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still locally break through the stratified abyssal-plain sediments. Acoustic basement thus forms a broad structural high under the eastern sector of the Greater Antilles Outer Ri dge, parall el to the east-west trend of the Puerto Ri co Trench. There is also some indication of smaller scale, WNW-ESE trending, basement structural ridges within the outer ridge - abyssal plain province (Fig. 3.4). The lineations are poorly defined, but they agree closely with the overall tectonic fabric of the oceanic basement in this region (Johnson and Vogt, 1971). Under the western sector of the Greater Anti lles Outer Ridge, acoustic basement lies at such great depths (~1.5 seconds) that it is rarely observed. Dredge hauls from near the level of the acoustic basement on the north slope of the Puerto Rico Trench have recovered basalt, serpentinite, chert and limestone. Bowin and others (1966) suggested that the 5.2 to 5.5 km/sec layer (layer 2) may be composed primarily of serpentinized peridotite with some altered basalt. However, Chase and Hersey '(1968) felt that basalt flows, possibly interbedded with limestone and chert, compose the acoustic basement, and they concl uded that the serpenti ni te came from the top of a deeper crustal layer of velocity 6.5 to 6.6 km/sec (the 1I0ceani c layer" or layer 3). It seems reasonable that acoustic basement (layer 2) in this region is basaltic crust which originated at the Mid-Atlantic Ridge (Bunce and 39 d) \ )
) ) others, 1973), and the upper portions probably contain subsequent local basalt flows interbedded with consolidated sedimentary rocks. Certai n 1 i mi ts can be pl aced on the age of acousti c basement and the "oceani c 1 ayer" under the eastern sector of the Greater Antilles Outer Ridge. The oldest sedimentary rocks recovered from the north slope of the Puerto Ri co Trench are middle Cenomanian (about 100 m.y.) in age (Todd and Low, 1964), and they probably originated from near the top of acoustic basement (layer 2) or from the base of the overlying stratified layer. Extrapolation of data from magnetic anomalies and JOIDES borehole results (Pitman and Talwani, 1972) into this area suggests a crustal age of 110-130 m.y. Thus the sea floor in this area was probably fi rst formed no earl i er than the early Cretaceous. THE S T RA T I FIE D LAY E R The acoustically stratified sediment directly overlying acoustic basement and forming flat-lying ponds between basement peaks under the Greater Anti 11 es Outer Ri dge is referred to hereafter as the stratified layer; it has compressional wave velocities of about 3.0 to 4.5 km/sec. A distinctive reflector observed in the stratified layer and here referred to as Datum A is ubiquitous in the area studied, except under portions of the Greater Anti l1es Out erR i d gee a s t 0 f 630 W 1 0 n g . (F i gs. 3. 4 - 3 . 6 ) . D a t u m A ma r k s the top 0 f the s t rat i fie d 1 aye run de r the e a s t ern 40
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I "a f IMods Hole '" ~ o c.,,~tlOGR
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Page 7 and 8: parent sediment on the eastern oute
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Page 11 and 12: Res u 1 ts. . . . . . . . . . . . .
Page 13 and 14: Figure 3.12 Echo-sounding profile (
Page 15 and 16: Fi gure 6.14 6. 15 7. 1 7.2 7.3 7.4
Page 17 and 18: \ I ) Table 4. 1 4.2 5.1 5.2 5.3 6.
Page 19 and 20: CHAPTER I INTRODUCTION The area inv
Page 21 and 22: ) \ .1 Fi gure i. 1. Bathymetry of
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Page 25 and 26: ) ) This is expected since most of
Page 27: GENERAL DES CRI PT I ON CHAPTE R I
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Page 32 and 33: egi onal contours. An area centered
Page 34 and 35: this region. However, all of these
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Page 38 and 39: ') ) ) /
Page 41 and 42: '"-, i~ 7t 70° 6f 68 67° 25° 72
Page 43: Fig u r e 3. 2 . CON RA D 10 s e is
Page 46 and 47: sequence corresponds to layered tur
Page 49: ) . .) Figure 3.3. Map showing domi
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Page 55: "- '''--.- 25° ................. .
