Deep Sea Drilling Project Initial Reports Volume 34

5. SITE 321

The Shipboard Scientific Party1

SITE DATA

Location: East edge of Nazca plate (Peru Basin)

Dates Occupied: 29-31 January 1974

Time on Site: 53 hours (2.21 days)

Position: 12°01.29'S; 81°54.24'W

Water Depth: 4827 meters (drill pipe)

Penetration: 134.5 meters

Number of Cores: 14

Total Length of Cored Section: 125 meters

Total Core Recovered: 85.8 meters

Percentage Core Recovery: 69%

Oldest Sediment Cored:Depth below sea floor: 124 metersNature: Ferruginous nanno oozeAge: Late EoceneMeasured velocity: 1.54 km/sec

Basement:Depth below sea floor: 124 metersNature: BasaltVelocity: 5.07-5.94 km/sec

Principal Results: The units penetrated at Site 321 are 34.5meters of greenish-gray clay, rich in siliceous fossils, 14.5meters of light yellow-brown clay with clear volcanic glass,9 meters of unfossiliferous brown zeolitic clay, 66 meters offerruginous nanno ooze, and 10.5 meters of basalt. The up-per section, of late Miocene-Quaternary age, reflects thehigh productivity of the Humboldt (Peru) Current in itsabundant siliceous fossils and the South American conti-nent in its terrigenous clay and volcanic ash. The nannoooze is late Oligocene-late Eocene in age, and, along withsediments of similar age at Site 320, represents the firstPaleogene strata found on the Nazca plate. Faunal age cor-responds well with ages based on magnetic anomalies andon the Sclater age-depth curve. The underlying extrusivebasalt is massive and generally aphyric, with vesicles,calcite amygdules, and sulfide and smectite veins.

'Robert S. Yeats, Ohio University, Athens, Ohio (Co-Chief Scien-tist); Stanley R. Hart, Carnegie Institution of Washington,Washington, D.C. (Co-Chief Scientist); James M. Ade-Hall,Dalhousie University, Halifax, Nova Scotia; Manuel N. Bass,Carnegie Institution of Washington, Washington, D.C; William E.Benson, National Science Foundation, Washington, D.C; Roger A.Hart, Physical Research Laboratory, Ahmedabad, India; Patrick G.Quilty, West Australian Petroleum Party Ltd., Perth, West Australia,Harvey M. Sachs, Case Western Reserve University, Cleveland, Ohio;Matthew H. Salisbury, National Science Foundation, Washington,D.C; T.L. Valuer, University of California at San Diego, La Jolla,California. Additional contribution by G. Blechschmidt, University ofWashington, Seattle, Washington.

BACKGROUND AND OBJECTIVES

Geologic SettingSite 321 is located on the eastern edge of the Nazca

plate immediately south of the Mendafia Fracture Zone(Figure 1). The sea floor is 400 meters deeper than atSite 320, which lies north of the fracture zone (Figure 2).Site 321 is located about 15 km west of anomaly 16 (39m.y. old), as recognized by Herron (1972). The halfspreading rate, based on the distance from anomaly 12to anomaly 16, is 7.9 cm/yr parallel to the MendafiaFracture Zone.

The site is located along an ASPER refraction line at12°S run by D. Hussong and others (personal com-munication, 1973) which shows low-velocity layers inthe upper part of the basement. The upper basementlayer has velocities of 3.1-3.8 km/sec; below this is a 5.2-5.8 km/sec, layer underlain by a 6.0-6.5 km/sec layer.About 50 km east of the site, the ASPER data suggest athrust fault, although gravity data have not verified itsexistence. The sea floor rises gently east of the site priorto the more abrupt descent into the Peru-Chile Trench;this apparently results from elastic flexure of the upperlithosphere produced by loading of the Nazca plate bythe leading edge of the American plate (Watts andTalwani, 1974; Ade-Hall, Underway Surveys, thisvolume).

Although the predicted crustal age at Site 321 isgreater than at Site 320, the sediment section is thinner,possibly reflecting greater water depths and a longertime below the CCD.

The site was located from Kona Keoki Leg 7 (Figure 3)and lies at 2230Z, 12 January 1972, at which point thesonobuoy marking ASPER Station 104 was dropped.The surficial sediments show on the high-frequency butnot on the low-frequency record, suggesting that theyare quite soft. An intermediate reflector is present at asubbottom interval of 0.086 sec (2-way time).

ObjectivesObjectives for drilling at Site 321 were the following:

(1) to compare velocities from the basalt core withASPER refraction data, (2) to determine the paleo-latitude of the plate from remanent magnetization ofbasalt and of sediments, (3) to compare the mag-netization of basalt at a site with and a site withoutlinear magnetic anomalies, (4) to describe the petrologyand geochemistry of the basalt, (5) to determine thehistory of the eastern Nazca plate for the last 40 m.y.,the history of the Humboldt (Peru) Current, and theconvergence of the Nazca and South American plates,(6) to compare the thinner sediment section over oldercrust at Site 321 with the section at Site 320, (7) to deter-

111

SITE 321

90'

40'

J\

Rise CrestGalapagosRise Crestwhere known

M M Trench Axis

Fracture Zone

Glomar Challenger TrackFigure 1. Location map of sites drilled during Leg 34.

112

SITE 321

16° -

mine the amount of airborne terrigenous matter in theplate, including ash from Andean volcanoes, and (8) todetermine the effectiveness of the Peru-Chile Trench as abarrier to turbidity current dispersal.

OPERATIONS

Site SurveySite 321 was located along an ASPER refraction line

at 12°S run by Hawaii Institute of Geophysics as part ofKana Keoki Leg 7 (1971). At ASPER Sonobuoy Station104 (2230Z, 12 January 1972 station), a small basinslightly deeper than adjacent terrain contains about 135meters of sediment, in contrast with the 80 meterscharacteristic of most of the area.

Glomar Challenger approached the site from thenorthwest and turned east along the Kana Keoki track.The basin was located at a depth about 50-60 metersshallower tha on the Kana Keoki line. After a William-son turn, the beacon was dropped on the run at 0745 hr(local time), 29 January as the ship steamed west overthe site (Figure 4). Detailed bathymetry and ships'tracks are given in Figure 5.

Drilling ProgramThe program was to continuously core, leaving time

for the bit to get maximum life in basalt (Table 1). Thebit took weight at 4827 meters, the same depth as in-dicated by PDR; this depth was confirmed by the 1.5-meter core recovery. The top of the basalt was reachedat 4941.5 meters, almost 1 meter above the bottom ofCore 13. That core recovered basalt and sediment, butthe actual contact was not preserved.

Core 14 was cut in basalt with an occasional 500 ampsof torque. Weight was added and the torque decreasedfor the last 4-5 meters, resulting in smooth drilling andgood recovery from a thick, massive cooling unit ofbasalt with relatively few fractures. The core barrel forCore 15 was dropped and the string worked to bottom(after being pulled above the basalt for the retrieval ofCore 14). When coring began, torque rose to 750 amps,then the Kelley was rotated and torque dropped, level-ing off at 150 amps. The bottom-hole assembly hadtwisted off above the mudline, forcing abandonment ofthe site.

Glomar Challenger left the site at 116 hr local time, 1January 1974. A box survey of the site was conducted,and the ship cruised south to 12°20'S to providemagnetic anomaly correlation with Kana Keoki 7 andProject Magnet lines.

LITHOLOGY

Description of Units: SedimentsThe hole was cored continuously to a depth of 134.5

meters with the exception of the interval from 96.5 to106 meters. Basalt was encountered at 124 meters andwas penetrated for 10.5 meters before twist off forcedabandonment of the site.

The sediments are divided into four lithologic units(Table 2, Figure 6) which overlie basalt. They consist ofgreenish-gray, siliceous fossil-rich detrital clay (Unit 1);yellowish-brown, volcanic glass-rich clay (Unit 2); darkbrown, zeolite-bearing brown clay (Unit 3); and palebrown to dark brown iron-rich nanno ooze (Unit 4).

Unit 1: Siliceous Fossil-rich Detrital ClayThe youngest unit (Core 1 through Core 5, Section 3;

subbottom depth 0-34.5 m) is a greenish-gray, gray, andolive siliceous fossil-rich detrital clay of Pliocene andQuaternary age. Clay is the major component, con-stituting about 70% to 85% of the sediments, andsiliceous fossils consist, in order of decreasing abun-dance, of diatoms, radiolarians, sponge spicules, andsilicoflagellates, and comprise as much as 25% of somesediments in the unit. Minor components include clearvolcanic glass (trace to 7%, with one sample having

113

Figure 2. Bathymetry of Sites 320 and 321 (in fathoms)from Mammerickx et al. (1975).

SITE 321

EAST 2300Z 2200Z 2180Z

jWEST

2-waytime(sec)

4.0

HDG 092°SPEED 6.4 Kts

SONOBUOY#104

HDG 092°SPEED 10 Kts

Figure 3. Kana Keoki Leg 7 profile showing location of Site 321 at 223OZ, 12 January 1972 at point where sonobuoy markingASPER 104 was dropped. Frequency was 40-100 Hz with a 5 sec sweep. Water depth at Site 321 is 4827 meters.

oooozL

GMT 31 JAN 74

2200Z 2000Z 1800Z 1200ZI I

1000Z

GMT 29 JAN 74

0800Z 0600ZI I

FRACTURE ZONE ;

2-waytime(sec)

- 7

2320HDG 086°

SPEED 7.9 Kts

2000HDG 043

SPEED 7.0 KtsHDG

SPEED 6.

1207150°

0 Kts

1115HDG 092SPEED 6

°.0 Kts

0840HDG 163SPEED 9

0

.5 Kts

0400HDG 159°

SPEED 9.5 Kts

Figure 4. Glomar Challenger airgun profile between Sites 320 and 321 and past Site 321 (10-sec sweep).

50%), feldspar and quartz in the fine silt-size range,heavy minerals (clinopyroxene, hypersthene, biotite,and opaques), and a few fish remains. Arbitrarily, theunit can be subdivided into two subunits on the basis ofsiliceous fossil and volcanic glass percentages. Cores 1through 3 have consistently higher amounts of siliceousfossils (10%-25%) and lower amounts of volcanic glass(trace to 3%), whereas Cores 4 and 5 (through Section 3)have lower siliceous fossil percentages (2%-10%) andhigher amounts of volcanic glass (l%-10%, with onezone of 50%).

Unit 2: Volcanic Glass-rich ClayThe next older unit, of late Miocene and possibly

younger age, is thinner than Unit 1 (Core 5, Section 3through Core 6; 14.5 m thick) and is easily recognized byits color and lithology. The unit consists of lightyellowish-brown clay near the top, below which is dark

grayish-brown volcanic glass-rich clay gradingdownwards to clayey volcanic ash. Distinguishingcharacteristics are the high contents of clear volcanicglass (ranging from 5% to 55%, with an average of about20%) and the yellow-brown and brown color. Some thinbeds of grayish-green, waxy, bentonite-like material oc-cur in Samples 5-4, 140-150 cm and 5-5, 24-30 cm.Although most of the volcanic glass is clear and fresh,some samples contain clumps and pieces of angular hardclay which suggest that they may be altered glass, andpart of the montmorillonite matrix in Unit 2 probablyformed by the alteration of fine volcanic ash. Somecalcareous nannofossils occur at isolated intervals (e.g.,Core 6, Section 3, 75 cm), and siliceous fossils areirregularly dispersed (trace to 5%). Heavy minerals in-clude clear and green clinopyroxene, hornblende,biotite, and opaques. Euhedral crystals of phillipsite oc-cur in the core catcher of Core 6.

114

SITE 321

12°S

KANA KEOKI LEG 72100

82°W 55' 81°50'W

Figure 5. Detailed bathymetry at Site 321 (in m) showing Kana Keoki Leg 7 and Glomar Challenger Leg 34 tracks. Time is inGMT.

TABLE 1Coring Summary, Site 321

Timeon

Core Deck

Depth FromDerrick Floor

(m)

Depth BelowMudline

(m)

Depth BelowTop Basalt

(m)Recovery

(m) (%) Remarks

1

23

4567891011121314

2100(29 Jan)22410019(30 Jan)01460315045006200750092512411423155918062225

4827.0-4828.5

4828.5-4838.04838.0-4847.5

4847.5-4857.04857.0-4866.54866.5-4876.04876.0-4885.54885.5-4895.04895.0-4904.54904.5-4914.04914.0-4923.54933.0-4942.54942.5-4952.04952.0-4961.5

0-1.5

1.5-11.011.0-20.5

20.5-30.030.0-39.539.5-49.049.0-58.558.5-68.068.0-77.577.5-87.087.0-96.5

106.0-115.5115.5-125125.0-134.5

0-11-10.5

1.5

6.19.29

6.08.59.28.99.19.34.54.11.03.84.5

100

6498

6389989196974743114047

100 Took weight at 4827 (8 m water core)

Down time; kink in sand line

Core liner partly crushed in barrelTop basalt 124 meters ( I m slow drilling)500 amp torque occasionally, weightadded last 4-5 meters, faster and smoother;large cooling unit, few natural fractures

115

SITE 321

TABLE 2Lithostratigraphic Summary, Site 321

Unit

1

2

3

4

5

SubbottomDepth (m)

0-34.5

34.5-49

49-58

58-124

124-134.5

Lithology

Greenish-gray detrital clay,rich in siliceous fossils

Light yellow-brown clay withsignificant amounts of clearvolcanic ash, up to 55% in afew horizons

Zeolite-bearing brown clay

Light brown nanno ooze in-terbedded with darker brownzeolite-bearing iron-richnanno ooze

Basalt

Core

1-5

5-6

7

7-13

13-14

Age

Quaternary andPliocene

Late Mioceneand possiblyyounger

Miocene (?)

