(Along-Slope) Near Desoto Canyon, Gulf of Mexico: a Product of an Enhanced Paleo-Loop Current Shane Christopher Dunn University of South Florida, [email protected]
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University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School 11-13-2016 Miocene Contourite Deposition (along-slope) near DeSoto Canyon, Gulf of Mexico: A Product of an Enhanced Paleo-Loop Current Shane Christopher Dunn University of South Florida, [email protected] Follow this and additional works at: http://scholarcommons.usf.edu/etd Part of the Geology Commons, Geophysics and Seismology Commons, and the Sedimentology Commons Scholar Commons Citation Dunn, Shane Christopher, "Miocene Contourite Deposition (along-slope) near DeSoto Canyon, Gulf of Mexico: A Product of an Enhanced Paleo-Loop Current" (2016). Graduate Theses and Dissertations. http://scholarcommons.usf.edu/etd/6494 This Dissertation is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Miocene Contourite Deposition (along-slope) near DeSoto Canyon, Gulf of Mexico: A Product of an Enhanced Paleo-Loop Current by Shane C. Dunn A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy with a concentration in Geological Oceanography College of Marine Science University of South Florida Major Professor: Albert C. Hine, Ph.D. Stanley Locker, Ph.D. Pamela Hallock Muller, Ph.D. Harry Roberts, Ph.D. Eugene Shinn, Ph.D. Date of Approval: November 10, 2016 Keywords: Sediment drifts, seismic stratigraphy, ocean gateways, Panamanian seaway Copyright © 2016, Shane C. Dunn Acknowledgments I would like to express my gratitude to my entire committee for their help throughout the dissertation process. I would especially like to thank Dr. Al Hine for all he has done for me during my PhD and Masters. Also, IHS Inc. deserves much thanks for the university grant program which provided The Kingdom software, a vital tool in this dissertation. Table of Contents List of Tables iii List of Figures iv Abstract x 1. Introduction 1 1.1 Background information 3 1.2 Current and future significance of the work 8 2. Data and Methods 11 2.1 Seismic data and interpretation 11 2.2 Bathymetry data and interpretation 16 3. Results 20 3.1 The DeSoto Canyon Contourite Depositional System 20 3.1.1 Drift 1 26 3.1.2 Drift 2 30 3.1.3 Drift 3 34 3.1.4 Drift 4 38 3.2 Features diagnostic of contourites (moats/channels) 42 3.3 Data limitations 50 4. Discussions 52 4.1 Seismic expression of sediment drift features in the DCDS 52 4.2 Sediments and cores (DeSoto Canyon area) 56 4.3 Formation of the DCDS 59 4.3.1 The Loop Current and the DCDS 62 4.3.2 Ocean gateways, Loop Current intensification and the DCDS 67 4.3.3 Sealevel/Climate effects on DCDS development 79 4.3.4 Miocene sediment supply to the DCDS 82 4.3.5 Summary of DCDS development 85 4.4 DeSoto Canyon-The modern day physiographic features 89 4.5 Return to down-slope deposition and demise of the DCDS 98 i 5. Conclusions 101 References 105 Appendix 1 117 Contourites 117 Appendix 2 122 Contourites in seismic data 122 Appendix 3 128 Permissions for previously published figures 128 ii List of Tables Table 1 Contourite facies and compositions, adapted from Stow and Faugères (2008). 56 iii List of Figures Figure 1 General location of the study area, northeastern Gulf of Mexico, U.S.A. 2 Figure 2 Multi-channel seismic record depicting elements of the DCDS, i.e., underlying erosional unconformity, low amplitude and transparent seismic facies interpreted as drift deposits, moat/channel features indicative of contourite deposition, and along-slope transition to chaotic seismic facies representing a down-slope depositional environment- channel-levee system (position shown in Fig.1) TWTT in seconds. 3 Figure 3 Original hydrographic chart depicting the bathymetry of DeSoto Canyon and its S-like shape, reproduced from Jordan (1951). 4 Figure 4 (Left) Approximate position of the Suwannee Strait given in McKinney (1984) where the DeSoto Canyon is located within the footprint of the strait. 7 Figure 5 Coverage map of 2-D seismic reflection data utilized in this study. 12 Figure 6 Well E66-73A shown here, is reported to have intersected middle Miocene sediments at it deepest point of penetration. 15 Figure 7 USGS Multibeam bathymetry of shelf-edge deltas in the vicinity of DeSoto Canyon, NE Gulf of Mexico. 17 iv Figure 8 Bathymetry data acquired by NOAA's Okeanos Explorer in 2012 of the DeSoto Canyon Region, Gulf of Mexico. 19 Figure 9 Structural map of erosional surface interpreted to be a middle Miocene unconformity. 23 Figure 10 Slope map generated from gridded surface of seismic horizon interpreted to represent a middle Miocene unconformity. 