TURBIDITE DEPOSITION ON THE BELLINGSHAUSEN
ABYSSAL PLAIN: SEDIMENTOLOGIC
IMPLICATIONS
by
M. BAEGI
A THESIS SUBMITTED
IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE
MASTER OF ARTS
APPROVED, THESIS COMMITTEE
Dr. Robert B. Dunbar, Assistant Professor of Geology
HOUSTON, TEXAS
APRIL, 1985 3 1272 00289 1040 ABSTRACT
A number of piston cores from the Bellingshausen abyssal plain contain gravel and sand units which are interpreted as turbidites deposited in submarine channels. Middle and outer fan deposits are lacking, although core coverage in the region is sufficiently dense that such deposits should have been cored if they exist. This implies that sediment supply to canyons in the area is presently limited, which is not surprising, given the fact that these canyons are presently isolated from potential source areas. Also, the continental shelf is quite deep, averaging 400 meters, so that sediment supply to canyons during low sea level stands is probably restricted. Indeed, a problem exists as to how the turbidites of the abyssal floor were derived.
Mineralogic analyses of turbidites indicate relatively restricted source areas for deposits of individual channels. This implies that sediments are supplied directly to canyons, possibly by meltwater streams, during times when the ice sheet is grounded at the continental shelf edge.
Miocene turbidites penetrated in DSDP Leg 35 sites display textural homogeneity with depth in individual units. This implies that these sediments were derived from already sorted source materials, possibly beach or fluvial deposits. Hence, a much different glacial setting is indicated for this time. ACt
I wish to express my sincere thanks to my advisor, Dr.
John 8. Anderson for his suggestions and constructive
c~iticism regarding my thesis. I thank him for the time and
energy devoted to overall development and training in the
skills of scientific thought and research.
I am e:.pecia.1l;.. · gr·ateful to Dr·. Richar·d E. Casey and Dr·.
Rc•b Dunbar· fc•r· :.er·'·ling a:. my committee member·:. a.nd fc•r· ti"teir·
comments and understanding.
Thanks goes to Mr. Dennis Cassidy, Florida State
University, Tallahassee, for sending the Eltanin piston core
samples. Thanks also goes to Amy 8. Altman, Scripps
Institution of Oceanography, La Jolla, California for
sending DSDP Leg 35 samples.
Robin Wright, Eugene Domack and all my fellow graduate students for their support both in their scientific comments and highly valuable friendship.
In closing, I would like to thank my wife Hazema, Ben
Musa and my children for their spiritual support and
:.acr· if ice·:.. TABLE OF CONTENTS
CHAPTER 1
I t·-JTF~ODUCT I Ot··.J
Physiography and Bathymetry of Bellings h au :.en :::;ea.. 4
General Geology of West Antarctica. 1 1
i .-. F .::c.n t· ..lode 1 ·:...... :.
Glacial Marine Sediments. 21
METHODS OF ANALYSIS.
CHAPTER 2
Description~ Distribution and Interpretation .-,...., of Piston Cores . .:..t
Description, Distribution and Interpretation of Tur·bi di te:.. 54
CHAPTER ::::
Mineralogy and Province of Turbidites .
CHAPTER 4
Origin of Sand Turbidites
CDt-··lC:LUSI Dt··.J~;. :34
F::E FE F::Et---JCE ~;
APPEND I/
APPEND I >< I I . L I ST OF F I GURE~:
FIG General location map of piston ccores
·"j FIG .<... Bathymetry of Bellingshausen Sea~
':• FIG •' Echo sounding across the outer ccontinental shelf of the study area
FIG 4
FIG 1::" General geology map of Western Anntarctica -· (Bellingshausen Sea)
FIG 6
FIG 7
FIG ._,·=· Gen er· a 1 1 i tho 1 ogy a.n d 1 c•c at i on c•f f pi :. ton c c•r· e:. in the Bellingshausen Sea
FIG 9 Lithology of sand body 1 (Adelaidde sand body)
FIG 10 Grain size distribution Core 10-25
FIG 11 Grain size distribution Core 10-5
FIG 12 Grain size distribution - Core 13-9
< ~. FIG .L ·=· Lithology of the Core 11-23 FIG 14 Grain size distribution -Core 11-23 (Upper Unit>
FIG 15 Grains size distribution - Core 21-23
FIG 16 Lithology of sand body 4
FIG 17 Grain size distribution - Core 17-20
FIG 18 Grain size distribution Core 13-13
FIG 19 Stratigraphy of DSDP Sites Leg
.-.c FIG 20 Gener·a 1 map shm,..ti ng DSDP Leg .;,• ._1 site:.
FIG 21 Grain size distribution of Core 4, Site 323
FIG 'j'j.;,_._ Gr· .:.. i n :. i z e d i :. t r· i bu t i c•n - Cc-r· e 1 , 6 , 10 , 1 1 , :::: i t e .-..- ..-, ..:~.::...t:. LIST OF FIGURES (cont.)
FIG Map showing the dist~ibution of mine~alogical suites in the Weste~n Anta~ctica Peninsula
FIG 24 Map showing the dist~ibution of heavy mine~als (piston co~es) in the study a~ea
FI~ Map showing the dist~ibution of light mine~al f~actions (piston co~es) in the study a~ea
FIG 26 Map showing the dist~ibution of 1 ithic fractions in the study a~ea
FIG 27 Map showing mine~alogical suites in the study a~ea TABLE 1 Se•j i men t a.r· '/ c r· i t er· i a. f c•r· the e r· ec c•gn i t i c•n of ma.r· in e s.ed i men t ·:.
APPEt··.JD I>< Te>:tur·a.l and miner·alc•gic datata fc•r· El tanin piston cores and DSDP Cores
G = 13r· .=t.'v'e l >~ 7. - - d -·lt [1 '- . t_: = !:;an : :::; 1 . : _:I a,::/ MGS = Mean Grain Size S.D. = Standard Deviation t;~:;:[L... J = :::;f APPEt·-lD I>< I I Loca.tic•n and Depth·:. of USt·-JS El El tanin pi:.ton cores used in this study CHAPTEF: 1 INTRODUCTION Statement of P~oblem A numbe~ of piston co~es collected f~omm the abyssal f~oo~ a~ound Anta~ctica have penet~ated sarnnd and g~avel depo-:.i t-:. pr·e-:.umed tc• be tur·bidi te:. t h e ·::. e t u r· b i d i t e =· ::. '=' c• r· c• b 1 em,:.. t i c • T r· ,:.. d i t i c• n• n .:., 1 mc• de 1 :. f or· deep sea fan development do not apply, as tthese models cal 1 for· t r· an -:.pc•r· tin g s.ed i men t into can ::•'C•n h ead-:.1-:. f r· om f 1 U\.' i a.1 sou~ces and by longsho~e cu~~ents, the lattte~ p~ocess occu~ing du~ing pe~iods of low sea level sttand. The~e a~e no r·i·...,·er ..::. or· be.aches in Ant.ar·ctica. The hi•ighly ir·r·egula.r· continenta.l s.hel f i-:. quite deep (a:v·er·a.ging ~ 500 meter.. :.), and typically slopes toward the continent. Thuus, sed~~ent t~anspo~t ac~oss the shelf is p~esently minhimal (Anderson et .:..1 . 1·;;:·:;::::) . The qtJ e:. t i on t her· ef c•r· e ar· i -:;.e·:. a. s. :. to h ov.J the turbidites of the Antarctic seafloor were d~erived. Th i ·:. the·:. i =· de-:.c r· i be:. the r· e:.u 1 t =· of a.n ·, i n'-/e:. t i g.:.. t ion into this problem. The research concentratEed on the Bellingshausen Abyssal Plain due to the wid~espread occurrence of tu~bidites in this area. Turbbidite deposition character of these turbidites has changed si.ince then. The c1 im.:..tic impl ic.:..tic•n·:. c•f thi:. cha.nge in :.ediliment.:..tion t.~. .ter·e also investigated. FIG 1. -Map showing the distribution and location of piston cores around Antarctica. Triangles designate piston cores which penetrated sand turbidites and dots piston cores which penetrated fine-grained terrigenous sediments interbedded with pelagic sediments. Squares designate DSDP leg 35 sites refered to in text. co C.· 4 Physiography and Bathymetry of the Bellingshausen Sea Detailed Knowledge of the bathymetry of the Bellingshausen Sea is limited due to its irregular topography and extensive ice cover. The most detailed discussion of the bathymetry of the area is given by Vanney .:..nd .Johns.c•n 1'??.:;.) • Figure 2 shows a bathymetric map of the .:w.r· e.a. The continent.:..! s.hel f in the Bell ings.h.:..u·:.en :::;ea i·:. ir- regular and typically slopes toward the continent (Fig. 3). The ·:.hei f is. quite deep, 1..... 1i th an .:._•._..·er·age depth of 400 meters~ and the shelf break is situated at approx1mately 400 .;..n d 500 meter.. : .. U-shaped glacial valleys D)~ which are characteristic of glaciated shelves (Shepard, 1931), also occur on the continental shelf. The continental slope in the Bellingshausen Sea region is more gentle than in the area adjacent to the Antarctic Peninsula. where the slope is extremely steep (up to 140). The width of the continental slope varies between 20 and 60 km, and numerous canyons are present. The larger of these include Charcot, Adelaide and Palmer Canyons (Fig. 4>. Of these. only Adelaide Canyon is known to be deeply indented into the Antarctic shelf. The continental rise generally lies at a depth which varies from 3,000 to 4,800 meters, and is up to 500 Km wide FIG 2. Bathymetric map of the Bellingshausen Sea. ( fr·om 1-)an n ey .:.,n d ,John :.on , 1'?7 6) I I l> CD z fT1 --1 r l> r :u () -z --1 G) - (J) () I l> -o c fT1 (J) z fT1 -z z (J) c (J) r fTl l> l> ..• 'f... J 11,,,, (]) 0 0 ...... ~ . : ' ... : . ·. :...... ·. .. . t. : • .••••••• . . . . . •• . .• . • .•••••• ... • • • . . • • • .40 ...... • • • • • • ...... ·...... •· ...... "'0 0 ~ 0 0 Q 7 FIG 3. Echo sounding profiles across the outer shelf and u p per· ·:. 