Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 51.
This AGU volume is a collection of papers which were presented at the IUGG Symposium U7 (Lower Crust: Properties and Processes) held in Vancouver, Canada in August, 1987. The principle objective of this symposium was to update our understanding of the properties of the lower crust and to review the physical and chemical processes which may have taken place and are still going on in the deep crust. Recent high resolution seismic experiments have thrown new light on the structure of the lower crust and crust-mantle transition which shows a much greater degree of complexity than had previously been assumed. In this symposium the complexity problem was examined from a multidisciplinary approach with papers being presented by earth scientists from the seismological, geological, geochemical, geothermal, geoelectric, geomagnetic and tectonophysics communities. A total of 38 oral and 33 poster papers were presented at the meetings. Eighteen of these papers were invited. Twenty nine of the participants have their work presented in this volume.
Preface
R. F. Mereu, St. Mueller and D. M. Fountain xi
I. THE LOWER CRUST FROM RESULTS OF NEAR-VERTICAL REFLECTION EXPERIMENTS
1. Large-Scale Lenticles in the Lower Crust Under an Intra-Continental Basin in Eastern Australia
D. M. Finlayson, J. H. Leven, and K. D. Wake-Dyster 3
2. Dating Lower Crustal Features in France and Adjacent Areas from Deep Seismic Profiles
C. Bois, B. Pinet and F. Roure 17
3. Styles of Deformation Observed on Deep Seismic Reflection Profiles of the Appalachian-Caledonide System
J. Hall, G. Quinlan, J. Wright, C. Keen, and F. Marillier 33
4. Laterally Persistent Seismic Characteristics of the Lower Crust: Examples from the Northern Appalachians
Francois Marillier, Charlotte E. Keen, and Glen S. Stockmal 45
5. Contrasting Types of Lower Crust
Scott B. Smithson 53
6. A "Glimpce" of the Deep Crust Beneath the Great Lakes
Alan G. Green, W. F. Cannon, B. Milkereit, D. R. Hutchinson, A. Davidson, J. C. Behrendt, C. Spencer, M. W. Lee, P. Morel-d-l'Huissier, and W. F. Agena 65
7. Crustal Extension in the Midcontinent Rift System—Results from Glimpce Deep Seismic
Reflection Profiles over Lakes Superior and Michigan
J. C. Behrendt, A. G. Green, M. W. Lee, D. R. Hutchinson, W. F. Cannon, B. Milkereit, W. F. Agena, and C. Spencer 81
II. THE LOWER CRUST FROM RESULTS OF REFRACTION/WIDE-ANGLE REFLECTION EXPERIMENTS
8. The Glimpce Seismic Experiment: Onshore Refraction and Wide-Angle Reflection
Observations from a Fan Line over the Lake Superior Midcontinent Rift System
Duryodhan Epili and Robert F. Mereu 93
9. The Complexity of the Continental Lower Crust and Moho from PmP Data: Results from
Cocrust Experiments
R. F. Mereu, J. Baerg, and J. Wu 103
10. A Petrological Model of the Laminated Lower Crust in Southwest Germany Based on
Wide-Angle P- and S-Wave Seismic Data
W. Steven Holbrook 121
11. DSS Studies over Deccan Traps Along the Thuadara-Sendhwa-Sindad Profile, Across
Narmada-Son Lineament, India
K. L. Kaila, I. B. P. Rao, P. Koteswara Rao, N. Madhava Rao, V. G. Krishna, and A. R. Sridhar 127
12. Synthetic Seismogram Modeling of Crustal Seismic Record Sections from the Koyna DSS
Profiles in the Western India
V. G. Krishna, K. L. Kaila, and P. R. Reddy 143
13. Study of the Lower Crust and Upper Mantle Using Ocean Bottom Seismographs
Yuri P. Neprochnov 159
14. A Seismic Refraction Study of the Crustal Structure of the South Kenya Rift
W. Henry, J. Mechie, P. K. H. Maguire, J. Patel, G. R. Keller, C. Prodehl, M. A. Khan 169
III. THE LOWER CRUST FROM RESULTS OF SEISMICITY STUDIES
15. Seismicity near Lake Bogoria in the Kenya Rift Valley
Philippa Cooke, Peter Maguire, Russ Evans, and Nicholas Laffoley 175
16. Anelastic Properties of the Crust in the Mediterranean Area
A. Craglietto, G. F. Panza, B. J. Mitchell, and G. Costa 179
17. Earthquakes and Temperatures in the Lower Crust Below the Northern Alpine Foreland of
Switzerland
N. Deichmann and L. Rybach 197
18. Heat Flow, Electrical Conductivity and Seismicity in the Black Forest Crust, SW Germany
H. Wilhelm, A. Berktold, K.-P. Bonjer, K. Jager, A. Stiefel, and K.-M. Strack 215
IV. THE LOWER CRUST FROM RESULTS OF OTHER GEOPHYSICAL STUDIES
19. On the Vertical Distribution of Radiogenic Heat Production in the Continental Crust and
the Estimated Moho Heat Flow
Vladimir &rmiik and Louise Bodri 235
20. Fluids in the Lower Crust Inferred from Electromagnetic Data
Leonid Vanyan and Andrej Shilovski 243
21. The Magnetisation of the Lower Continental Crust
Albrecht G. Hahn and Hans A. Roeser 247
22. Generalized Inversion of Scalar Magnetic Anomalies: Magnetization of the Crust off the
East Coast of Canada
J. Arkani-Hamed and J. Verhoef 255
23. Inversion of Magnetic and Gravity Data in the Indian Region
B. P. Singh, Mita Rajaram, and N. Basavaiah 271
24. Gravity Field, Deep Seismic Sounding and Nature of Continental Crust Underneath NW Himalayas
R. K. Verma and K. A. V. L. Prasad 279
V. THE LOWER CRUST FROM STUDIES OF GEOLOGICAL PROCESSES
25. Growth and Modification of Lower Continental Crust in Extended Terrains: The Role of
Extension and Magmatic Underplating
David M. Fountain 287
26. Granulite Terranes and the Lower Crust of the Superior Province
John A. Percival 301
27. Phase Transformations in the Lower Continental Crust and its Seismic Structure
Stephen V. Sobolev and Andrey Yu. Babeyko 311
28. Geophysical Processes Influencing the Lower Continental Crust
D. L. Turcotte 321
29. Geochemistry of Rb, Sr and REE in Niutoushan Basalts in the Coastal Area of Fujian
Province, China
Yu Xueyuan 331