6. MICROSCOPICAL SURVEY OF ORGANIC MATTER FROM DSDP SITES 361, 362, AND 364

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1 6. MICROSCOPICAL SURVEY OF ORGANIC MATTER FROM DSDP SITES 36, 362, AND 364 J.F. Raynaud and P. Robert, Elf-Aqutane Research Center, 3360 Boussens, France METHODOLOGY Eght samples from DSDP Stes 36, 362, and 364 were studed by both petrographcal and palynologcal technques, usng two knds of preparatons: ) For petrographc studes, thn rock sectons were examned n both reflected and transmtted lght wth one horzontal and one vertcal specmen for each sample. Ths was to determne the composton of the organc materal and the extent of ts thermal alteraton by measurement of the reflectance (n ol) of coaly partcles. 2) Palynologcal sldes were examned n order to determne the composton of organc materal and the Thermal Alteraton Index (TAI) of mcro fossls. Two sldes were studed for each sample. The sldes were prepared as follows: slde HC, HF, HC, separaton wth Znc Bromde; slde 2 HC, HF, HC, HN03 (50%, 5 mnutes), separaton wth Bromoform + Alcohol. SITE 36 Four samples were studed. Sample 28-6, cm: Lower Aptan Shale Petrography (Plates, 2) Slty shale wth nterbedded lenses of organc matter and frequent pyrte globules. The organc matter conssts of coaly partcles and btumnous venlets (Plate, Fgures la, lb) and partcles. The coal fragments are vared, wth vtrnte (telnte, phlobaphnte), fusnte, and spornte. Algae are abundant and show an ntense fluorescence n UV lght (Plate, Fgure 2). Other fluorescent macerals (manly algnte), are abundant and assocated wth fusntes and btumen (both not fluorescent). The reflectance measurements gve a scattered hstogram wth vtrnte and btumen, the latter havng a mean value of 0.50%. Palynology Slde 2 (Plate 3, Fgure 3): Brown flakes of amorphous sapropelc matter; less than 5% lgneous debrs (fusnte); spores, pollen grans, and marne dnoflagellates. Slde : Organc consttuents smlar to Slde 2, plus pyrte. TAI = 2.5. Corresponds to about 0.5% reflectance. Sample 32-5, cm: Lower Aptan Shale Petrography Slty shale wth thn organc lamnae and abundant dspersed partcles of fusnte, spornte and vtrnte. Some patches of algal materal or rarely fgurated cellular algae (flat, sphercal) are moderately fluorescent n UV lght, though less than n the prevous sample (28-6, cm). Some btumen venlets are present; they are not fluorescent and have a lower reflectance than vtrnte (0.5%). The reflectance dagram of vtrnte consttuents, spread wdely between 0.6% and.3%, has an average value of 0.8%-%. Palynology Mxed palynofaces (Fgure 2): lght brown flakes of amorphous sapropelc matter (30%, slde 2; 45%, slde ); brown lgneous debrs (5%); black lgneous debrs of fusnte (50%). Spores, pollen grans, and marne dnoflagellates are present. TAI of 3^ should correspond to a reflectance of about 0.70%. Sample 40-4, 0-04 cm: Lower Aptan Shale Palynology Mxed palynofaces. Slde 2:60% brown or red-brown flakes of amorphous sapropelc matter; black debrs (fusnte) 40%; rare brown lgneous debrs. Slde : dem but wth 30% black mcrodebrs wth pyrte and darker flakes. Spores, pollen grans. TAI of 3" should correspond to a reflectance of about 0.70%. Sample 47-, 96-0 cm: Lower Aptan Shale Petrography Shaly-slty rock that s locally slceous wthn a mcrocrystallne structure nterbedded wth thn organc lamnae. Abundant pyrte globules. Very rch n coaly reflectng partcles such as vtrnte, telovtrnte, fusnte, spornte. Some patches of algnte and uncellular flat or crcular algae wth a pale yellow fluorescence. The mean value of vtrnte reflectance s n the neghborhood of %. Palynology Mxed palynofaces. Slde 2 (Plate 2, Fgure ): 30% of amorphous sapropelc matter, 60% lgneous black debrs (fusnte), and 0% brown lgneous debrs. Slde shows the same components but wth fewer terrestral lgneous debrs (30%). Spores, pollen grans, and marne dnoflagellates. TAI of 3 should correspond to a reflectance of about 0.80%. Conclusons On the whole, these samples are rch n organc matter (Table ). Secton 28-6 shows a typcal sapropelc faces, whereas Sectons 32-5, 40-4, and 47- show a mxed faces wth sapropelc matter and terrestral lgneous debrs. Algal materal s frequent. The hstograms of reflectance (n ol) testfy to a moderate thermal dageness n sectons 32-5 and 47- wth an average value reachng % n the latter. The TAI evaluated on spores suggests slghtly lower values (0.70%). Secton 28-6 does not provde an adequate 663

