Foraminiferal biofacies on the mid-latitude Lincoln Shelf, South Australia: oceanographic and sedimentological implications

ELSEVIER

Marine Geology 129(1996) 285-312

Foraminiferal biofacies on the mid-latitude Lincoln Shelf, South Australia: oceanographic and sedimentological implications Qianyu Li a, Brian McGowran a, Noel P. James b, Yvonne Bone a ’ Department of Geology and Geophysics, The University of Adelaide, Adelaide, SA 5005, Australia b Department of Geological Sciences, Queen’s University, Kingston, Ont., K7L 3N6, Canada

Received 15 February 1995; revision accepted 8 August 1995

Abstract

Foraminiferal assemblages on the southern mid-latitude Lincoln Shelf comprise mixtures, more strongly in shallow waters, of Holocene and relict Pleistocene specimens. Over 200 benthic and 15 planktonic species were recorded, and a higher diversity was found in the central and deeper parts of the shelf and slope. Cluster analysis identified five assemblages or biofacies. Nearshore assemblage A (< 50 m) and inner mid-shelf assemblage B (50-90 m) are dominated by relict and Recent shallow-water species. The outer mid-shelf assemblage C (90-120 m) contains more cibicidids and is transitional between the shallow- and deep-water assemblages. Outer shelf assemblage D (120-170 m) is characterized by cibicidids and anomalinids and by a higher planktonic and benthic diversity, and it can be subdivided into three sub-assemblages Dl-D3. Unlike others, assemblage D was not recognized from the most western transect samples. The outer shelf to slope assemblage E (170-400 m) is typically deep-water, having forms like Hoeglundina elegans, Pullenia bulloides and Melonis afinis. The western, Great Australian Bight sector has the larger epifaunal benthic Sorites-Marginopora group, while the infauna is higher in the eastern, Neptune sector of the shelf. We attribute these contrasts to the influence of the warm Leeuwin Current and to the mixing between gulf, shelf and oceanic waters, respectively. A former lagoonal environment is largely responsible for the accumulation of relict tests during lower sea-level periods of the late Pleistocene when climate was more arid. The lack of Recent sediments preserved on the inner shelf is considered to be due to strong wave abrasion causing sediment starvation. Richer foraminiferal assemblages from the outer shelf to upper slope parallel an increasingly calcareous sediment. Fauna1 evidence indicates a warmer, nearly oligotrophic condition on Lincoln Shelf, compared to the mesotrophy on the adjacent Lacepede Shelf. This difference may be due to the separation of these two shelves by Kangaroo Island acting as a local oceanographic (environmental) and biogeographic barrier.

1. Introduction

The southern Australian passive margin hosts one of the largest cool-water carbonate provinces on earth. Among others, Gostin et al. (1988), James et al. ( 1992) and Fuller et al. ( 1994) have begun to document the details of carbonate pro0025-3227/96/$15&l0 1996Elsevier Science B.V. All rights reserved SSDZ 0025-3227(95)00124-7

duction and accumulation in the gulfs and on the shelves. Modern marine sediments on large tracts of this neritic margin are dominated by Recent and relict skeletons of molluscs, bryozoans and benthic foraminifera. Down to about 70 m depth due to wave abrasion, Recent fresh sediments are sparse, but relict skeletons and lithoclasts are

