Upper tertiary microfossils from the Alula Fartak Trench, Gulf of Aden

Deep-Sea Research, 1969, Vol 16, pp 25 to 43

Pergamon Press

Printed m Great Britain

Upper Tertiary microfossils from the Alula Fartak Trench, Gulf of Aden A T S RAMSAY*and B M FUNNELL* (Recewed 9 May 1968) Abstract Biostrahgrapincal studaes o f sediments obtained f r o m the sides o f the Alula F a r t a k T r e n c h suggest a Instory o f m o r e or less c o n t i n u o u s a c c u m u l a t i o n o f sediments in tins region since at least the late M~ddle M i o c e n e T h e a s s o c m t e d occurrence o f basalts a n d dolerltes, p r e s u m a b l y f r o m a n underlying v o l c a m c b a s e m e n t , indicates that the f o r m a t i o n o f tins part o f the G u l f o f A d e n m a y n o t long h a v e predated tins period (approximately 12 x 10 e years) Thirty-six species a n d sub-species o f late Caenozolc planktonic F o r a m i n i f e r a are descrxbed a n d listed (none new)

INTRODUCTION

DURING Cruise 16 of R R S Dtscovery (January-April 1967) a series of dredge hauls was made on the sides of the Alula Fartak Trench, a structural feature at the mouth of the Gulf of Aden This amcle discusses their general mlcropalaeontology, and the taxonomy and b~ostratlgraphy of the planktonic Foraminifera from seven of these dredge hauls LOCATION

OF D R E D G E

STATIONS

AND SAMPLING

TECHNIQUES

Sixty-three samples obtained from seven dredge hauls have been included in this study The posmon of the dredge stations together with their respective depths and recorded ages are hsted m Table 1, their position relatwe to the sides of the trench on Figs 1 and 2 The stations are restricted to an area of the Alula Fartak Trench between Lat 13 ° 5 0 3 ' N to 14 ° 2 2 4 ' N , and Long 51 ° 37 8'E to 59 I'E, depths recorded during dredging range from 2250 m to 4520 m The posmon of the area of study in relation to the mouth of the Gulf of Aden 1s shown in Fig 3 Of the 63 samples 48 were chosen for mlcrofaunal analys~s, the sole criterion of selection being the degree of induration of the sediment, highly indurated sediments

Table 1 Dredge station posmons and ages Station No Dy Dy Dy Dy Dy Dy Dy

6210 6211 6212 6213 6216 6221 6222

Lat 13 ° 56 13 ° 56 13 ° 52 13 ° 50 13 ° 53 14 ° 19 14 ° 22

Long 0'N 5'N 4'N 0'N 4'N 8'N 4'N

51 ° 39 51 ° 37 51 ° 45 51 ° 47 51 ° 45 51 ° 59 51 ° 56

Depth I'E 8'E 9'E 7'E I'E I'E 5'E

Time

(m)

(hours)

4100-3000 2700-2250 4720-4140 3950-3000 4800-4140 4520-3950 4330-3760

0730-1315 1445-1905 2000-0305 0410-0905 1030-1600 1145-1620 1728-2240

Date 21 F e b 21 F e b 21-22 Feb 22 F e b 23 Feb 25 F e b 25-26 F e b

*School o f E n w r o n m e n t a l Sciences, U m v e r s i t y o f East A n g h a , Norwich.

25

Age (see text) N19 N16, N I 7 , N I 8 N16, N 1 7 N18, N21, N 2 2 N20 N20

26

A T S RAMSAYand B 1V[ FUNNELL 52°E 5P30'

14o'~0 ' - - ' ~

5?.o~0'

\

__..~ ~o o ' /

%

/

/ /

)

/i

\

Go45'

~

51o30 '

_

\

_

--

52°E

13045 ' 52°t0 '

F~g 1. The topography of the Alum Fartak Trench and sketch map illustrating the pos~tions of the preomon echo sounder profile ( H IV[ S Owen, 1 9 6 3 ) and dredge statlons (H M.S Discovery, 1 9 6 7 ) , Depths are m corrected fathoms

did not dlsaggregate after repeated washings m H202 of any concentration Samples ranging from 2 cm 8 to 10 cm 3 depending on the size of the dredge sample, were taken etther from the centre o f the sedtment blocks, or, where applicable, as far removed as possible from evidence of burrowing organisms Where two hthologles or colour variations occarred within a single specimen, they were sampled separately THE SEDIMENTS AND THEIR GENERAL ENVIRONMENT OF DEPOSITION The Alula Fartak Trench, a steep sided hnear trough 150 nules long and 10 rmles w~de, which extends from Ras Alula on the Somalia coast to Ras Fartak on the Arabxan coast, has been tdentdied as a transform fault (MATTHEWS et al, 1967)

Table 2. Speczes range and occurrences m samples of Dredge Stats. Dy 6210, Dy 6211, Dy 6213, Dy 6216, Dy 6221 and Dy 6222 The arrangement of samples wtthm a zone does not zmply a chronological sequence G scltula G tumda plestotumtda tran G turrwdoples~tumlda G merotumdatronslurdda G merotumda G crossaformm trans tos, G crassaforn~s G truncatuhno~des G tosaer~s tronstruncatu G tosaens~s G multcamerata G tumlda G cultrato P obhquiloculata finahs P ddlquJloculata G venezuelana G humerosa G hexagona G dutertre0 G alhsptra G acostaensts 0 unwersa 0 suturahs 0 i~lobata S semmdma S dehmcens S sulxlehtscenstrans deft S subdehmcens G tnloba tmmatura G trdobo G saccul,fera G rubra G obhquus G emem~ G bolll, G siphontfera G nepenthes G cahdo G bullo0des G, uvula glutmato Dredge Sample Zone (Banner8 Blow,196~

[./'acing"p 26]

Upper Tertmry m~crofossdsfrom the Alula Fartak Trench, Gulf of Aden

27

assocmted with the M~d-Ocean ridge system where it enters the Gulf of Aden On the basis of the mlcropalaeontologlcal evidence presented here this structure has been the s~te of sedtmentatlon since at least the late Middle Miocene, the sediments apparently being derived m part from the Arabmn Shield via Wadl Hadramaut and its submarine delta at 51°E r L

i

I l

// ~tl( .....

6 !1 3/ / I 1

2400

m

-35nrn

Fig 2 Precision echo sounder profile (H M S Owen, 1963) The se&ments examined comprise an association of fine-grained clastlcs, often decalcified, which are texturally and mmeraloglcaUy immature For an oceanic suite they are dtstlngulshed by the absence of true calcareous orgamc ooze, and by thetr degree of induration (50% of the specimens from Dredge Sta Dy 6216 are highly indurated) The predominant se&ment is a grey to ohve green, silty lutlte with varying degrees of induration, other se&ment types are coarse friable silts and indurated calcareous Slits (Dredge Sta Dy 6211), dark shale, nodular or laminated Slits (Dredge Sta Dy 6216), and recrystaUlsed, sugary calcareous lutltes (Dredge Sta Dy 6222) The poor sorting, absence of calcareous ooze, and the mineralogical ~mmatunty of the sediments are probably attributable to rapid and continuous accumulation by turbx&ty flows, originating at the mouth of the Wa& or on its submarine delta slopes Numerous canyons and channels which emanate from the mouth of the Wadl dlssectmg the submarme delta (LAUGHTON, 1966) suggests the posslbdJty of such turbidity flows Organic oozes, which may form a thin veneer on the delta and trench slopes during periods of quiescence, are hkely to be incorporated with clastlc deposits during times of turbl&ty flow, and probably form the mare source of planktomc organisms contamed m the se&ment

28

A T S RAMSAYand B M FUNNELL 50°E

51°

53°E 7°N

52 °

16 °

15 °

L

--,

f (/ 0 422>

{ f'C?