2 J. F. RAYNAUD, P. ROBERT TABLE Organc Content and Dageness JOIDES LEG 40 ORGANIC FACIES ORGANIC DIAGENESIS SITE 36 Core 28-6 I.O.C. = 5.5% Core 32-5 I.O.C. = 3.4% Reflectance r rn r n j M [É 4- T t j P r I { u _ % t r r/ I I n 'l L r J-r J T r 2% 3% L 4 % j L + Core 40-4 I.O.C. = 4.4% T.A.I. = 3" Core 47-.O.C. = 4.3% rt * B L m JI AJ, r. J. f M. n \ I I SITE 362 Core 8-4 T.A.I. = 2 SITE 364 Core 32-2 I.O.C.=2.% r (I tu? r l Core 37-5 I.O.C.=2.% J m Tl J J T DI n 7 I l n Core 44-3 I.O.C. = % r, - f A. n r f!. rl I Amorphous n^> (sapropelc) b*à*à3 Fusnte vded amorph.fx^l Lgneous mat. *I.O.C. = Insoluble organc carbon extracted by CH Clg, % by weght Vtrnte and btumens Vtrnte alone I I Fusnte 664

3 MICROSCOPICAL SURVEY OF ORGANIC MATTER hstogram because of a lack of coaly partcles, although certan values are farly low, n accordance wth the TAI (2.5 reflectance 0.5%). What does te n wth these results s the strong fluorescence of algnte and fluornte n Secton 28-6 and weaker fluorescence n Secton 32-5 and 47-. In all samples, btumen partcles and venlets, wth a lower reflectance than vtrnte, show up as remnant traces of mgratng ol. SITE 362 Sample 8-4, 4-45 cm Palynology 00% small flakes of lght brown amorphous matter. Presence of a few modern pollen grans (Gramnae, Chenopodaceae, Compostae) and of Classopolls and some dnoflagellates. Thermal Alteraton Index = 2.5. Ths sample s obvously not representatve, and may have been polluted by drllng mud. SITE 364 Sample 32-2, cm: Alban Lmestone Petrography Farly slty cryptocrystallne marly lmestone. Some thn lamnae of brown organc matter; ths materal has no reflectance; t s rch n pyrte spherules. A few spores and algae that are only fantly fluorescent n UV lght are dspersed n the ground mass. No reflectance data are avalable. Palynology Heterogeneous amorphous matter; pyrte n slde. Spores, pollen grans, and dnoflagellates of upper Alban age. TAI 2.5% should correspond to a reflectance of about 0.5%. Sample 37-5, 28-3 cm Alban Marly Lmestone Petrography Marly shale wth carbonated patches of epgenzed foramnfers and fne dolomte rhombs. Abundant organc matter, n anastomozed beds, wth much pyrte. Pyrte also abundant n foramnfers and solated spherules. In UV lght, the organc matter shows, n mass, a pale yellow-brown fluorescence. Some brownsh spores and very rare algae are present. Reflectng organc partcles: humnte, fusnte, and resnte are present though not abundant. Humnte gves a pattern of low-rank reflectance (0.35%). Some small btumnous droplets and venlets testfy to ol mgraton. Palynology Amorphous matter exsts n a mass of mcropartcles as n Secton Presence of very rare partcles of fusnte and of small dark brown spheres. TAI of 2.5 should correspond to a reflectance of 0.50%. Secton-Alban Black Shale: 44-3 Petrography A faces rch n organc matter: ) The rock s quartzo-phylltc, cryptocrystallne wth detrtal slt and a great deal of dspersed frambodal pyrte. It contans a large amount of organc lamnae, whch represent about 40% of the whole (Plate 2, Fgure ). (2) Ths matter conssts of resnte, humnte together wth mcrnte. (3) The UV fluorescence s medum pale, dffused throughout the rock. (4) The mean reflectance of humntc materal s n the range of 0.45%. Palynology 00% compact flakes of amorphous matter (probably sapropelc) whch shows up dark on slde (pyrte) and yellow and reddsh on slde 2 (Plate 3, Fgures 4, 5). Very few lgneous partcles: fusnte. TAI of 2.5, should correspond to a reflectance of 0.50%. Conclusons The three samples from the Alban of Ste 364 are characterzed by sapropelc matter of probable algal orgn. Ths s partcularly evdent n Secton In all three samples, there are only a few lgneous partcles wth any defnte shape such as fusnte. The extent of organc dageness s low, wth a reflectance of about 0.45%. Ths s confrmed by the Thermal Alteraton Index of the mcrofossls, wth a value of

4 J. F. RAYNAUD, P. ROBERT PLATE 20µm **.. ; n 2α 2b 20 µm Fgure Fgure 2 Secton (a) reflected lght whte = fusnte; (b) UV lght (fluorescence), yellow (whte here) organc matter wthn fusnte Secton Btumen venlet (a) reflected lght; (b) UV lght (flurescence) wth yellow algal matter (whte here). 666

5 MICROSCOPICAL SURVEY OF ORGANIC MATTER 20 µm 20 µm Fgure Secton (a) reflected lght: the whte porton = pyrte, the gray area n the mddle of the feld = organc matter, humnte, resnte; (b) transmtted lght: black = pyrte + reflectng organc matter; whte and gray = reddsh translucent organc matter n the groundmass; (c) UV lght (fluorescence): gray = reddsh translucent organc matter n the groundmass. All fgures

6 J. F. RAYNAUD, P. ROBERT PLATE 3 All fgures 260 Fgure Fgure 2 Fgure 3 Secton Mxed palynofaces: lgneous partcles, fusnte, spores, and pollen grans wth flakes of amorphous organc matter. Secton dem nterferental contrast. Secton Amorphous organc matter wth a few lgneous and coaly partcles, spores, and pollen grans. Fgure 4 Secton Sold flake of sapropelc organc matter. Fgure 5 Secton Flake of sapropelc organc matter. 668

7 MICROSCOPICAL SURVEY OF ORGANIC MATTER PLATE 3 50 µm 669