1 C• p e ( f r· om T u c h cd k e -~ n d H o u t z , 1 '7'7 .::;. ) • 8 0 200300 400 600 800 1000 V.E. X 27 FIG 4. Map showing canyon systems of the Bellingshausen :3e.:.. ( f r· c•m 1).;:..n n ey .:.,n d .John ·:.on ~ 1 '7'7 .::=.) • 10 . "..... " ADELAIDE CANYON CHARCOT CANYON:\'···-···- 1 I .I . :. . . ~~ I BELLINGSHAUSEN .: ABYSSAL PLAIN ELLSWORTH LAND rrni l> ZCl 0-< ::0 0 1 1 with a slope of 3.6 m/Km. Channels are numerous on the cent r· .::..1 pe..r· t of the continent e.. 1 r· i s.e . These channels trend both transverse to the slope and to the west (Vanney and The Bellingshausen Abyssal Plain occupies the northern part of the study area. The depth varies from 4~700 meters to 5,000 meters with a gradient of 0.4:1000 (Vanney and In the north, the abyssal plain laps against the steep walls of numerous fracture zones. General Geology of West Antarctica The geology of West Antarctica is complex and not wei 1 established. The basement complex of West Antarctica is represented by a variety of intrusives (gabbroic to gr·e..nitic>, along t.•.Jith meta.mor·phic, -:.edimentar·y, and './olcB.nlc rocks that are widely distributed and strongly deformed. Intrusive rocKs of probable early Cenozoic age occur throughout much of the West Antarctica and the Antarctica Penin:.ul a. These rocks include granites, granodiorites and q1Jar·tz dior·i tes (Cr·addock, 1'7'72). Rocks of Precambrian age h .;:..·.,..·e y·e t t C• be d i sc o•.,,•er· ed ( Cr· addoc k , 1 '?72) . Adie (1955) studied rocks from the Andean Batholith on the Antarctica Peninsula and found quartz diorite to be the dominant rocK type. He concluded that these rocks contain 50% plagioclase, 20% quartz, 4% magnetite and 20% hornblende 12 and biotite. Also, WadeL WilbanKs ( 1972> studied the metasedimentary sequence that outcrops along the Eights Coast and Thurston Island. These rocKs are extensivelv folded and are mainly graywacKe, phyllite, quartzite and sl.:..te. Figure 5 summarizes the outcrop geology in the area around the Bellingshausen Sea. PRE'· ...-' 1 OUS ~·'lORt< Fan 1'1c•de 1 =· :;:; u bm .:.. r· i n e f a. n s a r· e c c•m p 1 ex ph ;.·· s i C• g r· a ph i c f ea. t u r· e s. t h a t commonly develop at the base of continental slopes. They .:..r· e u -:;.>J .:..1 1 ::l c •:•mpc•-:.ed of ou tv.Jar· d r· ad i .:.. t in g =·::/':. t ems. of distributary channels and prograding lobes. Later·al shifting in these channels will result in the abandonment of old distributary systems and the formation of new ones. As .:.. r· e·:.IJ 1 t , t u r· bid i t e :.a.n d:. t•ec orne emp 1 a.c ed on top c•+ interchannel deposits. In general, the facies distribution within the fan are controlled by several factors such as: the physiography of the depositional basin, climatic change, ·:. e ~. 1 e·v· e 1 f 1 u c t u a t i C• n :. ( e u :. t a. s. ;.--) , t e c t C• n i c h i :. t or· ::.-· , t h e nature of the sediment source, and the presence or absence of indigenous bottom currents. In the last decade, studies of submarine fans have FIG. C"·-' Map Showing Outcrop Geology of the Study Area. EXPLANATION INTRUSIVE IGNEOUS ROCKS D JKs- Jurassic and Lower Cretaceaua strata, .eaatern Alexander fil.)ij,J KTI-Cretaceous-Tertlory Andean Intrusive aeries llklnd and western Livingston laland(Antarctlc Penlnaula) Antarctic Peninsula 0 Ca- Carbonlteroua(!) strata, Antarctic Penlnaulo j:.·~:;j Mzi-Mesozoic Intrusive rocks, Ellsworth Land (Trinity Penlnaula serlea) mainly felalc In compaaltion 0 Tv- Tertiary volcanic rocka, Antarctic Peninaula • KI-Cretaceous intrusive rocka, Marie Byrd Land felsic in composition; Includes granite, granodiorite, tonalite, al!d adamellite ~~;~ Czv- Cenezolc volcanic rocka, Antarctic Peninaula, ~ Pzb- Poteozolcf.?) i!!truslve and medlum-to-hlqh .. ~rorte · • Ellsworth Land, Marie Byrd Land, Transantarctic Mountains, metamorphic rocks, Antarctic Peninsula, Ellsworth East Antarctica Land (@tfl Jv- Jurassic volcanic: rocks, Antarctic Peninsula ond ~ Pzi-Paleozoic('1) intrusives of Queen Maud Land Marie Byrd Land (syenite), the Antarctic Peninsuia(rocks here also include some volcanic types), and the Hort Hills(gabbro) 14 0 0 E L L (] +eo- .. z a: w .-,... 80•+ Cl) :;, 0 Cl z 0! < ~ C!) w z Ill c:[ • til~,... ., ..J .J • ..J .J+9o• +90" 1&.1 CD .J j greatly increased our knowledge of sediment properties and facies distribution, and because of their potential as targets for hydrocarbon exploration, they are now receiving considerable attention. Sand bodies formed in canyon channels and super fans provide good reservoir rocks, while fine-grained slope, interchannel and pelagic facies provide potential reservoir seals and source rocks. Ther·efor·e, the alternating association of these facies, which takes place during shifting and growing phases of the fan, may result in the formation of stratigraphic traps. More recently Walker ( 1978) and others have emphasized the possibility of petroleum reserves 1n canyons and fans. Several facies models for submarine fans have been ,je... /el•.:.ped (t···lc•r·mar·l<, 1'7'7121; t·'1utti a.nd Ricci L•Jcchi and ~-··lalker·, 1978). The model of t"'lutti .:..nd F.:icci Lucchi ( 1'7'72> is. one of the mos.t fr·equentl;.' cited (Fig ..~.). Their· model includes di-:.tr·ibutor·:·/ channel and inter·ct-•.:o.nnel a.r·ea.·:. s.a.n d·:. tone 1 abe·:. a.n d in t er·l c•be ar· e.:.. s. ( c•n the outer· f .:..n) , a.n d a fan edge to the basin plain region. This model was based on a study of flysch deposits and may best represent a large, medium to deep water fan type. t··-lor·m.:..r· k ·' s. ( 1 '7'7(1 , i 974 , 197B) :.u bma.r· in e f a.n mc•de l -:. ,j i ..._... i de the fan complex into three main parts, an upper fan with main leveed channel a middle fan with active and abandoned 16 FIG. 6- S!Jbmar·ine fan model of r1utti and Ricci Lucchi ( 1'7'72>. T.:..ken fr-om Ricci Lucchi, 1975. 17 BASIN PLAIN --~ I Depoaitionollobe.:r·---:---, '~ t .J \ I ', \ ...... ' \ ,... -- ,',, Interchannel areas I -> \ ,__ ' ..."""' "''\\ L--.-:....._,,,, '-:;,. ~.,- \ --"'- Matn distributary channel Mid fan ," v' '\ Outer fan \ '• Inner fan " \', \~~:· Main volley Lower sl~;e'Y""'"~ SLOPE ------, -~- ...... _ Passive slope __upper slope ~-11~~-- SHELF 1·=·.... super fan regions, and a lower fan which grades distally into the basin plain. This model was originally developed from studies of California continental margin fans, and thus best describes a small, deep water fan type. 1.-iaH This model was developed from several ancient fans and concentrates primarily on the nature and distribution of resedimented conglomerate and sandstone facies. It is me•·:.+: representative of small-to-medium size shallow water fan type·:.. The models described above are very useful for pre- dieting facies distributions, and thus in prospecting for sandstone reservoirs in ancient, deep marine sequences. However, some problems still remain. First, the character- ization and distribution of fine-grained turbidite facies ha.s. yet tc• be studied in a.dequate detai 1. Second, previous depositional models have been developed for ancient fans tha.t VJere c•f r·el ativel ::/ small size and for·med in sma.l i, tee tc•n i ca.l 1 y act i\1e bas.i ns ( F.:i cc i Lucch i, 1'7'75) . Ther·e- fore, these models do not exactly represent either very large deep sea fans, such as the Bengal Fan and Mississippi Fan,or shallow water fans and slope-apron deposits. Existing fan models rely upon rivers or longshore currents to transport sediment into canyons. F I G . 7 - t·'1c• de 1 Ct t ·:.u bm ~. r· i n e t .:.. n , r· e 1 a. t i n g t .:._ c 1 e ·:. , f :.. n mc.rphc.1c.gy, and depositional envirc.nment. D-8 indicates disc.rganized bed cc.nglc.merate. 1974) • FEEDER- CHANNEL ~ ' Debris D-8 I l Flow ~0~- ~ Sl m s j l I !:.OC?:_ ~00 I·-:>~ p T ___!___),1 " l_- _?. OQ 0 1 I >(~~ i SLOPE ' --- . L_9 • INTO BASIN- ~ /. \· ---- .:~.L _____~ I I Cong'o /l I --.. -~------1nvcrsc to ,. rnerotes• /'--f!i{ .___ _ ./ Thin bedd normolly ~ ~ i..,. ~',_.,__=::-~ oned,turuidites graded~~!·-- ~/,-~~ ~' '~-lJPPER . --- t e""e Graded bedd I ·.. • Terrae• -- ! I \ LOWER------· - - tng :-·· ~ • ...... --~ \ "\ u·~-'···~ ,...,...,.,.. ,,,,' , ,f/ , I '·....._ ' ~-"'. J bbly sc;rs -·· / ,--- ~' \\ ' ' ------•'':' "" - /7t.\ ~ , -roidQd ~~~~- Graded stratified 10-FAN '' \ \t---' "'~----~-1;~? ssrs \ ••.. Suprofon Lobes If::' ~~,X~I Smooth ~-( loss' ' Incised :\~ ~ 10:, Turbidites Channel ~\ .t --.. . LOWER FAN / !' w Suprafan . Lab Thin b e d ded----~/ e BASIN PLAIN {No scale impliedl t-..:• IS• 21 c c..n \'On·:. i s. mos. t act i 'v'e du r· i n g 1 ot.o,l s. tan d·:. of ·:.ea i e--./e 1 . Given the present glacial setting in Antarctica (no rivers) and great depth of the shelf~ these agents are virtually in act i \.-'l:f! t her· e. Even during a low sea level stand~ such as existed during Wisconsin time~ the Antarctic continental shelf was mostly situated below 250 meters~ thus, this eustatic change presumably had little or no influence on sediment supply to Antarctic submarine fans. AI s.o, coa.