_

,~o

c l

0

I-

13 °

I

Fig

3

R\..

J

General position of the Alula Fartak Trench and the area stu&ed BIOSTRATIGRAPHY

The dredge samples studied are not ideal material for detailed stratlgraphlc work Their fauna seems to be to a large extent displaced and has been depleted both by calcium carbonate solution and by sedimentary sorting Thus the Interpretation of their blostratigraphy can only be achieved within the framework o f an already existing scheme

3

@

Plate 1 Figs 1-2 GIobtgerma nepenthes Todd 1 hypotype, Sample Dy 6211 2, Zone NI7, No 1182, ventral view / 90 2 hypotype, Sample Dy 6211 8, Zone NI8, No I 183, ventral view, / 80 Fig 3 01buhna btlobata (d'Orblgny) Hypotype, Sample Dy 6211 69, Zone N17, No 1184,, 73 Fig 4 0 r b u l m a suturahs Bronnlman Hypotype, Sample Dy 6211 36, Zone NI7, No 1185, J 80 Fig 5 Sphaerotdmella de&scens (Parker and Jones) Hypotype, Sample Dy 6211 8, Zone N18, No 1186, ventral and dorsal view, × 90 Fig 6 Sphaerotdmella subdehlscens Blow, Hypotype, Sample Dy 6211 8, Zone N18, No 1187, ventral and dorsal views, × 90 Fig 7 Sphaerotdmellasemmuhna(Schwager)Hypotype, SampleDy6211 69,ZoneN17, No 1188, ventral view, × 90 Fig 8 Globoquadrma alttspua (Cushman and Jarws) Hypotype, Sample Dy 6211 85, Zone N17, No 1190, ventral wew, × 70 Fig 9 GloboquadHnavenezuelana(Hedberg) Hypotype, Sample Dy 6211 53, ZoneN17,No 1193, ventral view, × 50 Fig 10 Globoquadrma aeostaensts (Blow) Hypotype, Sample Dy 6211 69, Zone N17, No 1189, ventral view, × 80 lZlg 11 Globoquadrma humerosa (Takayanagl and Salto), Hypotype, Sample Dy 6221 2, Zone N20, No 1192, ventral view, × I00 Fig 12 Globoquadrma duterttet (d'Orblgny) Hypotype, Sample Dy6216 93, Zone N21, No 1191, ventral view, , 80 Fig 13 Pullematma obhqudo, ulata (Parker and Jones) Hypotype, Sample Dy 6216 93, Zone N21, No 1194, dorsal and peripheral view, ~ 70 Fig 14 Pullematma obhqudoculata finahs Banner and Blow, Hypotype Sample Dy 6216 93, Zone N21, No 1195, dorsal and peripheral view, ~ 70 Fig 15 Globototaha cultrata (d'Orblgny) Hypotype, Sample Dy 6211 2, Zone NI7, No 1198, ventral and dorsal wew, × 50

[facingp 28]

Sb

2a

2b

3a

5~, 4a

3b

5b

6

4b

m 9b

9e

Plate 2 Figs 1-2 Globorotaha metoturmda Blow and Banner Hypotypes, Sample Dy 6211 51, Zone N17, 1 No 1199, ventral and dorsal view, 2 No 2000, ventral and dorsal view of a form transitional to G turntda plestoturmda × 100 Fig 3 GIoborotaha tumtda plextotumtda Blow and Banner, Hypotype, Sample Dy 6211 36, Zone NI7, No 2006, ventral and dorsal view, × 80 Fig 4 Globorotaha tumtda (Brady), Hypotype Sample Dy 6216 30, Zone N22, No 2005, ventral and dorsal wew, × 64 Fig 5 Globototaha multtcametata Cushman and Jarvls, Hypotype, Sample Dy 6211 53, Zone NI7, No 2001, ventral and dorsal view, × 40 Figs 6-7 Globorotaha cpassaformts (Galloway and WJssler) 6 Hypotype, Sample Dy 6216 93, Zone N21, No I196, ventral view, 7 Hypotype, ventral view of a form transitional to G tosaensts, Sample Dy 6211 2, Zone N20, No 1197, × 80 Figs 8-9 GIoborotaha tosaensts Takayanagl and Salto 8 Hypotype, Sample Dy 6216 115, Zone N21, No 2002, ventral peripheral and dorsal view 9 Hypotype, ventral, peripheral and dorsal view o f a formtransltJonal to G truncatuhnoMes, Sample Dy 6216,93, Zone N21, No 2003 ~ 90 Fig 10 GIoborotaha truneatuhnotdes (d'Orb]gny) Hypotype, Sample Dy 6216 30, Zone N22, No 2004, ventral, dorsal and peripheral view, × 84

lb

2a

2b 3a

3b

5b 4a

6

4b

9e

Plate 2 F~gs 1-2 Globorotaha metoturmda Blow and Banner Hypotypes, Sample Dy 6211 51, Zone N17, 1 No 1199, ventral and dorsal view, 2 No 2000, ventral and dorsal view of a form transitional to G turntda plestoturmda × 100 Fig 3 GIoborotaha tumtda plextotumtda Blow and Banner, Hypotype, Sample Dy 6211 36, Zone NI7, No 2006, ventral and dorsal view, × 80 Fig 4 Globorotaha tumtda (Brady), Hypotype Sample Dy 6216 30, Zone N22, No 2005, ventral and dorsal wew, × 64 Fig 5 Globototaha multtcametata Cushman and Jarvls, Hypotype, Sample Dy 6211 53, Zone NI7, No 2001, ventral and dorsal view, × 40 Figs 6-7 Globorotaha cpassaformts (Galloway and WJssler) 6 Hypotype, Sample Dy 6216 93, Zone N21, No I196, ventral view, 7 Hypotype, ventral view of a form translt]onal to G tosaensts, Sample Dy 6211 2, Zone N20, No 1197, × 80 Figs 8-9 GIoborotaha tosaensts Takayanagl and Salto 8 Hypotype, Sample Dy 6216 115, Zone N21, No 2002, ventral peripheral and dorsal view 9 Hypotype, ventral, peripheral and dorsal view o f a formtransltJonal to G truncatuhnoMes, Sample Dy 6216,93, Zone N21, No 2003 ~ 90 Fig 10 GIoborotaha truneatuhnotdes (d'Orb]gny) Hypotype, Sample Dy 6216 30, Zone N22, No 2004, ventral, dorsal and peripheral view, × 84

Upper Tertiary mJcrofossflsfrom the Alula Fartak Trench, Gulf of Aden

29

Of the various zonatlons lncluchng the Upper Miocene and Phocene of tropical regLons pubhshed since 1963, BANNER and BLOW'S scheme (1965b, 1967) has been found the most convement for interpreting the fossil successions stu&ed. The original letter-number designations for the zones proposed by these authors are apphed as far as possible in th~s paper, although it is realized that some uncertamty attaches to their recognition in detail (see Table 2) The epoch boundaries used are also the boundaries of BANNER and BLOW with the exception of the Mlocene-Phocene boundary, which for the sake of convemence is that used by PARKER (1967) for Indo-Paclfic deep-sea cores, namely the junction between zones N18 and N19 Despite the effects of sorting and redeposltlOn indicated by grading of the planktonic and other constituents, the samples examined showed no clear evidence of faunal mixing of elements of chfferent ages, thus apart from samples which had been subject to strong calcmm carbonate solution, the ma3onty could be assigned to a single blostratlgraphlc zone On the whole the dredge hauls provided well-integrated collections Apart from Stas. Dy 6211 and Dy 6216, which covered three zones (N16, N17, N18, and N18, N21, N22 respectively) (Table 2), samples from the other stations were restricted to one or two zones and provided a total stratlgraphlc coverage from zone N16 to N20 The correspondence of geological features on both sides of the Gulf of Aden (see LAUGHTON,1966) suggests that the tectonic movements which culminated m the formation of the Gulf, and subsequently the Alula Fartak Trench, were lnltmted during the Miocene The blostratlgraphy of the Alula Fartak Trench se&ments does not provide unequivocal ewdence of the age of these events, but the following tentative inferences may be made The earliest sediments recorded seem to imply that the Gulf of Aden was an estabhshed feature by at least the late Middle Miocene (zone N16) The absence of pre-Mlddle Miocene mlcrofosslls in se&ments which may directly overlie volcanic basement (samples of which were also obtained from dredge hauls in the Alula Fartak Trench) could ln&cate that the formation of th~s part of the Gulf of Aden did not long pre-date the late Middle Miocene (approximately 12 × 106 years B P ) It is probable that, in its present form, the Alula Fartak Trench itself is of more recent origin, although the vertxcal distribution and hthology of se&ments of different ages on ~ts sides do not permit any close interpretation (they probably mostly achieved their present positions by faultmg or slumping) Further interpretation of the significance of the Tertiary mxcrofosslls of the Alula Fartak Trench sediments will depend on closer studies of the sediments themselves, which are being carried out elsewhere.

