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highly discontinuous, bright amplitude reflectors. Within the Tobago Forearc Basin, channels and channel fill facies have been identified that suggest that this basin was once a fairway for clastic sediment deposition (Figure 4.3). Joes River Formation The Joes River Formation is dark gray to black in color, slickensided, often oil soaked with a distinct bituminous odor. It is comprised of a mélange of structureless clays, sands, and scattered limestone rafts (Poole and Barker, 1980). It has been interpreted to be emplaced as diapiric shales and extrusive muds. Such mobile shale processes are common in accretionary prism settings (Wood, 2004). Mud volcanoes today are most active on the island of Trinidad and its offshore regions (Brooks and others, 2004). Offshore, evidence of continued mud volcano eruption indicates that this is an ongoing process triggered by over-pressurization created by compressional forces within the prism. On the island, this unit is intrusive and post-dates deposition of the Oceanic Formation. The timing of the intrusion of the Joes River Formation is based on observations by Speed (1991) that the Joes River Formation is mushroomed beneath the Oceanic Formation. This phenomenon suggests that although the matrix has been dated with pollen to be Paleocene to Middle Eocene (Speed, 1991) the timing of the deformation and emplacement of the diapirs is after the Oceanic Formation was deposited. The Joes River Formation on Barbados is interpreted as a complex of paleo- mud volcanoes which were extruded in response to the compressional regional setting. They pre-date the localized extensional faulting that characterizes the crest of the Barbados Ridge. Both offshore and onshore, diapiric shale and extrusive muds are isolated pods and more laterally extensive mounds. The unconsolidated nature of the unit makes it prone to mass wasting. These features can be easily identified in seismic reflection profile by the chaotic response of the subsurface material and capped by the spectacular extrusion of mud at the seafloor. 49
STRUCTURAL FRAMEWORK OF THE BARBADOS ACCRETIONARY PRISM Convergent margin settings tend to be structurally complex regions of the world, characterized by shortening and local extension or strike-slip tectonics. Deformation involves mud-rich sediments which are tectonized as they dewater, using fluid flow that can cause mud volcanism (Moore, 2001). The Barbados Accretionary Prism (BAP) region is no exception to typical convergent tectonic margins. Although the overall setting of the study area is convergent, as this study documents, there is large-scale, normal faulting that occurs on a sub-regional scale. The west and east margins of the accretionary prism are bounded by thrust faults that dip towards the west and east, respectively (Figure 4.4). The Barbados Ridge, the westernmost high of the prism, is dominated by northwest-southeast-trending normal faults (Figure 4.4, Figure 4.5). The prism is characterized by five structural regions: the zone of initial accretion, the zone of stabilization, the zone of piggyback basins, the Barbados Ridge, and the Inner Forearc Deformation Front (Figure 4.5) which includes the Tobago Forearc Basin—each having its own unique structural characteristics (Brown and Westbrook, 1987). Data availability did not allow for much analysis of the zone of initial accretion. The remaining regions are summarized in the following section on the basis of observations by Brown and Westbrook (1987), as well as those of the authors. 50
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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
Page 13 and 14: 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: STRATIGRAPHIC FRAMEWORK ONSHORE TO
Page 67 and 68: Sandy material is primarily quartz
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
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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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