24 Figure 11 Map depicting the boundaries of the 4 major contourite units comprising the DCDS (Drifts 1-4). 25 Figure 12 Map depicting the position of Drift 1 relative to the modern seabed. 26 Figure 13 Top panel is an isopach map of Drift 1 and the position of the 2-D seismic data depicted in the lower panel. 27 Figure 14 Top panel is an isopach map of Drift 1 and the position of the 2-D seismic data depicted in the lower panel. 28 Figure 15 Map depicting the position of Drift 2 relative to the modern seabed. 30 Figure 16 Top panel is an isopach map of Drift 2 and the position of the 2-D seismic data depicted in the lower panel. 31 Figure 17 Top panel is an isopach map of Drift 2 and the position of the 2-D seismic data depicted in the lower panel. 32 Figure 18 Map depicting the position of Drift 3 relative to the modern seabed. 34 Figure 19 Top panel is an isopach map of Drift 3 and the position of the 2-D seismic data depicted in the lower panel. 35 v Figure 20 Top panel is an isopach map of Drift 3 and the position of the 2-D seismic data depicted in the lower panel. 36 Figure 21 Map depicting the position of Drift 4 relative to the modern seabed. 38 Figure 22 Top panel is an isopach map of Drift 4 and the position of the 2-D seismic data depicted in the lower panel. 39 Figure 23 Top panel is an isopach map of Drift 4 and the position of the 2-D seismic data depicted in the lower panel. 40 Figure 24 Map depicting the position of the various seismic lines presented throughout the text. 42 Figure 25 Multiple moat structures are depicted in the subsurface resulting from erosion/non-deposition along the boundary between the slope and drift margins. 43 Figure 26 Moat features and a more pronounced slope-parallel erosional channel are depicted in this seismic section. 44 Figure 27 A succession of moat features is depicted in these data, the result of drift margins migrating up slope as contourite deposition continues. 45 Figure 28 Moat structures and a larger slope-parallel channel/moat feature are depicted in these data. 45 Figure 29 Multiple moat structures are depicted in the subsurface resulting from erosion/non-deposition along the margin of the subsurface erosional slope. 46 Figure 30 Moat/channel features in the subsurface adjacent to DeSoto Canyon. 47 Figure 31 Moat/channel features in the subsurface adjacent to DeSoto Canyon. 48 vi Figure 32 Moat/channel features in the subsurface adjacent to DeSoto Canyon. 48 Figure 33 Moat/channel features in the subsurface adjacent to DeSoto Canyon. 49 Figure 34 Interpreted seismic section depicting the stacking pattern of the drift deposits which comprise the DCDS. 49 Figure 35 Drawing depicting the primary controls on downslope and alongslope deposition, also the differences between the classic down-slope stratigraphic model and the more recent along-slope stratigraphic model, adapted from Brackenridge et al., (2011). 54 Figure 36 Map depicting the location of sediment cores relevant to seismic data interpretation along the DeSoto Slope. 58 Figure 37 Transition from down-slope to along-slope depositional styles interpreted from reflector geometry in seismic data. 61 Figure 38 Map of the larger Gulf of Mexico/Caribbean region. 64 Figure 39 Upper- Global paleo-geographic map depicting continent position and longitudinal connectivity through ocean gateways during the Eocene, 56-33.9 Ma. 70 Figure 40 Map depicting the location of ocean gateways integral to the development of robust circulation in the Miocene Gulf of Mexico and contourite deposition. 71 Figure 41 Chronology of key elements shaping the formation of the DCDS and sea-level fluctuations occurring during deposition of DCDS. 75 Figure 42 Seismic section from Mullins et al (1987) depicting some seismic characteristic of sediment drifts, e.g., transparent vii seismic facies, moats, and the upslope migration of sediment deposits. 78 Figure 43 Map of ancestral Tennessee and Mississippi Rivers during the middle Miocene. 83 Figure 44 Summary of factors contributing to the development of the DeSoto Canyon Contourite Depositional System or DCDS. 88 Figure 45 Map illustrating differences in the surficial geologic expression of the DeSoto Canyon and those submarine canyons/channels which occur along the DeSoto Slope to the west. 89 Figure 46 Map depicting the bathymetric footprint and surface morphology of the DeSoto Canyon. 93 Figure 47 Cartoon depicting large-scale erosional features of sediment drifts, i.e., contourite moats and channels. 94 Figure 48 Comparison of the surficial expression of the DeSoto Canyon to the Cadiz Contourite Channel (inset) as depicted by multibeam bathymetry. 95 Figure 49 Salt diapirs are common in the subsurface near the DeSoto Canyon, deforming the drift deposits and paleo-margins of the canyon.