286

Q. Li et al./Marine

Geology 129 (1996) 285-312

common (60-90%), resulting in a “shaved shelf” as termed by James et al. ( 1994). The earliest description of Recent foraminifera from southern Australia dates back to the last century, but much of the early work was systematic and little has been published on quantitative abundance or biofacies distribution (e.g., Chapman, 1941; Parr, 1932, 1950). In South Australia, Cann et al. (1988, 1993) surveyed late Quaternary and Recent foraminifera in gulf and harbour areas, and related spatiotemporal fauna1 changes to a fluctuating sea level. However, a large part of the southern shelves still remains undescribed, and only recently did we describe a mixed biofacies from the Lacepede Shelf (Li et al., 1995). Lack of data hampers a better understanding of the regional (paleo)ecology of foraminifera as organisms (Murray, 1991), but also conceals their role in local carbonate sedimentation as a carbonate contributor. This paper reports foraminiferal biofacies on the Lincoln Shelf and discusses their environmental implications. 2. Oceanographic setting The name “Lincoln Shelf” was informally coined after the town of Port Lincoln by a group of geologists on board R.V. Franklin in June 1994 while cruising offshore Eyre Peninsula, South Australia (Fig. 1). The cruise was the first of its type for a sedimentary-oceanographic survey in the area, sponsored by Commonwealth Scientific and Industrial Research Organisation (CSIRO). The shelf covers an area of about 250 x 150 km, extending NW-SE from the west and southwest of Eyre Peninsula to the west of Kangaroo Island, in a water depth mainly between 50 and 300 m. A large area of the northwestern shelf is shallower than 100 m, while the eastern shelf close to Kangaroo Island is mainly between 100 and 200 m. Oceanographically and sedimentologically, the Lincoln Shelf can be loosely divided into two sectors: the western, or Great Australian Bight sector (proximal to the eastern Bight) and the eastern Neptune sector (after the Neptune Islands near the Spencer Gulf mouth) (Fig. 1). Oceanic swells are the dominant oceanographic feature, invading the shelf from the southwest.

Swells are commonly high modal, deep-water waves, reaching >2.5 m high and 200 m long on the adjacent Lacepede Shelf (Wright et al., 1982). Storm wave base is generally in excess of - 100 m. Satellite data consistently show that the warm Leeuwin Current, originating in western Australian waters, flows southward then eastward into the Great Australian Bight (Legeckis and Cresswell, 1981). Together with warm waters from the Bight, the current extends its flow southeasterly, across the Lincoln Shelf, until becoming diffused into offshoots near Kangaroo Island. As a result, the sea surface temperature stays above 20” in summer and above 15”-17” in winter (Legeckis and Cresswell, 1981; Godfrey et al., 1986; Petrusevics, 1993). Bottom water temperature in winter on most parts of the shelf is almost the same as the surface water temperature. The in-situ measurement of 22 stations by NPJ and YB shows that most have no temperature gradient and some have a weak gradient of only 0.5”C. Salinity also varies little, between 35%0 and 36%0. Waters in the Spencer Gulf and the adjacent St Vincent Gulf are nevertheless much warmer and more saline (Nunes and Lennon, 1986). Gulf-shelf water exchange is weaker in summer because of the existence of sea surface temperature fronts at gulf entrances (Petrusevics, 1993). Bottom water flow on the shelf is very much also southeasterly (Hahn, 1986). In the Spencer Gulf, Bye and Whitehead (1975) found that bottom water inflow is northward in the west but southward in the east of the southern Spencer Gulf. The southerly outflow brings denser, more saline waters across the west of Kangaroo Island and onto the deep ocean floor (Lennon et al., 1987). 3. Material and methods We selected 48 dredged samples for this study from 68 collected during the R.V. Franklin 6194 cruise, under the supervision of YB and NPJ. These samples are all archived under the prefix “PL94-” which, however, is omitted here for convenience. All but three from the Investigator Strait are located along five observation transects (Lines I-V) (Fig. 1). They were

Q. Li et al.Jkfarine Geology 129 (1996) 285-312 E

134"

135"

136"

1370

13e

i a i

L.l-

c._.,.

.A.

locality

I

map

A._

,

‘CI

Fig. 1. Location of the Lincoln Shelf, showing sample sites and observation lines (1-v). The prevailing shelf current (stippled) flows southeast, while oceanic swells roar northeast towards the shore. The black arrows indicate the bottom water flow near the Spencer Gulf mouth. To the northeast of the Investigator Strait is the Gulf St. Vincent. Contours are in meters.

mainly from 50 to 200 m deep, with the shallowest being 22 m (sample 64) and the deepest 400 m (sample 22). Samples were prepared using standard processing techniques. Primarily, residue fractions between 150 and 1000 urn were used, although other fractions were also examined to detect species of an extreme size. A total of >25,700 foraminiferal individuals, equivalent to about 535 per sample, were picked and identified. Among these are many brown tests, stained with iron oxides, that represent relict individuals of late Pleistocene to early Holocene assemblages, as are those from the adjacent Lacepede Shelf (James et al., 1992; Li et al., 1995).