·:.t.:..l (wave dominated processes) and wind generated currents have only a minor influence on shelf sediments. Ther·ef or· e, glacial and glacial marine sediments of the continental shelf have undergone little or no sorting prior to their deposition in the marine environment. For these reasons~ those processes which control turbidity current deposition on the Antarctic seafloor may be unique, and~ therefore, existing depositional models may not apply. t::ii .:..c i .:.. i a.n d G1 a.c i a.l t··1ar· in e Sediment Glacial marine sedimentation in Antarctic seas is entirely dominated by ice sheets, which deposit most of their debr1s on the continental shelf (Anderson et al. The majority of piston cores collected from the Antarctic continental shelf consists mainly of glacial sediment (both tills and transitional glacial marine sediments deposited jn close proximity to the ice shelf gr· c•u n ding 1 in es) . Th e:.e depo·:. i t =· ar·e sh ar· p 1 ~, over· 1 a in by glacial marine sediments which show a greater marine influence. Studies of these deposits have been conducted on the continental shelves of the Rose Sea (Chriss and Frakes, 1'7'72), a.nd the 11-leddell Sea, and Gec•rge 1·...' Cc•ast (Ander·sc•n et al. 1980, Dom.:..cl<, 1980). The facies bc•undar·!"' betv.Jeen glacial and glacial marine sediment marks the previous pc•:.ition of the ice shelf gr·otJnding line. Lao.ndwar·d fr·c•m the gr·c•undi ng 1 i ne, ba:.a 1 t i 11 is depo:.i ted by 1 odgemen t. Seaward of this line, glacial marine sediments are depco:.ited, with the ice-r·afted component decr·ea:.ing in an offshor·e dir·ectic•n r·elative tc• the mar·ine cc•mpconent of the:.e sediments. Glacial marine sediments contain marine fossils, are usually stratified, and show some sorting. These char·acter·istics ar·e used to differ·entiate them from ti 11-:. (Tab 1 e 1) • Ander·:.on et al. ( 1'7'80) r·epc•r·ted that 1 ittle ice-r·.:..fted debris occurs in sediments collected on the continental rise and abyssal plain. This is because most basal debris is deposited near the grounding line of the ice shelf itself. Therefore, very little debris makes its way to the calving line and hence into icebergs. The basal melt rate of iceber·gs incr·ease:. dr·amatica.11!"' near· the :.helf edge VJher·e warm deep water impinges onto the shelf. Also, the drift path of icebergs tends to be in an offshore direction on the TABLE SEDil-!ENTARY CRITERIA FDR RECOGNITION OF !>lARINE SEDIMENI' TYPES (rrodified after Anderson et al., 1980, and Kurtz and Anderson, 1979) 2 3 Ccrnpound Glacial Marine Residual Glacial Basal Till Sediment Marine Sediment Stratificaion None Crudely st.ratified to well Crude or absent. stratified. Nature of up Sharp Gradual, sharp. Sharp or gradational per and lower contacts Texture Polym:Jdal size Broadly bimodal size distribu Poorly sorted sands distribution. tion with pronounced fine (silt) and gravels whose Matrix sorting trode consisting of current fine canponent has range fran 2.5 derived silts and unsorted ice been winnowed. to 3.3 phi. rafted trode, the relative Matrix is concentrations of these two coarse skewed. canponents varies with depth Individual units in the section. exhibit strong textural lnrogenei ty. Unit Thickness Mi.n.imun thick Ranges fran a few centimeters Insufficient data. ness ranges to a few tens of meters. fran 1.4 to 9.0 meters. Physical Overcanpacted Often water saturated with Loosely canpacted Properties cohesive strengths cohesive strength of less exceed 0.25 Kg/em. than 0.25 Kg/em. Pebble None Elongate pebbles aligned Elongate pebbles sh::M crude Fabric parallel to bedding. alignment parallel to bedding Fossil None or !>Iarine fossils with changing Abundant marine fossils. Evidence reworked diversities and abundances. Bathymetric Restricted to Continental shelf to Occur on shallow portions Position continental abyssal floor. of continental shelf (above shelf. about 250 m) , and on the continental shelf break. Origin Deposition by Deposition fran floating Deposition from floating grounded ice; ice in law-energy marine ice in high-energy marine lcrlgement environment. environment. processes. 24 shelf and then parallel to the shelf edge and slope, so that any debris that is carried by icebergs is most l1Kely to be depo:. i ted on the E.h e 1 f .;:..n d s.l ope (Ander· :.c•n e t a.l . 1 9::;:::::) • Kurtz and Anderson ( 1979) Wright and Anderson (1982) and ~··lr· i gr, t e t .:..1 • < 1 '7'83) h a·v•e :.h C•t.. •m t h a. t sediment gr· a: ....· i t y· f l o\.•,1·: play a Key role in redistributing glacial sediments on the continental shelf and slope. Debris flow deposits appear to be most common on the more gentle continental slopes. reflect the delivery of large amounts of unsorted debris to the outer shelf, most probably by ice (Kurtz and Anderson, The sediments may suffer subsequent failure during isostatic adjustment upon glacial retreat. Ander·:.on et .:.. ·1 ( 1979) described debris flow deposits in cores which were taKen from the eastern Ross Sea and western Weddell ~ea continental slopes. These deposits are characterized by sharp upper and lower contacts, strong textural homogeneity within a given unit, displaced shallow water foraminifera, .:..nd the::.' ·:.hov.J no e··./idence of ·:.or·ting b::.-' bottom cur·r·ent:.. Turbidites are also common on the continental slope around Antarctica. They consist of well-sorted, graded pebbly sand and sand. Turbidites are also common on the steep, 1ntercanyon portion of the upper slopes of the eastern Weddell ~ea, western Ross Sea, and George V Coast The·:.e turbidites are associated with poorly sorted glacial-marlne deposits and laminated silts and clays believed to be Contou~ cu~~ents have p~obably played a Key ~ole in m.:r.r· 9 in ( F' i per· ,:c.n d Br· i :.co , 1 ·;:'?!:"•; Tuchol f METHODS OF ANALYSIS Samples we~e selected fo~ textu~al and mineralogical analyses f~om Eltanin piston cores and f~om DSDP LEG 35 cores from the continental ~ise and abyssal plain of the Bellingshausen Sea. Piston core samples we~e selected on the basis of sedimentary st~uctures, contacts, and on the presence of Textural analyses we~e pe~formed using the Rice University automated Sediment Analysis System (RUASA, Ande~son and ~=::ur· tz, Data output from this system includes: cumulative and frequency cu~ves, moment measures of mean grain size, standard deviation, sKewness and kurtosis (FolK Mine~alogical studies were pe~fo~med on all co~es. Heavy minerals were sepa~ated f~om the 2.0 0 to 4.0 0 size fraction and the minera16gy and pet~ology of coarse sand 26 fractions were determined using a binocular microscope. A minimum of 150 grains was used for coarse fraction ana1ys1s and interpretation. The 2.0 D to 4.0 D size fraction was the interval chosen for investigation because this size fraction normally includes the highest percentage of heavy minerals, and is easy to work with using the above mentioned optical methods. Fine sand fractions (2.0 D to 4.0 D) were split into heavy and light minerals assemblages using tetrabromethene . d . . - - . . . ( ens1ty ~.~6 grr~cm). The heavy minerals were mounted on glass slides and coated with epoxy resin. In addition to heavy mineral studies, thin sections of epoxy impregnated sand fractions were examined for most cores. Mineralogical assemblages were determined from 300 grain counts per sample. The samples were identified using a petrographic microscope equipped with a mechanical stage. .-.~ L/ CHAPTER 2 DE::;cp I PT I ON, DI :;:;TF.: I BUT I Ot··.J AND I NTEF.:PRETAT I Ot·-J C)F P 1 ETON CORES INTRODUCTION Although ou~ p~esent unde~standing of sedimentation patterns on the continental shelf and slope of the Bellingshausen Sea is hinde~ed by 1 imited co~e cove~age, ~esults f~om studies of DSDP LEG 35 cores (Tucholke and Houtz, 1976) f~om the ~egion indicate that tu~bidity currents have played a major role in the deposition and redistribution of glacially derived sediment since late 01 igocene? - early Miocene time. Pi:.tc•n cc•r·e·:. r·eco·v·er·ed fr·om thi-s. ar·e.:.., l.. • ..thich penetr·.:..terj sand, have been described texturally and mineralogically in Based on textural data, these sands are interpreted as turbidites (see location and gene~al 1 i tho 1 o•;d c .:..1 1 og in F i g. 8> . The age of these tu~bidites 1s not Known because the cores did not penetrate underlying fossiliferous ho~izons needed to date them. Tucholke and Houtz ( 1976) studied seismic ~eflection ~eco~ds from the region and found that a st~ong reflection horizon, tentatively dated as Pliocene, occurs throughout the a.r·ea.. This horizon is interp~eted as having been caused FIG 8. - t1ap shc•wi ng di -:.tr· i t•u t i c•n c•f tur·bi di te bodi e-:. penetrated by piston cores on the Bellingshausen abyssal plain and continental rise. 29 by increased deposition of coarse clastics, related to an ea.r·l:/ F'lio•:ene gl.:..ciai pul:.e about 4.5 t··l/ a.gc• Hou t z , 1'7'7 t.) • The depth of t hi '=· h or· i z on r· B.n ge:. be tt.