A new concept of karst development based on hydrogeology and geophysics

A new concept of karst development based on hydrogeology and geophysics	1
Prefaces	7
Foreword	9
The authors	11
Introduction	13
1. The Poitou Threshold	17
Location and definition	17
Tectonic structure of the Poitou Threshold: a brief history of knowledge	19
Sedimentary coverage	26
Poitou threshold definition	29
References	30
2. The stratigraphy of the Middle Jurassic	35
Paleontological division of the Middle Jurassic	35
Deposit sequences	36
Stratigraphy of the Middle Jurassic on the Poitou Threshold	38
Aalenian	38
D6	39
D7 – Lower Bajocian	39
D8 – Upper Bajocian	40
D9 – Lower Bathonian	41
D10 – Middle and upper Bathonian	41
Stratigraphy of the Bajocian south of Poitiers: the cliffs of Passelourdin	42
Conclusion	49
References	49
3. Hydrogeology of the Poitou Threshold	57
Aquifers of the Poitou threshold	57
Two main aquifers	57
Piezometric map	58
The supra-Toarcian aquifer	62
Groundwater flow patterns in the supra-Toarcian aquifer	62
Comparison between lineaments and speleological networks	63
Typology of voids in Poitou threshold limestones	66
Pumping tests	69
Conclusion	75
Acknowledgements	76
References	76
4. The Hydrogeological Experimental Site of Poitiers University (France)	79
Origin of the hydrogeological experimental site (HES)	79
HES description	80
Scientific studies	82
References	83
5. Geophysical methods	85
5.1 Seismic and acoustic methods	87
5.2 3D seismic imaging	90
5.3 Full waveform acoustic logging	96
5.4 Vertical seismic profiles versus full waveform acoustic logging	101
5.5 Electrical methods	105
5.6 Conclusions	109
Appendix: Static corrections	111
Acknowledgements	114
References	114
6. Borehole electrical panels: an experiment	117
Material and method	118
Acquisition	121
Geological Interpretation	123
Summary	127
Conclusions	128
References	129
7. Hydrogeological flow logging and dye tracer tests on the Hydrogeological Experimental Site of Poitiers University (France)	131
Introduction	131
Borehole flow logging acquisition	133
Principle of flow logging	133
Downflow and upflow in the borehole	134
Flow logging with pumping in the tested boreholes	134
Flow logging with pumping in MP6 (crossed dynamics MP6)	139
Tracer tests	142
Tracer test protocol	142
Results	142
Conclusion and interpretation of pathways in karst horizons	146
References	147
8. Hydro-stratigraphic study of the Hydrogeological Experimental Site of Poitiers, France	149
Objectif and method	149
Aquifer stratigraphy of the HES	150
Stratigraphic context	150
Data available	151
Lithostratigraphy of the HES	152
Occurrence ok karst	159
Fracture inventory	159
Stratigraphy versus seismic and acoustic data	160
Stratigraphy versus borehole electrical methods	162
Stratigraphy and hydrogeological data	165
Conclusion	166
References	167
9. The Deffend hydrogeological model	171
Hydrogeological knowledge before Hydrogeological Experimental Site (HES) of Poitiers	171
Historical groundwater flow model of the Poitou Threshold	171
The Poitiers HES groundwater model	173
Karst dating	174
Syngenetic karstification hypothesis	176
Conclusion	180
References	180
Conclusion	185
Acknowledgements	189

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