Page 59 and 60: ) Figure 3.5. CONRAD 8 seismic refl
Page 61 and 62: . Q) 3W/L NOI.L~ l( . (Y CI s. :: 0
Page 63 and 64: .) Figure 3.6. Idealized profile al
Page 65 and 66: ) ) a: 0 ~ ~ (J L. Z Q) a: ~ lU UJ
Page 67 and 68: ) ) Figure 3.7. CONRAD 10 seismic r
Page 69 and 70: i- (Y (1 ~:: en or- LL 47
Page 71 and 72: ) ) THE TRANSPARENT LAYER The distr
Page 73 and 74: Fi gure 3.8. CH A I N 34 s e ism i
Page 75 and 76: co . (Y (l So :: O' "r- Li 51
Page 77 and 78: ) 53
Page 79 and 80: ) Figure 3.9. CONRAD 10 seismic ref
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Page 83 and 84: \ J ) Figure 3.10. Seismic reflecti
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Page 87 and 88: ì ) Figure 3.11. CONRAD 10 seismic
Page 89 and 90: l UJ .líliiiP',,:... ¡ '"'" ~ ' ~
Page 91 and 92: ) .I Figure 3.12. Echo-soundi ng pr
Page 93 and 94: N CV OJ s. :: 01 l. 62
Page 95 and 96: ) ) Figure 3.13. CONRAD 10 seismic
Page 97 and 98: (' r- (' (j $. :: en 'r- LL 64
Page 99 and 100: ) ) GENERAL LITHOLOGY CHAPTER iv TH
Page 101 and 102: ~ , ) Figure 4.1. General lithology
Page 103: .'-/ '..-/ AIr 60-8 A II 60-8 An60~
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average of 80% lutite (~ 2 ~m) and
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10 m2, with an average value of 1.3
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The laminated zones and overlying p
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) ) Figure 4.7. Graph of carbonate
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) ) z 0 N O~ E I i ,,_.' i." I ." .
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) ì i Figure 4.8. Curves of carbon
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currents have transported many Fora
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increased dissolution (elevated lys
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TABLE 4.1. MINERALOGY OF THE c 2 ~m
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the following peaks and weighting f
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Obvi ous ly, di 1 uti on of the nor
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The m i n era log i c a 1 com po si
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gray 1 uti t e s per s i s t n ear
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TABLE 5.1. AVERAGE RATES OF SEDIMEN
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and thus the T-Z zonation (Fig. 5.1
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TABLE 5.2. AVERAGE RATES OF SEDIMEN
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Cl z: c: l/ l. i- c: Cl z: o OJ IX
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consolidated (A.J. Silva, pers. com
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in age, and the ash is probably ass
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122 must result from mixing with th
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eas twa rd flow of NADW between 150
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whi ch recorded currents for about
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,) , ,
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ottom photographs in February, 1972
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Several important features were obs
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141 turn north in the western part
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145 bottle spacing. An example is t
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~() ~ 3.0 ~ ~ ) ~ ~i. ) .. ~ 2.0 ~i
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) ) Figure 6.6. Silicate ("g-atoms/
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) ) ~ 2.2 ~ 2.0 t2 ~ tt ~" 1.8 .. ~
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,) -) 152 structure persist at and
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) ~) 154 Figure 6.7. Current patter
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) ) 72° DEPTH IN CORR. METERS Fi g
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) ) speeds of 2 cm/sec (the stall s
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) I / Fi gure6. 8. 158 Progressi ve
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" ) / ) 10 19 17 5 5616 M 5801 M N
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) ) ~ 160 Figure 6.9. Polar histogr
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,) B(LOWER) START 22 B(UPPER) START
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) ) Figure 6.11. Polar histogram of
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) 2700 ) 00 1800 F; g u re 6. 11 C
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, ) ) _/ Figure 6.12. 168 Progress
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\ --~ E START 21 5 30 12 XI 21 xu )
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) / i I .~J the flow recorded at cu
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) Figure 6.13. Directions and relat
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') ./ ) ,j 70° 68° 66° ~~oo · "
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Fig u re 6. 14. i 75 Bottom photogr
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S e c t ion 2 (F i g s. 6. 1, 6. 7)
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northwest flow along the west flank
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filter (0.50 lJmpore size). After f