SYSTEMATIC

PALAEONTOLOGY

OF P L A N K T O N I C

FORAMINIFERA

Family CANDEINIDAE Cushman 1927 Genus GLOBIGERINITA Bronmman 1951

Globtgermlta glutmata (Egger) 1893 Globergermaglutmata EGGER, p 371, P1 13, Figs 19-21 1967 Globergermtta glutmata (Egger), PARKER, p. 146, P1 17, Figs 3-5

30

A T S RAMSAYand B M FUNNELL

Remarks Members of this species are either buUate or non-bullate varmtlon m both forms is confined to the apertural area. In bullate specimens the bulla is large or small, inflated or depressed, confined to the apertural region or extending along the sutures Non-bullate members have a narrow elongate aperture wah a conspicuous hp, m some specimens the hp extends on to the ventral surface of the opposing chamber. Occurrence G glutmata occurs m samples from Dredge Stas Dy 6211, Dy 6213 and Dy 6216

It ranges m these samples from Zone N17 to N22

Globtgerlmta uvula (Ehrenberg) 1861 Pylodexta uvula EHRENBERG,p 276, 277, 308 1960 Globtgerma bradyt Welsner, BANNERand BLOW, p 5, PI 3, Figs 1 (lectotype), 2 1962 Globtgermlta uvula (Ehrenberg), PARKER, p 252, P1 8, Ftgs. 14-26 1967 Globtgermtta uvula (Ehrenberg), PARKER, p 146, P1 17, Figs 8, 9 Remarks Th~s species is represented by two forms, one of which is small and charactensed by a few rapidly expanding chambers, the other is larger and has a greater number of smaller chambers Occurrence G uvula is present m samples of Sta Dy 6211, m which it ranges from Zone N16 to N18 Family GLOBIGERINIDAE Genus GLOBIGERINA d'Orblgny 1826

Globzgerma bulloldes d'Orblgny 1826 Globtgerma bulloMes D'ORmGNY, p 277, Mod61es no 17, lre hvralson (jeune), no 76, 4me hvralson (adulte) 1960 Globlgerma bullotdes d'Orblgny, BANNERand BLOW,p 3, P1 1, Figs 1 (lectotype), 4 1962 Globtgerlna bullotdes d'Orblgny, PARKER, p 221, P1 1, Figs 1-8

Remarks

Specimens of this dastlnctlve species occar m samples of Dredge Sta Dy 6211 m which they are confined to Zones N17 and N18

Globtgerma cahda Parker 1962 Globlgerma cahda PARKER,p 221, PI 1, Figs 9-13, 15. 1967 Globtgerma cahda PARKER, p 149, P1 18, Figs 6-12 Remarks All speomens of thts species are of the "pnmltxve t y p e " described and Illustrated by PARKER (1967) Some specimens however show a tendency towards the radial elongation of the final chamber

Occurrence G cahda occurs m samples of Dredge Stas Dy 6211, Dy 6213, Dy 6216, Dy 6221, and 6222, in which it ranges from Zone N16 to N21 Globtgerma nepenthes Todd P1. 1, Figs. 1, 2 1957 Globtgerma nepenthes TODD, p 301, P1 78, Fig 7 1967 Globlgerma nepenthes Todd, PARKER,p 150, P1 19, Fig. 10.

Upper Tertiary mlcrofosslls from the Alula Fartak Trench, Gulf of Aden

31

Remarks

Most specimens are tightly coiled with strongly embracing chambers, weakly arched apertures, and thickened walls, and are slmdar to the Sphaerotdlnellalike forms described and dlustrated by BLOW (1959) Typical forms of this species are rare, but are present in samples representing Zones N16 and N17

Occurrence This species IS present m samples of Dredge Stas Dy 6211 and Dy 6213, and ranges m them from Zone N16 to N18

Genus G L O B I G E R I N E L L A Cushman 1927

Globlgertnella slphomfera (d'Orblgny) 1839 Globtgerma slphomfera D'ORBIGNY, in DE LA SAGRA, p 83, P1 4, Figs 15-18 1879 Globtgerlna aequllaterahs BRADY, p 285 1962 Globlgerlnella stphomfera (d'Orblgny), PARKER, p 228 P1 2, Figs 22-28 1967 Globtgermella stphomfera (d'Orblgny), PARKER, p 152, PI 22, Fig 5 Remarks

All specimens of this species conform with group 1 of PARKER (1962). Varlanon is confined to the degree o f m v o l u n o n and the size of the ultimate chamber which ~s either larger than, equal to, or smaller than the penultimate chamber

Occurrence G slphomfela occurs in samples of Dredge Stas Dy 6211, Dy 6212, Dy 6213, Dy 6216, and Dy 6221 It ranges m these samples from Zone N16 to N21 Genus G L O B I G E R I N O I D E S Cushman 1927 This genus, as stated by PARKER (1967), iS undoubtedly polyphyletlc Although the lineages of its contained species are little understood, it appears from the study of modern representatwes of G saccuhfera by BI~ (1965) that this species and Sphaerotdmella dehtscens may be different depth stages in the life cycle of the same species, S dehzscens representing a deeper water and possibly gerontlc stage PARKER (1967) questions this relationship because the development of Sphaeroldmella dehlscens from S subdehtscens is not reflected in Globzgermotdes saccuhfera It is possible however that stages in the life cycle of a speoes could evolve independently of other stages (The development of G. flstulosus from G saccuhfera is not reflected in any sphaeroidinelhd form) The similarity between specimens of S subdehlscens, from which the cortex has been partially dissolved or mechanically removed, and G. saccuhfera would appear to be consistent with such an assumption In this treatment the G trlloba/G saccuhfera complex is retained in the genus Globlgermoldes because far more detaded research in terms of the life cycles of modern and if possible fossil representatives of this complex would be necessary before any firm taxonomic conclusions could be drawn

GloblgermoMes bolht Blow 1959 Globigerlnotdes bolht BLOW, p 189, PI 10, Fig 65 1967 Globtgerlnoldes bolhl Blow, PARKER, p 153, P1 20, Figs. 1, 2. Remarks All members of this species are characterlsed by the " cut i n " nature of the umbilical margin of the primary aperture, and a single supplementary aperture

32

A T S RAMSAYand B M FUNNELL

situated in the suture between the ultimate and penultimate chambers The outline of the final chamber varies from slightly flattened as described by PARKER (1967) to rounded and inflated

Occurrence Globigermotdes boHu occurs only m samples of Dredge Sta Dy 6211, which are restricted to Zones N17 and N18 Globtgermotdes emetsl Bolh 1966b Globtgellnotdes e m e t s t BOLLI, p 460, P1 1, Figs 11-13 Remarks This species is closely related to G obhquus from which its members differ an the nature of the final chamber which is globular or broad and ventrally flattened but not obliquely compressed The primary and secondary apertures are also higher and wider Transmonal forms between these two species are characterised by the high wide primary aperture of G emetst and the smaller more rounded secondary aperture of G obhquus

