Vannucchi, Paola; Leoni, Lorenzo (2007): Particel size distribution and microstructures of sediments from ODP Leg 205 sites (Table 1) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.714610, Supplement to: Vannucchi, P; Leoni, L (2007): Structural characterization of the Costa Rica decollement: Evidence for seismically-induced fluid pulsing. Earth and Planetary Science Letters, 262(3-4), 413-428, https://doi.org/10.1016/j.epsl.2007.07.056
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Abstract:
Ocean Drilling Program Legs 170 and 205 offshore Costa Rica provide structural observations which support a new model for the geometry and deformation response to the seismic cycle of the frontal sedimentary prism and decollement. The model is based on drillcore, thin section, and electron microscope observations. The decollement damage zone is a few tens of meters in width, it develops mainly within the frontal prism. A clear cm-thick fault core is observed 1.6 km from the trench. The lower boundary of the fault core is coincident with the lithological boundary between the frontal prism and the hemipelagic and pelagic sediment of the Cocos plate. Breccia clast distributions in the upper portion of the decollement damage zone were studied through fractal analysis. This analysis shows that the fractal dimension changes with brecciated fragment size, implying that deformation was not accommodated by self-similar fracturing. A higher fractal dimensionality correlates with smaller particle size, which indicates that different or additional grain-size reduction processes operated during shearing. The co-existence of two distinct fracturing processes is also confirmed by microscopic analysis in which extension fracturing in the upper part of the damage zone farthest from the fault core is frequent, while both extension and shear fracturing occur approaching the fault core.
The coexistence of extensional and shear fracturing seems to be best explained by fluid pressure variations in response to variations of the compressional regime during the seismic cycle. During the co-seismic event, sub-horizontal compression and fluid pressure increase, triggering shear fracturing and fluid expulsion. Fractures migrate upward with fluids, contributing to the asymmetric shape of the decollement, while slip propagates. In the inter-seismic interval the frontal prismrelaxes and fluid pressure drops. The frontal prismgoes into diffuse extension during the intervalwhen plate convergence is accommodated by creep along the ductile fault core. The fault core is typically a barrier to deformation, which is explained by its weak, but impermeable, nature. The localized development of a damage zone beneath the fault core is characterized by shear fracturing that appears as the result of local strengthening of the detachment.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 9.658090 * Median Longitude: -86.182435 * South-bound Latitude: 9.654530 * West-bound Longitude: -86.185810 * North-bound Latitude: 9.661650 * East-bound Longitude: -86.179060
Date/Time Start: 2002-10-11T00:00:00 * Date/Time End: 2002-10-26T00:00:00
Minimum Elevation: -4311.6 m * Maximum Elevation: -4182.8 m
Event(s):
205-1254A * Latitude: 9.661650 * Longitude: -86.179060 * Date/Time: 2002-10-11T00:00:00 * Elevation: -4182.8 m * Penetration: 367.5 m * Recovery: 125 m * Location: North Pacific Ocean * Campaign: Leg205 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 16 cores; 140.5 m cored; 227 m drilled; 89 % recovery
205-1255A * Latitude: 9.654530 * Longitude: -86.185810 * Date/Time: 2002-10-26T00:00:00 * Elevation: -4311.6 m * Penetration: 157 m * Recovery: 7.22 m * Location: North Pacific Ocean * Campaign: Leg205 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 4 cores; 34 m cored; 123 m drilled; 21.2 % recovery
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Event label | Event | ||||
| 2 | Sample code/label | Sample label | Vannucchi, Paola | DSDP/ODP/IODP sample designation | ||
| 3 | Sample comment | Sample comment | Vannucchi, Paola | |||
| 4 | Size fraction | Size fraction | Vannucchi, Paola | on board class (cm) | ||
| 5 | Lithology/composition/facies | Lithology | Vannucchi, Paola | |||
| 6 | Comment | Comment | Vannucchi, Paola | Visual description of SEM photo | fracture mode | |
| 7 | Comment 2 (continued) | Comm 2 | Vannucchi, Paola | Visual description of SEM photo | fractal dimension | |
| 8 | Particle size, minimum | Part size min | mm | Vannucchi, Paola | Visual description of SEM photo | |
| 9 | Particle size | Part size | mm | Vannucchi, Paola | Visual description of SEM photo | average |
| 10 | Particle size, maximum | Part size max | mm | Vannucchi, Paola | Visual description of SEM photo | |
| 11 | Number | No | Vannucchi, Paola | No of particles |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
92 data points
Data
| 1 Event | 2 Sample label | 3 Sample comment | 4 Size fraction | 5 Lithology | 6 Comment | 7 Comm 2 | 8 Part size min [mm] | 9 Part size [mm] | 10 Part size max [mm] | 11 No |
|---|---|---|---|---|---|---|---|---|---|---|
| 205-1254A | 205-1254A-12R-2,50-60 | 10-3 | Silty claystone | Mode I | 1.65 | 0.24000 | 15.82 | 102.80 | 61 | |
| 205-1254A | 205-1254A-14R-7,37-50 | 3-1 | Fine sandstone | Mode I | 1.73 | 0.03000 | 1.22 | 24.87 | 282 | |
| 205-1254A | 205-1254A-14R-7,77-97 | 3-1 | Fine sandstone | Mode I | 1.78 | 0.02000 | 7.29 | 37.53 | 334 | |
| 205-1254A | 205-1254A-15R-1,25-36 | 1-0.3 | Claystone with silt | Shear | 1.88 | 0.00700 | 0.14 | 7.48 | 276 | |
| 205-1254A | 205-1254A-12R-2,129-139 | 1-0.3 | Silty claystone | Shear | 1.85 | 0.01000 | 0.23 | 6.32 | 254 | |
| 205-1254A | 205-1254A-15R-1,83-88 | 1-0.3 | Claystone | Shear | 1.82 | 0.00400 | 0.58 | 9.38 | 145 | |
| 205-1254A | 205-1254A-14R-4,120-124 | 1-0.3 | Claystone | Shear | 1.86 | 0.00400 | 0.84 | 6.38 | 159 | |
| 205-1254A | 205-1254A-15R-2,7-10 | Thin section | <0.3 | Claystone | Shear | 1.93 | 0.00014 | 0.02 | 0.58 | 448 |
| 205-1254A | 205-1254A-12R-2,62-65 | Thin section | <0.3 | Claystone with silt with | Shear | 1.98 | 0.00032 | 0.07 | 0.27 | 595 |
| 205-1255A | 205-1255A-2R-3,31-45 | 10-3 | Siltstone with clay | Mode I | 1.63 | 4.11000 | 26.39 | 97.30 | 32 |