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. '! ) ) ,./ 2.2 ~ 2.i () '- 2.0 ~
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) ) Figure 7.3. Light-scattering pr
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'\. './. V 23-7 V 23-6 V 25-74 V 25
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extensive erosion on the lower cont
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) \/ (SEM) to determine composition
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\ ) ) Figure 7.4. 195 Scanning elec
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The less than 2 ~m (lutite) fractio
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201 In a sample where additional cl
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TAB LE 7. 1. CALCULATE D CLAY MI NE
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:1 / , ì j
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cannot always be accepted at face v
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The apparent enrichment of chlorite
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in favor of the concept that the su
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on the north flank of the far easte
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that enough suspended matter has be
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The following pages describe a mode
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series of ridges associated with an
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Eocene to 01 i gocene (Monroe, 1968
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(Table 8.1). The interbedded silts
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229 Chase and Hersey, 1968). The th
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\ ! Figure 8.3. 231 Schematic diagr
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Downslope sedimentation covered the
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) 235 Fi gure 8.4. Sketch showi ng
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'\ l ) ~z w u w a: o ~ wz w o u ~ w
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) / the same event of current-contr
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) Figure 8.5. Idealized representat
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) \ ) d / 'I i II I Ii I i I i I I
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) \ ) formed earlier depositional s
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) ) homogenei ty of the sediments o
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) ) 2 ) Sou t h S lop e - P u e rt
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248 Biscaye, P.E. and S.L. Eittreim
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Ericson, D.B., M. Ewing, G. Wollin
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Hersey, J.B. (1965) Sediment pondin
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McCullough, J.R. and G.H. Tupper (1
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Swallow, J.C. and L.V. Worthington
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259 approximation of the amount of
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s ~ 0 ~ Q) o '- CO 0 U ~ it \f0 Q)
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Crui se All 11 All 11 AII 60 Leg 8
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TABLE A2.1. BOTTOM PHOTOGRAPHS (Con
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TABLE A2.1. BOTTOM PHOTOGRAPHS (Con
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TAB LE A2. 1. BOTTOM PHOTOGRAPHS (C
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CH 19 CH 19 CH 19 CH 34 CH 34 TABLE
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KN25 KN 25 KN 25 KN 25 TABLE A2.1.
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LL 8 LL 8 LL 8 LL 8 LL 8 SA C ru is
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s. .. M i. 0 1. " .. QJ ..- N .. C'
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~.. c. 0' 0 .. Q)+l- ~ 0' 0' 0 ~ M
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TABLE A3.1. SUSPENDED PARTICULATE M
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) -) APPENDIX IV PHYSICAL PROPERTIE
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) ) Figure A4.1. Plots of water con
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) ) C\' 0 § to ~ ~ ~ 0 ~ ~ ~ CI Q:
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) /) 295 Figure A4.5. Plots of wate
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'-. ~, 160 SHEAR STRENGTH 30 50 (g/
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) ) Figure A4.6. Plots of water con
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) ) 307 Fi gure A4.11. Plots of wat
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"-, ',, WATER CONTENT (% DRY WEIGHT
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) j 309 Figure A4.12. Plots of wate
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) 312 WATER CONTENT (%DRY WT) SHEAR
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) J BIOGRAPHY Born: Ma rch 19, 1946
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') \ ) ~UWDATORY DISTRIBUTION LIST
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) J
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UNCLASSI FIED 1/31/74 SECURITY CLAS
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