•.teen 1 [1 [1 and to 400 meters. Piston cores from the area penetrate only the upper few meters of the sediment column, and are therefore younger than Pliocene age, probably Quaternary. The study area contains four relatively narrow sand bodies whose distribution and mineralogical differences are related to existing submarine canyons. These sand bodies are numbered 1 through 4 from east to west on the Bell ing:.h.:..u·:.en Ab::..··-:.sal Plain (Fig. f:). Sand bodies 1 and 2 are related to the Adelaide and Charcot canyons respect ively, while the canyons feeding sand bodies 3 and 4 are unna.med. DESCRIPTION OF SAND BODIES :;::.:..n d Bod··..o I Three cores penetrated Sand Body I . Cor·e H:~-1:=: v.. ta.-:. recovered on the upper continental rise just west of DSDP s.i te :325. Core 10-25 was recovered north of core 10-13 Dots show levels at which samples we~e collected and analysed; scale is in meter··::.. 0 N Cit en ~· ·I.•·· • • • 4.... • • .J Cor· e 1 (1- 1 :::: This core penetrated only 78 em of sand. The 'Jpper· 61 em is washed~ therefore no textural analyses were performed. However, the unit does exhibit grading from medium to fine ·:.and . It is darK olive gray in color and the grains are .:..n gu 1 a.r· . This core penetrated two massive sand units. The sand in both units consist of more than 35% angular grains, which supports a glacial derivation. The upper sand unit occurs fr·om 0 t C• 135 em and has mud clasts, which at to 25 em and at 45 em exceed the diameter of the core. A s.ec on d s ..:..n d unit is situated between 135 and 222 em (about 87 em thick) No mud clasts are present. The lower contact of this unit is irregular and is therefore probably erosional Te;.dur·a.l dc..t<:<. for· the upper· s.and 'Jnit (Fig. 10) s.hov.J that it is poorly sorted (standard deviation of 1.37 to 1.39) and massive (mean grain sizes ranging from 2.30 D at the t•a.:.e to 2. 7~: nea.r· the tc•p) . The 1 ov.Jer· unit i ·:. a 1 ·:.c• poorly sorted and massive. Cc·r· e 1 (1-5 Core 10-5 penetrated a 550 em thicK sequence of sand, silty sand, and mud. The upper sand unit (140 em- 220 em) 34 FIG 10. - Cumulative frequency curves for the upper sand unit of core 10-25. The sand is massive and poorly sorted. 100 60 0::-! w 40 > t= ct ..J ~ r~5-d :::> l u 20 ,,/1 I ' I0-25 0 -I 0 2 3 4 5 6 7 8 9 PHI SIZE exhibits grading, whereas the lower unit (300 - 250 em) is mc..·::.:. i '··.·' e an d poor· 1 ~/ s. or· t e d ( F i g . 1 1) • Poor sorting, absence of grading, and relatively high silt/clay content (10-20%) characterize those sand units sampled in cores 10-5 and 10-25. These features are typical of Antarctic turbidites as a whole and imply deposition from very high concentration flows. The cores which penetrated Sand Body II include cores 11-26, 11-25 and 13-9. This sand body is associated with the Charcot Submarine Canyon. Cor·e 11-26 This core penetrated 971 em of sand and mud. An upper sand unit occurs at 61 to 118 em and contains a large mud c 1 c..·:. t .=... t 75 em. Gravel occurs at the base of the unit. Texturally, the sand is poorly sorted, but sorting improves upwards (see Appendix l) The sand unit from 118 em to 135 em depth in the core is massive and poorly sorted. A thir·d sand unit occurs at the base of core (950-971 em). I t is. graded with silt and clay increasing upwards. Ccor·e 11-25 Th i ·::. c cor· e pen e t r· .=...ted tv,1co ·::.m.:o. 1 1 ·:.and u n i t s. An upper· FIG 11. -Cumulative frequency size d1stributions of the lower sand unit of core 10-5. The sand is massive~ 1 iKe core 10-25, but is finer than core 10-25. 38 I I I I I I I I l I I , Wft'' ttr'ft'M':-ts ¢' I- 100- / ;t""' Me r·~'fJ .' I _)·.. ,.-;,-· . : I //-" 80- /f (,,'/ .:-,:I ~ 60- 3ooslf )~2oo 0 l;, IJJ 220 ;Jt > t= ~I ~_. 250-(J: ::::> 40- :,. I ~ : I ::::> :. I u )1 :. I :) I ('tl !/ 20- // - .. :i,, I /h' 10-5 :·I ...... ,. .;/1 0 - ~..._.~/ I I I I I I I I I I 0 I 2 3 4 5 6 7 8 9 PHI SIZE unit occurs from 0-35 em and conta1ns a large mud clast from The unit i~ massive and poorly sorted (see Appendi >: 1) . em) . It grades from medium sand at the base to sandy silt at the top, with mean grain sizes ranging from 3.0 0 at the base to 4.~ at the top. This unit displays poor sorting (standard deviation at the base= 1.3 and at the top= 1.0). Cor· e 13-'? This core penetrated 1800 em of sand and mud. confined to the lower 500 em of the core. An upper· s ..;..n d unit is approximately 20 em thicK (1320 to 1340 em) and exhibits grading (mean grain size at the base= 2.8 D and a. t the top = 3. 2 0) . A second unit occurs from 1477 to It is only slightly graded, with a mean grain size C' ranging only from 3.2 at the ba.·::.e to ._·~•• ._1 near· the top (Fig. 12). Thi·::. unit cc•nta.in·::. betv.Jeen 20~···~ a.nd 30>; mudd:/ ma.tr·i::-::. A third sand unit occurs in the lower part of the core ( 1765 em to 1780 em) and exhibits grading from medium sand to s ..:..n dy· mud. ~:.;.:..n d·. ..- E:c•dv I I I Cor·e 11-23 Approximately 1370 em of sediment was recovered in this cc1r·e. The upper 720 em of the core consist mostly of clay FIG 12. - Cumulative frequency curves for samples between 1580 m to 1600 em in core 13-9. 41 100- 80 60 "ft. 1~&0 Cm 40 ~ t= l660 Cm c(. ~ ~ l600 Cm \) 2.0 0 13-9 ' -1 0 1 2 3 7 8 9 10 5 ' PHI SIZE 4:2 w1th dispersed silt and very fine sand clasts. sand and sand occurs at 7:20 to 1370 em, which includes three sharply bounded depositional units. Each of these units 1s t r· .:..n :. i t ion B.l tJ pt;_tB.r· d:. f r· om 9r· ::<.'v'e 1 1 ::/ :.and to :.B.n ,j t.J ..th i c !""1 i s. cr·udel ::--' 9r·aded ( Fi 9'=·. 1~: a.nd 14) . The lower unit has an irre9ular basal contact and contains a large mud clast which exceeds the diameter of the core. All thr·ee unit·:.. :..r·e of similar mineralo9ical composition and cons1st mainly of .:..n gu 1 ar· gr· B. in:. < 85>:> . Gravel units also exhibit crude grading near their tops. Cc•r· e 21-2~: Core 21-23 penetrated 710 em of sediment. The interval between 355 and 710 em can be divided into 3 sub-units, each bounded by sharp contacts. The first sub-unit is about ._,.... -·-·. em thicK (355-420) and grades from silty sand to sandy mud, 1.... .1 i t h .:.. me .:.. n 9 r· B. i n -::. i z e r· B. n g i n 9 f r· om :::: . 5 J3 .:.. t t h e b B. ·:. e t o 5.3 0 at the top. Sub-unit 2 occurs at 465 to 585 em ana includes 40X to 80X unsorted, muddy matr1x. I t i ·:. -::. i m i 1 .:.. r· to ·:.tJb-unit 1. Sub-unit 3 is about 55 em thicK (655 em to 710 em). ...i ...·- gr· .:..des. f r· om s ..:..n d +.: o mtJ dd::.-" sand (Fig 15) . The upper· tt.•.Jc ·:.u b- units contain matrix material which includes about 10X vclcanic shards and ash. 43 FIG 13. -Lithology of sand units in Core 11-23. 44 Cm. 6 1-oo M" SK • 2 .en -t- 0.752· • • 0 • • . . Mt•d clo.st • . .. ---· s 0.650 • Boo • ...... • . . . • . . ·. t ·... 2.443 . t .. • :·: .. ,· iG• -1.078, :.···-:· ~. ·.. : ~------....:...--1.. • ...... ·...... 0.718 ...... • o 0 o o o I I , .. 5 ...... : .. 1000 . . : ...... ~-···:,: .•.. '. ·. .. .·i · · · · · Ga· ·~ . . . ,, ...... - 1.236 ...... • ...... - 0.61~ f1 00 ...... •...... o •, •', ,o o I .... . o:: o o . o o I s . .... (2.00 . • • • 0 •• 0 • . • ..•••••. . . • • • • 0 o f 0 0 1 0 0 0 I ... ·. ·. ·... ·.. /)oo . :. ·... ': . . Mudclast • t ...... ·.· ...... f • .. • .·.. . : •.. .· Ga 2.317 - 1.493- ...... Core II-23 FIG 14. -Cumulative frequency curves for the upper sand unit of Core 11-23. 100 80 60 w > t= <1: ..J ::> :E 40 ::> (.) 20 11-23 0 2 3 4 5 6 7 8 9 10 PHI SIZE 47 FIG 15. - Rep~esentative g~ain size dist~ibution cu~ves fo~ Co~e 21-23. 4::: 100- ---...... :...... ,.....:.·:...:··.:..-· .. · ,...... ! I ... ········~ __;~--' · ... I ...... · ~--/ .--I 80 I I I . ~--/ ..~700 ,--I 1 I I ~ 0 60 .···· I _/ r..-655 w _.../ I > I F I -I 0 2 3 4 5 6 7 8 9 PHI SIZE 49 ·'":··-=·-·J"- ._, "- This co~e penet~ated 550 em of mud and a small unit of light olive g~ay silty sand. Textu~al data fo~ the sand in this co~e is simila~ to that of sands f~om co~e 21-23. The co~es that penet~ated this sand body a~e sho~t. The·:.e incl1Jde cor·e':. 17-20, 1:::-12, 17-25, 13-13 a.nd 13-li. The most inte~esting featu~e of the sands in these co~es is thei~ st~ong so~ting and a~Kosic composition. Lithologic logs of these co~es a~e shown in Fig 16. Cor· e 17-2(1 This co~e penet~ated a 120 em thicK a~Kosic sand that is massive and well so~ted. This sand unit contains a 20 em inte~val of la~ge mud clasts which exceed the diamete~ of the co~e. The fine mat~ix in these sands accounts fo~ less t h a.n T--~ c•f the tot a.l :.ed i men t . Textu~al data fo~ these sands display unimodal dist~ibut1ons with a dominant mode at 2. 