Though taxonomically identical, brown and fresh tests were counted separately. Selected common species are listed in the Appendix. The taxic database comprises species identifications, species number and relative species abundance (in percentage). Cluster analysis and principal component factor analysis were performed using JMP statistic package (version 3) for MacintoshI. Over 100 variables were selected, including the abundance of various species groups and species which occurred at least in two sites

’ JMP Statistical Software, 1994, SAS Institute, Cary, NC 27513, USA.

288

Q. Li et al./Marine Geology 129 (1996) 28.5-312

A. nearshore assemblage

and attained >2%. Similarity in cluster analysis was calculated with the Ward method without weighting. Various data files are not presented here, but are available from the senior author.

This shallow water assemblage occurs between -22 m (sample 64) and -78 m (sample 49, but mainly ~50 m. It is characterized by abundant brown tests and abundant shallow-water benthics like Elphidium spp. and Discorbis dimidiatus. All but sample 45 contain a very low planktonic to benthic ratio (P/B: ~0.02). It is restricted to the mouth of Spencer Gulf, Investigator Strait, and shallow-water sites along the west coast of Eyre Peninsula (Fig. 3). Of the five assemblages, assemblage A displays the least mutual similarity amongst its samples (Fig. 2).

4. The five assemblages Fig. 2 is the cluster tree, showing similarity between individual clusters and cluster groups. The five cluster groups (A-E) are distinct in representing five assemblages from nearshore to slope. As they appear to be depth-related, they are named, respectively, A-nearshore assemblage, B-inner mid-shelf assemblage, C-outer mid-shelf assemblage, D-outer shelf assemblage and E-outer shelf to slope assemblage. The spatial distribution of these assemblages is shown in Fig. 3, and their major fauna1 features are listed in Table 1.

B. inner mid-shelfassemblage

Overall this assemblage is similar to assemblage A, particularly in having a high number of brown

Table 1 Foraminiferal assemblages and fauna1 characteristics on Lincoln Shelf Assemblage

Depth (m)

Plankton

Benthos

diversity

abundance

diversity

dominant group typical species

relicts

A. near shore

20-50 m (78 m)’

O-5

l-1.5%

30-70

discorbids elphidiids

Discorbis dimidiatus, Elphidium spp., Cibicides refiilgens

15-55%

B. inner mid-shelf

50-90 m


115%

30-70

discorbids elphidiids miliolids

Discorbis dimidiatus, Elphidium spp., Cibicides refulgens, Parredicta porifera

30-65%

(90%)2

C. outer mid-shelf

90-120 m (145 m)3

8-14

15-50%

60-80

cibicidids discorbids

Cibicides mediocris, Parredicta portfera, Heterolepa spp.

15-55%

D. outer shelf4

120-170 m

8-14

25565%

65-105

cibicidids agglutinated other hyalines

Cibicidoides pseudoungerianus, ‘%tomalina” semipunctata, Anomalinoides spp.

5-20%

E. outer shelf-slope

(1 50-)5 170-400 m

8-15

30-70%

75-105

agglutinated other hyalines

Karreria maoria, Hoeglundina elegans, Melonis a&is

l-1570

‘Sample 45 (78 m) from Line V contains more discorbids and probably has been displaced. ‘This high occurs only in sample 12 (45 m) from Line II. 3Part of the fauna in sample 38 (145 m) from Line IV appears to have slumped from shallower waters. 4This assemblage is not recognised at Line I, on the western Great Australian Bight sector of the shelf. ‘Assemblage E includes sample 8 at Line I from 150 m deep.