Occmrence Specimens of this speoes are present in samples of Dredge Stas Dy 6211, Dy 6213, and Dy 6216, in which they are confined to Zones N17 and N18 Globtgermotdes obhquus Bolh 1957 Globlgermotdes obhquus BOLLI, p 113, P1 25, Figs 9, 10, text Fig 21, no 5 1965 Globzgermoldes obhquus extremus BOLLIand BERMt3DEZ,p 139, Pt 1, Figs 10-12 1967 Globlgerlnotdes obhquus Bolli, PARKER, p 155, P1. 20, Figs 5. 6 Remarks A very variable species m which variants from the typical form intergrade either with G emetst or forms considered as the subspecies G obhquus e.xtremus by BOLLI and BERM6DEZ(1965) Occurrence G obhquus occurs in samples of Dredge Stas Dy 6211, Dy 6213, and Dy 6216, in which it ranges from Zone N16 to N l 9

Globlgerlnoldes ruber (d'Orblgny) 1839 Globtgelma rubra D'ORB1GNY, in DE LA SAGRA, p 82, P1 4, Figs 12-14 1960 Globtgerma rubra d'Orblgny, BANNERandBLOW, p 19, P1 3, Fig 8(lectotype) 1962 Globtgermotdes rubes (d'Orblgny), PARKER, p 230, Pl 3, Figs l 1-14, P1 4, Figs 1-10 1967 Globtgermoldes ruber (d'Orblgny), PARKER,p 153, P1 20, Figs l, 2

Remarks Members of this species are similar to PARKER'S(1962, group 3) Variation w~thln the species is restricted to the size of the primary aperture and the shape of the final chamber which is either inflated and rounded in outline, or somewhat flattened and oblique Occurrence This species is present in samples of Dredge Stas Dy 6211, Dy 6216, Dy 6221 and Dy 6222, in which it ranges from Zone N17 to N22 Glob~germotdes saccuhfera (Brady) 1877 Globlgerma saccuhfera BRADY, p. 535, (no figs).

Upper Tertlary mlcrofossdsfrom the Alula Fartak Trench, Gulf of Aden

33

1879 Globtgerma saccuhfera BRADY, p 287, (no figs) 1884 Globtgerma saccuhfera BRADY, p 604, P1 80, Figs 11-17, P1. 82, Fig 4 1957 Globlgermotdes trdoba saccuhfera (Brady), BOLLI, p 113, P1 25, Figs 5a-6, text Fig 21, no 4 1959 Globtgermoldes trtloba saccuhfera (Brady), BLOW, p 188, PI 11, Figs 63a, b 1960 Globtgermotdes saccuhfera (Brady), BANNERand BLOW, p 21, PI 4, Figs 1, 2 1962 Globlgermoldesquadrdobatussaccuhfer(Brady), PARKER,p 229, P1 3, Figs 6-10 1967 Globtgermotdes saccuhfer (Brady), PARKER,p 156, P1 21, Figs 1,2, 4, text Fig 5

Remarks The most variable characters of tins species are the ultimate chamber and ~ts primary and accessory aperture The final chamber ~s either minute or large relatwe to the penultimate, it is axially elongate or depressed, and its profile varies from comcal to rounded The primary and dorsal accessory aperture are both arched and are either equal or unequal Occurrence G saccuhfera occurs m samples of Dredge Stas Dy 6210, Dy 6211, Dy 6213, and Dy 6216 It ranges m these from Zone N16 to N19 Globtgermozdes trdoba (Reuss) 1850 Globtgerma trdoba REUSS, p 374, P1 47, Fig l l a - d 1956 Globtgermotdes trdoba (Reuss), BLOW, p 62, text Fig. 1, nos 1-3 1957 Globlgermotdes trtloba trdoba (Reuss), BOLLI, p 112, PI 25, Figs 2a-c, text Fig 21, no. la, b 1959 Globtgermotdes trtloba trtloba (Reuss), BLOW, p 187, P1 11, Figs 60a, b 1960 Globtgermotdes trtloba trdoba (Reuss), JENKINS, p 353, pl 2, Figs 5a-c

Remarks Members of tins species are extremely dwerse Variable characters include the size of the final chamber relative to the earher part of the test, the primary aperture winch is low and sht-hke or weakly arched, and the earher chambers which show various degrees of inflation on the umblhcal surface Forms considered mtermedmte to G trtloba trnmatura are characterlsed by less inflated final chambers and weakly arched primary apertures. Occurrence Tins species is found m samples of Dredge Stas Dy 6211, Dy 6213, and Dy 6216. It ranges in these from Zone N17 to N21 Globtgermozdes trtloba tmmatura Le Roy 1939 Globtgermotdes saccultfetus (Brady), var tmrnatura LE Roy, p 263, PI

,

Figs 19-21 1945 Globtgermozdes saccuhfera (Brady), CUSHMAN and STAINFORTH, p 68, PI 13, Fxg 3 1949 Globtgermotdes saccuhfera (Brady), BERMI3DEZ,p 278, P1 21, Fig 49 1957 Globtgermotdes trtloba tmmatura (Le Roy), BOLLI, p ll3, P1 25, Ftgs 3a-4c, text Fig 21, no 2 1960 Globtgerlnoldes trdoba tmmatura (Le Roy), JENKINS,p 354, P1 2, Figs 7a-c 1960 Globtgermotdes quadrtlobatus (d'Orblgny), BANNER and BLOW, p 19, Pl 4, Figs 3a-b 1964 Globtgertnoldes trdoba (Reuss), BANDY,p 36, text Fig 3b

34

A T S RAMSAYand B M FUNNELL

Remarks This subspecies occupies an almost lntermedmte position in the Globtgermotdes trtloba/G saccuhfera complex Typical forms are generally larger than forms of G trtloba and unhke that species are charactensed by a radmlly elongate somewhat less inflated ultimate chamber In forms transitional to G saccuhfera the ultimate chamber becomes less inflated and the primary and secondary apertures more strongly arched Occurrence. This subspecies occurs in samples of Dredge Stas Dy 6210, Dy 6211, Dy 6213, Dy 6216 and Dy 6221, and m them ranges from Zones NI6 to N22

Genus ORBULINA d'Orblgny 1839 Orbuhna btlobata (d'Orblgny) PI 1, Fig 3 1846 1956 1957 1959 1960 1960

Globtgerma btlobata D'ORBIGNY, p. 164, P1 9, Figs 11-14 Btorbuhna bdobata (d'Orblgny), BLOW, p 69, text Fig 2, no 16 Orbuhna btlobata (d'Orblgny), BOLLI, p 116, P1. 27, Fig 6 Btorbuhna btlobata (d'Orblgny), BLOW, p 199, P1 13, Figs 80, 81 Btorbuhna bdobata (d'Orblgny), BANNER and BLOW, p 2, P1 3, Fig 9 Orbuhna unwersa (d'Orblgny), JENKINS, p 356