7!5 .1:::1 (Fig 1 7) . This co~e penet~ated 400 em of a~Kosic sand and mud. The sand unit is only 60 em thicK (f~om 340 to 400 em). It is massive and exhibits mode~ate so~ting. 50 FIG 16. -Lithologic logs of cores from sand body IV. 13-13 13-12 13-11 17-25 17-20 r-__ _ .------. 0 ~-- . -·.·.·... ..· . , ------~___--- '·:':: .·::· s M -=--=- 1 . ------" --- [2]1.. 4595.12M. s ,:i-·:.·... ::·:: .. ·:·JI ~ ~-- s · .. · M -- -:_---""' ·. ·. M~-=---= 4408.5M. 2 _-_--:._-... ~-- -- -- 3 4597M. h- ·- s 1:::'- . ~--~- ... ,,, ;.. ''14 4628.4M. 4 Sl_:,·::_::::-:·:;::·:;: I MI--.:::-:-:... 5 I=""-- 4737.8M. 6 en ...... 7 52 FIG 17. - Cumu 1 &. t i 'v'e f r· equ err c ;.' c u r·•..-·e~. for· ~.amp 1 e~. f r· om Cor· e 17-20. Note the strong sorting and lack of grading in this unit. C'·':f-·-· 100 eo I- 60 17-20 20 0 - I 0 I. z ] I .., I 9 10 PHI SIZ[ 54 Cor·e 1:3-1:::: Two sand units were penetrated. The first unit iis about em thicK (from 165 to 190 em) and exhibits gradinng and poor sorting~ but sorting improves upwards in the unitt (Fig 18) The s.econd unit occur·s. fr·c·m 400 em tc• 440 em a.nd ~ e>~hibits. grading. The sand in this unit ~oorly sorted~~ with standard deviations ranging from 1.1 D at its basse to 1.8D .:..t its. top (Fig 18). This core penetrated 300 em of silty sand andj clay. The silty sand unit is only 5 em thicK (75-80 em) andj is graded. The lower part of the core is mud which contains nmud clasts. Cc•r·e 1:3-11 This core penetrated about 100 em of silty sand and is gr· .:..ded. Hot.. •,te·-..-·er· l bee a.u s.e the s.a.n ,js. in this. e e•r· e v..ter· e disturbed during recovery, no textural analyses were DE:::;cF.: I PT I Ot·-l, D I :;:;TF.: I E:UT I Ot···l AND H·HEF.:PRETAT I Ot···l OF o:::;DP TUF.:E:l DITE:::; .-.=- The Bellingshausen sea floor was drilled during DSDP LEG •.:~ ._1 • FIG 18. -Cumulative frequency curves for the upper sand unit of Core 13-13. 100 .,. 80 • 1- ;t w eo > 1- < ~ 4 :::> ::e 180cm 166cm ::e :::> 0 20 13-13 0 3 4 5 6 7 8 9 10 PHI SIZE Tu~bidites as old as M1ocene age we~e co~ed. Su b-·::.. ::..rrn:• 1 e·::. f~om these sites we~e studied as pa~t of this p~oJect to dete~mine how these sands may be related to glaciation of the continent~ and to compare them to more recent sands obtained in piston co~es. The following description of turbidites is mainly taKen from a discussion by TucholKe et Figu~e 19 shows 1 ithologic logs from sites d~illed du~ing LEG 35. Site 323 is located in the central pa~t of the Bell ing:.ha.us.en Ab::·'·::.·:.a.l Pl a.in (Fig 20). The cores. penetr·a.ted silt and silty clay of Oligocene to ea~ly Miocene age. :=;i 1 t::/ cla.::.' units. (i.e. cor·e 1::::-.::;:.) ~'.1er·e identified c•n bc•ar·d and we~e inte~p~eted as distal tu~bidites. They consist of a. thin ba.s..::..l 1.::.,::/er· of qu.:..r·tz ·:.ilt and ci.:..::.,. (of equ.:..l r·atio) and g~ade upward into laminated clay to massive clay. Also~ coarse silt and sand pods (core 7 of lower middle Miocene age) were reccr~ered and interpreted as distal tu~bidites (Tuchol ke et a.l., 1'7'7~.). A massive~ coarse sand was recovered in core 4. Poor ~ecovery between 100-600 meters sub-bottom depth was attributed to the occurrence of coarse, uncons.c,j ida.ted s.a.nd v..ti thin this. inter···./.:..1 (Tucho·l Ke et .:..1., The sand samples from co~e 4 are texturally and mineralogically diffe~ent from any sand co~ed to date in the FIG 19. -Stratigraphic columns of DSDP LEG 35 sites (from DSDP Vol . 35) . l'·!·.LLJ liG:~Iii\USI~N J\FYS.';J\L PLAIN .l\t!TARCT 1 C CC 1 ~l'l'rt:~;N1'l\L HI:;~<; :~ l '1:' ). ) ' .. :'l·.. L-)', &0°0t4'S, 79°255'w 6'5°40.11'5, 97°597-W &1°03 z's, tll!ltT.z·w es•oz.e's, 73°4o.4'w WATER DEPT~ 5026(ml wnTER DEPTH 4993 lml WATE:R DEPTH 4449 IIIII WATE~ DEPTH 3 74!1 tml ... r; • ,.. ... ; ,.. B 9 B B i g ~~~; ~ LESCR!JTH:t' t~!iJ ~ IJESCRliTION "::W !Jl·.:~CHlf''!:HN ~1 !iJ ~ Dr~SCR I P'I' I ON o I"' I~ ~ -::~ ~ -~a 5 ~ ~ :; r;ray •'l n.y with r. Gr11 y clnv VIi th ;jp~:. rn..v r! >J.Y with Clay and silty interhddcd silt. ~ interbeddect sil ~t-.--=~}1- ,,t.:r·b.,dJe,J ~~~ c~ay, locally __ ancl ~:ru-:-rilft.Pd :--;:-..;: silt, scatter·ed o. ~"'" :.d~~~- Di a torn ooze, o xr-:-:"': dctrL> _ ~ :2fi~ ice-~aftpd 2oo-11 .z.~::.--:.:- ~-~ ~i~t,or~Raeg~~ ~ ~F-:""-:__;:/ ;~r"' c;.l"'-'•one G> ~~-='i:- debris ~ LJhtom•~eous ~~ y, . -·Y n. •·:·:.·, •. ,'r:cf's~dt·J c·ar.d -~ '~~:: ~.:;, c 1 ay 1..- :...;:-: 1 D: • l. '" 2 ~: 3oo-J ~ -3. =¥ ' ~ i;~ ~l~~gry clay- _ , ..~~~ I"', ~-=::: (,ny c.hy!1tone -~~!11':\·:.-~·;:'_- UnC'n::;ldtd sand ~ c:11Y Interbedded ~- ~ ~~ Claystones and '1, - ,rv flar: :-; one ~ ~~ C~r>.y::;tones anl 1-::::=1b.:-:d ·''. 1 . ••1 •1· r••. · \ --r siltstonPs with ) __._-=.. •.~rcPn ,·rny u..~ ::.-:..- dlator.la2'POUs ~ icP-raltcd :5::-::_-::· silty rlaystom• ''· :..~- clay~tonPs r-::-:1 ------· ''PI: ~, Ld dPbris Lhr&;;. S i 1 i c i f i et! ,, l a v [2]] ...... , ;-:: t-""~~ s t.one ( eher t; ' r: lay" ton'~ ~~~~ > ~j,:i'J!' 11m s;, and Clystone , }~: .R'r· '2 ~·:l:..! ras~tl t ~ Cb•vntone with l'lyers of ~ i 1 +.y r: 1 ays ton<> fi:'' f'i.•~ f··r· ·:.s l LS Til: 5'-'hM 9 nannofo!1s.il , .~- ;, , T 1 '600 ~ L:L ~ cr•r:un: ~ ch"!tk, ~ilicifi~C<' ' . F-.A~~l v r/! c('I·:~:::·~ c- 1 "Yfl t _o_n_e_____ 1 _1"' ,-f-,~-r:-;-;_r-rF? r n tert pddt>d Altrrnqttn~ hPrlR satl(!~tonP~, ~jlt of clavstc:1,..., ~if "i . rr. ~' t C'IIP>: 'lll sorted with standard deviations of 0.24 B to 0.18 B, and ma.·:.·:.l'v'e, ~,,,ith a mean gr·a.in s.ize c•f 13.35 f) (Fig 21>. Th 1 :. sand is entirely composed of rocK fragments wh1ch include pinK granite, pegmatite, granodiorite, quartz diorite, gabbro, sedimentary rocK fragments, and possible chert. Quartz diorite and sedimentary rocK fragments comprise the highest percentage of rocK fragments. Quartz grains account for less than 5 percent of the sand. Site 324 No turbidites were recovered at site 324, but inter bedded silts and clays were interpreted as being conto,Jr·ites., pr·oba.bly· der·i·v·ed initi.:..il::.' fr·om tur·bi:•idit>... c u r· r· en t ·:. ( T u c h c.J Ke e t a 1 • , 1 9 7 6) • Thi·:. ·:.ite v,,a..:. dr·i lied c•n the centr·a.l cc•ntinent.:..l r·i·:.e in what is believed to be a braided fan system (Fig 20). of the cores recovered at this site show little evidence of bottom current activity. Turbidites were recovered within the lower portion of the site (Oligocene?- early Miocene s. e c t i on ) , t,,, h i c h t y p i c a. 1 i y c on t .:r. i n c om p 1 e t e 8 o u ma. s. e q u en c e s .. The turbidites show irregular bases and contain angular mud cla.s.ts.. 63 FIG 21. -Cumulative curves for samples from core 4- Site ~~~ ~~~· 100- 80- 0 ~60 w > ~ ...J :::> 41 ~ :::> 40- u 20- 0 I 8 9 PHI SIZE FIG Cumulative frequency distribution -=.ample-=· fr·om~ DSDP Site 322 core=· 1, 6~ 10, 11. 67 100 eo 60 - 322-6- II 101 Cm.J r,.,\ r /[ \ . ).i .,,_, .. """' ~' ,,_,_,,.,"', .1\U \' . i I' v 0 \, -1 0 1 1 3 ll 5 6 7 8 9 10 PHI SIZE f?O eo so 0 -1 0 1 2. 3 'I s 6 7 8 9 10 PHI SJZE from sorted sed1ment~ as for example beach deposits. sorted sediments may have been transported do~n slope during low stands of sea level. Such a low stand occurred at 10 c..n d 6 t··"1Y BF' >:. i.. )a. i 1 :!:.:; Ha.r· denbo 1 1 '7'7'?) . Middle Miocene sands in Core 4 from Site 323 are well-sorted and mineralogically immature. The lacK of grading in these sands indicates derivation from a sorted source and later transport by turbidity currents. Again, reworKing of this sand may have occur· r· ed du r· in g 1 01.. •,1 s. t c..n ds of ·:.ea 1 e·.,..·e 1 • theY maY have been sorted by contour currents before being transported to the abyssal floor. This conclusion is based on the presence of sediment dunes in the area which are .attr·ibuted to ·:.tr·ong cc•ntoiJr· CIJr·r·ents. (Tuchol Ke et a.l., These dunes are recognizable in seismic records collected north of Peter I Island. The second important conclusion is that the sand is angular and str1ated, which indicates glaciers probably existed in the source area, at least in high mountains, at the time these turbidites were depc•s. i ted. CHAPTEF: ;:: MINERALOGY AND PF:OVINCE OF TURBIDITES Pr· e·v· i ou ·:. ~-··l•::.r· k Petrographic studies of marine sediments in the study area have been conducted by Edwards ( 1968) and Peter and Hol·l i-:.ter· ( 1976). Edwards made a comprehensive study of surface sediment in the Antarctic Peninsula region using phelger cores, trigger cores, piston cores and grab samples. He defined three sedimentary provinces around the area (Flg. a metamorphic province in the eastern portion, a granitic province along the west coast of the peninsula, and a volcanic province in the northwest part of the region that is associated with the South Shetland Islands. The vast majority of the sands analysed by Edwards are ice·rafted m.:..ter·i~.l, thu:. hi·:. di:.tr·ibution m.:..p r·eflect:. iceber·g dr·ift Peters and Hollister ( 1976) examined mineralogies of sands collected at sites 322, 323, 324 and 325 of DSDP LEG 35. They concluded that the sediment of sites 322 and 325 were derived from upper Cretaceous or possibly younger intrusive rocks of the Antarctic Peninsula, while sands ot sites 323 and 324 were derived from older metamorphic and intrusive rocKs of the Eights Coast and younger volcanic rocks of the Jones Mountains and Peter I Island. FIG :;:;ed i men tar· y· P r· o··./ i n c e m a. p of Edl;.. •a.r· ds. ( 1·:,;·.:=.:;::) • The sand mineralogies of turbidites of the Be 1 1 in g~.h a.u ·:.en Ab·:.