Q. Li et al/Marine

Geology 129 (1996) 285-312

289

CLUSTER ANALYSIS (Ward Method)

~~~._

.._.._ !!!!!!?:e

2 24 3 13 44 25 12 47

B inner mid-shelf assemblage .

%,=1

,

C outer mid-shelf assemblage 46:47 ,6.._............' ._............. __...........................................................-._................... . __

27

Dl

1

4o...............~.......~................. . ....................... . ...-..........................

D outer shelf Dzassemblage

D3 52 ___ __

________ __________ ____________ _________ ' _______ __

. .

E outer shelf -slope assemblage

cluster history

Fig. 2. Cluster analysis identifies 5 assemblages and 3 sub-assemblages, based on 108 fauna1 variables. A nearly log-linear plot of cluster history shows similarity of the clusters. Note that samples in the nearshore assemblage (A) appear to be mutually the least similar.

290

Q. Li et al./Marine Geology 129 (1996) 285-312

,...-‘,,i LINE I--f

$__,NJ

““.....I i._.._j

,G LlNEii e r

,., ___,,m

m I- ... .. IIIII]

A. nearshore assemblage

13.inner

mid-shelf assemblage

C. outer mid-shelf

Ll.outer-shelf m 0

E. outer-shelf 20

40

60

assemblage to s/ape assemblage 60

1OOkm

Fig. 3. Distribution of the assemblages and sub-assemblages. assemblage D from Line I in the west is special (see text). -

tests (usually >50%) plus many shallow-water benthics. It can be distinguished by the frequent occurrence of Cibicides refulgens, C. mediocris, Heterolepa spp. and other mid-shelf benthic species. The plankton is consistently present, though P/B ratio is still low (~0.1). The outer boundary of this assemblage closely parallels the 100 m contour (Fig. 3).

They are generally related to the water depth, but the absence of

the benthic fauna, together with the occurrence of such deeper-water species as Eponides lornensis and Karreria maoria. The assemblage mainly occurs at - 110 m, but extends to > 120 m along Line I in the western part (Great Australian Bight sector). Containing a similar fauna, sample 38 from Line III at 145 m is also clustered here, but it might well have been slumped from the 110 m interval (Figs. 2 and 3).

C. outer mid-shelf assemblage D. outer shelfassemblage

In this assemblage, brown tests reduce to about 15-55% from the 30-65% in the assemblage B. Both plankton and benthos increase their species number (Table 1). As shallow-water species reduce in number, mid-shelf species become dominant in

This assemblage was recognized only along Lines II-V, at depths between 120 and 170 m (Fig. 3). It has less brown tests (commonly < 15%) and less shallow-water elphidiids and discorbids,

Q. Li et aLlMarine Geology 129 (1996) 285-312

291

but deeper-water agglutinated and calcareous species are common to dominant, including

species include Globorotalia scitula, Globigerinoides trilobus (s.l.), Neogloboquadrina dutertrei and

Gaudryina convexa, Globocassidulina subglobosa, Astrononion sp., “Svratkina” sp. and Anomalinoides spp.

Globigerinita glutinata.

It can be subdivided into three sub-assemblages, based on differences in the species number and in the abundance of certain depth-bound species (Table 1). Having 80-100 benthic species, subassemblage Dl contains less Anomalinoides (l-4%) and ‘Anomalina” semipunctata is rare or absent. Sub-assemblage D2 has a similar species number, but these two taxa are common, comprising > 5% and l-4% of the assemblage respectively. In subassemblage D3, however, the benthic species number is low (N 65), but the infaunal Uvigerina and cassidulinids are relatively high. Spatially, Dl and D2 occur along Lines II-IV, while D3 is restricted to Line V, in the eastern Neptune sector (Fig. 3). E. outer shelf to slope assemblage

This assemblage contains the least relict forms but many deep-water species. In plankton, Globorotalia truncatulinoides increases dramatically to lo-20% (from <5% in previous assemblages). Deep-water benthic species restricted to this assemblage include Hoeglundina elegans, Melonis affinis and Gyroidinoides sp. In addition to these, the first occurrence of many agglutinated species contributes to a maximum species number, -80 from Line V and 100 or more from other transects (Table 1). Assemblage E occurs from 150 m (Line I) and 180 m (other lines) to upper slope, and includes the deepest site at 400 m (Fig. 3).

5. Fauna1community structure and distribution 5. I. Planktonic foramintfera Dominated by Globorotalia inJata (Fig. 4), the planktonic assemblage is the typical temperate type (Be, 1977). Globigerinoides ruber, Globigerina bulloides, G. falconensis and Orbulina universa are also common. Rare but consistently occurring

