18. PHYSICAL PROPERTIES

Size: px

Start display at page:

Download "18. PHYSICAL PROPERTIES"

Valerie May
5 years ago
Views:

1 18. PHYSICAL PROPERTIES A. C. Pimm, Scripps Institution of Oceanography, La Jolla, California This chapter has two limited objectives as follows: 1) To graphically summarize various physical and chemical properties for each site and show their relationship to other important parameters such as lithology, diagenesis, authigenesis and acoustic character. 2) To illustrate at the section (150 cm) level how some physical properties respond to important cyclical variations in lithology and also to some major stratigraphic boundaries. These variations in the physical properties were too subtle to be recorded in the data presentation for each site. Figures 1 through 9 and downhole summaries of various physical and chemical properties. Tables 1 and 2 list the first occurrences of lithified sediments and some authigenic minerals, respectively. It must be emphasized here, that no firm conclusions should be drawn from these figures and tables because of the scarcity of data points due to spot coring. Furthermore, major hiatuses were detected at Sites 135, 136, and 140, and small hiatuses at Site 144; other hiatuses may also exist at other sites, but the cored data are insufficient to detect them (see site reports and Chapter 27). The duration of the hiatuses cannot always be accurately determined and no reliable estimate can be made of the amount of sediment that may have been removed by erosion during the time represented in the hiatuses. Despite the uncertainties mentioned above, it is hoped that the presentation of this data for Leg 14 will be useful for integration into future studies based on the results from many of the DSDP cruises. Figures 10 through 17 show the natural gamma radiation (counts/7.6 cm/1.25 minutes) and porosity (), and in some cases wet bulk density (gm/cc) on analog graphs adjacent to the section photographs. Where the composition of the sediment is listed under percent of components, these data were obtained from the visual smear slide estimates made on board. Xray diffraction data were kindly provided by Ulrich von Rad (see Chapter 20); the occurrences of components under this category are listed by initials for abundant, common, rare, and trace. TABLE 1 First Occurrence of Lithified Sediments Site Number Sandstone Depth (m) Age Mudstone/ Shale Depth (m) Age Depth (m) Limestone Age Depth (m) Chert Age Maestrichtian Senonian Miocene Cretaceous Cretaceous/Tertiary Paleocene Senonian Cretaceous Cenomanian Cretaceous _ Cenomanian Turonian Cretaceous/Tertiary Paleocene? Site Number Pyrite Depth (m) Age Cretaceous Senonian Turonian Upper Oligocene Lower Miocene Early Miocene Upper Paleocene Depth (m) 345 c _ 165 TABLE 2 First Occurrence of Authigenic Minerals Dolomite Age Lower Eocene Early Miocene Cenomanian Cenomanian Middle Miocene Middle Eocene Maestrichtian Campanian Depth (m) Palygorskite a Age Lower Eocene Early Miocene 9 Lower Tertiary? Early Oligocene to Late Eocene Early Pliocene Miocene Paleocene jpalygorskite recovered on Leg 14 is considered to be of authigenic origin (see Chapters 20 and 27). mostly clinoplitolite ^dolomite may be reworked in part phillipsite Depth (m) d Zeolite Age Lower Eocene Early Miocene Upper Cretaceous Early Miocene Miocene Oligocene 655

2 Porosity Water Penetrometer IO' 1 Dri11i ng speed m/mi n sand/silt /clay CaCO, d ph Eh Consolidation Diagenetic Effects Acoustic Character ** 'J. V : v.. loo r firm Transparent zone pelagic calcareous ooze > Major Reflector unconformity Figure 1. Site 135.