·:.ya.l F' 1 .::.. in v..1er· e e::-:: a.m in ed a. s. pa.r· t of t: i""t i ·: 1nvestigation. The object was to define source areas for these turbidites 1n the hope that this information would provide a basis for determining their origin. Two heavy mineral suites were defined in the Bellingshausen Sea, based on the frequency distribution of pyroxene, hornblende, epidote and garnet. 1 n the ea.~.ter·n part of the study area, high percentages of pyroxene characterize the samples, whereas in the western part of the area, hornblende is of greater relative importance (Fig 24J. Mineralogies of the light fraction of sand samples indicate three potential source areas. This is done using potassium feldspar (orthoclase) and plagioclase. In the ea.·:. t er· n pa.r· t c•f the s. t u d::.-" .:..r· ea. (cor· e·:. 10-25, 1(1-5 .:..n d 1 i -26.1 sands contain more plagioclase than orthoclase, while in the western part of the area (core 13-13 and 17-20) orthoclase i :. d c•m i n a. n t . I n t h e c en t r· .:.. i p a. r· t of t h e a. r· e .;:.. ( c c• r· e 1 1 - 2 3) , the percentage of orthoclase and the plagioclase are s1milar (Fig 25) . The lithic composition of the coarse sand fractions of samples display trends similar to those reflected in the light minerai fraction. Three lithic suites can be defined - 1 1 . F. - .. a. =· t c~ c•t,.J ·:. ~~ 1 g :.:: ~~~ ) : Suite 1 :This suite occurs in the eastern portion of the 72 The sand mineralogies of turbidites of the E:e11ing:.hau·:.en Ab·=·=·::.-'·:<.1 F''!.:..in v.Jer·e e;.::.:..rnined .:..:. p.:..r·t of thi·:. 1nvestigation. The object was to define source areas for these turbidites 1n the hope that this information would provide a basis for determining their origin. Two heavy mineral suites were defined in the Bellingshausen Sea~ based on the frequency distribution of pyroxene, hornblende, epidote and garnet. In the eastern part of the study area~ high percentages of pyroxene characterize the samples, whereas in the western part of the area~ hornblende is of greater relative importance (Fig 24J. Mineralogies of the light fraction of sand samples indicate three potential source areas. This is done using potassium feldspar (orthoclase) and plagioclase. In the e.::..·:.ter·n p.:..r· t of the :.tud::.-" .:..r·e.:.. ( cor·e·:. 10-25 ~ H1-5 .:..nd 11-2.~.) sands contain more plagioclase than orthoclase, while in the western part of the area (core 13-13 and 17-20) orthoclase i ·:. d c•m i n .:.. n t . I n t h e c en t r· a. 1 p .:.. r· t of t h e .:.. r· e .:.. ( c or· e 1 i - 2 3 > • the percentage of orthoclase and the plagioclase are similar (Fig 25). The 1 i t hi c c orrq:~~:·=· i t ion of the c c•.:<.r· se ·:.a.n d f r· .:..c t i c•n ·:. of samples display trends similar to those reflected in the i i gh t m i n er· .:.. i f r· .:..c t i on . Three lithic suites can be defined a.:. fo11 m ..,,:. (Fig 26) : Suite 1 : This suite occurs in the eastern portion of the 73 FIG 24. -Heavy mineral distribution map for turbidites of the Bel linshausen Abyssal Plain. HR =Hornblende PX = Pyroxene EP/G = Epidote and Garnet (dotted area) 74 cnr, . •~ FIG 25. -Light minerals distribution map for turbidites of the Bellingshausen Abyssal Plain. QTZ = Quartz PLAG =Plagioclase K.F. =Potassium Feldspar R.F. = Rock Fragments ~::, . . ~, t ... "~ n EJ , \"""" ~ .\ ...... '2.. ~~ ,o e11- 2 5 o""\~ e\c- ~ • '2..~ \\"" 77 F I 13 Lithic fractions of turbidite sands of the Bellingshausen Abyssal Plain. GRANITE PEGMATITE GRANODIORITE I ~.. . ~ ~.. .. •• •,o~2s • \\'J'O ~ 11-25 ,t£~ -...j (0 ·::. t u d::.' .::..r· ea. ·::. i 1 t -::. t c•n e . Suite 2 : This suite occurs in cores 11-23 and 21-23. The lithic fragments in these sands are granite, granitic pegmatite, granodiorite, quartzite~ and siltstone. Suite 3 : This suite occurs in core 13-i3. lithic fragments are pinK granite with smaller percentages of ·::. i 1 t '=·tone . Petrographic data for the coarse sand fraction and fine sand fraction are used to define mineralogic and lithologic province boundaries within the study area (Fig. 27). The·::.e pr· C•\·' inc es. a.r· e: A. A metamorphic, quartz diorite~ granite, gabbro and volcanic province siturated in the eastern part of the area. E:. Gr·anite~ gr·.:..nc•dic•r·ite, met.::..mor·phic (qu.:..r·tzite) .;.nd sedimentary (siltstone) province in the central part of the .:r.r· ea.. C. A province in which granitic rocKs predominate, located in the western part of the area. 80 FIG 27. Petrographic province map for the Bellingshausen Sea. 1- 2 =metamorphic, Quartz-diorite, granitic =Granitic granodiorite, quartzite 4 =Granitic 81 CHAF'TEF~ 4 ORIGIN OF SAND TURBIDITES If the sand bodies acquired in piston cores from the Bellingshausen rise and abyssal floor were depos1ted after the ice sheet formed and the continental shelf was lowered t h r· o u g h g 1 a. c i a. 1 i s. o -;:. t a.-;:.::.-· a. n d e r· o ·:. i on ,. t h e c• r· i g i n c• f t h e -;:. e sands is problematic. That is, their origin cannot be explained using traditional deep sea fan models. Such models ascribe considerable importance to eustasy in r·egul.:..ting s.ediment -;:.upply to fans., (i.e. t·,lor·ma.r·k, 1'?7E: .:..nd c•ther··s) . ~-··lh en sea 1 e\.·'e 1 i -;:. s i t u .:.. ted at or· near· c a.n y·on heads, sediment supply to canyons via rivers and/or coastal processes is greatest. Du r· i n g h i g h s. t an d s C• f -;:. e a 1 e·v• e 1 , sand supply may be greatly reduced. The continental shelf in Antarctica is deep, averaging 500 meters, and fluvial processes and wind generated currents are essentially inactive as sedimentary agents on the shelf. The ·:.ed i men t delivered to the continental shelf is brought there mainly b::,... ice. Therefore, other potential sources for these sands must be considered. ~-··lr· i gh t a.n d Ander· ·:.on ( 1 '?E:2) infer· r· ed t1.1K• pos.s. i b 1 e s.ou r· c es. for turbidite sands of the Weddell Sea. First, subglacial melt water streams may deliver sediments directly to submarine canyons. If the subglacial melt water hypothes1s is correct, then the mineralogies of turbidites should reflect a more restricted source which may be traced back to coastal outcrops. The second hypotheses is that contour cur·r·en t s, which ar·e l places, these currents impinge on the upper slope and shelf- break where they may erode glacial sediment and transport sand and finer sediment along the slope and into canyons ( ~-··lr· i gh t .:r.n d Ander ~-c•n 1'7'82) • t-1i ner·a 1 c•gi c.:r.l data fr·om pi ~.tc•n cor·e~. (Fig. 27) ~·-·a~. used to define 4 petrographic provinces. Also, the presence of cc•ar·se ~-and and gr·a.·v·el in ~.ome tur·bidite~. (i.e. 11-23) supports the subglacial melt water hypotheses. Hc•v.J ever· , Weertman (1982) concluded that subglacial melt water streams are unlikely in Antarctica. He further observed that there ar·e no knovm gra-.lel a.nd coarse -:.and depc·~-i ts on the shei f that are related to subglacial melt water processes. However, the data provided in this thesis suggests that the supply of sediment directly to canyons by melt water streams is the most logical source for turbidites of the Bellingshausen abyssal floor. Although the bathymetric data at the continental shelf of the Bellingshausen Sea is sparse, the canyon heads of the Antarctica Peninsula region, the Adelaide Canyon for examcle 84 The~efo~e~ du~ing a grQ~~al advance, sediment may be delive~ed di~ectly to canyon heads. Such a mechanism would account fo~ the p~esence of coa~se sand and g~avels in piston co~ed tu~bidites and would also explain the ~est~icted p~ovince fer~ these sediments. A mo~e detailed bathymet~ic and sampling effo~t is ~equi~ed to ~esolve this pr·ob 1 em. c ot···l c L u :::; 1 Ot···l ::;; Examination of Eltanin piston co~es f~om the cent~al ~ise and abyssal plain of the Bellingshausen Sea indicates that tu~bidity currents have played a major role in the redistribution and deposition of glacially derived sediment on the deep sea floor. These turbidites are associated with major canvons and occur in linear sand bodies. I n d i ·...,· i du a.l sand units are both