Remarks Specimens assigned to this species vary only m the size relationship between the ultimate and penultimate chambers In some forms they are equal, m others the ultimate chamber is more than twice the size of the penultimate Where visible the apertural pores tend to concentrate around the suture separating the last two chambers, but areal apertures are present on both. The Miocene representatwes of this species differ from their modern counterparts m possessing a much narrower equatorml constriction as noted by PARKER (1967) Occurrence O. bdobata as found m samples of Dredge Stas. Dy 6211, and Dy 6213 It ranges m these from Zone N16 to N17 Orbuhna suturahs Bronmman, P1 1, Fig 4 1951 Orbuhna suturahs BRONNIMAN,p 135, text Fig 2, nos 1-2, 5-8, 10, text Fig 3, nos 3-8, 11, 13-16, 18, 20-22, text Fig 4, nos 2-4, 7-12, 15, 16, 19-22 1956 Orbuhna suturahs Bronmman, BLOW, p 66, text Fig 2, nos 5-7 1957 Orbuhna suturahs Bronmman, BOLLI, p 115, P1 27, Fig 4 1960 Candorbuhna umversa Jedhtschka, JENKINS, p 357, PI. 3, Flg 11 Remarks All specimens of this species are small and exhibit httle variation either m size or surface texture which is coarsely cancellate In all forms the earher chambers are pronounced although the last envelopes at least 75-85 % of the earlier part of the test, pores are both sutural and areal m position Occurrence This species is confined to samples of Dredge Sta Dy 6211 and restricted to Zone N17 Orbuhna umversa d'Orblgny 1839 Orbuhna u n t v e r s a D'ORB1GNY, In DE LA SAGRA, p 2, PI 1, Fig 1 1956 Orbuhna umversa d'Orblgny, BLOW, p 16, text Fig 2, nos 8-9

Upper Tertiary mlcrofosslls from the Alula Fartak Trench, Gulf of Aden

35

Remarks Specimens of this species are subject to distinct size and textural variations and both factors are directly related Smaller forms (up to 525/,) have a thick, coarsely cancellate test with strongly or weakly developed apertural pores, larger forms generally have a thinner smoother test with &stlnct apertural pores Occurreme 0 umversa is present in samples of Dredge Stas Dy 6210, Dy 6211, Dy 6213, Dy 6216 and Dy 6221 It ranges in these from Zone N16 to N20 Genus S P H A E R O I D I N E L L A Cushman 1927 In accordance with the views of PARKER (1967) the authors consider this genus synonymous with SphaeroMmellopsts on the grounds that the type species of Sphaerot&nellopsts, Sphaerotdmella subdehtscens, is so closely related to Its descendant

S dehtscens SphaeroMmalla dehtscens (Parker and Jones), P1 1, Fig 5 1965 Sphaerotdma bullotdes d'Orblgny var dehtscens PARKERand JONES, p 369, P1 19, Fig 5 1960 SphaeroMma bulloMes d'Orblgny var dehtscens Parker and Jones, BANNER and BLOW, p 35, P1 7, Fig 3 (lectotype) 1962 Sphaerotdmella dehtscens (Parker and Jones), PARKER, p. 234, P1 3, Figs I, 2

Remarks This species IS rare Forms transitional between SphaeroMmella dehlscens and S subdehtscens which are charactensed by a small recipient supplementary aperture on the dorsal surface occur in samples apparently as low as low Zone N18 We suspect that m these specimens, which otherwise closely resemble S subdehtscens, the mctplent opening up of the dorsal aperture may be m part a solution effect Occurrence S dehtscens and forms transmonal to tt occur in samples of Dredge Stas Dy 6210, Dy 6211 and Dy 6216 In these samples S dehtscens is confined to Zone N19 and transitional forms to Zone N18

Sphaerol&nella subdehtscens Blow PI 1, Fig 6 1959 Sphaerzodmella dehtscens subdehtscens BLOW, p 195, P1 12, Figs 71, 72 1967 SphaeroMmella subdehtscens Blow, PARKER, p 162, PI 23, Figs 6, 7 Remarks All specimens are characterlsed by the absence of a supplementary aperture ola the dorsal surface Forms in which the cortex has been partially removed elther by solution or by mechamcal processes are similar to forms of Globtgermotdes saccuhfera

Occurrence This speoes is present in samples of Dredge Stas Dy 6211, Dy 6213 and Dy 6216, m whlch it is confined to Zones N17 and N18 Sphaerol&nella semmuhna (Schwager) P1 1, Fig 7 1866 Globtgerma semmuhna SCHWAGER,p 256, P1 7, Fig 112 1960 Globtgerma semmuhna Schwager, BANNERand BLOW, p 24, PI 7, Fig 2 (neotype) 1967 Sphaerotdmella semmuhna (Schwager), PARKER, p 161, P1 23, Figs 1-5 Remarks Members of th~s species vary m outline and in the number of chambers

36

A T S RAMSAYand B M FUNNELL

of the final whorl (3-4½) The shape of the final chamber ranges from conical, or radially elongate and inflated, to an elongated laterally compressed sac-hke form In nearly all specimens the outer cortex is dissolved to some degree resulting m varying grades of rugoslty and retxculatmn

Occurrence S semmuhna is present m samples of Dredge Stas Dy 6211, Dy 6213, and Dy 6216, and m these is confined to Zones N17 and N18

Family CATAPSYDRACIDAE Bolls, LOEBLICHand TAPPAN, 1957 Genus GLOBOQUADRINA Fmlay, 1947

Globoquadrma acostaensts (Blow) P1 1, Fig 10 1959 Globorotaha acostaensts BLOW, p 208, P1 17, Fig 106 1967 Globoquadrma acostaensls (Blow), PARKER, p 164, P1. 24, Figs 3-9 Remarks Most specimens of this species are characterlsed by a bulla-hke apertural tooth on the final chamber, which conceals the umblhcal-extra-umbdlcal aperture Smaller trmngular teeth of earher chambers are observed m specimens where the final tooth is broken Occurrence This species is found m samples of Dredge Stas Dy 6211, Dy 6213, and Dy 6216 It ranges m these from Zone NI6 to N22 Globoquadrma alnsptra (Cushman and Jarvls) P1 1, Fig 8 1936 Globtgerma alttsptra CUSHMANand JARVm, p 5, P1 1, Figs 13, 14 1957 Globoquadrma alttsptra almptra (Cushman and Jarvls), BotH, p 111 P1 24, F~gs 7, 8 1957 Globoquadrma alttsptra globosa BOLLS,p 111, P1 24, Figs 9, 10 1967 Globoquadrma alttsptra (Cushman and Jarvls), PARKER, p 165, P1 25, Fig 8

Remarks

Speomens of this species range from low to median trochosplral and include both subspecles of BOLH (1957)

Occurrence This species occurs in samples of Dredge Stas Dy 6211, and Dy 6213, and is restricted m these to Zones N17 and N18 Globoquadrma dutertret (d'Orblgny) P1 1, Fig 12 1839 Globigerma dutertret D'ORBmNY, m DE ea SAGRA, p 84, P! 4, Figs 19-21 1962 Globoquadrma dutertret (d'Orblgny). PARKER,p 242, P1 7, Ftgs 1-13, P1 8, Figs 1--4

Remarks Smaller specxmens of ttus species are difficult to dlstlngmsh from Globoquadrma humerosa, though aduk speomens are usually more umblhcate, some form~ exhibit typical globoquadrme teeth

Occurrence G dutertret is found in samples of Dredge Stas Dy 6216 and Dy 6221, it ranges m these from Zone N21 to N22

Upper Tertmry mlcrofossllsfrom the Alula Fartak Trench, Gulf of Aden

37

Globoquadrma hexagona (Natland) 1938 Globtgerma hexagona NATLAND,p 149, P1 7, Fag 1 1962 Globoquadrma hexagona (Natland), PARKER,p 244, P1 8, Figs 5-13 Remarks Members of this speoes have an umblhcal or umbdlcal-exembdlcal aperture A single, variously developed umbdlcal tooth is present on the final chamber

Occurrence G hexagona is present m samples of Dredge Stas Dy 6210, Dy 6211, Dy 6213 and Dy 6221 It ranges m these from Zone N16 to N20

Globoquadrma humerosa (Takayanagl and Salto) PI 1, Fig l 1 1962 Globorotaha humerosa TAKAYANAGIand SAITO, p 78, P1. 28, Figs 1, 2 1967 Globoquadtma humerosa (Takayanagl and Salto), PARKER, p 164, P1 24, Figs 3-9