3 Semiconsolidated clayey to silty mud and mudstone Palygorskite Dolomite rhombs Reflective Zone clayey, silty sandy mud Some sandstone w/ carbonate cement Dolomite rhombs Recryst. CaC0 3 cement in some sands ZeoliteTr Recryst. sponge & Rads. j Disordered Chert, limestone, SiSJlflòüte' C H * toba J ite shale, silicified Clinoptilolite hridymite mudstone beds Palygor. but some semi Recryst. CaC0 3 consol. Dolomite & Siderite Pyri te 620 Reflector? Figure 1. (Continued). Limestone Indurated shale Some ooze still Dolomite Recryst. CaC0 3 Palygorskite

4 Porosity Water Penetrometer lo^mm Drilling speed m/mi n sand/silt /clay CaCO, J PH Eh Consolidation Diagenetic Effects Acoustic Character ? Reflector I firm «A, Silty clayfirm Clay firm Semiconsol. clay & ash beds (some calcite cemented) Semiconsol. clay Palygorskite Auth. Carbonate Zeolite R Dol omi te Lussatite Palygor. Smectite Dolomite Recryst. CaCO 3 Smectite, Palygor Transparent Zone calcareous ooze, brown clay, ash beds Basement Reflector basalt Figure 2. Site 136.

5 Porosity Water Penetrometer Drilling speed m/min sand/silt /clay CaC0 3 ph Eh Consolidation Diagenetic Effects Acoustic Character i. 1 4 i ' 1 ; Disturbed by coring Firm clay Palygor. Transparent Zone pelagic brown clay 120 Reflector? 140 *i i * Palygorskite * 1 Palygor. Clinoptilolite Hectori te Sepiolite *. Palygor., Lussatite Clinoptilolite Smectite, Zeolite Transparent pelagic brown clay s * y \ 1 ' * t Λ 1 i. * ' Chert, but unconsol. clay ooze interbeds Semiconsol Thin mudstones Indurated zones Large pyrite 6 cm diam. Recryst. Rads Smectite, Palygor. Smectite, Palygor. Zeolite & DolomiteTr Reflective Zone n > I *. Semi and indurated Zeolite zones 5 O 3 H W Figure 3. Site 137.

6 Porosity Water Penetrometer IO' 1 Drilling speed m/min 1 4 sand/silt /clay CaCO, 3 ph Eh Consolidation Diagenetic Effects Acoustic Character 60 m s it.. '... Disturbed by coring Zeolite Zone of Reflectors clay with sand interbeds 80 loo 120 : ZeoliteR Transparent Zone clay, silty clay Semiconsol. Shaly partings Palygorskite, Smectite Zone of Reflectorsmostly clay, reflections due to indurated layers? Indurated shale mudstone, chert Tridymite Firm clay Zeolite casts after Rads. Palygor. 360 Transparent Zone pelagic clay Indurated & cherty black mud, dolostone, some semiindurated dolomitic silty clay Dolomite Smecti te Ankerite Palygorskite Reflective Zone dolomite, chert, basalt Figure 4. Site 138.

7 Porosity Water Penetrometer Drilling speed m/min sand/silt /clay CaC0 3 PH Eh Consolidation Diagenetic Effects Acoustic Character 20 : i ; ',' 1 4 ** *. '^ t "i 'i t * Possible reflective zone pelagic calcareous ooze 80 't 'i t i Firm clay Palygorskite Zeolite (?) * i. Palygorskite * 'i Firm Clay Palygorskite Nonreflective zone clay 220' Figure 5. Site 141. Firm sand in n> r 50 O <n w 50 w

8 Porosity Water Penetrometer IO~ 1 Drilling speed m/mi n sand/silt /clay CaCO ph Eh Consolidation Diagenetic Effects Acoustic Character Transparent Zone pelagic calcareous Weak reflective zone? Figure 6. Site 139.

9 Smectite Dolomi te Carbonate rhombs weak reflective zone? Carbonate rhombs Sandstone Calcite cemented Strongly reflective zone siliceous ooze interbedded with sand Figure 6. (Continued)., firm mud & silt > r 13 a W

10 Porosity Water Penetrometer I0" 1 Drilling speed m/mi n sand/silt /clay CaCO, J PH Eh Consolidation Diagenetic Effects Acoustic Character loo 120 Mostly transparent pelagic calcareous ooze t f Firm mud/ooze & silty clay Smectite Reflective Zone Siliceous ooze and silty clay t Firm sand & clay Palygorskite Figure 7. Site 140.