Early Mioceneto lateEocene

(?)

Unit 3: Brown ClayAn undated zeolite-bearing brown clay unit, about 9

meters thick, was cored from 49 to 58 meters (all of Core7 down to Section 6, 130 cm). Colors are dark brownand dark grayish-brown. Phillipsite composes from 3%to 7% of the sediment, and opaque minerals (includingrare semi-opaques, the so-called RSOs) range from 2%to 5%. Trace amounts of calcareous nannofossils werenoted in Sections 4 and 5; however, they may be ex-ogenous.

Unit 4: Nanno OozeFrom 58 meters to the top of the basalt at 124 meters,

the section is nanno ooze, late Eocene to early Mio-cene (?) in age, that has varying amounts of ferruginousgrains, forams, microscopic calcite fragments, andphillipsite. The unit is yellowish-brown, pale brown, anddark brown in color. Sediment types include nannoooze, ferruginous nanno ooze, foram-rich nanno ooze,and iron/foram/zeolite-bearing nanno ooze. Highpercentages of ferruginous particles (RSOs) occur in theupper part of Core 9 (10%-25%) and in Core 13 (15%-35%). Core 9 also has a high percentage of phillipsite(5%-15% in the first two sections). Phillipsite forms asmuch as 15% of individual samples, and euhedralcruciform twins are common. Foraminiferal tests com-pose a significant proportion of Cores 11 and 12, inwhich contents range from 2% to 20% and average about7% in five samples. Generally, high iron and high zeolitepercentages occur in the dark brown beds. Like the iron-rich sediments at Sites 319 and 320, Unit 4 at Site 321contains only a small amount of clay. The brown colorsare mainly the result of iron particles.

The basalt-sediment contact was encountered at adepth of 124 meters. Samples from directly above thecontact, with high RSO and phillipsite percentages andalso abundant (about 20%) particles of green alteredvolcanic glass (nontronite?), suggest that the contact isdepositional.

Discussion of SedimentsSeveral points about the sediment section should be

made:1) The sediment-basalt contact is depositional. The

late Eocene age of oldest sediment is that predicted from

magnetic anomalies and from bathymetry. A heavymineral separation from the oldest sediments above thebasalt contains basalt-derived crystal and rockfragments.

2) The basal sediments are iron rich, apparentlysimilar to basal sediments cored elsewhere in the world'soceans.

3) High RSO content in Core 9 (late Oligocene) is ob-viously not a basal iron-rich facies.

4) The contact between nanno ooze and brown clay(base of Core 7) indicates that the sea floor crossed theCCD in late Oligocene time.

5) There may be a hiatus within the brown clay unit(Unit 3), although the entire unit can be accounted forby a sedimentation rate of 1.0 m/m.y. during the earlyand middle Miocene.

6) Abundant volcanic products reached the site in thelate Miocene (Unit 2), when clear volcanic glass becamean important sediment component. These materialsrecord the beginning of major pyroclastic activity in theAndes Mountains. High volcanic glass input has con-tinued to the present time.

7) Although siliceous fossils are not abundant in Unit2, their appearance may mark the beginning of increasedproductivity, either because of the initiation of theHumboldt (Peru) Current or because the site moved un-der the influence of that current for the first time in thelate Miocene.

8) The top unit is marked by large quantities of greendetrital clay and siliceous fossils. The high clay contentis related to the site's proximity to the South Americancontinent, whereas the siliceous fossils are related to thehigh biologic productivity associated with the cold,nutrient-rich waters of the Humboldt (Peru) Current.

9) In summary, major events which affected the sedi-ment column at Site 321 occurred: (a) in the late Eocene-early Oligocene, when high contents of iron oxide weredeposited; (b) in the early late Oligocene, when onceagain ferruginous particles formed a significant portionof the sediment; (c) in latest Oligocene, when the seafloor subsided below the CCD; (d) in the late Miocenewhen abundant pyroclastic materials reached the site;and (e) in the Pliocene-Quaternary, when siliceousfossils and detrital clays were deposited.

116

SITE 321

LITH UNIT DEPTH(m)

AGE

m.y. zone ' epoch 'SEDMENTATION RATE

VOID

VOID

10

11

12

UNIT 1Det.clayrich insi lieeousfossils

— V O I D

UNIT 2

Claywithvol. ash

UNIT 3

Brownclay

VOID

VOID

UNIT 4

Nannoooze

UNCORED

INT .

VOID

4 8 3 0 -

10

204 8 5 0 -

30

£04 8 7 0 -

50

604890-T3

§70

4910 —

90

JOO jöj4930-1

110

l_204950 -

5-0-4

1-2

1-5

N22-23

N22

N22

N18-22

QUATERNARY

PLIOCENE-

PLEISTOCENE

V_ i 4-5 m/m.y.

-1

- \

8-12

22-26

26 30

26-32

32-35

mid-

late

NI-2

P-19

l a t e

32-38 I P18-19 >>

BASALT

35-38

39-40

P18

P16 late

Unconformity or sed./ rate of ca 1 m/m.y.

MIOCENE

EOCENE -

)

\

\

4-5 m/m.y.

\

>

»

J L10 20 m.y.

AGE

30 40

Q• PLIO.MIOCENE

Late JMiddle Early

OLIGOCENE

Late Early

EOC.

Late

Figure 6. Stratigraphic column at Site 321, showing age data and sedimentation rates. Horizontal lines on sedimentation ratediagram show precision.

Description of Units: Basalt

Basalt was recovered in the lowest 25 cm of Core 13and in Core 14 with about 50% recovery. The rock isremarkably uniform from top to bottom of therecovered section, varying from fine-grained, massive,dark gray, almost aphyric basalt at the top, to verycoarse grained but otherwise identical basalt at the bot-tom. No glass was recovered except for one angularfragment of dark brown glass in the +63 micron frac-tion of a slurry from the liner of Core 14. Grain sizevariations indicate two cooling units with a contact atCore 13, Section 4, 125 cm. The basalt-sediment contact

is disturbed; the top 15 cm is a half cylinder bounded bythe surface of the core and a steep to vertical joint, and italmost certainly would not have survived coring had theother half of the cylinder originally been sediment. Theother half of the basalt cylinder must have been lost dur-ing coring. Nonetheless, the basal sediment is rich inbasaltic minerals and altered palagonite andfibropalagonite and undoubtedly was originallydeposited near the contact. Therefore, either the originalcontact was lost in coring, or it had been previouslyeroded.

The lower, thicker cooling unit is homogeneous.Although neither contact was recovered, the fine grain

117

SITE 321

size of the uppermost pieces recovered indicates prox-imity to the upper contact, and the decrease of frequen-cy and continuity of joints and veins near the bottom ofthe recovered core may indicate proximity to the lowercontact. Most of Core 14 is composed of nonrotatedcore pieces that can be refitted into an almost con-tinuously recovered section, from which we infer thatthe lost 50% of the drilled section was the lower half ofthe core, which may have been a relatively nonjointed,coarse-grained portion of the thicker cooling unit whichfor some reason was not retained in the core barrel, or apillowed, finely jointed section below that unit whichwas destroyed by the bit as in Hole 320B.

Microphenocrysts are rare. Plagioclase is most abun-dant and ranges in size from 0.4 X 0.1 mm to 3 × 0.2mm, with maximum dimensions rarely exceeding 2 mm.The cores of Plagioclase microphenocrysts from Core14, Section 4, 34-49 cm are An65-72. Olivinemicrophenocrysts are very rare; one from the thin, up-per cooling unit is Fθ87-8β. A clinopyroxenemicrophenocryst was seen only as a component of aglomerocryst. The Plagioclase and olivine compositionssuggest normal, ridge-type olivine tholeiites. An intervalfrom 14-2, 45 cm to 14-4, 2 cm is totally devoid ofmicrophenocrysts and suggests the existence of a com-plementary cumulate zone below the recovered section.In a general way, the abundance of microphenocrysts in-creases in finer grained rocks near inferred contacts ofcooling units, and such abundance variations inmicrophenocryst-poor rocks may offer one criterion forproximity to contacts.

Textures are intergranular, verging on subophitic.The groundmass contains sector zoned pyroxene withwavy extinction, Plagioclase microlites, opaqueminerals, and smectite pseudomorphs after late olivine.In the coarser grained rocks the last-crystallized,quenched mesostasis includes elongate, skeletal opaqueminerals and skeletal Plagioclase in a smectite (alteredglass?) matrix. This terminal quench is similar to that in-ferred from the coarse-grained rocks from Site 319 andsimilarly suggests a flow rather than a sill. The presenceof groundmass olivine indicates that the magma lay onthe olivine-plagioclase cotectic or the olivine-plagioclase-augite three-phase cotectic throughout thecourse of crystallization. Thus, as expected in such fine-grained rocks, fractionation was not pronounced.

High titanium titanomagnetite is the dominant opa-que phase in all 12 basalt samples examined. Grain formvaries from skeletal to anhedral or subhedral. Grain sizevaries from the limit of visibility at about l/4µ, in thefiner grained basalts of Core 13, to 30µ in the massivebasalts of Core 14. Two size generations are often evi-dent in the massive basalts, with the finer size generationgrains often forming overgrowth rims on the largerskeletal to anhedral grains. Titanomagnetite alterationis limited to the low-temperature effects resulting fromthe halmyrolysis of the lavas, which produces cation-deficient titanomagnetites, and leads ultimately to theformation of titanomaghemites. The development of ca-tion deficiency can be followed by changes in magneticproperties (see Ade-Hall et al., Rock Magnetism ofBasalts, Leg 34, this volume). In turn, changes in

titanomagnetite detected with the ore microscope can beassigned arbitrary numerical values of cation deficiencyon a scale from 0.0 to 1.0 calibrated by the magneticmeasurements. Low degrees of cation deficiency areidentified by the presence of volume change cracks inotherwise apparently unaltered grains. Cation deficien-cies in excess of 0.6 are identified by lightening in color,increased reflectivity and expulsion of iron into surroun-ding silicates. The degree of cation deficiency oftitanomagnetite correlates with the type of basalt, thetitanomagnetites in the fine-grained basalts being highlycation deficient, and those in the massive basalts beinglittle if at all cation deficient.

Natural fractures of joints (inferred from vein dis-tribution) are low dipping near the top and steeply in-clined in the lower portion of the recovered section. Thelow-dipping joints appear to form preferentially in fine-grained rocks near contacts of cooling units, the steeplyinclined ones in coarser grained rocks from the interiors.The continuity of joints decreases and their spacing in-creases downward, and these changes correlate with im-proved core recovery.

Veins include green and blue-green unoxidized smec-tite in the lower, relatively fresh, sparsely jointed part ofthe recovered section; and red, brown, and yellow ox-idized smectites in the higher, relatively altered, jointedand veined portions nearer the contacts of the coolingunits. Sulfide and phillipsite occur with some of the un-oxidized smectite, and sulfide is locally the dominantvein mineral. The light grayish or whitish-yellow colorof much of the sulfide gave a shipboard clue to thepresence of marcasite, later confirmed by X-ray diffrac-tion analysis, which occurs with pyrite in veins in basaltfrom Site 321 as well as Site 319. As at Site 319, detailedtextural relationships of the variously colored smectitessuggest an earlier, nonoxidative stage of alteration and alater oxidative one. Calcite is commonly a minor com-ponent of veins and less commonly the dominantmineral. Overall, it is much less abundant than in veinsfrom Site 319. Aragonite, despite optical suggestions ofits presence during shipboard examination, was not con-firmed by X-ray diffraction analysis. If ever present, asat Site 319, it totally inverted to calcite during the ad-ditional 15 m.y. of time available at Site 321.

Vesicles appear throughout, constituting about 1% ofthe rock. Maximum diameters increase from less than 1mm near the top of the recovered section to 2 mm nearthe bottom; diameters are generally 0.7 mm or smaller.They commonly contain quenched, very fine grainedbasalt in their bottoms. Locally the vesicles coalesce toirregular holes up to 4 mm across. The vesicles are com-monly empty or thinly lined by oxidized smectite in thealtered rocks. In the fresher, grayer rocks there is agreater tendency to partial or complete fillings (i.e.,amygdules) which are commonly smectite or sulfidenear smectite or sulfide veins, respectively. Below 321-14-1, 55 cm, many vesicles are partly to wholly filled bycalcite, often radial, which may enclose a sulfide grain orbe rimmed by green smectite. Many empty or thinlylined vesicles are evidently artifacts of drilling and saw-ing due to the tendency of smectite to swell and pluckout, especially in fresh water. In the lower part of Core

118

SITE 321

14 the carbonate-filled vesicles decrease rapidly in abun-dance parallel to a notable decrease in frequency andcontinuity of joints and veins of all types.

BIOSTRATIGRAPHYNeogene opaline microfossils are the dominant fossils

above 58 meters (just above 321-7, CC), and planktonicforaminifera apparently are totally absent above 58meters, although a few agglutinated forms are present inthe core-catcher samples of Core 4 (30 m). Below 58meters, the sediments are dominantly nanno oozes,Oligocene-Eocene in age, with abundant planktonicforaminifera. Biostratigraphic information is sum-marized in Figure 3.

Neogene Radiolarian StratigraphyNeogene Radiolaria were recovered only from the up-

per part of Site 321. Core catchers 1-3 (0-20.5 m) containwell-preserved Quaternary faunas; core catcher 4 (30 m)has a Pliocene or Quaternary assemblage; core catcher 5(39.5 m) contains a sparse assemblage lackingstratigraphically useful forms; core catcher 6 (49 m) con-tains a very sparse earliest late Miocene (lower part)fauna; and core catchers 7 (58.5 m) to 13 (124 m) containvirtually no Radiolaria. In addition to Radiolaria, thereare numerous well-preserved diatoms and silico-flagellates in core catchers 1-3.