Remarks This species as slmdar to Globoquadtma acostaensts from which at developed, but as more umbahcate and lacks the comphcated tooth structure of that speoes Small trmngular teeth were observed on one specimen

Occurrence G humerosa occurs an samples of Dredge Stas Dy 6210, Dy 6211. and Dy 6221 It ranges an these from Zone N17 to N20 Globoquadrma venezuelana (Hedberg) P1 1, Fig 9 1937 Globtgerma venezuelana HEDBERG,p 681, P1 92, Fig 7 1959 Globoquadrma venezuelana (Hedberg), BLOW, p 186, P1 11, Figs 58, 59 1967 Globoquadrlna venezuelana (Hedberg), PARKER, p 171, PI 26, Figs 4-10 Remarks Members of this species vary in outline, the degree of inflation of their chambers and the development of the umbdlcal tooth on the final chamber where st is sometimes rudimentary or even absent Occurrence G venezuelana occurs m samples of Dredge Stas Dy 6210, Dy 6211, Dy 6213 and Dy 6216 It ranges m these from Zone N16 to N19 Genus PULLENIATINA Cushman 1927

Pullematlna obhqudoculata (Parker and Jones) PI 1, Fig 13 1862 Pullema obhqutloculata Parker and Jones, m CARPENTER, p 183 1865 Pullema sphaerotdes (d'Orb~gny), var obhqutloculata, PARKERand JONES, p 365, 368, P1 19, Fig 4 1927 Pullematma obhqudoculata (Parker and Jones), CUSHMAN, p 90, PI 19, Fig 5 (after Brady) 1960 Pullema sphaerotdes (d'Orblgny), var obhqutloculata, Parker and Jones, BANNER and BLOW, p 25, P1 7, Fig 4 (lectotype designated by BOLLI et al, 1957) 1962 Pullenttatma obhqudoculata (Parker and Jones), PARKER, p 234, P1 4, Figs 1316, 19, 22 1967 Pullennatma obhqudoculata obhqudoculata (Parker and Jones), emended BANNER and BLOW, p. 137, PI 3, Fig 4 (lectotype refigured), P1 4, Fig 9

38

A T S RAMSAY and B M FUNNELL

Remarks Members ofthls species are dastmgmshed by their partmlly dorsally involute last whorl whach consists of 412-5 wstble chambers, a low ventral mtero-margmal aperture, and a continuous angular suture formed by the ventral junctaon of the innermost margm of the last chamber with the ends of the prewous three chambers Occurrence Forms asstgned to thts spectes are present in samples of Dredge Stas Dy 6216, Dy 6221, and Dy 6222 They range an these from Zone N20 to N22 Pullentattna obhqudoculata (Parker and Jones) finahs Banner and Blow P1 1, Fig 14 1967 Pullematma obhqudoculata (Parker and Jones)finahs BANNERand BLOW, p. 140, PI 2, Figs 4-10, PI 3, Fag 5, PI 4 Remarks This subspeoes Is slmdar to P obhqudoculata, but has a higher wider aperture and a more dorsally involute last whorl in which only 4 chambers are visible Occurrence P obhqudoculatafinahs occurs m one sample of Dredge Sta Dy 6216 which Is referable to Zone N21 Famdy GLOBOROTALIIDAE Cushman 1927 Genus GLOBOROTALIA Cushman 1927 Globorotaha cultrata (d'Orblgny) P1 1, Fig 15 1839 Rotahna cultrata D'ORBIGNY, In DE LA SAGRA, p 76, PI 5, F~gs 7-9 1960 Rotaha hmbata Fornasml, BANNERand BLOW, p 30, P1 5, Fig 3 (lectotype) 1960 Rotaha menardn Parker, Jones and Brady, BANNER and BLOW, p 31, P1 6, Fig 2 (lectotype) 1960 Rotaha nmda Fornasml, BANNER and BLOW, p 33, P1 6, F~g 3 (lectotype) 1960 Rotaha cultrata d'Orbigny, BANNERand BLOW, p 34, PI 6, Fig I (lectotype) 1967 Globorotaha cultrata (d'Orblgny), PARKER, p. 177, PI 31, Figs 2, 3 Remarks Changes m the coJhng ratm and structure of the " cultrata-complex '" have been recognlsed and used by ERICSONet al. (1963, 1964) and PmLLIPSetal (1968) as one of the crJterla for the definmon of a Pllocene-Plelstocene boundary Too few Pleistocene and Phocene forms are present m the present samples to comment on changes m coding ratios and test structure during this mterval of time Upper M~ocene representatives ofth~s species however showa complete mtergradat~on wath G multtcamerata and G tumtda Occurrence This species Is present in samples of all dredge stations and ranges in them from Zone N17 to N22 Globorotaha merotumtda Blow and Banner PI 2, Figs 1-2 1965 Globorotaha merotumtda BLOW and BANNER, m BANNER and BLOW, p 1352, Fig la-c 1967 Globorotaha merotumtda Blow and Banner, BANNER and BLOW. PI 4 F~g 4 1967 Globorotaha merotumtda PARKER, p 180, P1 32, Fxg 4 Remarks Members of this species are differentiated from the subspecies Globorotaha tumtda plestotumtda by their smaller size, a slower increase m whorl height coupled

Upper Tertiary nucrofossds from the Alula Fartak Trench, Gulf of Aden

39

with more uniformly enlarging chambers, a thinner keel, greater ventral convexity and their broader apertural face Intraspecific variation xs confined to the thickness of the test wall wluch varies from translucent to opaque, and to the development of granules on the ventral surfaces of the earher chambers The two are apparently related as granules are generally more abundant on the thick-walled forms Forms transitional to G tumlda pleswtumMa (P1 2, Fig 2) are characterised by less umformly enlarging chambers and a relatively greater increase in whorl height in the last few chambers The keel is generally wider and the test wall thicker dorsally In some specimens the relative breadth of the apertural face IS reduced

Occurrence G merotumMa and forms transitional to G tunnda plestotumMa occur m samples from Dredge Stas Dy 6211 and Dy 6213, and are confined to Zone N 17 Globorotaha tumlda pleswtumtda Blow and Banner P1 2, Fig 3 1965 Globorotaha tumtda plestotumtda BLOW and BANNER, in BANNER and BLOW, p 1353, Fig 2a--c 1967 Globorotaha tumtda plestotumtda Blow and Banner, BANNnR and BLOW, PI 4 Fig. 3 Remarks Thts subspecies can be &fferentlated from Globorotaha tumtda by its smaller size, narrower keel and unequally convex dorsal and ventral surfaces (The ventral side is generally more convex than the dorsal) Forms transitional to G tumtda are generally larger and characterised by an almost equally biconvex test, a wider keel and more strongly granular ventral surface Occurrence G tumtda plestotumtda IS present in samples from Dredge Stas Dy 621 I, Dy 6213, and Dy 6216, In which It IS confined to Zones N17 and N18 Globorotaha tumMa (Brady) P1 2, Fig 4 Pulvmuhna menardu (d'Orblgny), var tumtda BRADY,p 535 Pulvmuhna tumtda BRADY, p 692, PI 103, Figs 4-6 Pulvmuhna tumtda Brady, var flexuosa KOCH, p 357, text Figs 9, 10 Globorotaha tumtda (Brady), CUSHMAN, p 19, Fig 12, (after Brady) Pulvmuhna menardn (d'OrbIgny), var tumtda Brady, BANNER and BLOW, p 26. P1. 5, Ftg 1 (lectotype) 1965 Globorotaha tumtda tumtda (Brady), BANNER and BLOW, p 1353, Fig 3a-c