11 320 t f Semi consol. silty clay Palygorskite Smecti te Sepiolite Dolomite Indistinct reflective zones occur throughout 380 * * Semiconsol Firm clay & chert Palygorskite Lussatite Very firm clay, Palygorskite silty clay & Lussatite Reflective chert Dolomite Zone chert do! omi te clays tone Shale & chert Lussatite Smecti te Figure 7. (Continued). Al Semiconsol. clay Firm sand & silt Smectite Palygor. Lussatite O m H m C

12 Porosity Water Penetrometer Drilling speed m/min sand/silt /clay CaCO, 3 ph Eh Consolidation Diagenetic Effects Acoustic Character loo Unconsol. Si derite Reflective zoneinterbedded sands, calcareous mud, and calcareous ooze and unconsol. to semiconsol. sand Siderite Figure 8. Site 142.

13 300 Carbonate rhombs Some redeposited and semiconsol. marl mud \ f 1 V *. Consol. to Zeolite? T««e»* semiconsol. Authigenic Jone carbonatetr. ca1careous ooze, calcareous clay, foram sand Prominent Consol. Authigenic Reflector carbonatetr j. ( i 1».» i Consol. Consol. Smectite Zeolite Reflective zonesi lty calcareous mud marl, foram sand, chalk , r 1 Indurated Palygorskite _. Rise Reflector i,. Calcareous marl 600 Figure 8. (Continued). W

14 * * Porosity Water Penetrometer I0' 1 mm Drilling speed m/min sand/silt /clay CaCO, PH Eh Consolidation Diagenetic Effects Acoustic Character t*. :.. * V x P '. ; ; V J with soft and firm layers, few thin semiconsol. marl beds Rads partly pyritized mostly soft Pyritized Rads 60 * * x : Firm clasts in soupy matrix (drilling) 80* * * Soupy due to drilling * * * Calcitized Rads Indurated chalk,_.,_... ^.,.. and calcisiltite Smectite Clmoptilolite and calcisiltite Palygorskitej i USSatite Marl mudstone Authigenic Carbonate BariteTr. Marl & marly Clinoptilolite, lussatite claystone cement in claystone Shale and Limestone _... _, Smectite, Clinoptilolite Semiconsol. clay and limestone clinoptilolite, authigenic carbonate, lussatite, siderite, pyrite Sparry calcite cement in limestone calcitized Rads 260 * Semiindurated marl Clinoptilolite, authigenic carbonate Smectite, Palygorskite, Indurated marlstone.sepiolite, ChalcedonyTr. limestone, Sparry & micritic claystone calcite cement in limestone Pyritized Rads. Indurated mudstone and claystone Figure 9. Site 144.

15 PHYSICAL PROPERTIES GAMMA COUNTS r~ POROSITY Quartzose feldspathic sandy silt, becomes more indurated downwards Qtz Mica Clay 10 Feldspar 15 Carbonate 10 Heavies 1 Porosity increase due to drilling deformation Quartzose sandstone cemented carbonate low porosity Lower gamma than elsewhere as feldspar, micas, and clay lower Sand as above, but not cemented Silt Sand Silt Calcite cemented quartz siltstone (Carb. 70, Qtz. 20 ) Silt Clay ball Slightly graded sand Figure 10. Quartzose silt Qtz 60 Feid.10 Clay 15 Mica 5 Authigenic Carb

16 A. C. PIMM J I 1 POROSITY 70 0 GAMMA COUNTS i Pelagic brown silty clay with common MnO streaks and blebs. Clay (Montmorillonite, Quartz, Palygorskite) 80 Feldspar, mica, kaolinite, dolomite 20. This interval represents hiatus of 50 m.y. Only lithology break occurs at 49 cm on scale note increase in porosity jmostly brown clay with irregular white layers of palygorskite, some ash Ash sand size Ash probably originally contiguous with above Clay (Montmorillonite & Silty clay Quartz) 75 Carbonate 15 FeO 10 Figure 11. Ash beds with discrete coarse ash layers. Clay (Mont. & Qtz.)4070 Opaques 525. Glass 120, Feldspar and Heavies 110 Clayey ash Ash 670