Core catchers 1-3 contain diverse and well-preservedradiolarian faunas which resemble those of the PanamaBasin and Equatorial Pacific. The assemblage of corecatcher 1 contains Pterocanium praetextum, Ommatartustetrathalamus, and Theoconus minythorax. TheAmphirhopalum ypsilon generally shows about fivechambers on the forked arm before bifurcation. Thistends to put this sample in the uppermost QuaternaryZone, but the dominant form, Buccinosphaera invaginatawas not encountered. The absence of Stylatractus univer-sus probably indicates that core catcher 1 sediment isless than about 400,000 yr old, if the North Pacific dis-appearance datum represents extinction.

Core catchers 2 and 3 contain assemblages as rich asthat of core catcher 1, and also increasingly abundantStylatractus universus, indicating an age greater thanabout 400,000 yr. In both, the Amphirhopalum ypsilontends to have only two chambers on the forked armbefore bifurcation, indicating earlier Quaternary ages.Core catcher 3 is considered to be Quaternary becausePterocanium prismatium was not found, despite theabundance of other Pterocanium species. It isnoteworthy that neither Spongaster pentas (lowerPliocene) nor S. tetras was encountered at Site 321.

Core catcher 4, from an ash-rich zone, contains arather sparse fauna with post-Miocene affinities. Om-matartus tetrathalamus, Stylatractus universus, and Lam-procyclas maritalis are present. The "Amphirhopalum'''present have three completely separate arms. In theabsence of any Pterocanium or either Spongaster pentasor S. tetras, discrimination between Pliocene andQuaternary was not feasible.

Core catcher 5 is nearly barren, with rare robuststylatractoids including one Stylatractus universus.Because the range of this form extends into the late

Miocene, its presence offers little significant strati-graphic information.

Core catcher 6 contains a sparse fauna with mostforms broken. Cannartids are dominant, but end capsare almost never preserved. Positive identification ofOmmatartus hughesi from several partial samples and acomplete end cap strongly indicate that the faunabelongs to the Ommatartus antepenultimus Zone, ofearliest late Miocene age.

Paleogene Planktonic Foraminiferal StratigraphyThe nanno ooze section (58-124 m; Cores 7-12) con-

tains a virtually complete Oligocene (P18-N3) sectionand the sample examined from Core 13 (124 m) isEocene (PI6) in age. There is a gap in the sequencebetween 96.5 and 115.5 meters.

In Core 7 (core-catcher sample) the fauna consists ofvery few species, those remaining are the survivors ofquite obvious dissolution effects. The fauna consistsmainly of benthonic foraminifera and a concentrate offish teeth and bone fragments. Significant planktonicspecies are Globigerina prasaepis, G. venezuelana, Catap-sydrax unicava unicava, and C. dissimilis ciperoensis.

The fauna in Core 8 consists only of small species ofplanktonic foraminifera showing no signs whatsoever ofdissolution. No large species such as these characteriz-ing the 7, CC sample are present. Dominant forms arespecies of Chiloguembelina, and also present areCassigerinella chipolensis and Catapsydrax stainforthipraestainforthi.

The Core 9 sample consists of a concentrate of fishfragments resulting from marked carbonate dissolution.Characteristic planktonic foraminifera are Globigerinaprasaepis, G. sellii, Globorotalia opima nana, and Cata-psydrax unicava unicava of the Oligocene (PI9).

Core 10 is of early Oligocene age (P18). Foraminiferaagain suffer the effects of dissolution but not as marked-ly as in some samples above. Characteristic species areGlobigerina angiporoides minima, G. prasaepis, G.winkleri, and ?G. tapuriensis.

The fauna in Core 11, of early Oligocene age (P18)consists of very abundant diverse foraminifera showingno dissolution effects. Characteristic forms areGlobigerina prasaepis, G. tapuriensis, G. ampliapertura,G. angiporoides, Globigerinita unicava unicava, and rareChiloguembelina species.

Again, the fauna is very rich in Core 12 (earlyOligocene, PI8), and makes up the largest proportion ofthe ooze of any samples from this hole. The fauna is un-usual in being very much dominated by Chiloguembelinaspecies (more than 30% of the fauna) and Cassigerinellachipolensis. G. eocaena also is present. Pseudohastigerinanaguewichiensis and Globigerina tapuriensis are the otherkey fossils.

The sample from Core 13 is within about 30 cm of thebasalt contact, and is the oldest sediment identified onthe Nazca plate and represents the only Eocene fromLeg 34. Dissolution effects are very marked, and thefauna is a rich concentrate of fish teeth and fragments.Hantkenina spines are common but no completespecimens were recovered. Cribrohantkenina inßata isidentified on the basis of a single apertural face and

119

SITE 321

spine. Other key species are Globigerapsis index, G. mex-icana (G. semiinvolutá), and Pseudohastigerina micra.

The sediments above 58 meters represent sedimenta-tion below the CCD as no calcareous microfossils (apartfrom rare nannoplankton) are present, and there is noevidence that they were ever present. The nanno oozebelow 58 meters probably was deposited near the CCDas some faunas show dissolution effects but others shownone. During the Eocene-Oligocene time interval, theCCD probably fluctuated enough to account for thevariation in preservation that is seen.

Calcareous Nannoplankton

For the most part, Cores 1 through 6 are barren ofcalcareous nannofossils. Occasional badly corrodedplacoliths are present in some samples, but these are notage diagnostic. Sections 1 through 5 of Core 7 are alsobarren of calcareous nannofossils, but Section 6 con-tains a well-preserved and fairly diverse nannofossilassemblage of early Miocene-late Oligocene age. Areasonably complete late and middle Oligocene sectionis present in Cores 7 through 11. Precise zonal deter-minations are difficult due to reworking of earlyOligocene and late Eocene taxa, which form a minorcomponent of all assemblages found. Cores 8 and 9 arelate Oligocene in age and are tentatively assigned to theSphenolithus distentus-Sphenolithus ciperoensis zones(NP24-25). Cores 10 and 11 contain middle Oligocenenannofossils, probably representing the Sphenolithuspredistentus Zone (NP23). The lowermost Oligocene iseither missing at this site or has been lost in coring. Core13 is late Eocene containing common Discoaster bar-badiensis and Discoaster saipanensis.

SEDIMENTATION RATESThe Oligocene-Eocene sediments at Site 321 (Cores 7-

13 inclusive; 58-124 m) accumulated at 4.0-5.0 m/m.y.(Figure 6). The Miocene (early part of the late Miocene)and younger sediments at Site 321 also yield a sedimen-tation rate of 4.0-5.0 m/m.y. although this is an averagevalue and it actually may be lower in the Miocene andhigher in the Pliocene-Quaternary.

No middle Miocene has been identified from Site 321,and the lithologic change at 58 meters from nanno oozewith abundant planktonic foraminifera upward, tozeolite-bearing brown clay may include either an uncon-formity of about 12 m.y. or there may be an interval ofvery slow sedimentation at a rate less than 1.0 m/m.y.

Although no diagnostic fossils were found in thezeolitic clay at Site 321, dating of sediments immediatelyabove and below indicates that this unit accumulatedfrom about 24 to 10 m.y. ago. The unit is nine metersthick, so its average sedimentation rate is very low,about 0.6 m/m.y. If sediment like that above or belowthe zeolitic unit had accumulated instead, with anaverage accumulation rate of about 3.0 m/m.y., the sec-tion would have been about 45 meters thick instead of 9meters. It is interesting to note that this difference is ap-proximately the difference in total sediment thickness atSites 320 and 321. More importantly, the sedimentationrate observed, the reduction from the "expected" sedi-ment thickness, and the lithology of the unit all indicate

that the zeolitic clay represents more-or-less continuousaccumulation beneath the CCD without abnormallyhigh terrigenous influx.

The figures given here indicate a low organic produc-tivity rate throughout all of the Cenozoic, except thePleistocene-Holocene (Kulm et al., this volume).

GEOCHEMICAL MEASUREMENTSSix fairly equally spaced "mini-core" samples were

taken at subbottom depths ranging from 6.0 meters to118.5 meters in the 124 meters of sediment. pH valuesfor this site should be considered qualitative rather thanquantitative. Measurement problems occurred withboth electrodes and, for one depth (24.5 m), they gavepH values varying by 0.8,/>H units. The combinationelectrode gave a surface seawater pH of 8.17. In thesediments it began at 7.65 (at 6.0 m), rising to 8.23 (at24.4 m) then dropping at 7.45 (at 45.4 m) and graduallyincreasing to 7.50 at the lowest sample depth. Thepunch-in electrode gave a similar surface seawater pH of8.11, but started much lower in the sediments at 7.09 (at6.0 m). The trend paralleled that of the combinationelectrode, but the readings were lower.

Alkalinity values from potentiometric titration of thesix samples varied irregularly down the length of thesedimentary column and the results from the less ac-curate colorimetric indicator method verify this trend.Surface seawater alkalinity was determined to be 2.39meq/kg.

Surface seawater salinity was measured at 35.5°/oo.The interstitial water salinities are 34.9°/oo in the surfacesediments, rising to 35.2°/oo at 24.4 meters and remain-ing at that value throughout the rest of the sedimentarycolumn.

Ten analyses of H2O (released above 35°C) and CO2were made on Site 321 basalts and are summarized inTable 3. High values of CO2 reflect high concentrationsof calcite-filled amygdules in Site 321 basalts. The singleH2O value measured on the uppermost basalt core (atthe bottom of the thin, upper cooling unit) is significant-ly higher than those on the massive section recovered inCore 14. The uppermost section is similar to the morealtered sections of Site 320 in H2O content, while themassive underlying unit has very similar H2O values tothe massive unit cored at Hole 319A, and these relationsare consistent with the expectation from lithologic com-parison.

Sample(Interval in cm)

13-4, 119-12414-1, 42-4514-1, 99-10214-2, 9-1214-2, 127-13014-3, 7-1014-3, 93-9614-4, 7-1014-4,61-66

CO2 (%)

0.140.280.421.190.360.381.200.240.30

H2O Total (%)

1.640.631.220.781.271.461.221.391.32

120

TABLE 3H2O and CO2 Contents of Site 321 Basalts

SITE 321

PHYSICAL PROPERTIES

Wet-bulk density, porosity, sonic velocity, acousticimpedance, thermal conductivity, and magnetic proper-ty determinations were made throughout the sediments.These measurements, with the exception of thermal con-ductivity and the addition of electrical resistivity, werecontinued in the underlying basalt. The results of thesedeterminations are presented with the core descriptions.

The upper 58 meters of sediment displays a slight in-crease in sonic velocity (1.52 to 1.54 km/sec) downward,while wet-bulk density and thermal conductivity remainalmost constant (1.30 ±0.16 g/cc and 1.83 ±0.12mcal/cm sec°C, respectively), reflecting an almost con-stant porosity (4 ±7%).

Below 58 meters the porosity decreases abruptly to60%, a value maintained with little variation (±7%)throughout the rest of the sediment column. Con-comitantly, wet-bulk density rises abruptly to a relative-ly constant value of 1.70 ±0.08 g/cc, whereas sonicvelocity and thermal conductivity values rise slowly (andin the instance of sonic velocity, erratically) over thesame interval, with values ranging, respectively, from1.51 to 1.57 km/sec and 2.08 to 3.09 mcal/cm sec°C.

It was observed for Site 319 and 320 sediments thatmost sediment properties are strongly porosity depen-dent. It is particularly clear at this site that porosity isstrongly lithology dependent, the clays having muchhigher porosities than oozes, due to absorbed water.

As can be seen in Figure 7, the basalt bulk densities inthe upper, thin cooling unit, adjacent to the sediment-water interface, are quite low, ranging from 2.72 to 2.86in the uppermost meter. Below this level, however, den-

0

0

10

20

30

B 40

5 50

g 60

sZ 70a

jj• 80

90

100

no

120

130

r\/-\_

REFLECTION COEFFICIENT (R)

0.05 0.10 0.151 1 1

- - - - - ' ^

1J_

\0.69

0.20 LITHOLOGY

Sea Water

Detrital clay, rich insiliceous fossils

Yellow-brown clay withvolcanic ash

Zeolite-bearing brown clay

Nanno ooze with interbeddedzeolite-bearing, iron-richnanno ooze

Basalt

Figure 7. Reflection coefficients (R) versus depth and lith-ology below the sea floor, Site 321.

sides abruptly increase to approximately 2.92 g/cc, avalue maintained with very little variation (±0.04 g/cc)throughout the rest of the cored basement interval.Though the degree of alteration in the topmost meter isconsistent with the age of the site, the shallow penetra-tion of oxidative weathering was unexpected, and isprobably due to the relatively unfractured, impermeablenature of the thick lower unit. Seismic velocities ofbasalt are density dependent, and densities may begreatly reduced by progressive submarine weathering.Local variations in weathering due to the massive versusfractured nature of the basalt, which is so well illustratedby the basalts from Sites 321 and 319, may be responsible for much of the great variability in velocities observedfor crustal layer 2.

Sonic velocities measured using the Hamilton frame(Ph=0) are very low (5.07 km/sec) in the uppermostmeter, and rise to an average of 5.8 km/sec ±0.2 km/secat greater depths.

MAGNETIZATION OF THEBASALTS AND SEDIMENTS

Shipboard and shore-based paleomagneticmeasurements on the basalts recovered at this sitesuggest that at least three time units were penetrated.After alternating field remanence cleaning, originalmagnetizing field inclinations for these units of +22, -22, and -16 ±2° were obtained. These inclinations areclosely grouped around the dipole field inclination forthe present latitude of the site of 23°. The agreement ofthe paleomagnetic and present inclinations for the siteindicates that negligible net latitudinal absolute platemotion has taken place during the last 40 m.y.Paleomagnetic inclinations for the basal part of the sedi-ment column overlying the basalts also average close tothe dipole field inclination, supporting the interpreta-tion of the basalt paleomagnetic results.