1877 1884 1923 1927 1960

Remarks Flexuous forms of this species Illustrated by PARKER (1967) are absent in the specimens examined Intraspeclfic varlatxon IS confined mainly to the shape of the test which is either elongate or broad All forms are characterlsed by a heavy keel and both surfaces are strongly and equally convex Occurrence G tumMa occurs in samples of Dredge Stas Dy 6216 and Dy 6221 It ranges in these from Zone N19 to N22 Globorotaha multtcamerata Cushman and Jarvls P1 2, Fig 5 1930 Globorotahamenardtt (d'Orbagny) var multtcamerata CUSHMAN and JARVIS p 367, P1 34, Fig 8 1967 Globorotaha multtcamerata Cushman and Jarvls, PARICER,p 180, PI 31, Figs 5, 6

40

A.T. S RAMSAYand B M FUNNELL

Remarks Speclmens of this species are distinguished from Globorotaha cultrata by the greater number of chambers m the last whorl, a maximum of 7½ as compared with 5½ chambers of that species, the rounded outhne of the test and the narrowness of the chambers relative to their height Occurrence This speoes is present m samples of Dredge Stas Dy 6210, Dy 62ll, Dy 6213 and Dy 6216 It ranges in these from Zone N17 to N19 Globorotaha scttula (Brady) 1882 Pulvmuhna scttula BRADY,p 716 1884 Puh'muhna patagomca (d'Orblgny), BRADY, p 693, P1 103, Figs 7a-c (non Rotahna patagomca d'Orblgny 1839) 1957 Globorotaha scttula (Brady), BOLLLp 120, PI 29, Figs lla-12c 1959 Globorotaha scttula scttula (Brady), BLOW, p 219, P1 19, Figs 126a-c 1962 Globorotaha scttula (Brady), PARKER, p 238, PI 6, Figs 4--6 Occurrence This species is common and present m samples of Dredge Stas Dy 6211, Dy 6213, Dy 6216, and Dy 6221, and ranges in them from Zone N16 to N21 Globototalla crassaformts (Galloway and Wlssler) PI 2, Figs 6-7 1884 Pulvmuhna crassa BRADY,p 694, P1 103, Figs 11, 12 1927 Globtgerma crassaformts, GALLOWAYand WISSLER,p 41, P1 7, F~g 12 1949 Globorotaha (Turborotaha) oceamca CUSHMAN and BERMt~DEZ, p. 43, PI 8, Figs 13-15 1953 Globorotaha punctulata PHLEGi~R,PARKERand PEIRSON, p 20, PI 4, Figs. 8-12 1962 Globorotaha crassaformts (Galloway and Wlssler), PARKER, p 235, PI 4, Figs 17, 18, 20, 21 1967 Globorotaha crassafotmls (Galloway and Wissler), PARKER, p 176, PI 30, Figs 1-3 Remarks All specimens of this species are characterised by left coihng, an angular outhne and a flat spiral surface Forms transitional to G tosaensls (P1 2, Fig 7) present in sample Dy 6221 2 have a sharp periphery, more curving sutures on the last whorl and show the development of a fifth chamber Occurrence Globorotaha crassaformts is found m samples of Dredge Stas Dy 6216, and Dy 6221 It ranges m these from Zone N20 to N21 Globototaha tosaensts Takayanagl and Salto. P1 2. Figs 8-9 1962 Globorotaha tosaensts TAKAYANAGIand SAITO, p. 81, P1 28, Figs 11-12 1967 Globorotaha tosaensts Takayanagl and Salto, PARKER.p 181, P1 30, Figs 4-7 Remarks Typical members of this species are charactensed by a rounded outhne and a weakly acute periphery which lacks a keel or thickening Forms transitional to G truncatuhnotdes (P1 2, Fig 9) have rounded, weakly thickened peripheries and show traces of a keel on the final chambers Occurrence G tosaensls and forms transitional to G truncatuhnotdes occur in samples of Dredge Sta Dy 6216 m which they are restricted to Zone N21

Upper Tertm~y m~crofossils from the Alula Fartak Trench, Gulf of Aden

41

Globorotaha truncatuhnotdes (d'Orblgny) P1 2, Fig 10 1839 Rotahna truncatuhnotdes D'ORBIGNY, In BARKER, WEBB and BERTHOLET,p 132, P1 2, Figs 25-27

Remarks Members of this species are characterlsed by an angular acute thickened periphery with a well developed keel Occurrence

Globorotaha ttuncatulmotdes occurs in one sample of Dredge Sta

Dy 6216 and is restricted to Zone N22

OTHER

MICROFOSSILS

Besides planktonic Foraminifera the calcareous sediments from the Alula Fartak Trench also contain abundant coccohths, dlscoasters, and benthonic Foraminifera A few samples contain In addition diatoms, slhcoflagellates, Radiolarla, and sponge spicules Coccoliths were found in all the calcareous sediments except those in which no microfossils were present, the carbonate content in these being in the form of small rhomblc crystals Dlscoasters of the Dtscoaster btouwert, D pentaradtatus and D aster types were abundant in the Miocene samples, not always present above N19 In the Phocene samples, and absent altogether, except as stray, reworked individuals in the upper Phocene (N21) and Pleistocene samples Sdiceous microfossils were absent from the Miocene and lowest Plaocene (N19) samples, but all groups (diatoms, sihcoflagellates, radiolarlans and sponge spicules) are present in some abundance in the later Phocene and Pleistocene (N20 to N22) sediments This may indicate a change to increased productivity conditions in the Gulf of Aden towards the end of the Tertmry The depth indications of the benthonic Foraminifera in the sediments have not been investigated Most appear to be relatively deep water forms (1 e deeper than 200 m), but occasional examples of Ammoma sp, which may have been displaced from shallow inner subhttoral waters less than 50 m deep, were seen in one or two samples

Acknowledgements--We wish to thank Dr J R CANNwho prowded us with the samples, and Dr D H MATrHEWSand Dr A S LAUGHTONwho allowed us to abstract information from their charts of the area and kindly crltlCised our draft manuscript This work was supported by a N E R C Research Grant, and carried out in the Department of Geology, Cambridge Hypotype and illustrated specimens have been deposited m the SedgwlckMuseum, Cambridge REFERENCES BANDY O L (1964) The type of Globlgerma quadrtlohata d'Orblgny Contt Cushman Fdn foramm Res, 15, 36, 37, text Figs 1-3 BANNER F T and W H BLow (1960) Some primary types of species belonging to the superfamlly Globlgerlnacea Contr Cushman Fdn foramln Res, 11, 1-42, Pls 1-8 BANNERF T and W H BLOW(1965a) Two new taxi of the family Globorotahmae (Globtgermacea, Foraminifera) assisting determination of the late Miocene-Middle Miocene boundary Nature, Lond, 207 (5004), 1351-1354, text Figs la-3c BANNER F T and W H BLOW(1965b) Progress m the planktonic foramlnlferal blostratlgraphy of the Neogene Nature, Lond, 208 (5016), 1164-1166 BANNERF T and W H BLOW(1967) The origin, evolution and taxonomy of the foraminifera genus Pullematma Cushman 1927 Mtcropaleontology, 11 (1), 81-97, Pls 1, 2