massive and graded, and thus reflect deposition from both high and low concent~ation flows. units are gravelly. Deposition in mid-fan channels is implied by these characteristics. Outer fan sequences have not been penetrated, even though core coverage on the abyssal plain is fairly extensive. This implies that sediment supply to the canyons is presently restricted, so extensive fans are not being fo~med. An important question exists as to the origin of turbidites since the Bellingshausen shelf is deep (averagi~ing 500 m) and canyon heads may be isolated from nearshore sources. This situation would still exist during a eustattic low stand. Wright and Anderson (1982) have suggested thatt contour currents, which are believed to be fairly strong oon the continental slope, may supply canyons with sand. Alternatively, sediments may be supplied to canyons by subglacial melt water streams during glacial maxima when t~he ice sheet grounds on the continental shelf. Mineralogic analyses of turbidites show significant differences in source material for sands of individual canyons. This, pluus the occurrence of gravels in some cores, favors the meltwater stream origin for these deposits. An alternative explanation for the source of turbiditees on the Bellingshausen rise and abyssal floor is that thesee sands were supplied to canyons before the shelf was lowereed by erosion. Turbidites penetrated in DSDP LEG 35 sites display remarkable textural homogeneity at depth (Miocene turbidites), whereas Plio-Pleistocene turbidites penetrateed at Leg 35 sites show a greater range of grain sizes being supplied to canyons. It is possible that the older turbidites were derived from previously sorted coastal deposits and under less severe glacial conditions than ex11st 86 today. Plio-Pleistocene turbidites, on the otherhand, are more similar to those penetrated in piston cores, so their glacial origin is more obvious, though the mechanism(s) which supplied these sediments to canyons are uncertain. REFERD··JCE~; ADIE, R.J., 1955. The Petrology of Graham Land: II The Andean granite-gabbro intrusive suite. Scient. Rep. FalKland. Islands Depending Survey, No. 12, 39pp. ADIE, F.: ..J., 1972. Recent ad•v·a.nce~. in the Geolcrgy of Antarctic Pininsula. In : F.:. ,..J • Ad i e 0:. Ed i t err·) , Ant ar· c t i c Geology and Geophysics. Universitetsforlaget, Olso, pp. 121-124. ANDEF.:SON, J.B., and KURTZ, D.O., 1Q7Q F.:UASA: An automated rapid sediment analyzer. Jour. of Sed. Petrology, v. 49, No. 2, p. 625-627. ANDERSON, J.B., KURTZ, D.D., and WEAVER, F.H., 1979. Sedimentation on the Antarctic Continental Slope. In: Doyle, L.J. and PilKey, O.H., (eds.), Geology of Continental Slopes, Society of Economic Paleontologists er.nd t·-1iner·.:r.logi~.t~., Spec. Publ. 27, p. 61-73. ANDER:3ot"··l, .J. 8. , ~:::UF.:TZ , D. D. , DOt·'lACK, E .1-'·l. , .:r.n ,j E:AU:;HAI···l, K.t-i., i'?80. Gl aciai and ql a.ci.:r.i m.:r.r·ine ~-ediment~. c•f the Antarctic continental shelf. Jour. Geology, v. 88, p. 399-414. ANDERSON, J.B., BRAKE, C., DOMACK, E., MYERS, N., and ~-··lR I GHT, R. , 1983. De·.,·e 1 C•pmen t c•f .:r. Po 1 ar· G 1 ac i a.l Marine Sedimentation Model from Antarctic Quaternary [:•epo~.i t~. B.nd Gl B.ciol crgic.:r.l Infcrr·m.:r.tic•n. In : B.F. t·1o1 n i a (Editor·) , Gl a.c i a.l -t·1ar· i ne ~;edimen ta. t i c•n. Plenum p. 2:33-2t-4. CHRISS, T., and FRAKES, L.A., 1972. Glacial marine sedimentation in the Rose Sea. In Adie, R.J., ed., Antarctic Geology and Geophysics, Universitetsforlaget, Oslo, p. 747-762. CRADDOCK, C., 1972. Geologic map of Antarctica, scale 1 : 5 , tll3 0 , 0 0 0 : Am. Gec•gr· . Sc•c . t... ~ew ·y· c•r·l< . CURRAY, T.R. and MOORE, D.G., 1975. Sedimentary and tectonic processes in the Bengal Deep Sea Fan and I n : C.A. Burk and C.L. Drake, eds., The Geology of Continental Margins: New York, Springer Verlag, p. 617-628. DOt1ACK , E . ~·'-' . , 1980 . Glacial marine geology of the George V -Adelaide Continental shelf, East Antarctica. Rice University Masters Thesis. EDWARDS, D.S., 1968. The detrital mineralogy of surface sediment of the ocean floor in the area of the Antarctic Peninsula, Antarctica. Florida State University Masters The:.i : .. FOLI<, R. L. a.n d ~'!AF:D, ~·'l. C. , 1·;:·57. E:r az c•:. River· ba.r· : Cl. :. t IJ d::l in the significance of grain size parameters. Sed. Petrology, v. 27, p. 3-26. GOODELL, H.G., 1965. Marine Geology, U.S.N.S. Eltanin Cruises 9-15 Sedimentol Res. Lab., Florida State University, Contrib. No.: 237 pp HOLLISTER, C.D. and ELDER, R.B., 1969. Contour currents in the Weddell Sea. Deep Sea Res. v. 16,:99-102. PETERS, C.S. and HOLLISTER, C.D., 1976. Heavy mineral characteristics and dispersal patterns from DSDP leg southeast Pacific basin, in Hollister, C.D., Craddock, C. , ( eds.) , In i t a 1 r· epor· t s of the Deep Sea Dr· i l 1 in g Project, v. 35, U.S. Government Printing Office, Washington, D.C. p. 291-300. I sedimentologic description of recent debris flow deposits from the Ross and Weddell Seas, Antarctica. ,Jour·. Sed. Petrol c•g::.-·, v. 49, nc•. 4, p. 1159-1170. tv1UTTI, E. a.nd FUCCI LUCCHI, F., 1972. Tur·bidite-:. of the Northern Apennines. Introduction to Facies Analysis r::Engl i-:.h Tr·an-:.la.tion by· T.H. Ni lsc•n, 1'7'78). Inter·na.t. Geol. Review. V. 20 p. 125-166. NOF:.t1ARI<, i·'l. R. , 1'7'70 . Gr· Cll,oJ t h pa. t t er· n :. c•f deep-:.ea. f d.n -:.; Am. Assoc. Petr·c•. Geol. Bull., ...... 59, p. 2170-2195. t··.JORt'1ARI<, i~.F:.., 1974. S•Jbmar·ine canyons and fan '-/alley·:.: factors affecting growth patterns of deep-sea fans, in Modern and Ancient Geosynclinal Sedimentation. Soc. l.. :;:. Econ. Paleontologists and Mineralogists Spec. Pub. .. ' NORMARK, W.R., 1978. Fan valleys, channels, and depc•-:. i t ion .:o. 1 1 obe-:. on mc•der· n -:.u t•ma.r· 1 n e fan·:.; c h .:o. r· .:o. c t e r· -:. for recognition of sand turbodite environments. Bu 1 i . Am. A-:.soc . P,:;:. t r· eo. Geed • '.) 2 p. '7' 12-'7' 1 :;: • PIPER, D.J.W. and BRISCO, C.D., 1975. Deep-v,1.;:.. t er· continental margin sedimentation, DSDP Leg 28, Ant a.r- c t i ca.. In Ha.::-·-:., E. D., Fr·a.ke·:., L.A. Rep. Deep Sea Drilling ProJect, v. 28, U.S. Government Printing Office Washington, D.C. p. 727-756. RI C:::CI LUCCHI, F., 1 '7'75. Depositional cycles in two turbidite formations of Northern Apennines Jour. Sed. Petrology, v. 45, p. 3-43. SHEPARD, F.P., 1931. Glacial tr·c•ugh-=· c•f the cc•ntinenta.l she l 'v'e-:;.: Jour. Geology, v. 39: TUCHOLKE, B.E., HOLLISTER, C.D., WEAVER, F.H., VENUM, W.R., ·:;· '";' .:. 1 .· ,. ~~. Continental rise and abyssal plain sedimentation in the Southeast Pacific Basin - Leg 35, Deep Sea Drilling Project. i n HC• 1 1 i -:;. t e r· , C • D • , C r· a. ,j d c": k , C • , [eds.J Init. Rep. Deep Sea Drilling Project, v. 35, [Washington, D.C.l U.S. Government Printing Office p. :359-400. TUCHOLKE, B.E., and HOUTZ, R.E., 1976. ::::ed i men t .:...r· y framework of the Bellingshausen basin from seismic pr· of i 1 er· data.. in Hoi lister, C.D., Craddock, C., et .;:.. 1 • , I n i t i .;.. 1 r· e p c• r· t -:. eo f t h e Deep :=; e a. Dr· i 1 1 i n g P r· o ..i e c t , 91 1eg 35, ~·-lashington (U.S. Go•v•er·nment Pr·inting Office) p. VAIL, P.R. and HARDENBOL, J., 1979. "Sea-level changes during the Tertiary". Oceanus, v. 22, p. 71-79. l.)ANNE\', .J .R. and JOHN~;ON, G.L., 1976. The Bell ingshauE.en- Amundsen Basins •Jni tE. and pr·otol ernE.. Mar·ine Geed c·g~l. '·v-'. 22, p. 71-101. WADE, F .A. and I-'ll LBAt·..JKS, ,J. R. , 1972. Geology of Marie Byrd Land and Ell swor·tt"t LandE., in Ad i e , R ..J • ( ed • ) , Antarctic Geology and Geophysics: Oslo, Universitets- forlaget, p. 207-214. ~'lALI their relationship to proximal and distal depositional environments: Jour. Sed. Petrology, v. 37, p. 25-43. WALKER, R.G., 1976. Facies models. 2, turbidites and associated coarse classtic deposits: Geoscience Canada, 1 "•/ I 3' J=l a 25-3t~l a WALKER, R.G., 1978. Turbidites and associated coarse clastic deposits: In Walker, R.G. (ed.), Facies models, Geoscience Canada Reprint Series 7, p. 91-104. '7'2 ~·-lEEPTt·.-1At···l, .J . a.n d 8 I RC:HF I ELD, G. E. , 1·:;:·:=:2. Su bgl ac i a 1 wa t er··r· f i Ot.J.J u n ,j e r· i c e s. t r· e a.m :. a. n d ~'l e s. t An t .:.. r· c t i c I c e-S h e e t stability: Annals of Glaciology, v. 3, p. 316-320. ~·-lF:. I GHT , F.:. , a.n d At·-JDERSON, ..J • 8. , 1 '?B2. The- i mpc•r· t a.n c e- c•f sediment gravity flow to sediment transport and sortinng in a glacial-marine environme-nt, Weddell Sea, Ant .;:..r· c t i ceo.. Geo 1 • Soc . Arner· . Bu 1 1 • , ·..... ·• '7'3, p. '?5 1-'7'633. WPIGHT, P., ANDEPSON, .J.B., and FISC:O, P.P., 19B3. Distribution and Assocation of Sediment Gravity Flow Deposits and Glacial/Glacial -Marine Sediments Around the Continental Margin of Antarctica. I n : 8. F • t·.