The massive basalts for Core 14 have large soft com-ponent contributions to their NRMs. These haveshallow downward inclination and presumably largelyrepresent the present earth's field at the site. NRManalysis, together with anhysteritic magnetization ex-periments, show that the soft and hard components arein opposition for the unit with cleaned NRM inclinationof-16°. Original magnetization during a reversed polari-ty epoch is implied by this opposition of hard and softcomponents.

NRM intensity varies by two orders of magnitudefrom 3.9 × 10~4 to 333 × 10~4 emu cm~3, with themassive basalt of Core 14 being most strongly mag-netized. Induced magnetization contributes negligibly tothe overall magnetization of the basalts.

Variation of NRM intensity, initial susceptibility, andsaturation magnetization is largely controlled by thedegree of cation deficiency of titanomagnetite, themagnetic phase of the basalts (see Ade-Hall et al., RockMagnetism of Basalts, Leg 34, this volume). The degreeof cation deficiency ranges from 0.00 to 0.79 on a 0 to 1scale. Stoichiometric titanomagnetite occurs only in afew massive basalt samples and has a composition of0.63Fe2Tiθ4θ.37Fe3θ4. Mild cation deficiencycharacterizes the titanomagnetite of other massive

121

SITE 321

basalts while a high degree of cation deficiency is typicalof the oxide phases in the fine-grained basalts of Core13. The three magnetic properties listed above alldecrease sharply with increasing cation deficiency. Thus,the halmyrolysis history of the basalts, which is respon-sible for cation deficiency in the titanomagnetite, hasdetermined the magnetic state of the basement sequencedrilled at this site.

CORRELATION OF REFLECTIONPROFILE WITH DRILLING RESULTS

The airgun survey of the site suggests the presence of athin (0.134 sec total 2-way travel time), but relativelycomplex sediment cover with two strong reflectors, thedeeper of which reflects very strongly and separates thesediments from the basement.

As at Site 319, a marked discrepancy (0.022 sec)between PDR and airgun reflection times from the seafloor suggests the presence of a thin surficial sedimentlayer which is acoustically transparent at airgun fre-quencies. The 2-way travel times presented in Table 4are thus increased by this amount to get the final values.

Correlation of the reflection profile (Figure 7) withboth the drilling record and the physical properties dataare straightforward. If the intracore reflectivity coef-ficients are computed from measured velocities and den-sities and plotted as a function of depth below the seafloor, a strong reflector is anticipated at 58 meters. Thisreflector lies at the estimated depth of the 0.086-secreflector and thus clearly marks the major lithologicboundary between the two major units at this site,namely, that between the Miocene through Quaternaryclays in the upper part of the column and the Eocenethrough Oligocene nanno ooze in the lower part of thecolumn. It is interesting to note in the context of sea-floor spreading, that a lithologic change of the sametype is responsible for the only major reflector seen atSite 319, in which instance its age is upper Miocene. Itshould also be noted that the strength of this reflector atSite 321 is due to the comparatively short depth intervalover which the clay-ooze transition occurs. The absenceof a lithologic transition zone is due to the presence ofan unconformity at this site in the early Miocene.

The weak reflector seen in Figure 7 at 0.042 secprobably corresponds to the slight increase in reflectivi-ty at approximately 35 meters caused by a change fromclay with siliceous fossils to clay with volcanic glass. Thezeolite-bearing clay unit between 49 and 58 meters depthis apparently too thin to be detected. The strong basalreflector, of course, represents the sediment-basalt con-tact.

Subbottom2-way

Time Interval

Characterof

Reflector Evidence

0-0.042 Weak PDR, drill recovery,airgun

0.042-0.086 Strong Airgun0.086-0.156 Strong Airgun

As for Sites 319 and 320, the mean sediment velocitycomputed from the drilled sediment thickness andobserved travel times is in excellent agreement withmeasured Hamilton frame velocities, despite core distur-bance.

SUMMARY AND CONCLUSIONS

Site SurveyIn addition to the Glomar Challenger survey con-

ducted on the approach to Site 321, an extensive surveywas conducted on departure. The topographic relief inthe immediate vicinity of the site is low. Below the sur-face, a nearly transparent, faintly layered unit (siliceous-fossil and zeolitic clays) overlies a more strongly reflect-ing layer (ferruginous nanno ooze) which in turn restsunconformably on basaltic basement of moderate relief.North of the site is a fairly steep, east-trending scarp.The general topography within several kilometers of thesite suggests block-faulted basement with faults trendingeast to southeast (see Figure 4). These are not obviouslycorrelated to major tectonic features.

Between Site 320 and Site 321, Glomar Challengercrossed the Mendafia Fracture Zone, a broad, north-east-trending belt of faulted basement blocks whichlocally rise above and locally sink below the generallevel of the terrain. These blocks are mantled with sedi-ment, and sediment thicknesses on the high-standingblocks are significantly less than at Site 321. The strongreflector at the top of the nanno ooze may be tracdnorth into the Mendafia Fracture Zone where, at twoplaces, (0230Z and 0900Z, 29 January, 1974) the nannoooze appears to be overlain with angular unconformityby the siliceous-fossil clay (Figure 4).

SedimentsThe uppermost 34.5 meters of sediment consist of

greenish-gray detrital clay, rich in siliceous fossils whichindicate a Quaternary and Pliocene age. The presence ofgreen clay suggests a terrigenous origin, presumablyfrom South America. The absence of coarse-grainedsediments, for example turbidites, such as those found inthe continental margin of Peru, indicates that the Peru-Chile Trench has been an effective barrier to sedimentstransported by bottom currents, and suggests that theclays may have reached the site by nepheloid layertransport. Minor amounts of clear volcanic glass arepresent, most abundantly near the base of the unit. Nocalcareous fossils were found, and the sediments werepresumably deposited below the CCD.

The next lower unit consists of 14.5 meters of lightyellow-brown clay with 0.5% to 55% clear volcanic glass.Most of the clay is smectite derived from the alterationof volcanic sediments. Siliceous fossils are much lesscommon than above and indicate a late Miocene age.This clay is underlain by 10 meters of zeolite-bearingbrown clay which is unfossiliferous except for traceamounts of nannofossils.

The sedimentation rates in the younger sediments arehigh (especially the top 35 m) and may be due to thelarge percentage of siliceous fossils and to an increase interrigenous input from the South American continent(Kulm et al., this volume). This may reflect higher

122

TABLE 4Reflection Intervals From PDR and

Airgun Surveys, Site 321

SITE 321

biologic productivity due to the influence of the nearby,strong, north-flowing Humboldt (Peru) Current. It ispossible at this site to distinguish between Humboldt(Peru) Current influences (higher biologic productivity,cooler water fauna) and continental influences (higherclay and/or volcanic ash content). The larger amount ofvolcanic glass in the Miocene, when presumably, the sitewas farther from South America than in the Plioceneand Quaternary, may reflect either a higher level ofvolcanic activity or a shift in prevailing wind directions.

The rest of the section, from 58 to 124 meters, is lightbrown ferruginous nanno ooze, late Eocene toOligocene in age. These are the first Eocene sedimentsfound on the Nazca plate, and, together with those atSite 320, the first Oligocene sediments as well. Becausesome faunas in the upper part of the nanno ooze showdissolution effects, the lithologic transition (to zeoliticclay) probably marks subsidence of the site through theCCD.

Sedimentation rate during deposition of the nannoooze was 4.0-5.0 m/m.y., compared to 5.0-9.0 m/m.y.for the early Miocene-late Oligocene nanno ooze at Site320 and 30-40 m/m.y. for that at Site 319. Thus, the siteseast of the Galapagos Rise had a lower rate of nannoooze sedimentation than the one on the west side. Judg-ing from out-of-sequence fossils at Site 319, thisdifference probably reflects local "ponding" and slum-ping at Site 319, but there may be real productivitydifferences as well.

As at Sites 319 and 320, the nanno oozes containmetalliferous components; certain zones contain up to35% (visual estimates) of RSOs. The RSO percentagemay be controlled by the sedimentation rate ofcalcareous fossils, but is not clearly related to proximityto the Galapagos Rise crest since the highest concen-trations are not found at the bases of the sections.

The fossil-based age of the base of the section is 39-40m.y., the same as the age based on magnetic anomalies(39 m.y.). The radiometric ages on the basalts show con-siderable variation, with best estimate of about 42 m.y.in essential agreement with the magnetic age. This in-dicates that sediments began to accumulate at the sitealmost immediately after the basaltic crust accumulatedat the rise crest. The basal sediments contain somebasaltic detritus, but most of the section is relatively freeof it.

The close correspondence of the paleontological ageof the basal sediment, the radiometric age of the basalt,the magnetic anomaly age of the crust, and the Sclaterage-depth curve prediction for 4820 meters water depth(38 m.y.) add confidence in using magnetic anomaliesand sea-floor depths to predict crustal age in this area ofthe Nazca plate. Using a half-spreading rate of 7.9cm/yr, based on the distance between anomalies 12 and16 near Site 321, and assuming that the Galapagos Riseis 9.5 m.y. old (anomaly 5, according to Herron, 1972),the position of the rise crest, south of the MendanaFracture Zone, should be 2400 km southwest of Site321. Using 8.5 ±1 cm/yr, the minimum permissible ratebased on the age of oldest sediment at Site 320 and theknown position of the rise crest north of the MendanaFracture Zone, the crest south of the fracture zoneshould be 2900 km from the site. Using either spreadingrate, the Galapagos Rise crest cannot be at the location

shown by Herron (1972), but must be farther west, asMammerickx et al. (1975) have suggested frombathymetry.

BasaltAlthough both basalt and sediment were recovered in

Core 13, the actual contact is not believed to have beenrecovered. Nonetheless, the abundance of basalticminerals and altered palagonite in the basal sedimentssuggests that the contact is depositional. The basalt isrelatively uniform from top to bottom of the recoveredsection, varying from fine-grained, massive, dark gray,almost aphyric basalt at the top to very coarse grainedbut otherwise identical basalt at the bottom. Subtlevariations in grain size suggest at least two cooling units,and this suggestion is augmented by additional data, asdiscussed below.

On-shore chemical analyses show that the Site 321basalts, while of the typical spreading ridge type(MORB) in a general sense, are nonetheless significantlyenriched in Fe and Ti (the "FeTi basalts" of recentauthors; see S.R. Hart, Basement Rock Synthesis, thisvolume) as well as LIL (large-ion-lithophile) elements.In fact, of the five chemical subgroups established by theshore-lab investigators among the Leg 34 basalts, thethick, lower cooling unit at Site 321 is distinctly the mostfractionated or evolved, and the pattern of fractionationis that expected under low pressures. Mineralogically,the high degree of fractionation is expressed in thepresence of minor pigeonite, and chemically in the lowAl contents of the augites and relatively high Na con-tents of the plagioclases. The absence of chemical,mineralogical, and textural evidence within this unit fordifferentiation in situ implies derivation from a highlyfractionated magma body in the crust or upper mantle.The unusually abundant amygdules may imply arelatively high volatile content, perhaps another reflec-tion of the highly fractionated nature of the magma;alternatively, or, in addition, the amygdules may reflecteruption at low pressure, which may shed light on thedepth of the crest of the Galapagos Rise in late Eocene-early Oligocene times.

Textures are intergranular to almost subophitic in thecoarse-grained rocks except for quenched mesostaseswhich suggest rapid cooling, hence flows or shallow sillsrather than deep sills. Microphenocrysts are uncommonand almost exclusively Plagioclase whose composition,along with those of the rare olivine microphenocrysts,are consistent with fractionated ridge-type tholeiiticmagmas. Groundmass olivine (smectite pseudomorphs)indicates that olivine remained on the liquidus to theend, and, hence, that fractionation was not extreme dur-ing posteruptive cooling, again consistent with rapidlycooled flows or shallow sills rather than slowly cooled,deeper sills.

Early nonoxidative alteration and later oxidativealteration account for veins and amygdules of smectite,calcite, pyrite, marcasite, and phillipsite, as well as forhalmyrolitic titanomaghemite which replaced titano-magnetite in the uppermost part of the thick coolingunit and throughout the thin one.

Water contents of the basalt average 1.21% and rangefrom 0.63 to 1.64%, which are low for DSDP basaltcores. The highest water content was measured in a sam-

123

SITE 321

pie from the thin, upper cooling unit. On the other hand,CO2 content is high, apparently reflecting the calcite inamygdules. The densities of the basalts increase from2.75 g/cc at the top to 2.92 g/cc immediately below thetop and throughout the rest of the core. The densitiesand water contents indicate preferential alteration of thethin, upper unit and of the chilled upper contact of thelower unit, and suggest either that the physical integrityof the lower unit prevented deep penetration bydiffusion-controlled submarine weathering, or that thefiner grained, chilled rocks were somehow more suscep-tible to alteration, due possibly to a greater content ofreadily alterable phases (see S.R. Hart, Basement RockSynthesis, this volume, and M. Bass, SecondaryMinerals in Oceanic Basalt, this volume, for more ex-tended discussions).

Remanence inclinations for the basalt suggest thepresence of three volcanic flow units, two with reversedand one with normal magnetization. The lower two"magnetic" units, both of reversed polarity, constitutethe single, thick, lower unit as inferred from grain sizeand other petrographic features, and ask the questionwhether the middle "magnetic" unit is a contactphenomenon of the thick cooling unit, perhaps inducedby secondary alteration or, as suggested below, a realrecord of field inclinations which varied during the finitecooling time of a thick magma unit. In contrast with ex-pectations (and as at Site 319), the coarse-grained flowor sill interior shows the strongest remanent intensity,with the highest single value (333 × 10~4 emu/cm3)found at any site on Leg 34.

