassfurt-Folge (Zechstein 2) .......... 81
3.3.1.2 Leine-Folge (Zechstein 3) .............. 89
3.3.1.3 Aller-Folge (Zechstein 4) ............. 120
3.3.2 Structure of the Gorleben salt dome ............ 124
3.3.2.1 Large-scale folding in the Gorleben
salt dome ............................. 124
3.3.2.2 Investigation of the structural
geology in the shafts ................. 129
3.3.2.3 Geological structure of the
infrastructure section ................ 132
3.3.2.4 Structural geology of Exploration
Area 1 (EB 1) ......................... 135
3.3.3 Mineralogy and geochemistry of the salt
rocks .......................................... 141
3.3.3.1 Bromide standard profile of the
Stassfurt-Folge (Zechstein 2) ......... 141
3.3.3.2 Bromide standard profile of the
Leine-Folge (Zechstein 3) ............. 146
3.3.3.3 Mineralogical and geochemical
investigations of the Kalifiöz
Stassfurt ............................. 150
3.3.4 Hydrocarbons, gases and brines in the
Gorleben salt dome ............................. 160
3.3.4.1 Gaseous hydrocarbons and
condensates ........................... 160
3.3.4.2 Other gas inclusions in the salt
formation ............................. 167
3.3.4.3 Brines ................................ 169
3.3.4.4 Pressures in solution and gas
reservoirs ............................ 177
3.3.4.5 Permeabilities of the rock salt in
the vicinity of solution and gas
reservoirs ............................ 177
3.3.5 Water content of the rock salt ................. 178
4 Evaluation of the results .................................. 179
4.1 Size of the Hauptsalz as the host medium for a
potential repository .................................. 179
4.2 Fissures and potential migration paths for saline
solutions and gases ................................... 180
4.3 Consequences of subrosion for the long-term safety
of a repository ....................................... 182
5 Summary .................................................... 185
References ................................................. 189
Abbreviations ................................................. 215
List of tables ................................................ 217
List of figures ............................................... 218
List of appendices ............................................ 223
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