-1o 1 n i a. ( E d i t or· ) , 13 1 a. c i a. 1 -t···1 a. r· i n e :=; e d i men t a t i c• n • P 1 en um Pr· e:.:., New YorK. p. 265-300. A P P Et--.J 1:> I >< I Ll GHT ( L. F.) Al-ID HEAVY (H. F) 11WERAL FRACT I ON:3 'I COF:E T.\-'LG. COARSER SAt··.JD FINE SAND L.F...... H.F. /, <2-40) 11-23 ( 11.:)f1-,52) :3.85 5 3.:35 3.65 '?4. 805 0 . 20 5. 1'?4 11-2.:) ( 110-111) :3. 17 1 ,138 2 ,13'7' 2.03 ·n. 124 0.0.:) 2.:371 10-25 ( 1.60 C.t·D 3.21 1. 10 2. 119 1.892 84.668 0.218 10.:331 10-':· (200-2132) 4.:313 0.71 3. ,:)1339 3.3'?3 '7'4. 171 0. 211) 5.:328 13-12 (490 Cl"1) :3. 24!5 0.330 2. '?15 2.865 98.3 0.05 1. 17 17-213 ( 1:30 Ct·D :3.7.54 0.02 3.744 3.644 96.8 0. 120 3. 18 13-13 ··(! ,f::, DISTRIBUlTct~ OF MINERALS IN THE HEAV'J' FRACTI(N CORE NO. HR GR EP PYROXENE ZIRCON APALITE BIOTITE CHLORITE UNIDENTIFIED ROCK FRAG. 'j I 11-23 ( 1160-62) 24 6.6 8.3 15.3 .... 2 6.3 I 25.6 11-26 (118-111) 21.3 1.38 7.6 28.4 - 1.4 2.3 2.4 35.3 10-25 <160 CH> 22 1.09 10.9 32.3 - - .....'j .:>' 2.1 3.0 10-5 (200 (1-1) 19.3 0.1 8.6 31.3 1.2 TRACE 3.1 3.6 32.9 13-12 <490 CH) 30.2 1.3 10.1 14.2 - 1.7 2.3 ....'j 36.3 17-20 ( 139 1}\) 37.2 0.9 10.2 16 .s - 1 3 8.6 28.1 13-13 <430 CH) 34.1 3 16.2 14.7 - 0.5 4 3 24.5 ·(! ... rt DI:3TRIBUTION OF 1··1H~ERALS IN LIGHT FRACTIOI"··l CORE NO • ( CI·'D G!UARTZ FELDSPAR PLAGIOCLASE ORTHOCLA:3E UNIDEIHIFIED ROCK FRAG. r:-, 10 0 11-23 ( 1160-62) ..Ji ' . ' 8 11. 1 23. 1 11-2·5 ( 110 -111) 44.7 20.7 16.4 4.3 :34 •.~ ·"j 'j r: 10-25 ( 160) 40.6 .L..,_Jo...J 17.3 .~. 2 35.9 10-5 ( 200) 4:3. 1 21.4 16 5.4 3~3 13-12 (490) 48 20.7 4.7 16 31.3 ·)/ ·j 17-20 ( 130) 55 .L. I • "- 3.2 24 16 .-_, L. 13-13 (430) 50 24 6 1'.:0._. .1... ._, ··{1 1)·. CORE PC 10-25 CORE DEPTH G:S:Z:C STANDARD HAIN GRAIN SKEWNESS (ern) % DEVIATION SIZE 18 0 : 79. 0 : 15.5 : 5. 5 1 . 3 95 2.784 u. 1 4 7 35 0 : 86.6 : 8.6 : 4. 8 1 . 21 3 2.614 0.067 65 0 : 89.1 : 8. 1 : 2.8 1 . 215 2.355 0.218 80 0 : 88.2 : 9 . 2 : 2 • 0r' 1 . 36 9 2. 1 76 0.080 90 0 : 89.0 : 8. 1 : 2.9 1 . 3 06 2.304 0.012 135 0.04 : 87.7 : 8.7 : 3. 6 1 • 3 7 3 2.305 0.028 160 0 : 87.3 : 1 0. 2 : 2.5 1 . 31 0 2.526 0.102 180 0 : 85.5 : 11. 9 : 2.6 ------ 215 0 : 86.5 : .J:0.6 : ;,.:.8 1 • 56 5 2.457 0.073 220 0 : 83.5 : 1 4. 7 : 1 . 9 1 . 3 0 7 2.774 0.082 ··{! •· .. J CORE PC 10-5 CORE DEPTH G: S : z : c STANDARD MEAN GRAIN SKEWNESS (em) % DEVIATION SIZE 1 38 ------150 ------160 0 : 52 •. 1 . 43.4 : 4. 5 0.878 4.064 0. 1 04 180 0 : 82.1 : 14,7 : 3 . .;;: ------ 200 0 : 80.0 : 1 6. 2 : 3.8 1 . 0 '71 3.145 0.100 220 0 : 82.8 : 1 3. 4 : 3. 8 1 . 05 7 2.970 0. 1 3 9 250 0 : 82.0 : 1 4. 3 : 3.7 1 . 06 3 2.950 0.166 300 0 : 78.2 : 1 5. 9 : 5. 9 1 . 1 02 3.058 0.210 400 0 : 81 . 4 : 1 5. 0 : 3.6 ------ 500 0 : 80.2 : 1 6. 3 : 3.5 1 . 1 26 3.097 0.176 550 0 : 82.0 : 1 4. 9 : 3. 1 1 • G93 1 • 0 9 3 0.970 '·(I ((! CORE PC 13-9 CORE DEPTH G : S : SL : C STANDARD MEAN GRAIN SKEWNESS (ern) % DEVIATION SIZE 1320 0 : 65 . 1 4. 6 : 20.4 1 . 1 9 5 3.~30 0.208 1330 0 : 77.3 : 15. 3 : 7.4 1 • 251 2.890 0. 16 9 1477 0 : 81 . '1 : 1 2. 2 : 6. 1 0.792 3.469 U.280 1490 0 : 80.0 : 10.82: 1 2. 4 9 0.809 3.342 0.420 1500 0 : 79.8 : 1 4. 3 : 5.9 0.998 3. 1 4 9 0.384 1550 0 : 68.0 : 1L..75: 16. 1 2 0.915 3.536 0.454 1560 0 : 77.9 : 1 5. 0 : 7. 1 0.620 3.122 0.239 1580 0 : 69.0 : 1l! . "i : 16. 3 1 . 135 3.096 0.331 1600 0 : 79.C : 11.34: 9.72 0.988 3.065 0.280 166C 0: 81.2 : 1 5. 3 : 3.4 0.977 3.240 0.247 1765 0 : 43.5 : 4.4 : 5~.2 ------1780 0 : 81.4 . 11 . 5 : 7. 1 ------ ··(1 ··(I CORE PC 11-25 CORE DEPTH G : S : Si : C STANDARD MAIN GRAIN SKEWNESS (em) % DEVIATION SIZE 20 0 : 63.0 : 21 . 9 : 1 5. 1 1 . 7 96 2.824 0. 16 0 26 0 : 4. 8 : 1 6. 1 : 79.1 Hud clast 30 0 : 9. 1 : 76.5 : 1 4. 4 35 0 : 80.4 : 1 4. 7 : 4.9 1 . 25 9 2. '773 0.208+ 100 0 : 13.2 : 72.3 : 1 4. 5 1 • 04 7 2.835 6.358- 0 : 71 • 8 : 1 5. 6 : 1 2. 7 ------G I 1 05 11 0 0 : 72.8 : 1 8. 2 : 8.9 1 . 3 3 9 3.006 6.228 ...... I::;: I 1:::::1 CORE PC 11-26 CORE DEPTH G : S : Z : Clay STANDARD MAIN GRAIN SKEWNESS (em) % DEVIATION SIZE 61 Q : 72.6 . 13. 0 : 14.44 ------ 65 0 : 93.:G : 4.0 : 2.8 0.896 2.965 0.111- 75 0 : 31.9 : 52.5 : 15.54 0.263 mud clast 3.906 0.042- 81 0 : 70.3 : 23.0 : 6.7 0.707 3.820 0.447 95 0 : 88.6 : 7.84: 3.56 0.697 2.854 0.126- 11 0 0 : 85.3 : 8.05: 7.0 1 • 019 2.714 0.069 11 5 0.02 : 88.4 : 6. 2 : 4.0 1 . 185 2.581 0.126+ 120 0 : 85.7 : 9.65: 4.65 1 . "2.07 L:.266 0.237+ 135 0 : 89.1 . 5.0 : 5.9 1 . 058 2.494 0.206- 954 0 : 75.7 : 1 9. 0 : 6. "12 1 . 798 4.088 0.776 graded 960 0 : 88.9 : 4. 3 : 6.72 ------unit ----- 971 0 : 90.3 : 4.0 : 6.L:3 0.9031 2.000 0.364 ...... IS• .- CORE PC 11-23 CORE DEPTH G:S:Z:C STANDARD MAIN GRAIN SKEWNESS (em) % DEVIATION SIZE 726 1. 413 4.054 0.494. 735 0.8 : 89.1 : 4.U : 6.0 0.726 2.877 0.233 750 ------760 0 : 93.1 . 2.7 : 4.2 0.565 2.639 0.029 770 0 : 94.9 : ~.4 : 2. 7 0.536 2.606 0.042 780 2 .., : 93.5 : 2.2. : 1 • 5 0.650 2.698 0.137- 800 0 : 92.0 : 3.8 : 4.2 0.861 2.497 0.156- 8JO :-L. 4 : 81.9 : 3.1 : 7. 5 0.155 2.009 0.427- 830 4.0 : 87.2 : 3. 1 : 4. 5 1 . 11 9 2.192 0.378- 845 13.4 : 78.7 : 2..7 : 5 • 1 0.981 2.387 0.535- 910 8. 1 : 84.4 : 3.5 : 3.9 1. 078 2.443 0.345- 9~~ 0 0 . 91 • 3 : 3.9 : 4.7 0.527 2.619 0.527+ 940 0 : 93.2 : 2.7 : 4. 0 0.718 2.754 0.046+ 958 0 : 90.6 ~ 4.7 : 4.6 0.583 2.508 0.889- 982 0 . 92.8 : 3.3 : 3.9 0.850 2.245 0.289- ~ ...... ·~ I'·) CORE PC 11-23 CORE DEPTH G:S:Z:C STANDARD MAIN GRAIN SKE~'iNESS (em) % DEVIATION SIZE 1 0 21 1 • 6 : 91 • 8 : 2. 6 : 5.4 0.936 2.091 0.440- 1 060 2 7. 9 : 66.2 : 2 . 1 : 4. 0 1 . ~36 2. 1 44 0.476- 1 080 1 . 4 : 91 • 9 : 2.9 : 3.7 0.615 2.509 0.114- 11 05 3. 3 : 88.5 : 3. 8 : 3.3 1. 2'/9 2.044 0.362- 1120 2. 8 : 8 9. 3 : 3.7 : 4.2 1 • 053 1 . 53 0 0.154- 1160 26.2 : 63.7 : 3.6 : 6. 4 1 • 24 7 1 . 4 22 0.:216- 1200 1 6. 8 : 6 7. u : 5. 2 : 8.0 1 . 4 23 1 . 5 91 0.111+ 1 240 19.6 : 68.5 : 3.9 : 8.0 1 . 254 1 . 445 0.345+ 1280 22.0 : 66.5 : 5.5 : 6.0 1 • 546 1 . 4 35 0.423+ 1290 1 6. 8 : 70.0 : 6.3 :6.8 1 . 4 2 9 2.122 0.024- 1320 0 : 23.6 : 4.2 :72.2 1 . 57 2 2.351 0.105- 1340 28.8 : 58.6 : 6.5 : 6.0 1 . 7 7 2 1 . 51 0 0.122 1369 6. 0 : 70.6 : 9.4 : 1 3. 9 1 . 4 93 2.317 0.177 ...... ~' (1) CORE PC 21-23 CORE DEPTH G : S : z : c STANDARD MAIN GRAIN SKEWNESS (em) % DEVIATION SIZE 355 0 : 35.~ : 27.8 : 37.0 2.222 5. 31 0 0. 14 0 365 0 : 39.0 : 52.0 : 9.0 2.016 5.148 0.175 377 0 : 35.0 : 55.0 : 1 0. 0 2.008 5. 116 0.139 395 0 : 34.0 : 51.0: 15.0 ~.251 5.475 0.224 420 0 : 68.U : 27.0 : 5.0 2.053 3.567 0.570 465 0 : 10.0 : 68.0 : 22.0 1 . 7 58 6.780 0.008 500 0 : 8.0 : 43.0 : 49.0 2.019 7.556 0.315- 570 0 : 43.0 : 51.0 : 6.0 1 . 9 06 4.848 0.164 580 0 : 54.0 : 42.0 : 4.0 1. 833 4.320 0.334 585 0 : 60.0 : 30.0 : 1 c. 0 2.207 4.300 0.547 655 0: 51.9 : 1 8 . 1 : 30.0 2.412 4.894 0.480 "i 00 0 : 73.2 : 1 2. 3 : 14. 5 2.128 3.650 0.568 710 0 : 83.2 : 9. 0 : 7.7 1 . 7 4 6 3. 16 7 0.463 ,_. ~~:\ _f::, CORE PC 17-20 CORE DEPTH G : S : z : c STANDARD MAIN GRAIN SKEWNESS (em) % DEVIATION SIZE 20 0 : 58.8 : 5.7 : 35.5 ------40 0 : 91 . 8 : 7. 7 : 00.5 ------ 82 0 : 95.8 : 2. 0 : 2.3 0.611 2.890 0.233 1 00 0 : 93.0 : 1 . 9 : 5.2 0.486 2.909 0.147 130 0 : 9L.6 : 2.9 : 4.5 0.379 2.878 0.147 150 0 : 95.4 : 1 . 4 : 3.L 0.493 2.856 0.182 170 0 : 95.2 : 2. 5 : 2.3 0.447 2.861 0.199 200 0 : 89.1 : 4. 7 : 6.2 0.814 2.915 0.316 ,_.. l~f Ul CORE PC 13-13 CORE DEPT G : S : SL : C STANDARD MAIN GRAIN SKEWNESS (em) % DEVIATION SIZE 165 0 !' 1.00: 95 : 4. 0 0.450 5. 811 0.412 180 0 : 72.4 : 1 8. 1 : 9.0 0.718 3.600 0.410 1 . 1 2 3 2.628 0.268 190 0 : 84.0 : 10.2 : 5.4 415 0 : 58.0 : 36.G : 6.0 1 . 896 4.380 0.442 430 0 : 68.0 : 28.0 : 4.0 1 . 988 3.755 0.407 433 0 : 79.7 : 1 2. 1 : 8. 2 1.117 1 . 9 01 0.242 CORE PC 13-12 380 0 : 88.L. : 5.4 : 6. 4 0.701 2.997 0.285+ 460 0 : 91 • 0 : 2.7 : 6.3 0.605 2.821 0.164+ 490 0 : 81 . 9 : 5.7 : 1 2. 4 0.797 2.974 0.566+ I:;:I 1)·. DSDP SITE 322 CORE 6-10-11 CORE NUMBER CORE DEPTH S.D. M.G.S. SK 322 - 1-2 32 em 0.428 3.358 0.069 322 - 6-1 81 em 0.716 3. 1 35 0. 11 0 322 - 6-1 101 em 0.474 3. 1 7 2 0.201 DSDP SITE 323 CORE 4 CORE NUMBER CORE DEPTH S.D. M.G.S. SK 323 - 4-2 ( 41 em) 0.184 0.332 0.075 323 - 4-2 (102 em) O.:L73 0.354 0.023 ,_.. 1S1 "· .. j APPEt·-..JC) I X I I Location and Depths of USNS Eltanin Piston Cores Used in This Study Core No. Latitude Longitude Depth Lengh s ~'l m em 5-13 59°46.00' 68°5:i.OO' 3901.8 212 5-27 51°00.00' 71°00.00' 41 98. 1 93 10-05 59°22.10' 82°31.10' 4939 560 10-11 65°58.00' 82°51.08' 4317 220 10-13 65°00.00' 74°57.00' 3841.5 98 10-23 67°09.07' 89°39.04' 4~80.5 1377 11-25 65°05.35' 86°54.03' 4535.6 351 11-26 63°39.04' 86°56.00' 4655.5 993 13-09 63°05.09' 89°39.08' 4664.6 1782 13-11 66°23.06' 93°31.05' 4595.1 440 13-12 66°15.06' 98°16.01 I 46L8 884 13-13 66°11.08' 102°16.06' 4737.8 552 17-20 67°55.00' 103°04.00' 4408.5 120 10-25 ------...... ------17-25 65°59.00' 94°L9.00' 4597 21-23 62°30.00' 99°48.05' 4961 23-02 62°22.00' 95°32.00' 4908 ...... ::::1 ··(1