42

A T S RAMSAVand B M FUNNELL

B~ A W H (1965) The influence of depth on shell growth m GlobtgermoMes saceuhfer (Brady) Mtcropaleontology, 11 (1), 81-97, Pls 1, 2 BERMt3DEZ P J (1949) Tertiary smaller foraminifera of the Domimcan Republic Contr Cushman Fdn foramm Res , Spec Publ , No 25, 1-322, Pls 1-26 BLOW W H (1956) Ongm and evolution of the foramlmferal genus Orbuhna d'Orbigny Mwropaleontology, 2 (1), 57-70, text Figs 1--4 BLOW W H (1959) Age correlation and biostratlgraphy of the upper Tocuyo (San Lorenzo) and Pozon Formations eastern Falcon Venezuela Bull Am Paleont, 39 (178), 67-251, Pls 6--19 BOLLI I4 M (1957) Planktonic Foramlmfera from the Ollgocene-Mlocene Cipero and Lengua formations of Tnmdad, B W I , Bull U S natn Mus, 215, 3-50, text Figs 1-9, Pls 1-11 BOLU H M (1966a) Zonatlon of Cretaceous to Phocene marine sediments based on planktonic Foramlmfera Boln mf Asoc Venezolana geol Mmer Petrol, 9 (1), 3-32 BOLLI H M (1966b) The planktonic Foraminifera in Well Bodjonegoro-1 of Java Eclog geol Heh', 59 (l), Pl 1 BOLLI H M and P J BERMI3DEZ(1965) Zonatzon based on planktonic foraminifera of Middle Miocene to Pliocene warm-water sediments Boln Inf Asoc Venezolana geol Miner Petrol, 8, (5), 121-149, Pl 1 BOLLI 14 M , A R LOEBLICHJr and H TAPPAN (1957) Planktomc forammlferal families Hantkenlnldae, Orbuhnldae, Globorotahldae, and Globotruncanldae Bull U S natn Mus, 215, 3-50, text Figs 1-9, Pls 1-11 BRADY H B (1877) Supplementary note on the Foraminifera of the chalk (7) of the New Britain Group Geol Mag, 4, 534--536 BRADY I-{ B (1879) Notes on some of the retlcularlan Rhizopoda of the Challenger Expedition Q Jl microsc Sct, 19, 20-26, 261-299, Pls 3-5 BRADY H B (1884) Report on the foraminifera dredged by H M S Challenger during the years 1873-1876 Challenger Exped 1873-76, Rept London, Zool, 9, Pt 22, 1-814, Pls 1-115 BRONNIMANN P (1951) The genus Orbuhna d'Orblgny m the Ohgo-Miocene of Trinidad, B W I Contr Cushman Fdnforamm Res, 2, 131-138, text Fig 131 CARPENTER W H (1862) Introduction to the study of the foramtmfera Ray Soc, London, 1-319, Pls 1-22 CUSHMANJ A (1927) An outhne of a re-classification of the Foraminifera Contr Cushman Fdnforamm Res, 3, 1-105, Pls 1-21 CUSHMAN J A and P J BERMI3DEZ(1949) Some Cuban species of Globorotaha Contl Cushman Fdn foramm Res , 25, 26--48, Pls 5-8 CUSHMANJ A and P W JARVIS(1930) Miocene Foraminifera from Buff Bay, Jammca d Paleont, 4, 353-368, Pls 32-34 CUSHMANJ A and R M STAINFORTH(1945) The foraminifera of the Clpero Marl formation of Trinidad, B W I Contr Cushman Fdnforamm Res, Spec Publ, No 14, 1-75, Pls 1-16 ELLIS B F and A MESSINA(1940 et seq ) Catalogue of Foramtmfera American Museum Natural History, New York, Spec P u b , 30 vols and supplements ERICSON D B , M E W I N G and G WOLLIN (1963) The Phocene-Plelstocene boundary in deep sea sediments Sewnce, 139 (3556), 727-737, 14 text Figs 1 P1 ERICSON D B (1964) The Pleistocene Epoch m deep-sea sediments Scwnee, 146 (3645), 723-732 GALLOWAYJ J and S. G WlSSLER(1927) Pleistocene Foraminifera from the Lomlta Quarry, Palos Verdes Hills, Cahfornm d Paleont, 1 (1), 35-87, Pls 7-12 HEDBERO H D (1937) Foraminifera of the Middle Tertiary Caraplta formation of Northeastern Venezuela J Paleont, 11 (8), 661-697, Pls 90-92 JENKINS n G (1960) Planktomc Foraminifera from the Lakes Entrance oil shaft, Victoria, Australia Mtcropaleontology, 6 (4), 345-371, Pls 1-5, text Figs 1-10 JENKINS D G (1964) Location of the Phocene-Pleistocene boundary Contr Cushman Fdn foramm Res , 15, 25-27 KOCH R (1923) Die jungtertmre Forammiferenfauna von Kabu (Res Surabaja, Java) Eclog geol Helv, 18 (2), 342-361, text Figs 1-11 LAUGI-I'rONA S (1966)The Gulf of Aden PhdTrans R Soc, 259A, 150-171 LE RoY L W (1939) Some small forarmnffera, Ostracoda and otohths from the Neogene (" Miocene ") of the Rokan-Tapanoeh area, central Sumatra Natuurek Ttjdschr Ned-Indt~, 99 (6), 215-296, Pls 1-14, Tables 1-8

Upper Tertiary m~crofossfls from the Alula Fartak Trench, Gulf of Aden

43

MATTHEWS D H , C WILLIAMSand A S LAUGHTON(1967) Mid Ocean Ridge m the Mouth of the Gulf of Aden Nature, Lond, 215 (5105), 1052-1053 NATLAND M L (1938) New species of Foraminifera from off the west coast of North America and from the later Tertiary of the Los Angeles Basin Scripps Inst Oceanogr, tech Ser 4 (5), 137-164, Pls 3-7 D'ORBIGNY A D (1839a) Foramlnlf6res In DE L,a SAGRA, R , Htstolte physique, polmque et natmelle de l'lle de Cuba, Paris pp xlvnl, 1-224, Pls 1-12 D'ORBIGNY A D (1839b) Forammlf6res des Iles Canaries In BARKER-WEBB, P and S BERTHELOT, Hlstotre Naturelle des lies Canaries, B6thune, Paris, Vol. 2, pt 2, Z o o l , pp 120-146, Pls 1-3 D'ORBIGNY A D (1846) Forammlfems fos~des du Bassm teltlale de Vlenne Glde & C o , Pans, pp 1-312, Pls 1-21 PARKER F L (1962) Planktonic forammfferal species in Pacific sediments Mlcropaleontology, 8 (2), 219-254, Pls 1-10 PARKER F L (1967) Late Tertiary blostratigraphy (Planktonic Foraminifera) of tropmcal Indo-PaclfiC deep-sea cores Bull Am Paleont, 52 (235), 115-208, Pls 17-32 PARKER W K and T R JONES (1865) On some Foramxmfera from the North Atlantic and Arctic Oceans, including Davis Strmts and Baffins Bay Tram R Soe Lond, 155, 325-441, Pls 13-19 PHILLIPS J D , W A BERGGREN,A BERTELSand D WALL (1968) Palaeomagnetlc stratigraphy and mlcropalaeontology of three deep-sea cores from the central North Atlantic Ocean Earth Planet Set Lett , 4, 118-130 PHLEGER F B , F L PARKER and J F PEIRSON (1953) North Atlantic Foraminifera Rep Swed Deep-Sea Exped, VII, Sediment cores from the North Atlantic Ocean, no 1, 3-122, Pls 1-12, text Figs and charts REcSS A E (1850) Neue Foraminaferen aus den Sch~chten des osterrelch~schen Tertlarbeckens K Akad Wtss Wren, Math Natutw C1 Denksehrtft, Berhn, 1, 365-390, Taf 46--51 RIEDEL W R , M N BRAMLETTEand F L PARKER (1963) "Pllocene-Plelstocene" boundary m the deep-sea sediments Science, 140 (3572), 1238-1240 SCHWAGER C (1866) Fossde Forammtferen yon Kar Ntkobar Novara Exped, 1857-1859 Men, 2, Geol TheI1, 187-268, Taf 4-7 TAKAeANAGI L and T SAITO (1962) Planktonic Foraminifera from the N o b o n Formation Shlkoku, Japan Setenee Repts Tohuku Umv, 2nd ser (Geology), spec v o l , 5, 67-106, Pls 24-28 TODD R (1957) Geology of Salpan Manana Islands Part 3, Palaeontology Smaller Foraminifera U S Geol Sul Prof Paper 280-H, 265-320, Pls 64-93