17 PHYSICAL PROPERTIES DENSITY(gm/cc) GAMMA COUNTS Dolomitic silty clay Feldspar & Montmorillonite Mica C Dolomite CA Highest density correlates with maximum dolomite note occurs at base of unit compared with center of other units Carbonaceous Clay Dolomitic silty clay Altered tholeiitic basalt. As rock fractured density curve interrupted; however, high densities are indicated. Note high gamma emissions. Believed that actual basalt/ sediment contact lost during coring operation. Note only about 11 cm of sediment cycle (between 42 and 106 cm) present compared with minimum unit size of 30 cm in Carbonaceous clay Density peaks correspond to lighter dolomiterich layers; four alternations indicated between 106 and 142 cm. Figure 12. Ash layers Carbonaceous clay 671

18 A. C. PIMM DENSITY(gm/cc) 1.50 GAMMA COUNTS "Dolostone" Composition Black Layers: Quartz A, Montmorillonite, Pyrite, Palygorskite C, Feldspar, Mica Tr Light Layers: Dolomite, Quartz, Montmorillonite A, Feldspar, Pyrite C, Mica, Palygorskite Tr. Cyclic development of dolomitic silty clay and carbonaceous clay Note highest density where dolomite is greatest in center of light unit in places sufficiently dense (cemented) to be called "Dolostone". Lower density in carbonaceous layers, but higher gamma counts Silt 80 cm 48 "Dolostone Clay cm cm cm Silt Clay "Dolostone Figure 13. "Dolostone" Composition Ankerite A Quartz, Montmorillonite, Pyrite Tr 672

19 PHYSICAL PROPERTIES 50 GAMMA COUNTS I POROSITY Calcareous clay displaced by drilling Sand S1lt Foram sandnote low gamma counts 81 Forams 35, Nannos 20 Carbonate frags Mica, quartz, FeO, Opaques 20 Calcareous clay with Mn laminae Drilling break Silty clay note high gamma increasing downwards, porosity decreases downwards: this due to increase of CaCO~ upwards, color also lightens Clay minerals 5060 Nannos 1020 Carbonate frags. 510 Pyrite, Mica, Quartz CaC0 o Sand Silt Graded cl ayey silt/ sandy si 1t. Note higher gamma than foram sand, lower than silty clay. Porosity increases slightly downwards. Quartz 30, Clay minerals 20, Foram nanno. & carb. frags. 25. Rest chlorite, feldspar, heavies 8 FeO, opaques, biotite Clay grading down to silty clay Figure

20 A.C.PIMM POROSITY 50 GAMMA COUNTS A31 Foraminiferal nannoplankton chalk ooze Gamma curve indicates fairly uniform composition slight variations due to minor components such as zeolite, chloritemica. Nanno 60, Foram 30, Zeolite5 Chloritemica, pyrite, quartz, Rads.5 Rapid changes in porosity due to varying consolidation. Possibly this is related to activity of burrowing organisms which are restricted to definite zones; the burrows are mostly horizontal and contain disseminated pyrite grains. Figure

21 PHYSICAL PROPERTIES POROSITY 50 GAMMA COUNTS A32 Foraminiferal nannoplankton marl/chalk ooze Minor variations in clay and zeolite content indicated by gamma curve. Porosity values are low because sediment highly indurated (<5xlO~ penetrometer) except from cm where unconsolidated. Note few pronounced spikes indicating very low porosity at depth of 40 cm spike coincides with lense of small ( mm) pyrite cubes grown together. Similar composition to 144A31 but mottling and burrowing less pronounced Note: in several places porosity curve goes below zero the grain density here is greater than section average of used for calculating porosity. Figure

22 A. C. PIMM GAMMA COUNTS POROSITY A35 Zeolite foraminiferal nannoplankton chalk/marl ooze Faintly mottled, also darker horizontal burrows Nanno 30, Foram and Carbonate fragments 25, Zeolite 15, Rest clay minerals, some pyrite, quartz, chlorite Time hiatus of 89 m.y. At Tertiary/Cretaceous boundary Thanetian stage of Paleocene rests on M. Maestrichtian Interval cm beneath hiatus shows increase in gamma emission and decrease in porosity Figure

17. CARBONATE SEDIMENTARY ROCKS FROM THE WESTERN PACIFIC: LEG 7, DEEP SEA DRILLING PROJECT

17. CARBONATE SEDIMENTARY ROCKS FROM THE WESTERN PACIFIC: LEG 7, DEEP SEA DRILLING PROJECT Ralph Moberly, Jr., Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii and G. Ross Heath,