As indicated by the plankton to benthos (P/B) ratio, the plankton is low in nearshore and inner mid-shelf assemblages A-B, in sites shallower than - 100 m (Fig. 4). It gradually increases to almost equal the benthics in outer mid-shelf assemblage C and even higher in outer shelf to slope assemblages D-E. This is paralleled by an increasing species number to > 10 from inner mid-shelf (B) to further offshelf (C-E) (Fig. 5). Fig. 4 shows the abundance profile of selected species, as well as the P/B ratio and ruber/inJata ratio. The dominance of G. inflata is alternated by fluctuations of other species, particularly Gs. ruber, G. bulloides-G. falconensis and (in deeper sites) surely Gr. truncatulinoides. Their fluctuations reflect the influence of some local hydrological and other environmental factors. For example, the high in ruberlinflata ratio may signal the existence of a warm shelf current, and it shifts from inner midshelf (B) on Line I to outer shelf (D) on Lines III-IV and back to outer mid-shelf (C) on Line V (Fig. 4). Considering that our assemblages are in general related to depth, this shift would indicate the wandering of the current, as discussed further below. 5.2. Benthic foramintfera Benthic foraminifera are rich and diverse, with some endemic forms. In shallow sites (< 100 m), in assemblages A-B, they are dominated by typical shallow-water miliolids, discorbids and elphidiids (Fig. 6). Further offshore, cibicidids, agglutinated and other trochospiral rotaliid taxa increase steadily and become dominant in sites > 130 m. Their abundances, however, fluctuate widely (Fig. 6). Similarly, the number of species is low nearshore (<60), but increases rapidly with depth (Fig. 5). Except on Line V, at least 90 or 100 species are found in any single sample from outer mid-shelf to slope assemblages D-E. A constantly low number from Line V, about 70 species, is rather special. The abundance of selected hyaline taxa is shown in Figs. 7 and 8. It is apparent that some are

7

LINE I \

Globorotalia truncatulinoides

.

Globigerina bulloides EZZI

~ Globorofalia inflata

Gs. rubezo Gr. inflata ratio

LINE II

\

PA

LINE III )

G. falconensis ED

&-

LINE V

Fig. 4. Plankton-to-benthos ratio (P/B) and planktonic species abundance. Bottom profile and fauna1 assemblages are superimposed. The far right column represents the content of the three samples from the Investigator Strait (also in subsequent figures). The dominant species is Gr. infura, featuring the temperate fauna1 province. A higher number of the warmer-water Gs. ruber reflects the flow of the warmer shelf water. Note the different scales.

10

%

20 "4

0

20

40

60

80

%

0

20

%I

_

1.5 -j

Q. Li et al./Marine Geology 129 (1996) 285-312

v-

b

5

.!I

miliolids

LINE II

LINE III

Fig. 6. Abundance profiles of major benthic groups, mainly epifauna. Relict forms are mostly shallow-water miliolids, discorbids and elphidiids. On outer shelf and upper slope, cibicidids, other trochospiral and agglutinated forms are dominant.

0

10

20

30

% 40

Q. Li ef al./Marine Geology 129 (iP%)

285-312

295

.. .-!i’~ W 0

.. . . .

0

=

s I?

i

porifefa

Gkbocassiduha

A

:

i

‘ISvratkina’ sp. m

subglobosa

Epmides iomensis

Parfedica

i

:

:

:

! i

LINE V

_d_c j q

Fig. 8. Abundance profiles of selected hyaline forms (other than cibicidids). Deeper waters are characterized by Hoegiundlnu eleguns, Melonis afinisand ‘Mom&d semipunctara (in Fig. 7). On the eastern Neptune sector (Lines IV and V), the infaunal G. subglobosa is high, and that could have been influenced by a fertile, mixed waterrnass.

10

%

0

5

0

2

4

%

Q. Li et al./Marine Geology 129 (1996) 285-312

widespread at various depths but others are depthrestricted. Cibicides spp., Heterolepa spp. and Parredicta portfera represent the first group, and ‘fAnomalina” semipunctata,

Hoeglundina

elegans

and Melonis afinis are deep-water examples from the second group. Among the cibicidids, C. refulgens is dominant in shallow sites; in deeper waters, it is replaced by C. mediocris and C. pseudoungerianus. Line V registers a particularly high frequency of Karreria maoria (Fig. 7), and several infaunal forms including Astrononion and Globocassidulina subglobosa are also high (Fig. 8). Coupled with a low species number, such features may indicate that Line V might have been affected much more than other transects by a mixing between gulf and oceanic waters. We will explore this as well as other explanations below. Fig. 9 summarizes the depth-range of 35 most common species in three categories: total range, > 1% range and >5% range. It is so arranged to