Copyright by Nysha Chaderton 2009 - The University of Texas at ...

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Zone of Initial Accretion The zone of initial accretion, composed of an imbricate fan of east-facing thrust faults, marks the youngest phase of deformation in the prism. Because it is the zone where previously undeformed sediments are first accreted to the prism, it is the starting point or initiation of accretion. These thrusts all sole into a décollement, below which Atlantic Abyssal Plain sediments are passing relatively undeformed beneath the prism proper, to be ultimately subducted along with the downgoing Atlantic Plate. Zone of Initial Stabilization Deformation in the zone of initial stabilization appears less intense than in areas to the east and west. This zone marks a transition in the direction of thrusting in the prism; to the east of this zone, thrusts and thrust sheets dip westward, while to the west of this zone, thrusts and thrust sheets dip eastward (Figure 4.5). Zone of Piggyback Basins The zone of piggyback basins is a region in which several asymmetric basins have formed on the eastern side of thrusts that dip toward the west. Huyghe et al. (1999) called this zone “the arcward piggyback basins.” These basins are filled with Holocene sediments derived from the Venezuela-Trinidad margin to the south, as well as from pelagic deposition and sediments transported on offshore currents from regions along the Amazon shelf. Several canyons and channels cut these basins, as well as form linkages across uplifts that separate the basins. Dropcore measured by Faugeres et al., (1993) shows that the most recent fill of the basin is prevalently thin, silty to sandy sequences; however, some thick, sandy sequences are present. The clay portion makes up 10 to 50% of the succession and is primarily illite with minor smectite (Faugeres et al., 1993). 51
Sandy material is primarily quartz (75–95%) with minor lithic grains, micas, and heavy minerals (Faugeres et al., 1993). The largest of the prism’s many piggyback basins, the Barbados Basin, was the focus of a 2001 exploration well, the Sandy Lane #1 (Figure 4.1). A near- seafloor dredge sample taken from the basin as part of this effort recovered fine- grained quartzose sandstone. These sediments were measured from what was interpreted on the basis of seismic morphology to be a deposit of deep-marine lobate sediments, internally composed of tabular sheet sands (Dolan et al., 2004). These results suggest that even in this confined, tectonically active basin setting, reservoir quality sands are deposited as fans and sheet sands in very deep water. Barbados Ridge The Barbados Ridge is the topographically highest part of the accretionary prism and the region along which the island of Barbados is emergent. The island of Barbados is rising at a rate of approximately 0.44 mm/yr (Taylor and Mann (1991). The arcuate ridge, subparallel to the Lesser Antilles Island Arc (Figure 4.1), is formed as accretionary prism material moves westward and interacts with the string basement of the Caribbean Plate, moving up and over the metamorphic basement. In some cases, this material is overriding the lowermost Tobago Forearc Basin sediments, which are deformed by these movements. As a result, the west side of the Barbados Ridge is characterized by large, west-facing thrust faults, while a number of northwest-southeast-striking normal faults dominate the crestal region (Figure 4.6). The east margin of the Barbados Ridge is characterized by a step-like succession of normal faults. The largest of these, the Barbados Fault, bounds the east coast of the island of Barbados (Figure 4.6). This fault has more than 3 km of down-to-the-east vertical displacement. Underplating of forearc basin and accretionary prism sediments, as well as the presence of basement ridges (Brown 52
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Copyright by Nysha Chaderton 2009
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Sedimentation within the Tobago For
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Acknowledgements I would like to th
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Table of Contents List of Tables ..