The on-shore investigators distinguish only onechemical subgroup in the basalts from Site 321, in con-trast to two subgroups each in those from Sites 319 and320. The chemical coherence of the Site 321 basaltsstems from the fact that all analyses but one were per-formed on samples from the thick, lower cooling unit towhich all but the upper meter of recovered basalt coreappear to belong. Strikingly, the single analysis of asample from the thin upper unit (321-13-4, 119-124 cm;Rhodes et al, Petrology and Chemistry of Basalts fromthe Nazca plate: Part IV, this volume) is olivine nor-mative, whereas 11 analyses of the lower unit are quartznormative (calculated with the oxidation state of Fe nor-

malized to Fe+3/(Fe+3 + Fe+2) = 0.1, atomic); indeed,this chemical contrast, which cannot be ascribed toolivine accumulation at the base of the upper unit, con-trolled the precise placement of the boundary betweenthe proposed cooling units. Further, the only positivemagnetic inclination reported for a Site 321 basalt(+22°; Ade-Hall and Johnson Paleomagnetism ofBasalts, Leg 34, this volume) was measured on a samplefrom the thin upper unit. All other inclinations,measured on samples from the lower unit, are negative.Of those, the value on the uppermost sample (321-13-4,142-145 cm) is so distinct that Ade-Hall and Johnsonentertain the possibility that it represents a distinct"middle" time unit. We would stress only that such atime unit need not be an independent eruptive unit, butpossibly the chilled margin of the thick flow or shallowsill, as stated above. The remainder of the measuredsamples from that unit, constituting the third tentativetime unit, may have crystallized later, following anabrupt or gradual change of magnetic field inclination;in fact, the great variability of the many measured in-clinations in that third time unit may be interpreted asdue to continuous or numerous discontinuous changesof inclination. In any case, we again see, as for Sites 319and 320, permissive to persuasive evidence of at leasttwo time and chemical units in a thin basalt sequence,which again emphasizes the complexity of spreadingridge basalts and the necessity of extensive sampling andanalysis if the story in any vertical basalt sequence, evena nominally "thin" one, is to be accurately unraveled.

REFERENCESHerron, E.M., 1972. Sea floor spreading and Cenozoic history

of the East Central Pacific: Geol. Soc. Am. Bull., v. 83, p.1671-1692.

Kelleher, J.A., 1972. Rupture zones of large South Americanearthquakes and some predictions: J. Geophys. Res, v. 77,p. 2087-2103.

Mammerickx, J., Anderson, R.N., Menard, H.W., and Smith,S.M., 1975. Morphology and tectonic evolution of the eastcentral Pacific: Geol. Soc. Am. Bull., v. 86, p. 111-118.

Watts, A.B. and Talwani, M., 1974. Gravity anomaliesseaward of deep-sea trenches and their tectonic im-plications: Geophys. J., v. 36, p. 57-90.

124

Site 321 Hole Cored Interval: 0.0-1.5 m

FOSSILCHARACTER

LITHOLOGIC DESCRIPTION

CoreCatchei

5Y 5/1

10YR 3/3

5Y 5/3

5Y 5/1

SILICEOUS FOSSIL-RICH DETRITAL CLAY

Core is slightly deformed. Colors aregray (5Y 5/1), olive (5Y 5/3), anddark brown (10YR 3/3). Gray coloredclay contains more siliceous fossils.

Characteristic Smear Slides

det. claysi lie. foss.nannosvol. gls.quar + feldmicaheavies

Grain Size1-58

sand . 7s i l t 16.9clay 82.4

Carbon-Carbonate

t. carb 0.50. carb 0.4CaC03 1.0

amorquarK-Feplagkaolmicachlomontbari

1-9073TO25.72.7

21.96.7

30.14.77.60.7

Explanatory notes in Chapter 2

toON Site 321 Hole Core 2 Cored Interval: 1.5-11.0 m

S2t-n

FOSSILCHARACTER

CoreCatcher



Core is mostly moderately to intenselydeformed. Color is olive gray (5Y 5/2).


det. claysilic. foss.nannosvol. gls.palag.quar + feldpyritemicaheavies

Grain Size

1-758215T1T11TT

2-757720-TT3-TT

4-757025--13T1T

5Y 5/2

1-50 2-20 3-18 4-28sand ~T74 in ~ O "078s i l t 18.8 19.2 26.4 30.7clay 79.8 80.5 73.3 68.5

Carbon-Carbonate1-39 2-10 3-9 4-17

t . carb 0.6 0.3 0.4 0.3o. carb 0.3 0.3 0.3 0.2CaC03 2.0 -

Bulk X-

amorquarK-Feplagkaolmicachlopalymontclinbariamph

ray1-607474"25.71.4

21.34.524.74.8-16.0-1.7-

2-30737329.1.

23.5.23,3.-13---

.3,5.0.1.5.7

.9

3-34737728.45.5

21.36.221.22.3-12.4-1.01.7

4-3476.025.8-21.72.321.91.4

12.211.90.50.91.4


DEPTHIN

CORE

WET BULK DENSITYGRAPE -2-MINUTE +GRAVIMETRIC A

(g/cc)

2.0 3.

Pfcj~

I

Core 3 Cored Interval: 11.0-20.5

to-J

FOSSILCHARACTER

Cg-

0.5-->>>>>r÷:

CoreCatcher



Core is intensely deformed, and firm tosoupy. Colors are olive gray (5Y 5/2)near the top (Sec. 1 and 2) becomingmarbled with gray green (10GY 5/2) and(5G 5/2) and f i na l l y , in Sec. 6, thecolor is olive (5Y 5/3).


det. claysi l i e . foss.vol . gls.quar + feldpyritemicaheavies

1-75 3-95 5-75

5Y 5/2Grain Size

1-96 2-20 3-20 4-20 5-20 6-28sand ~"073 ~OT4 ~O "OTTs i l t 23.7 28.4 20.8 16.5clay 76.1 71.2 78.9 83.4

Carbon-Carbonate

N4

5Y 5/2color change:olive gray tograyish green

10GY 5/2and5G 5/2

t. cao. caCaC03

amorquarK-Feplagkaolmicachlomontphilbariamph

1-90rb 0.4rb 0.4

1.0

2-100.40.4

1-102 4-3076.6 76.227.72.223.93.825.61.5

13.9--1.5

28.00.324.73.322.12.115.53.01.1-

3-14 4-10 5-10 6-180.3 0.7 0.4 0.50.3 0.6 0.4 0.4

1.0 -

5Y 5/3

DEPTHIN

CORE


(g/cc)

2.0 3.

o_ eg"1

a e" E


Site 321 Hole Core 4 Cored Interval: 20.5-30.0 m » z ^ g° > ^ ^ jg 2 ^ g J~ g W

~l 7nNr I FOSSIL FT I I I ZJ| >:— t"C S^,* D ? z | I « £ § ^ " g o o»•3 £_. £ to* 0 N E CHARACTER ^ 2 g! WET BULK DENSITY ~*\ g j S § §S T | P ? § § „ d ~ & § P U P ^ | g ^ 2 ~ H-

S ^ S 8 8 S B | LITH0L0GY I 2 LITHOLOGIC DESCRIPTION DEPTH GRAPE^ - | | g | y ^ 8 £ ~ ,,« | 1 | | " ^ | ^ ^ P | f J g l g£S S i ^ S = ' " " 0 0 1 1 2? CORE GRAVIMETRIC A ü S ° 5> × S " S z _, u j " f: 3

_ii£liil ii * (9/cc> 1 I s i l l | i I E E i j I£ V 0 I° SILICEOUS FOSSIL/VOLCANIC GLASS-BEARING m ." ] ^ ^ V ^ —

- bç:r;lrl-:r-^;l:: DETRITAL CLAY ' 'I g>-r-->>>qcç: Core is intensely deformed throughout.

0 .5 - H < A ÷ ÷ - ; - ; - : 1 Colors are mostly grayish green (5G 5/2), Z ÷>>r÷÷":---- cr c/o and (10G 5/2), with some olive gray , ?1 - r$s_i:>i>:>>: ' (5Y 5/2) in Sec. 4. In general, there is

, n ^ r>>z>>-zA>i- l n n a decrease in the amount of siliceous ,_ !1 •u - Eg>>>>>>>: fossils and a small increase in the per- i

- b->röp->si >: centage of clear volcanic glass with (1 ^>>> b ÷1!1 depth in the core. Minor lithology in (

— b-i->>:->:->>: Sec. 2 is a clayey volcanic ash. There * •2 >>>>>>I÷:-: are no ash beds; rather, there are

" - §§?-»»!-:- zones where volcanic glass is moreI ^ : : 50 abundant. j .. ; 2 I SHXHJ, * ' *S 7 5 Characteristic Smear Slides 2o - i->Z-i•jJ*U. 2-50 2-75 4-75

B- -° -E>>>S>S?: 10GY 5/? det. clay 8 5 " 43 80B- ^ ::->>>>>>-->:> 10GY 5/2 si l ic. foss. 5 5 10

£ - ESYE-<?JS vol . gls. 7 50 7g * I bgf-i÷z÷÷= quar + feld 3 2 2 - . .y i b÷>r÷>>>>: opaques - - 1 '

^ •2 I ^ fe÷>>> l - ; Grain Size 1.83 - i-:-÷-l-Z-I-I->: 2-40 3-12 "4^T8S , I >>>>>>';!>: sand " T I 0.4 0.3"S3 - »^:=>»»I silt 30.0 25.7 26.0 3 + 1 - 5 3 gg λ s

ü J >r<>I>->g] clay 59.0 73.9 73.7 4 .

B_ α ; jH>z->z3>:|_*_S?: Carbon-CarbonateI rl-Z->I-Z->r-I~ 2-30 3-6 4-9 i ? 4 Qr,

-z>>>>c->^: t . carb-OTT TT3 "074 - 1.24 90

I >SJJg=E÷Si ^ o. carb 0.3 0.3 0.3Igègggg 10GY 5/2 C a C ° 3 "- fz->i- i-S>-S ?Hd Bulk X-ray 5 "

4 -:-:-:->>>_-:-:-: 75 ' lz50 3-35 4-36 *I :-»:::-:SJco amor 757T 7575" 7577

B- - :>--:>»:: quar 25.1 22.9 21.9B- I >>>goAE>i K-Fe - 1.4 0.9

->>¥:>>-:>>-: plag 26.2 24.6 21.0_ | ; rZcf-z>->÷-:H kaol 5.6 5.8 4.3 A. .

>-z->>z-z>->>: mica 21.0 20.3 20.5„. Co»"e

c c chlo 2.6 5.2 2.9B- Rf" Catcher:-:---:-:-:-^-:-: ^ p a l y . . 3 - 4

' '—'—' ' ' '—' r^^^-^^ 1 ' •— mont 18.3 18.2 22.8cliπ 0.5 0.5 0.5bari - 0.3 0.9 5

| amph 0.7 0.8 0.8 | 7 .Explanatory notes in Chapter 2

8-

6

91 I — i — i I—I I I I I I I I I L J I

Site 321 Hole Cored Interval: 30.0-39.5 m

FOSSILCHARACTER

Tf-

1.0- HCz:-i=rz---

CoreCatcher


VOLCANIC GLASS-BEARING DETRITAL CLAY ANDVOLCANIC GLASS CLAY

Core is roughly divided into two partsby lithology, color, and deformation.The top part (Sec. 1-3) is olive gray(5Y 5/2), intensely deformed, and mostlydetrital clay. The bottom part (Sec. 4-6)is light yellowish brown (2.5Y 6/4), darkgrayish brown (2.5Y 4/2),olive green (5GY 3/2) in cslightly deformed, and isclay and clayey volcanic aunit).

Characteristic Smear Slide

nd grayishlor, is onlyvolcanic glass

h (tuffaceous

5Y 5/2

det. claysi lie. foss.vol. gls.quar + feldheavies

Grain Size

1-85 2-75 5-7585~~" 3S~~ 65

5 2 28 10 302 2 3T T T

2-30 3-10 4-12 5-18 6-33sand 1.9 0.3 0.1 0.4 3.6s i l t 36.2 26.5 36.1 43.2 65.5clay 61.8 73.2 63.8 56.4 30.8

27

75

40

_ color changeandl i th . break

2.5Y 6/4

- 5GY 3/22.5Y 6/4

; 5GY 3/2

2.5Y 6/4

2 2.5Y 4/2

Carbon-Carbonate2-20

t. carb ~ Oo. carb 0.3CaC03

Bulk X-ray

amorquarK-Feplagkaolmicachlopalymontclinphilban-am ph

2-40ST7T20.41.6

24.73.9

17.80.31.8

22.10.44.11.91.0

3-10T72

0.2

3-19T O22.4-

25.75.4

18.03.7-

23.0-

0.71.0

4-4"073

0.3

4-228T7421.2-

26.27.5

16.62.07.0

18.4-

1.1-

5-9T72

0.2

5-3579.815.3-

37.82.9

18.71.62.9

16.0-2.72.1-

6-10"572

0.2

6-198 8 318.2-

28.95.9

16.75.95.5

18.7-

-

2.5Y 6/4

- 2.5Y 4/2

2.5Y 6/4_ color change~ (see Core 6)

10YR 6/4

DEPTHIN

CORE

WET BULK DENSITYGRAPE —2-MINUTE +GRAVIMETRIC A

(g/cc)

2.0 3.