show at which depths these taxa are more likely to occur, because, due to post-mortem transport, the total range might not necessarily represent this. Although subject to a poor sampling at depths < 50 m and > 300 m, these distributions reveal a pattern similar to the pattern in the five assemblages. Shallow waters are mainly occupied by elphidiids, discorbids and miliolids (see also Fig. 6), while cibicidids and others dominate the fauna in samples from outer shelf and slope. Rare and unusually enriched occurrences of some shallow-water species at deeper sites are believed to have been transported downslope. They are mainly robust taxa like Discorbis dimidiatus, Elphidium spp., Notorotalia clathrata and Parrellina imperatrix (Fig. 9). 5.3. The relict fauna Many benthic tests, either brown and ironstained or severely abraded, are considered to be relict. The inner mid-shelf assemblage B has more relict tests, often on the scale of 50-70%. Most relict forms are miliolids, discorbids (including rosalinids) and elphidiids (including rotaliids s.s.) (Fig. 6). At species level, Quinqueloculina spp., Triloculina spp., Discorbis dimidiatus and Elphidium spp. constitute >70% of the total relict

291

fauna. On average, about 10 species in a single sample are found to have no fresh specimens, suggesting that they are relict (Fig. 5). Our relict figure might have been biased because not many relict deeper-water forms were included. Deeper-water species have fewer brown individuals, but that does not mean that relicts are scarcer. They would never become as brown as their contemporary shallow-water forms if they remained underwater at the time of sea-level fall. Thus it is difficult to determine how many of them have been relict from earlier older sediments. We only counted brown forms as relict, and we assumed that all fresh tests are from the most recent. The fact is that relict forms become dominant only in nearshore and inner mid-shelf assemblages A-B, at depths < 100 m (Table 1; Fig. 6). This suggests that wave abrasion causing starvation of the modern sediments is strongest in this interval, if we consider wave abrasion to be the prime mechanism in producing “shaved shelves” along the southern margin of Australia (James et al., 1994; Li et al., 1995). Our data, however, show the abrasion maximum as deep as -90 m, which is slightly deeper than that found from other shelves including the Lacepede Shelf, where it is at about -70 m (James et al., 1992; Li et al., 1995).

6. Comparison with the Lacepede Shelf biofacies Li et al. (1995) described foraminifera from the adjacent Lacepede Shelf, which is located immediately east of Kangaroo Island. Foraminiferal biofaties on the Lacepede Shelf were also strongly mixed between the Recent and late Pleistocene, relict forms. Five assemblages were recognized: I, slope and deeper water; II, mid to outer shelf; III, upwelling centre, “mixing A” on Bonney Shelf; IV, mixing B; and V, shallow relict (Table 2; Fig. IO). Planktonic and many benthic taxa from the Lacepede and Lincoln shelves are virtually identical, though they vary in individual abundances. An exception is that the benthic diversity is higher on Lincoln Shelf due to the occurrence of such specialised forms as the Sorites-Marginopora group (Fig. 9). Relict Ammonia beccarii typifies

Q. Li et al./Marine Geology 129 (1996) 285-312

298

Om

I

I

I

I

200 m

100 m

I

I

I

I

I

I

I

300 m

I

400 m

I

1

I

I

‘Anomalfna * semipuncta ta Anomalinoides spp. Astrononion sp. Baggina philippinensis Bigenerina sp. Bofivina striatuta Cibicides mediocris Cibicides re fuigens Cibicidoides pseudoungerianus Cribrobulimina mbcta Discorbis dimidiatus Elphidium macellifonne Elphidium crispum Eponides lomensis Gaudtyina convexa Gaudryina quadrangularis Glabratelfa australensis Globocassidulina subglobosa Hetefoolepaspp. Hoeglundina elegans Karreria maoria Melonis affinis Miliolina australis Miniacina miniacea Notoro talia c/athrata Parredicta porifera Parrelina imperatrix Pullenia bulloides Rosalina austrafis

Siphogenerina costata Sorites-Marginopora group ‘Svratfdna’sp. Textmaria sagittula Textmaria agglutinans Uvigerina bassensis

-

total range

-

21%range

------ >5% range

I l

I

probably downslope

transported

Fig. 9. Depth range of selected 35 species. Note that Cribrobulimina mixta and the Sorites-Marginopora group are restricted to the western Great Australian Bight sector of the shelf (Lines I and II), while Pullenia bulloides and “Svratkina” sp. rarely occur in the east (Line V).

Q. Li et al.jMarine Geology 129 (1996) 285-312

299

