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IODP Nankai Trough Seismogenic Zone Experiment
Stage 1 Expedition 316 "Shallow Megasplay and Frontal Thrusts" |
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OVERVIEW |
| Expedition Number |
Expedition 316 |
| Expedition Prospectus |
Expedition 316 is intended to comprehensively evaluate the deformation, inferred depth of detachment, structural partitioning, and fault zone physical characteristics at the frontal thrust (proposed Site NT1-03B) and at the shallow portion of the megasplay system (proposed Site NT2-01B).
The primary goals for Expedition 316 are to drill and core two proposed sites, NT1-03B and NT2-01B. Site NT1-03B will be drilled and cored to a total depth (TD) of 950 meters below seafloor (mbsf), and Site NT2-01B will be drilled and cored to a total depth of 1000 mbsf. Hole C at Site NT2-01B will also be fitted with a reentry cone and cased to TD in preparation for cross-hole hydrologic experiments and installation of monitoring equipment planned for future operations. |
| Location |
Nankai Trough, Kumano-nada, Offshore Kii peninsula, Japan |
| Duration of Expedition |
From Dec. 19 2007 to Feb. 5 2008 |
| Drilling Vessel |
The Chikyu |
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EXPEDITION SCIENTISTS |
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Gaku Kimura
University of Tokyo (Japan)
Elizabeth Screaton
University of Florida (USA) |
| Daniel Curewitz (Syracuse University) |
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Summary of drilling result |
Summary of Coring Operation
| Drilling site: C0004(Proposed site:NT2-01I) |
| North Latitude:33°13.0’ East Longitude:136°43.0’ |
Hole
Name |
Water
depth |
Core sampling depth
(below seafloor) |
Summary of Result |
| C |
2627.0m |
0~89.2m (HPCS)
~127.2m (ESCS)
~135.0m (HPCS) |
131 meters cored, 135 meters recovered in slope basin, slope apron deposits. Evidence for unconformity, minor faulting, and understanding of sedimentary processes in shallow trench slope deposits. |
| D |
2630.5m |
0~100.0m (Drilled)
~400.0m (RCB) |
300 meters cored, 130.7 meters recovered in accretionary prism deposits, upper portion of megasplay, and underthrust slope basin deposits. Evidence for faulting, recovery of a wide variety of fault rocks. Understanding of the internal deformation of the accretionary prism and the mechanism by which the prism rocks are being thrust up and over slope basin deposits. Will shed light on timing and degree of thrust faulting in the megasplay system. |
| Drilling site:C0006(Proposed site:NT1-03B) |
| North Latitude:33°01.0’ East Longitude:136°47.0’ |
Hole
Name |
Water
depth |
Core sampling depth
(below seafloor) |
Summary of Result |
| C |
3880.5m |
0~9.5m (HPCS) |
Single core in sediments above the hanging wall of the frontal thrust. Hole abandoned because sediment-water interface was not recovered. |
| D |
3877.5m |
0~9.5m (HPCS) |
Same as above |
| E |
3875.8m |
0~79.3m (HPCS)
~409.4m (ESCS) |
409 meters cored, 330.3 meters recovered in sediments deposited on the hanging wall of the frontal thrust and in rocks making up the accretionary prism material that has been transported along the frontal thrust. Several age reversals, recovery of many different kinds of fault rocks, recovery of a wide array of materials comprising the thrust sheet. Will shed light on the internal deformation and tectonic history of the deformed accretionary prism. |
| F |
3875.5m |
0~395.0m (Drilled)
~ 603.0m (RCB) |
208 meters cored, 56.4 meters recovered in the rocks making up the older portions of the hanging wall of the frontal thrust system. Several faults and different kinds of fault rocks recovered in association with age reversals. Will shed light on the internal deformation and history of the hanging wall of the frontal thrust system. Hole had to be abandoned due to deteriorating drilling conditions. |
| Drilling site:C0007(Proposed site:NT1-03A) |
| North Latitude:33°01.0’ East Longitude:136°47.0’ |
Hole
Name |
Water
depth |
Core sampling depth
(below seafloor) |
Summary of Result |
| A |
4081.0m |
0~3.1m (HPCS) |
Single core taken at the sediment-water interface. |
| B |
4081.0m |
3.1~12.6m(HPCS) |
Single core taken from 3.14 t0 12.5 meters. For operational and curatorial reasons the hole was renamed, but is the same as Hole A and Hole C. |
| C |
4081.0m |
12.6~43.0m(HPCS)
~147.5m (ESCS)
~176.0m (HPCS) |
163.4 meters cored, 59.3 meters recovered in the sediments uplifted by transport along the frontal thrust. Will shed light on the timing and extent of thrust faulting along the frontal thrust. As a result of coring in sand, the hole had to be abandoned after mechanical failure of the coring equipment. |
| D |
4049.0m |
0~175.0m (Drilled)
493.5m (RCB) |
318.5 meters cored, 87.9 meters recovered in uplifted trench deposits and into older materials transported along the frontal thrust. Sampling of a wide array of faults and fault rocks, and sampling of the material in the footwall of the frontal thrust will shed light on the timing and degree of shortening, the mechanisms for internal deformation within the accretionary prism, and the tectonic history of the frontal thrust region. |
| Drilling site:C0008(Proposed site:NT2-10A) |
| North Latitude:33°12.0’ East Longitude:136°43.0’ |
Hole
Name |
Water
depth |
Core sampling depth
(below seafloor) |
Summary of Result |
| A |
2751.0m |
0~224.7m (HPCS)
~357.7m
(ESCS and HPCS) |
357.7m cored, 271.2m recovered in clay and sand deposited in a slope basin just trenchward of the megasplay fault system. Recovery of a wide array of sedimentary materials and sedimentary structures will shed light on the depositional systems and changes in depositional patterns associated with structural changes in the accretionary prism over recent geological periods. Understanding of the character of slope basin deposits before they are incorporated into the accretionary prism during underthrusting, and comparison to similar materials sampled beneath the megasplay fault will allow understanding of the changes in physical state of materials over time during tectonic compression and thrust faulting. |
| B |
2796.3m |
0~9.5m (HPCS) |
Single core recovered in clay and sand deposited in a slope basin just trenchward of the megasplay fault system. Hole abandoned because sediment-water interface was not recovered. |
| C |
2797.0m |
0~139.1m (HPCS)
~176.2m (ESCS) |
176.2m cored, 189.6m recovered in a slope basin just trenchward of the megasplay fault system. |
*About core sampling system
Hydraulic Piston Core Sampling System (HPCS) : Applied to very soft formations. Stub edgy tip like knife into layers using hydraulic pressure, and collect core without rotate drill bit.
Extended Shoe Coring System (ESCS) : Applied to soft formation that is difficult to collect. Tip of the system can adjust to layers intensity using spring power.
Rotary Core Barrel Sampling System (RCB) : Applied to layers of middle to high intensity. Collect samples while rotating drill bit and scraping layers. Good for consolidated layers with less ruptures.
Drilled only : Zone at where only drilling was operated (no core sampling) in accordance with scientific objectives.
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Expedition 316 Scientific Prospectus |
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