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lutites (the word lutite is used in this text as a descriptive term for unconsolidated sediment with grain size less than 2 ~m, and no genetic associations are implied). Ericson and oth~rs (1952) examined cores from the Greater Antilles Outer Ridge and described them as IItypical deep-sea red clay throughoutll and lIentirely red clayll. Seismic reflection profiles taken in this"region (Ewing and Ewing, 1962; Savit and others, 1964; Bunce and Hersey, 1966) demonstrated that a blanket of acoustically transparent sediment up to 0.8 km thick covers and actually forms the Greater Antilles Outer Ridge in many places. The origin of this accumulation of sediment and the geologic evolution of the Greater Antilles Outer Ridge was chosen as the topic of this research effort. The most puzzling problem in reconstructing the geological history of the Greater Antilles Outer Ridge is the origin of the upper, acoustically transparent layer, and several working hypotheses can be tested. Extensive accumu- lations of sediments with a similar acoustic nature occur at numerous other locations in the world oceans, and some are attributed to'rapid deposition of biogenous material beneath regions of high surface productivity (see for example, Ewing and others, 1969). Thi s mechani sm coul d provi de much of the sed i me n t on the G re ate r An till e s 0 ute r Rid g e; how eve r , sed i - ment cores from the transparent layer contain low-carbonate, texturally homogeneous, variegated, terrigenous silty lutites with only scattered zones enriched in biogenous carbonate. 17 )
) ) This is expected since most of the Greater Antilles Outer Ridge lies below the carbonate compensation depth. Further- more, the surface waters of the overlying southern Sargasso Sea are r e 1 at i vel y un pro d u c t i ve (Ry the ran d Men z e 1, 196 0 ; Be~ and others, 1971). Core data from Site 28 of the Deep Sea Drilling Project on the south flank of the outer ridge (Bader and others, 1970) also indicate that the upper 170 m of sediment, corresponding to the transparent layer, is g r e e n - gray and b row n 1 uti ten ear 1 y de v 0 i d 0 f b i 0 g e no u s material; thus accumulation of biogenous material can be ruled out as an important factor in the deposition of the t ranspa ren t 1 aye r. Bunce and Hersey (1966) suggested that the transparent layer may be the remnant of a continental rise which extended northward from Puerto Rico and pre-dated the formation of the Puerto Rico Trench. However, continental rise sediments in the western North Atlantic typically exhibit numerous strong internal reflectors (Hoskins, 1967; Emery and others, 1970), and cores from true continental rises contain numerous beds of silt and fine sand (Ericson and others, 1961; Hollister and Heezen, 1972). On the Greater Antilles Outer Ridge, such rise-type sediments might also contain rapidly deposited calcarenite layers similar to those found by Schneider and Heezen (1966) on the Caicos Outer Ridge just 200 km to the west. None of these features is observed in the transparent 1 aye r. 18
Page 1 and 2: 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 27: GENERAL DES CRI PT I ON CHAPTE R I
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Page 32 and 33: egi onal contours. An area centered
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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 and 56: "- '''--.- 25° ................. .
Page 57 and 58: ) ) others, 1973), and the upper po
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
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co . (Y (l So :: O' "r- Li 51
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) 53
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) Figure 3.9. CONRAD 10 seismic ref
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0' (V CJ s. :: O' ... LL 55
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\ J ) Figure 3.10. Seismic reflecti
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or- . (V Q) S- :: rn Li 58
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ì ) Figure 3.11. CONRAD 10 seismic
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l UJ .líliiiP',,:... ¡ '"'" ~ ' ~
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) .I Figure 3.12. Echo-soundi ng pr
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N CV OJ s. :: 01 l. 62
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) ) Figure 3.13. CONRAD 10 seismic
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(' r- (' (j $. :: en 'r- LL 64
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) ) GENERAL LITHOLOGY CHAPTER iv TH
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~ , ) Figure 4.1. General lithology
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.'-/ '..-/ AIr 60-8 A II 60-8 An60~
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) )
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average of 80% lutite (~ 2 ~m) and
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) )
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.\ ! ') )
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ì/ )
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10 m2, with an average value of 1.3
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) ) /
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The laminated zones and overlying p
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) )
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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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) )
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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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) ) )
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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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) ) _/
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\ ) \ ì ../
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in age, and the ash is probably ass
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') .I \...../
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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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. ì )
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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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) )
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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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) \ ./
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'i j
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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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I ) \ )
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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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) )
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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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:') ¡i )
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\ i / ') ./
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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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" ) )
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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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) )
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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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) )
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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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) . ) .
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) , )
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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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) ) ./
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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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