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

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that extends 180 km from the Atlantic Abyssal Plain in the east, westward to the east flank of the Lesser Antilles Island Arc High (Figure 4.1). Two additional lines are contained in the data set that trend north-northeast from the north-coast marine area of Trinidad, paralleling the east and west coasts of the island of Tobago, extending northward and paralleling the east and west flanks of the Barbados Ridge. The two additional north-south-oriented, southern regional lines intersect the long east-west- trending regional line. These southern regional lines allow a tie to well data southward in the north-coast marine area of Trinidad (Figure 4.1). Published age data from wells on the southernmost margin of the Tobago Basin were used for chronostratigraphic control on the younger, Tertiary parts of the stratigraphic section (Robertson and Burke, 1989). However, little information exists in the public domain regarding the age of fill to the north. This lack of data meant that we had to rely on published accounts of stratigraphic ages, as well as personal communication with industry colleagues who had access to proprietary information. 47
STRATIGRAPHIC FRAMEWORK ONSHORE TO OFFSHORE The layered Tobago Forearc Basin units (Figure 4.2) are equivalent to the Oceanic Formation recognized in outcrop on the island’s eastern side. Although within the TFB it is believed that this unit ranges from Middle Eocene to Upper Miocene in age, onshore units are at youngest Middle Miocene in age (Barker and Poole, 1982) and are believed to have been deposited in water depths between 2000 to 4000 m based on foraminiferal data (Saunders, 1984). The Middle Miocene marks the initiation of TFB closure and the emergence of the Barbados Ridge. Based on onshore analyses, these rocks are interpreted throughout the region as deep marine pelagic clays and marls which are interbedded with volcanic ash deposits (Speed, 1989, 1994). The entire unit thins to the west onto the Lesser Antilles Island Arc high and post Mid-Miocene unconformity sediments thin onto the Barbados Ridge. Sediments below the Mid-Miocene unconformity drape over the Barbados Ridge and extend into the zone of piggyback basins. The seismic character of this unit is that of layered, continuous reflectors with minimal deformation by small-scale normal faulting. This seismic character is expected as the pelagic deposits are interbedded with volcanic ash layers and are locally cut by normal faults in outcrop. Scotland Formation The Scotland Formation is dated in outcrop as Lower Eocene in age and includes the oldest rocks exposed on the island. This unit thickens onshore into a thick, (up to 2800 m), succession of sands and clays comprised of very coarse grained turbidites and leveed channels deposits, with a conglomerate lag at the base of some large channels indicating a high energy erosive system. In seismic data, this formation has been equated with the western portion of the Barbados Accretionary Prism sediments and shows up as 48
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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
Page 11 and 12: 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: The highest point of the island, is
Page 65 and 66: STRUCTURAL FRAMEWORK OF THE BARBADO
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
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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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