<x. o

3 5 iii*

Explanatory notes 1n Chapter 2

^ Site 321 Hole Core 6 Cored Interval: 39.5-49.0 m £• S ^ ~ o - C £ o £ -J t « fc

I I Z0NE I FOSS.L 1 1 I r r m 1 . ^ i i § 5 I I i i i l 1«; - L i t 2- A - T A T T E | ° 8 | I WET BULK DENSITY t gjd | ~g | g ^ f ^ ^ J ^ | 2 2 = | | ^ g ^ to

3 •Λ α, </, •/> » h S LITHOLOGY I "J LITHOLOGIC DESCRIPTION DEPTH GRAPE - g - _j • o "S 8 "" 5 * e g ITfc~ ~ ~ £ § S ° H ^ ^ – £ 1 uio°S S ^ i g ^ S S ^ £ S IN 2-MINUTE + g . =».* - „ g fe *o § ^ | g o 3 «- °• ^ | = ! 1-ü S "

-iililli !l C0RE GRA™)CA 1 i l l ^ | s § | | I S i ? f § 5

(1 min «i ° β ~ f-E § g £ ° d E ii i-. " VOLCANIC GLASS-RICH CLAY m <5j 1.0 2.0 3.0 S § Si

- b£>-~-*-;-~-: 1 I Sec. 1 is intensely deformed, whereas theI iZZyoiDZH H Z remainder is stiff and only slightly de-

0.5-:-:-:-:->>>37* ~ T " 10YR 6/4 formed. Colors are light yellowish brownI ^ V L Q U = = p = (10YR 6/4) and grayish brown (10YR 5/2)

1 _ Pr-i-i-;-;-;-;:>* '5 in the top 4 sections and then become more 1

, - =>>>zö>> ° _ varied with light olive gray (5Y 6/2),' U 1 EosE÷BE?1 invp ^i•> b r o w n (10YR 5/3> a n d d a r k b r o w n ^OYR 3/3) 1-

- ->>toi>i; s 1UI ' in addition. Of importance in this core is

3 >>---->S" the abundance of fresh clear siliceous vol-;-»;-I-I-I-: '*. - canic glass within a clayey matrix. The

~ bç-i-z-ro2•:t*i clayey matrix may also be volcanic in- gijHjSSS** origin. There seems to be no close corre-2_ ---;-:---i-i-i- »* I lation between color and glass content._ :•i-i-i-z-i-i-:-I* Minor lithology is clayey volcanic ash. 2-

B- 0 "»»»"-: * ^ . yr_ I-I-I->I-I-I-J:-* I Characteristic Smear Slides 2

— :-z->>i->>z: / 1-75 3-75 6-140R I b-E-E-k-E>-:r*' det. clay 85 60 37

Z B=BBSSSE •" s i l i e . foss. T T T- b-i-i-i-i-i-i-:. nannos - 10 -I b>>-z>>->:^ I vol . gls. 12 25 55 3- •- dsö =S>: quar + feld 3 3 3I S K H S S S ' ' mica T T T

— - ; - - - > : ^ * . ' heavies T T T

s 3 \mm?. I 75 opaques - 2 5

o - ;II:»;;*-; I l n ¥ R c,* Grain Sizej _-:>-:-:-:-:-:-:# l u m D / H 2-128 3-12 4-14 5-113 6-16 4-°T ~ --_- = !_: = :,*; I sand 1.5 TT? ^TT 0.2 0.2z I C->I-÷÷-1:*' s i l t 49.6 56.0 54.9 36.0 36.6g S > ÷ I> "" c laV 49•° <2-1 43 4 63 8 63 2

E - i> io iö>> i % I Carbon-Carbonate- >>>>>I->dN I 2-142 3-4 ^]_ jy± 6 ^

~-->>>z>i-d , t . carb 0.3 0.4 0.2 0.3 0.2 5 - 1-94 " •->÷->>rx>: ' o. carb 0.2 0.2 0.2 0.2 0.2

B- I :>>>>>>;:** ' CaC03 1.0 2.0 - 1.0 - 4 + 1 5 4 2 Q 0

- ÷E$r-E-E-E:: V I Bulk X-rayB- I >c->>I->>> ' 2-113 3-23 4-29 5-28 6-29

- - I - > I ÷ > > : - : . * amor 81.3 86.0 83.5 78.7 80.7 . ,I->>-;>>-!-->- quar 13.5 15.1 11.5 13.9 10.7 6 • '• y l

- b-÷-l-S÷ cV* K-Fe - - 21.7 17.1 17.3;:->>>>>>:»' 4 0 plag 27.8 28.0 20.4 14.4 18.4

_ :::;-l-:>>÷:>» _ kaol 4.3 4.0 2.8 3.3 5.2I à - 3 S § S * 7r mica 19.1 20.9 31.8 15.2 16.9

5 _ I÷>>>>> i* 10YR 5/2 chlo 2.8 1.8 - 3.8 1.4 5

B- " E:B8885S5 »* mont 29.8 23.8 11.1 29.8 21.6„ T >>->i-;>ö; i 110 5Y 6/2 phi 1 1.5 3.6 - - 4.0 7-

- cE>>> > */" - Bari 1.2 1.3 0.8 2.5 3.8I g gc? « 10YR 5/3 amph - 1.6 - - 0.8

u | - i SSS>÷E: 10YR 6/4 \

S ? B- 6 ü i ^ 75

3 ^ I EE-E÷iL »*"•*' 10YR 3/3 \™ - BSS 1 1 1 * ' 1 4 0 and J| -I>>>>>i-y.* 10YR 3/2 Core catcher sample contains 2% ph i l l ips i te 9 X I *• I | I I I I I I I I I I

0 Core ^--;-;>-I>-I-- In the very dark grayish brown portion withTp- Catcher >>>>>>>:1»« CC 10% vol. gls.


f=x ^ " t" °<? 2Site 321 Hole Core 7 Cored Interval: 49.0-58.5 m » ö — 5 5 .__- ^ £ £ 0 t 1 u <; g

1—1 1—^STL—π—1 r ~ π 1 - s"« ε s s"g s §~ § «° «*_ρ &CHARACTE— g g « | WET BULK DENSITY « . ^ J £ g i ü £ I P _ § £ „ d ~ & ^ P fc* E - § ™ g ~

S ^ „ , . P £ LITHOLOGY i 1 LITHOLOGIC DESCRIPTION DEPTH GRAPE - g ^ J • ,_, ^ ° " 5 " z ó P t ^ " " b? I 2 ° C 5 « - * | UJ <=u

f g ^ i i o Q i ü ^ o g IN 2-MINUTE + g i > ü Pu , _ iB o § g g α ^ ^ o• ^ = á S g i SS i α I S S 1 0 & >- CORE GRAVIMETRIC A y 2 f > 2 × £ ~ < ^ _, ° 2 5 " fT 3

£ _ V Q I D ZEOLITE-BEARING BROWN CLAY m ^ 1-0 2.0 3.0 5c _ £ " ^ ^

- PS—7-iococ-: Top section is intensely deformed, whereas~ :_: Z"---->>>5 the remaining sections are s t i f f and only

0.5— '"-"-"-">i-z-z-zo s l ight ly deformed. Color is mainly dark2 b-i-r-SSS- rθθ brown (5YR 2/2), with some intermixed

1 _ z V _ V ; 5 5 ] = : grayish brown (5YR 3/2) in Sec. 5 and 6 1-f•-z~-zzocjZ>" 90 and a color change to l ight yellowish

'^~i>>>-z-z>-zo>x 10° brown (2.5Y 6/4) near the base of Sec. 6. l- igS30Sc-2lE-: ZEOLITE-BEARING NANNO OOZE becomes major- >>>>>>÷>>: lithology near base of Sec. 6.

- Pzocöz>>Jx>: Characteristic Smear SlidesI gEg=E÷giS 1-90 2-75 4-75 CC- K:-;-Z-Z-Z-Z-Z-Z-Z-: , c lay 90 88 87 5

~ SHH8SSSS-: I RSO + opaq. 3 5 3 3 2 -o -—-•-_-_-_-_-_- 75 nannos T 82

B- izzz-:-;-:-:1:1 phil 3 6 7 10 2

B- Z >>>>>>z÷z-ö quar + feld 4 1 2 T- i>z÷>>>r÷i÷ mica T T 1 -I >->I-I-I-I-I->>: heavies T T - -

~ >>>-> S?" Grain Size 3•-=->>>>>---z>> 2-41 3-13 4-17 5-7 6-12I aöHHS >: sand 0.1 0.1 0.0 0.1 0.0

- g>áSK Z>: s i l t 23.2 23.7 32.8 32.1 29.8 , g

I E aBSSE>-BS clay 76.7 76.2 67.2 67.9 70.2 +* 1.54 2.03

B- - U S 5 S 5 S j-vo , , , Carbon-Carbona te <- :-z;z-z-z-:-z-z=:=:=: S>IK <=/^ J -35 3-7 4^8 5 ^ 6 ^ 1 6^147 4 - } . .- : iV . "J•£ r zf f f5 : t . c a r b T T ~OTl 0 .2 0 .2 " 0 . 2 10.7 \ ' •9

I S S X K X X X X X S o. c a r b 0 . 1 0 . 1 0 . 1 0 . 1 0 . 1 - )E=zzzz>=ioS> CaC03 - - - - - 8 9 . 0 _ i

- : > Y E > > = £ § ? : Bu lk X - r a y , 1-46 81- >--÷>r÷z-z-z 2-44 3-27 4-33 5-20 6-17

~ :-z>->:-z÷z÷z: amor 77.6 74.8 72.9 70.6 70.5 5-Λ - =z>>>>>Iz>o• 7K feld 32.3 23.3 19.6 12.3 7.2

B- „ µ I i8> SS388>= quar 14.7 13.6 18.2 10.0 9.2 4

B " I :-Z-:-:-:-:-I-ZZI-: k a o l 2.7 3.3 1.1 -- j&>>fsc>>=si mica 18.0 20.4 23.3 17.2 15.4I ^ - - o > > > > : chlo - 2.6 1.6 - 2.5- g÷r=~Hr=^ . goet - - 3.9 22.4 25.1

: hz:zö::>÷-z::: m o n t 1 7 6 1 5 9 4 4 8 • 6 9 J 6 " "- &-55Sg‰ c l i n 1.8 0.6 0.9 - 0.7I bozözöz-z>-z: phil 12.9 19.4 27.0 29.5 30.2

_ Ef;>:£>:÷z÷z: amph - 1.0 - - 0.7

B - B . 5 = E S S S S z " 5YR 2/2 5

- E>>>??^1-- w i t h 7-Z KX>Z-Z-Z-Z-Z-Z-Z- someI EEfCzEgz>g: 5 Y R 3 / 2

ö - zZz-Z-Z-Z-Z~Z÷Z1^ I C13 I ------------------- _ c 0 l 0 r a π < ) \ ^ _ ^5 Ag- J ; ".Z. _ i _ . 1 4 0 ü t h . change V, . 0.12 +09 +19 OO

fc T Core ."{"j-^Zx." I 2.5Y 6/4 ^, - ^ z z Rf- B- Catcher . - ^ - j . - ^ i . - I CC PjOJ ' ' — ' — ' — ' ' ' ' ' L^ d ' ' : ' K>

i—> Explanatory notes in Chapter 2 i—»

t oHole Core 8 Cored I n t e r v a l : 5 8 . 5 - 6 8 . 0 m

FOSSILCHARACTER

Rg-

Rg-

Rg-

Rg-

Rg-

Rg

Ag-

Ag-

Ag-

Ag-

CoreCatche

PID-7^


2.5Y 7 / 4

2.5Y 7/3

2.5Y 5/4

NANNO OOZE

Core is intensely deformed and iswatery in places. Colors are paleyellow (2.5Y 7/4 and 2.5Y 7/3) andlighter pale yellow near base(2.5Y 5/4).


clayRSOnannosmi carbforamsphil

6-75T1

9045T

1-19 2-20 3-34 4^17 5-123 6-21sand 0.0 0.0 0.0 0.0 0.0 0.0s i l t 59.6 57.5 58.1 55.5 57.2 57.8clay 40.4 42.5 41.8 44.5 42.8 42.2

Carbon-Carbonate

t . carb TT7 TT74 11.4 11.4 11.2 TT*o. carb 0.1CaCO, 95.0 95.0 94.0 95.0 93.0 95.0

1-46 4-4317.3 16.1

100.0 100.0

DEPTHIN

CORE


(9/cc)

2.0 3.i

•-1 ε

is I


Site 321 Core 9 Cored Interval: 68.0-77.5 m

FOSSILCHARACTER

Tp-

Tp• Af-

Tp-

Cg-

Cg-

Tp•

Tp- A r

Ag-

CoreCatche

w


10YR 3/3and10YR 6/4

10YR 6/4

" 10YR 4/4- 10YR 6/4

10YR 5/4andsome10YR 4/4

10YR 4/4

10YR 3/3

10YR 6/6

IRON/ZEOLITE-RICH NANNO OOZE

Core is intensely deformed. Colors arevarious browns and yellow browns,including dark brown (10YR 3/3), darkto light yellow brown (10YR 4/4,10YR 5/4, and 10YR 6/4), and brownishyellow (10YR 6/6). Core is mostly ananno ooze which has decreasing amountsof zeolite with depth and a high RSOcontent in the darker colors. Bottomof core is NANNO OOZE.