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List of Tables Table 2.1: Latitudes
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Figure 2.14: Planar parallel lamina
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Figure 2.42: Coarse, cobble and peb
Page 15 and 16: Figure A.3a: Chalky Mount Ridge mea
Page 17 and 18: 1. Development history of the south
Page 19 and 20: Formation. This interpretation requ
Page 21 and 22: DATA AND METHODOLOGY Extensive work
Page 23 and 24: DESCRIPTIVE METHODOLOGY Each sectio
Page 25 and 26: Two or more channel complexes stack
Page 27 and 28: These poorly sorted sands are later
Page 29 and 30: East Coast Road Although the East C
Page 31 and 32: succession of interlaminated siltst
Page 33 and 34: Mount All The beds of the Mount All
Page 35 and 36: Lobes are non-channelized bodies, 3
Page 37 and 38: Sandy units are the most resistant
Page 39 and 40: SUMMARY DEPOSITIONAL SETTING OF THE
Page 41 and 42: Chapter Three: Petrographic Analysi
Page 43 and 44: had not been buried deeply or long
Page 45 and 46: Feldspars Calcium Plagioclase Felds
Page 47 and 48: Authigenic Minerals Authigenic mine
Page 49 and 50: amounts of chlorite and kaolinite c
Page 51 and 52: Sample: WRA 16 This sample was take
Page 53 and 54: cementation is observed. A number o
Page 55 and 56: COMPARISON WITH PREVIOUS WORK Punch
Page 57 and 58: K feldspar preservation to slightly
Page 59 and 60: CONCLUSIONS 1. No quartz cementatio
Page 61 and 62: The highest point of the island, is
Page 63 and 64: STRATIGRAPHIC FRAMEWORK ONSHORE TO
Page 65: STRUCTURAL FRAMEWORK OF THE BARBADO
Page 69 and 70: esult of extension caused by flexur
Page 71 and 72: 1994). The origin of the Oceanic Fo
Page 73 and 74: Oligocene-age sediments are deposit
Page 75 and 76: The observation of channel geometri
Page 77 and 78: Pudsey, (1982) interpreted smectite
Page 79 and 80: The interpretation of the Scotland
Page 81 and 82: Figure 1.2: Convergent margins arou
Page 83 and 84: NSF Study Lines Grenada St. Kitts S
Page 85 and 86: Figure 2.2: Generalized vertical se
Page 87 and 88: Figure 2.4: Detailed Geological map
Page 89 and 90: Figure 2.6: Photographs and illustr
Page 91 and 92: Figure 2.8: Bedsets on the channel
Page 93 and 94: S 50 m Figure 2.10: Photo-panorama
Page 95 and 96: Figure 2.13: Laminated silt and mud
Page 97 and 98: Figure 2.16a: Measured section at C
Page 99 and 100: Figure 2.16c: Measured section at C
Page 101 and 102: Figure 2.18: Correlation of section
Page 103 and 104: Figure 2.21: Parallel laminated sil
Page 105 and 106: Wach, Vincent and Chaderton March 2
Page 111 and 112: Figure 2.24: Channel element identi
Page 113 and 114: WRB S N Fresh rock face exposed by
Page 115 and 116: Figure 2.28: Photograph of Diplocra
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Figure 2.31: Conglomerate with eros
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Figure 2.33: Thalassinoides trace f
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Figure 2.35: Mount All measured str
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Figure 2.37: Medium grained sand be
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Figure 2.38b: Inner Turner’s Hall
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Figure 2.38d: Inner Turner’s Hall
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Figure 2.39: Spa Hill measured stra
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Juniper Ridge, California Scotland
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Figure 3.1: Fractured quartz grain
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SGRF 1C SGRF 9C Figure 3.5: Measure
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Figure 3.8: Photo of sample SGRF 11
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Figure 3.10: Photo of sample SGRF 1
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Figure 3.12: Photo of sample WRA 16
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Figure 3.14: Photo of sample WRB 8
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Figure 3.16: Photo of sample ITR 9
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Figure 3.19: Photo of sample CMRA s
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Figure 3. 23: Composition of Scotla
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Figure 4.1: Base map showing seismi
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Figure 4.3: Channels within Unit Fi
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Figure 4.5: Seismic reflection prof
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Figure 4.7 Isochron maps of the old
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Figure 4.9: Illustration of the Spe
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Figure 4.11: Illustration of Hypoth
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necessary to clear a path. Keep to
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2006 Figure A.2a: Lidar Ridge measu
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Figure A.3b: Chalky Mount Ridge mea
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2006 Figure A.4a: Chalky Mount Ridg
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2006 Figure A.4c: Chalky Mount Ridg
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2006 Figure A.6: Chalky Mount Ridge
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Figure A.7b: Measured Section of Ch
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2006 Figure A.8a: Sleeping Giant Ri
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2006 Figure A.9: Sleeping Giant Rid
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2006 Figure A.11: Sleeping Giant Ri
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Figure A.13a: Sleeping Giant Ridge
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2006 Figure A.14a: Coast Road Below
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2006 Figure A.14c: Coast Road Below
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2006 Figure A.14e: Coast Road Below
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2006 Figure A.14g: Coast Road Below
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2006 Figure A.15: Ermy Bourne Ridge
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2006 Figure A.17: Spa Hill Fold Mea
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2006 Figure A.19: Ermy Bourne Ridge
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Figure A.20b: Walkers Ridge Measure
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Figure A.21: Walkers Ridge Measured
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Figure A.22b: Walkers Ridge Measure
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2007 Figure A.23b: Inner Turner’s
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2007 Figure A.23d: Inner Turner’s
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Framework grains Quartz Feldspar Ro
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CRIMES, T.P., 1977, Trace fossils o
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MONTGOMERY, S.L., BARKER, C.E., SEA
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RICHARDS, M., BOWMAN, M., and READI
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WEBER, J.C., DIXON, T.H., DEMETS, C
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