Table 2 A correlation between foraminiferal assemblages from Lincoln and Lacepede shelves. Lacepede Shelf data are from Li et al. (1995, table 1). There are more well-defined assemblages from Lincoln Shelf, though the assemblages V and III on Lacepede Shelf may indicate the influence of some local factors like river (on V) and upwelling (on III) Lincoln shelf Lacepede shelf assemblage assemblage

V shallow, relic

depth

plankton

benthic diversity

dominant benthics

typical benthics

relics, reworking

<55 m

O-3%

<45

Ammonia beccarii

Ammonia beccarii

50-80%

35-70 m (but 150-338 m on Robe transect)

l-8%

40-60

elphidiids,

20-60%

~82 m on Robe transect

< 10%

Elphidium crispurn, Elphidium macellum, Glabratella australensis Parrellina imperatrix Globocassidulina subglobosa Cibicides refulgens, Gaudryina quadrangularis Karreria maoria, Anomalina semipunctata, Gaudryina convexa

(off river mouth)

A-B

IV mixed B

III mixed A

Discorbis dimtdiatus

40-60

Discorbis dimidiatus,

cibicidids

C-D

II mid-outer shelf

60-130 m

5-30%

40-75

E

I slope and deeper water

>130 m

lo-50%

60-> 80 agglutinants

the shallow-relict assemblage V on Lacepede Shelf specimens from (Fig. lo), where reworked Miocene rocks are also found in assemblage III but do not occur in any Lincoln Shelf samples. Assemblages I (Lacepede) and E (Lincoln), both containing forms like Karreria maoria and Ttnomalina” semipunctata, are considered as representing a deeper-water fauna1 province, in which agglutinated taxa are common or dominant (Tables 1 and 2). Mid to outer Lacepede Shelf assemblage II is characterized by cibicidid species, thus it can be correlated to the Lincoln Shelf assemblages C and D. It is noteworthy that C. refilgens appears to have a slightly different depth preference: on Lincoln Shelf, it prevails from inner to middle parts (Fig. 7); on Lacepede Shelf, it dominates only the mid-shelf fauna (Li et al., 1995, Fig. 12). No fauna1 assemblage from Lincoln Shelf has been found to resemble either assemblage III or V of the Lacepede, two local assemblages comprising mainly reworked and relict forms (Table 2). However, the Lacepede assemblage IV is considered an equivalent to the Lincoln A and B

cibicidids

20-50%

20-40%

O-20%

assemblages, because they are similar in having a fauna dominated by Discorbis dimidiatus and elphidiid species. To sum up, many foraminifera from Lacepede and Lincoln shelves are taxonomically similar and appear to have a similar distribution pattern, particularly in relation to water depth. Three major differences are: 1, Lacepede Shelf has two local assemblages (III and V); 2, it has a lower benthic diversity, 60-80 species on average (compared to 80-100 on Lincoln Shelf); and 3, fauna1 community structure appears to be better defined on Lincoln Shelf, as more (sub) assemblages have been identified.

7. Discussion 7.1. Fauna1 sub-provincialism with water depth?

Two conventional methods commonly used to interpret shallow-water benthic foraminifera are Fisher’s absolute species richness (a index) and ternary plot (ratio) of three supergroups-

300

Q. Li et a~.~~ar~~ Geology 129 (19%j285-312

36%

37%

1WE

138%

139OE

140°E

Fig. 10. Foraminiferal assemblages on the Lacepede Shelf (Li et al., 1995). Two local assemblages are distinct in representing upwel~ng (~~mblage #I) and former estuarine deposits (assemblage v). See text for explanation. Contours are in meters.

agglutinated, miliolid and hyaline forms (Murray, 1973, 1991). As our data were collected on a basis of relative abundance, no 01index could be determined. Depth preferences of selected species were shown in Fig. 9; we limit our discussion here to some groups which appear to be env~onmentally more sensitive. Fig. 11 shows two triangular plots of the three benthic supergroups, based on counting of the fresh and relict specimens respectively. The closely packed distribution in fresh specimens suggests that the modern fauna1 composition at supergroup level is exceptionally similar regardless of water depth. This unifo~ity may imply the constant influence of a mechanism or a combination of mechanisms. Locally both the temperature and salinity vary little, which must account for at least part of this phenomenon. As discussed below, a