Characteristic Smear Slides1-75 5-75 6-100

clayRSOnannosmicarbforamsphil

Grain Size1-69 2-94 3-52 4-85 5^7T57T "OTT "OTTsand

SiltClay

169 294 352 485 5 7 6*3"T57T "OTT "OTT 0.0 0.0 "OTT39.5 46.2 39.6 33.0 42.3 27.960.3 53.8 60.3 67.0 57.6 72.0

Carbon-Carbonate

1-98 2-112 3-65 4-66 5-4 6-49t. carb T O 9.2 9.9 9.0 9.5 6.4o. carb 0.1 0.1 0.1 0.1 0.1 0.1CaCO, 56.0 76.0 82.0 74.0 78.0 52.0Bulk

amorcalcfeldquargoetphil

X-ray1-118 4-113 5-'3575" 42.5 457?83.0

4.31.57.14.0

87.51.61.19.9-

78.51.71.4

17.01.4

6-5826.895.5

-0.44.1-

WET BULK DENSITYDEPTH GRAPE -

IN 2-MINUTE +CORE GRAVIMETRIC A

(g/cc)

£ „

ë Er

1.0 2.0


Site 321 Core 10 Cored Interval: 77.5-87.0 m

FOSSILCHARACTER

Rp-

Cg-Ag-


1OYR 5/4

NANNO OOZE

Core is only slightly disturbed throughoutSec. 2 and 3, moderately deformed 1n Sec.1. Colors are yellowish brown (1OYR 5/4and 10YR 6/4).


clayRSOnannosmicarbforamsphi 1

Grain

Tb

751073

Size

13

Bb1011

1OYR 6/4

1-93 2-22 3-20sand 0.1 0.0 0.1silt 46.0 48.3 49.6clay 53.9 51.6 50.3

Carbon-Carbonate1-100 2-10 3÷TO~

t . carb TO~" 11.0 11.1o. carb 0.1 0.1 0.1CaC03 90.0 91.0 92.0

Bulk

amorcalcquargoetphi l

X-ray1-8423.596.0-4.0-

2-30237697.90.31.9-

3-30237396.70.22.40.7


DEPTHIN

CORE


(g/cc)

2.0 3.

z

Site 321 Hole Core 11 Cored I n t e r v a l : 87.0-96.5 m S" « -― ; ° >-* „ ^ « g « j ë " S• • • | | — _ _ _ _ - ^ _ ^ ^ _ _ ^ _ _ ^ ^ _ _ _ ^ _ ^ _ ^ _ _ _ _ _ ^ _ _ ^ _ _ . o^J n i l H " E § ° o ^ g "– I p ,_

ZONE CHARACTER ^> α? ? - ^ ' ~ ' U ^ C N J Q O U S ^ M * : I : ! Z J ^ 1 - > 2 2 C * S J Z — ' o— I — I — • • . o £ i- 5 " ^ ""^K DENSITY j ; y j j S B ^ ^ - E P—- o~-- ^ ~ S j ^ 1 - t * >- " " 1 «•? °-~

S | g | S i I L I T H 0 L 0 G Y I 2 LITHOLOGIC DESCRIPTION DEPTH G R A P E ^ - | | rf| « * 3 jj ~£ |j> g | ^ | ~ | • | °P||| g | g£S l i l l a r I E CORE GRAVIMETRIC A ^ g 5 1^ I S rfH ^ §5" 1 3

0 « " NANNO OOZE m I 1.0 20 3.0 " _ _U_ 1__ J 1_ I f i_ JA g ' - L ~ ^ T J - ~ ^ J ^ „ invo C ?'?/ i d Core is intensely deformed in Sec. 1 , only

1 " ^ ~ ! L • ] f • : 34 : ' s l i g h t l y deformed i n Sec. 2-4. Sec. 1 is0.5— ~ _ l _ α _ . most diverse i n l i thology and in co lor ,

; - -*- - 1 - with 0-29 cm interval of very dark brown

R I I _ _i_ _i_" (10YR 2.5/2) z e o l i t i c brown clay and yellow '*" - -*- . - ^ i • brown (10YR 6/6) nanno ooze, and a 6 cm bed

'•°~ ~ - l _ - I - , - (29-35 cm) of black (10YR 2.5/1) and grayish- ' – 0 0 5 + 0 6 + 0 7

- "j_ j_ . green (1OGY 5/2) d e v i t r i f i e d ash (bentonite).Z -i-*-!-1- Tne bottom part of Sec. 1 and Sec. 2-4 are

- I - - i - • l i g h t yellowish brown (10YR 6/6 and 10YR 7/6)2 _ _ l _ _L-" nanno ooze. \

= - "-1-"J~-L."f~. I Characteristic Smear Slides \

| ^ A g - 2 \ ' ± ^ . 75 clay ^ f f ' \ »•» *" *»

^ - J-_1_-1-_1_- nannos 2 90 85 ?°• I ~-i_ _i_ . , micarb - 6 3 f• - - i . - 4 - i . - 1 - forams - 3 8 ç

ë " - JL- . -L-" ' phi 1 1ö = . ^ J _ ^ J _ • palag. 43 3 - -

3 <x> ;-J_-f--l_-f-. I 10YR 6/6 Grain Size ° 0 2 + 0 2 +12° S1 É _ - j . - 1 - . ! . - 1 - . and 1-54 2-20 3-20 4-18 , .

Cg- . - -i-L-_L_-J- I 10YR 7/6 sand TTT 0.1 0.3 "OTT J '5 * 3 - _ J_ J_' 75 s i l t 54.9 52.0 54.1 51.7 3 + 1.57 2.76Q j . -u_i.- t• j_" clay * 5 0 4 7 9 4 5 6 48.2

- ~^TL~^.'X~. Carbon-Carbonate 2 5

I -_L-«-_,_J- 1-48 2-10 3-10 4-7. , - U ~ • j - • t . carb T172 TT72 TTT7 TT7θ . A , „ ,„

Z-.J-.J-• o. carb 0.1 0.1 0.1 0.1 '•™ b y

0 . 0 4 + 0 5 + o g

- -Kt.- 1-.!.- CaC03 93.0 93.0 92.0 91.0- " - i _ JL. .- ~- l_ J - - Bulk X-ray 5 I I I I I 1 1 I I I 1 I I I I I

Cg- Λ "_i_ J_ I 1-30 2-30 3-30 4-26"A 9 • I - , - 1 - , - 1 - amor 7 9 . 8 20.5 19.7 2 1 . 3

- _ j _ _L-" calc - 98.6 98.2 98.2" -L-_1_-1-_1_• . quar 8.6- ~_u -u . K-Fe 2.8 -;-J _ -

1- J _

J- . I plag 17.7 -

- , J- . -L- kaol 1.7 -Core _ α_ ^.• I mica 7.6 -

rα. Catcher _ -

t-

J_

J- j

l_ CC goet 10.9 1.4 1.8 1.8

1 I I I—LI I I I r ~ J , -L• J ' I mont 47.3 -| phi! 3.3 -

Site 321 Hole Core 12 Cored Interval: 106.0-115.5 m

I TΠNP I DOSSIL T~| I I z I 1W"1 CHARACTER z ^ 2 ^

< £ „ „ , „ „ C Λ S ? LITHOLOGY % * LITHOLOGIC DESCRIPTION

_ J.I1J. J. J. J. JL2.0

FORAH-RICH NANNO OOZE

I VOID

^ - Core liner collapsed during coring;S cZ. section 1s extremely disturbed. Colors§ °•

i are very pale brown (10YR 7/4) and dark

3 l - i_•*"j_"~‰• 1 yellowish brown (10YR 4/4).° °- X I I . - 1 - ^ . - 1 - • 7 5 10YR 7/42 1 o- x i r • - Characteristic Smear SlideSE ' -1_ _I_ .r 1-85•" Cg- Iu J- . r 1 1 5 10YR 4/4 clay T

-T- – i -H-1 I I Rso 3 cy,nannos 70 I-Hmicarb 10 Hforams 15 CD

>_

J phil 2 OJ

J-J I ^ 1 L —1 tOJ T Explanatory notes in Chapter 2 H-»

Site 321 Hole Core 13 Cored Interval : 115.5-125.0 m —

FOSSILCHARACTER

Rp-

Tp-

Ag-

l_ -A-A - . Z•


10YR 3/2

IRON-RICH NANNO OOZE AND BASALT

Sediment core is only slightly deformed.Color of sediment is dark grayish brown(10YR 3/2 and 10YR 3/3). Contact of nannoooze and basalt Is at 3-130. Void in thebottom part of Sec. 3 and the top of Sec.4 is artificial; core catcher materialand bottom of Sec. 3 were included in anew Sec. 4. There 1s an increase 1nphillipsite and green devitrified glassnontronite!?) contents directly abovethe contact.


clayRSOnannosmicarbforamsphi 1vol. gls.palag.feld

Grain Size

1-125 3-116 3-125 3-126

1OYR 3/31-90 2-20 3-16

sand 0.1 0.0 ""OTTs i l t 70.9 70.5 69.9clay 29.0 29.5 30.0

Carbon-Carbonate1-88 2-14 3-10

t . carb TOT? TlTT 9.8o. carb 0.1 0.1 0.1CaCO3 86.0 84.0 81.0

Bulk X-ray

amorcalcquargoetphi 1

1-94 2-35 3-116353 38.3 TTT~95.6 94.4 93.40.2 0.2 -4.2 5.3 4.0

2.6

DEPTHIN

CORE


(g/cc)

2.0 3.


2.86 A,2.84 %'2.79

Site 321 Hole Core 14 Cored Interval: 125.0-134.5 m > | ^ - 5 § >-" - . •1" « _ 2 « g § ~ S

FOSSIL U J ^ S ^ c j o c b w ^ ^ z ^ ^ ^ u j z

**TC CHARACTE f S | WET BULK DENSITY E g g £ ~6 | » § | P ~ g K ~ S r | | | U P 1 |5 2-

§ ! « . / > C O < Λ •Λ £ £ LITHOLOGY | * LITHOLOGIC DESCRIPTION DEPTH ftwrrr I « " ^ 1 - " S E " t" ES fcE~ 5 ~ § * S ° P 5 ? " * § Uj£

l l o l l o i " 1 * & CORE GRAVIMETRIC A ü 2 2 - 5 × S ^ < ë _ , ° SS" » gu. z tf u- g o: σ ^ _ j-J^ _ ^ . V 9 / C c / o ° — ^ E ^ Z ^ Q tij S O ^ . ^ Q:

£ _ T J ^ _ BASALT JI-I 'j ^ ° I H ^ . l _ l _ _ l l i JZ\-iy:<' , Original recovery about 5 meters. Core 4 5 , + 1 Q , 1 3 4 5 g

.-'*'>**'"< appears longer because of styrofoam , Q 1 2 92 # 1 2 2 6 5 +14 -10 43.1 9.4 2.2 208° 5~%'•< l»^'•'> spacers that are used to separate parts d'9 l% % 62.6 75 -08 -10 22.9 8.8 r, 1 37 162

i - / . " . ' . ' . ' Λ V of the cores. See individual section , 2•92?"92 * 27 f ] 1 0 S2 " i i c ] 7 , c , 1 0 , 1351 : « { V Λ * Λ V descriptions for petrography and sone ' f j f * 6.06 17.7 83.5 05 -05 -08 1.3 5 4 .9 1 g|

1.0-= '.VlV.':i«: interpretations. , . 2.91 A ||jj ^ T ) .?§ _07 ' I0 4 5 ? 1 6 3

:,%'»*''/>NVJ . 2 ?? A 140 115(T) -07 -08 I0 7 0

- " . ' , " / , ' • ' oqc A 137 135 -03 -16 49.0 9.3 1.9 149I *»;*•*; V* 2;gl A 172 80 -17 -23 49.0 12 2.0 157

^ £ ; - > £ : < ; N 4 2- 2•95 A 102 7 n -?§ -21 , 3 105 i 5 0

2 - .vA- iV*, 2 •22 2 7 5 1 9 J ]•41 1 5 0

i^'•>:^• 9 1

75 -17 -

14 34 !0

3 2

I "\«*»*TV*' 2 902^90 * ?4 45 +04 -22 95.3 3.3 2.0 120

-**.V"<V' 6 4 6

35 -10 -20 45.8 4.5 1.43 136

-"/-'•/"'/" 3

" 2'89 * 56.4 40 -12 -39 55 I02 125

Z ^ V Λ V > 292 5 5 8 6 0 " 0 2 " 3 7 • 9 4•7 K 5 5 1 6 0

".'//.'li'" 2 ' 9 Z 2 ! 9 0 X 333 25 +01 -13 58.9 19 3.0 176- ; λ . * J s V « * 2.89 A 61.1 75 -09 -12 44.1 4.6 0.16 157

3 " • ; , * * » * " ; ~19 6 5 1 4 2 2 2 1 5 7

- «:V*' "''*X 4 2 9 1 * HO 45 -16 -10 53 I02 4

-'.'>*"*/* 9 0 ° 5 5 -°7 " 1 6 3 8•2 7 6 ! 3 9 I 3 6

; Λ ? V - » " - V ? 9 | J 77.9 90(T) -11 -25 59 I05 140- V > V • - U V 2 9 2 90.0 55 -22 -19 121 2.5 q l 6.7 125- r J»V«« * 2 922 92 * 14° -1° - I 4 I05 1

- ^ ^ ^ ^ ^ V ^ ^ 1 • 5 - ? • q ? 2 . 9 2 I . 117 40 -14 -21 49.4 7.6 1.36 125I I I I I I I -\-.. • •'• ••>l I I I 2 9 2 2 93 1 5•7 2 1 6 7 1 0° 70 -01 -21 91.5 3.6 1 9 125

Explanatory notes i n Chapter 2 4 8 4 • 6 4 0 " 1 2 " 1 4 5 ° 7 5 4 1 •4« 1 "

6• •

5

7-

8-

6 £2HW

w 9X I 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 ^

SITE 321

I—Ocm

-25

f—50

h-75

—100

—125

• ;

K

321-1-1 321-2-1 321-2-2 321-2-3 321-2-4 321-3-1

138

SITE 321

321-3-2 321-3-3321.3-4 321-3-5

321-3-6 321-4-1

139

SITE 321

I—Ocm

—25

—50

75

— 100

125

1—150321-4-2 321-4-3 321-4-4 321-5-1 321-5-2 321-5-3

140

SITE 321

Ocm

h-50

h-75

100

—125

L—150321-5-4 321-5-5 321-5-6 321-6-1 321-6-2 321-6-3

141

SITE 321

I—Ocm

25

—50

75

— 100

— 125

1—150321-6-4 321-6-5 321-6-6 321-7-1 321-7-2 321-7-3

142

SITE 321

Ocm

1—25

I—50

1—75

100

1—125

L—150

321-7-4 321-7-5 321-7-6 321-8-1 321-8-2 321-8-3

143

SITE 321

I—Ocm

—25

-50

—75

— 100

125

1—150

W

j

:

321-8-4 321-8-5 321-8-6 321-9-1 321-9-2 321-9-3

144

SITE 321

—Ocm —f•

—25

—50

— 75

— 100

125

1—150321-9-4

i\ i

321-9-5 321-9-6 321-10-1 321-10-2 321-10-3

145

SITE 321

Ocm

321-11-1 321-11-2 321-11-3 321-11-4 321-12-1 321-13-1

146

SITE 321

Ocm

\-25

h-50

h-75

—100

—125

1—150321-13-2 321-13-3 321-13-4 321-14-1 321-14-2 321-14-3

147

SITE 321

— Ocm

r-25

•50

— 100

— 125

— 150321-14-1

148

SITE 321

Site 321 Hole Core 13 Section 4

oM- O O to I Λ

O> CU E 4-> O_ 4-> «? n JL •

Φ^ I oS c S £ DescriptionI S u 2 13 ° ? w *-l-> U O_ S_ +J+-> CUC α (D fOQ- OO r-flu<u o •>- s - < u α> . c - c o

C_> I— Q. Ci3QT 0 0 Q - I— OO

0

Styrofoam spacers, each about 2 cm wide, separate piecesof core that are not part of a continuous core segment.An unknown amount of basalt is missing from the placeswhere the styrofoam has been added.

Fine-grained, light to medium gray or brownish gray,generally unoriented, joint-bounded blocks with outer,

2 5 _ relatively altered rims of medium brown or dark brownishto yellowish gray. Aphyric (less than 0.2 mm grain size)except for 2 plagioclases (0.8 x 0.5 and 0.4 x 0.1 mm)and 1 olivine (Ny slightly greater than 1.6784, Fo

8 7_

8 8)

in interval 89-98 cm.

0.5% or fewer vesicles up to 0.7 mm diameter (rare largerVOID holes up to 1.1 mm). Generally they are empty in fresher

interiors or rarely have blue smectite lining. The outerCQ rims are filled or lined by brown or yellow-green

smectite, or stained by Fe-oxide.

Many bounding joints remain where not abraded duringiij drilling. Interior joints are few and nonpenetrative;< all other joints were broken during drilling.

- _ i

$ Veins of Fe-oxide, Mn-oxide, and brown, brown-green,red-brown, yellow and yellow-green smectite. In 119 to

-jr ai 124 cm, piece 4, a relatively fresh, medium gray, almost2 unjointed piece, the veins are tan, cream, yellow-green,o brown-green and blue smectite.o

zr.

777 -7-7-r-r-, -> O

g^t V ΛI fragments

149

SITE 321


CDQ.GO

Description

25-

50-

75—

100— 10

125-'13

14


Dark gray, fine- to wery fine-grained, massive basalt.Coarsens very slightly downward near the top. Apparentdecrease in grain size near 86 cm (piece 8) and 113 cm(piece 11); these reversals of the normal increase ofgrain size downward correspond to the appearance of theonly microphenocrysts observed (3 plagioclases and aglomerocryst in pieces 8 and 9, 86 to 105 cm; 2 plagio-clases in piece 11, 113 to 121 cm). Otherwise the rocksare aphyric. The changes suggest two contacts separating3 cooling units.

The top of the section is altered, with marked changes ofcolor in pieces 1 through 3. Green-gray rock occurs in34 to 40 cm. Dark gray or pinkish gray rock occurs in40 to 43 cm. Below 43 cm the rock is uniformly gray; noalteration, zoned or otherwise, appears except in veinsin piece 8 (86 to 92 cm) and piece 12 (124 to 133 cm).

Fractures bound the surfaces of most core pieces, butinternal fractures are absent or nonpenetrative. Vesicles(0.5% to 2%, generally 1%) are present throughout, withmaximum sizes less than 1.0 mm, except rarely up to 1.5mm in 39 to 48 cm; the maximum size is slightly smaller(0.6 to 0.8 mm) in the upper part, above 36 cm. Raresulfide crystals in carbonate amygdules occur in piece 9(95 to 105 cm). Near smectite and sulfide veins theamygdules tend to be filled by the vein mineral. Thesmectite-filled amygdules may be color zoned, and in-complete fillings may have botryoidal inner surfaces.

Veins are composed of smectite, calcite, aragonite,phillipsite and sulfide. Down to 36 cm the smectites arebrown, red-brown, and tan, except in 34 to 43 cm wheresome veins are bright green. Below 36 cm the smectitesare blue, blue-green, blue-gray, gray, gray-green,greenish gray, green, yellowish green and black. In 86to 92 and 124 to 133 cm (pieces 8 and 12) the veins arelocally oxidized to yellow-brown and brown. Phillipsiteappears in 39 to 48 cm (piece 4) and is last seen in 86to 92 (piece 8 ) ; it is never abundant and appears to bevuggy in some cases. The sulfide first appears at about42 cm and persists throughout the rest of the sectionas a major or minor vein component.

150

SITE 321


oM- O O in in

'43 <u +J o SS- O -Q <ö _c .,- si

S^ I u§ £ £ Description• ^ α £S °? «+-> O Q . S - + J + J CoC CL Qi fOQ. U O i - mo j o > - s - α j cu_c: .c α_

O H - O-l CD O£ W Q . 1— OO

i l^VvJ j-/ ]p'×

nJ*^^^^ I Styrofoam spacers, each about 2 cm wide, separate pieces^-^é^^àáh^ °f core tnat are not P a r t °^ a continuous core segment.~ ? I r

v <β ^

n u

11^

11^

11 amount of basalt is missing from the places

lV,rJ• where the styrofoam has been added.

/ / j ^ / ' / / ^ ]lery fine- to medium-grained (mainly fine-grained), dark•f>

v

g j | gray, virtually aphyric basalt. Decrease of grain size

2 5 _ 3•<iv

v>•t-ri—'

a t ^

9 c m correlates with the appearance of rare plagio-

• >-7M clase microphenocrysts (1 crystal seen, 1 x 0.3 mm), and

-7~

7^y^^^P,

m ay mar

'< t'ie ^°P °^

a c o°li

n9 unit. Below that there is

^•^j•JI• i a

slight coarsening with depth.'-^má^Emg^m Gently to steeply dipping veins are scattered through the-, 5/ fc-iE•^^T top of the section. From 56 to 150 cm, one dominant— M^w^‰jM vertical to steep, branching system of veins is present.

50— 6 ^ ^ • i r ~ T ^ Vesicles vary from a trace to 1.5%, and are generallyΛ^.V• 0.5% to 1%. Maximum sizes vary from 0.6 to 1.2 mm, and

___ Mtmaj^^l increase in a crude way with depth. Small dikty taxi tic

^"•^•^^•^• v u g s a r e

P1^

65611^ ln

Pi'ece 3 (19 to 29 cm, the top of the

- 7 Λ J inferred lower cooling unit); they are the only ones seen-^vv/v^^^J .j

n k

asait;

S from Site 321. Most vesicles are partly or

~^- fTr^j•βtó• wholly filled by carbonate except near smectite veinsJ 8 • V ^ M (as in piece 3, 19 to 29 cm, piece 5, 37 to 41 cm, and

^ ^ ^ ^ P ^ l piece 6, 42 to 54 cm) where the vesicles are lined or7 5_l_HP^^Ltafcl— filled by smectite like that in the veins. In the inter-

^ V v • mediate zone smectite-lined vesicles may have vuggy,~ • % • terminated carbonate crystals on their walls. Apparently,

\jj^ empty vesicles appear to be due almost wholly to plucking- Jv<• °"f smectite or carbonate amygdules during coring.

i* ~1 | i II ' '"in p ^ ^ • Veins are mainly smectite -– green, blue-green, blue,_ IU 'V,v

t• dark gray, and gray-green. Sulfides occur in the smectitev ' * • or form the major component of other veins. Vein carbonate

100 — 5r^rT•wr~•r~ 1S mai'n"'y calcite, in some cases drusy, but includes some^t/JH aragonite in piece 6 (42 to 54 cm); in general, carbonate

Λ' V I •

1 S minor in veins. In pieces 3 (19 to 29 cm) and 6 some

V r % • smectite is locally oxidized brown, red or red-brown along

"ll <T<•^• ^ c e n

te r s

of s o m e

veins. In general, though, the veinsV'J v I L - ^ 4

w e r e tight and oxidizing fluids did not penetrate the

.r^\

vβ interiors of the flow units.

12B- < r M

151

SITE 321


25-

50-

75—

7-i

^ M

13

1 2 5 - I

17

Description


Continuous core from 0 to 119 cm of medium- to verycoarse-grained, dark gray, aphyric basalt. It coarsensdownward. Vesicles are up to 1.3 mm in diameter and formclusters 4 mm across. Down to 119 cm carbonate fillingsare common. Below 119 cm they decrease in abundancerelative to smectite fillings, and this decrease accom-panies a general decrease in abundance of vesicles andamygdules of all sorts to trace amounts at the bottom ofthe section. Near the top, carbonate amygdules are notablyless common near smectite veins than farther away, butthrough most of the section they occur everywhere, nearand far from veins. Other vesicles are smectite-lined or-filled, especially near smectite veins. The smectite islight blue in amygdules in pieces 6 (65 to 80 cm) and 11(92 to 100 cm). The decrease in vesicle abundance down-ward in Section 3 emphasizes the local maximum of 1.5%seen in 115 to 131 cm of Section 2, which is the maximumconcentration seen in the cooling unit, the top of whichoccurs at 19 cm in Section 2. The reversal in vesiclefrequency below that maximum suggests that the lowercontact is approached in Sections 3 and 4, but apparentlynever quite reach it.

Smectite veins are abundant and of various orientations.They are thick (up to 1.5 mm near the top, thicker below)and tend to swell and cause the core to break up. Themain colors of the smectite are gray-green, blue-green,dark gray and green. The blue-green smectite tends to bebotryoidal, as it has been throughout Core 14. Scatteredsulfide crystals and patches occur in minor amount in theupper part of the section and decrease downward. A calcitevein at 111 cm dips 10°. Below 126 there are thick zonedveins up to 5 or 6 mm thick composed of light tan layersof radial carbonate sandwiched between green smectitezones; locally there may be a total of 3, 5 or 7 layers(i.e., 1, 2 or 3 carbonate layers).

152

SITE 321


o

W+3 CU "£ § SS- C_> -Q (0 - C r- C~α> α> E +-> Q . + J < n . . .

Φ^ I u δ c £ £ Description•^ « I S ° g1 <" 5+-> ( J Q . S - +->+J C oc α Φ αj α o o t-cum o r s. α) <u _c .c Q_O h α cDoi IΛQ. I— OO

IL^β Styrofoam spacers, each about 2 cm wide, separate piecesof core that are not part of a continuous core segment.

- 2 1 ' s • l An unknown amount of basalt is missing from the placesF ~ > ^ Λ J where the styrofoam has been added.

_ ~wFTJWEt^m V e r

y coarse-grained, dark or medium gray basalt, either

•"V>• aphyric or with at most a trace of phenocrysts. Eight2 5 — 3•^

v^

vBfe—1~

1 plagioclase microphenocrysts in piece 4 (34 to 49 cm)

• ^ Y ^ • are up to 1.8 × 0.7 mm and may be locally clustered.1 %

Λ

7• | Their cores are An6

5_

7 2 (Tsuboi method). In pieces 5

—IµP^E^•><J] a n d 6

(51 to 67 cm) there are 10 visibly large crystals

' FP^• ranging in size from 0.6 x 0.2 to 2.4 x 0.6 and 3 x 0.2

I Λ V - > • This Section is much less fractured than those above;

|L Λ %*• most veins are steep and those in piece 6 die out within

5Q '^‰mmnλ~" I t

'ie c o r e ; t

'1is w a s n o t

observed higher in the core,

jE where all veins were penetrative, and may mark an

- 5 ^ ^ • approach to a cooling unit contact.- •JP^fl Vesicles in the interval 2 to 16 cm are more abundant

P^ ç| (1 to 1.5%) than in the base of Section 3, and may mark~ 6 • Λ ^ • a

second maximum in this cooling unit (the other being1%%^™ in the interval 115 to 131 cm of Section 2). The maximumWi J Wm,- Jl size of the vesicles is 1.6 mm. Below 16 cm the abundance

,c 7/ /////, of vesicles drops to 0.5%. A few carbonate-filled vesicles7 frag- occur in 2 to 34 cm, and they may be locally concentrated

- ~~ m e n t s

in certain areas, but the general decrease observed inSection 3 continues, and carbonate amygdules are not seenfrom 34 to 67 cm.

Veins in 2 to 16 cm are flat to steep, zoned smectite-carbonate veins like those in the lower part of Section3, but with the addition of light blue spots inside the

100 veins that resemble the light blue amygdules in the hostrock (and may be continuous with wall rock amygdules thatintersect the vein wall). The main vein component is darkgray-green smectite. Vein sulfide is present as traces

yQjß at the top of the section. None was seen in the bottom.

125-

150—I—J L LLJ

153

Deep Sea Drilling Project Initial Reports Volume 34

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Transcript of Deep Sea Drilling Project Initial Reports Volume 34