persistent high percentage in the planktonic species Gs. ruber bears similar information, though it is related more to the surface water tem~rature. It is interesting that most samples fall into the normal marine lagoon category of Murray (1973) when only the relict specimens are considered (Fig. 11). The relicts were produced by a fluctuating sea level during the late Pleistocene, and in particular they represent the low sea-level deposits. Although most of our samples were taken from >40 m deep and represent a normal marine environment (Fig. 1), their relict foraminifera indicate that a vast area of the shelf may have been covered by saline lagoons in the past. The hyaline supergroup is the most dominant and diverse, so that fluctuations in different hyaline groups may have some environmental implication. Three prevalent hyaline groups, the discorbids,

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elphidiids and cibicidids, were chosen for plotting in Fig. 12. When only the fresh forms are counted, the outer shelf to slope assemblages D-E are strongly united in having more cibicidids. Sites belonging to the shallow-water assemblages A-B, however, are randomly distributed, indicating that the fresh specimens may not represent the modern fauna in shallow waters due to distortion by waves and swells. A reversed pattern is found in the plot of relicts, in which the inner mid-shelf assemblage B is well defined (Fig. 12), so a near in-situ occurrence of this assemblage thus can be inferred. In other words, the recent wave abrasion has little effect on those previously deposited, shallow-water tests, though it does remove most of the recent sediments, and the shelf becomes “shaved” (James et al., 1994). The other side of this argument is that perhaps this phenomenon was mainly due to sediment starvation, rather than sediment removal, and the shelf remains in disequilibrium following the early Holocene sea-level rise. The arid climate in southern Australia limits terrigenous sediments flowing to open marine environments such as the Great Australian Bight, and few sediments have been released from gulfs or estuaries to the inner shelf. A lack of sediment input from these sources would have contributed to part of sediment starvation on the modern shelf. However, wave abrasion should be the main factor in controlling the indigenous, carbonate sediment accumulation, because modern carbonate production is high in areas protected from oceanic swells, such as in gulfs and embayments (Gostin et al., 1988; Fuller et al., 1994) and in deeper waters (James et al., 1992, 1994). Perhaps, a certain state of equilibrium exists between wave abrasion and carbonate production on the shelf, resulting in a low accumulation of modern sediments. We attribute the primary cause of this sediment starvation and slow accumulation to wave abrasion, other than the arid climate. Results from principal component factor analysis also point to a similar conclusion. Two factors accounting for 89% of the total variance are considered significant (Fig. 5). Factor 1 (77%) represents, particularly, the number of species and the abundance of cibicidid and other deep-water forms, thus a positive relation with depth. Factor

2 (12%) combines the shallow-water discorbid and elphidiid benthics, thus a negative relation with depth. This trend is more impressive when the factors are superimposed with the five assemblages, as in Fig. 13. Shallow-water sites in assemblages A and B are widely distributed, suggesting a fauna with more variable features. Unlike this, the deeper-water samples within assemblages D and E are closely packed, so are more similar to each other in terms of the fauna1 content. Though the assemblages on Lincoln Shelf are closely related to water depth, we are still skeptical of this collective environmental factor, because depth alone cannot explain: (1) Why is the supergroup composition in samples of all depths so similar? (2) Why does Marginopora not occur in the eastern Neptune sector? and (3) Why is the diversity low but infauna are higher along the eastern transects? Perhaps the physical structure of currents, trophic level of sea water, thermocline variation and many other factors had all played a significant role in controlling the distribution of foraminifera on Lincoln Shelf. 7.2. Current and trophic indices The prevailing southeast flow along the shelf is a permanent current system, advancing from the west “at least from the head area of the Great Australia Bight” (Hahn, 1987), and represents the eastern, extended part of the Leeuwin Current (Cresswell, 1991). This warm and saline water contrasts with both the cool and less saline oceanic water and the warmer and more saline gulf water. Though rare, typical warm-water planktonic species Globigerinoides trilobus and Neogloboquadrina dutertrei occur from mid to outer shelf, but rarely in the deeper water (Fig. 14). Our concept of G. trilobus includes the sac-bearing phenotype Gs. sacculifer which occurs sporadically. Their combined > 1% abundance, as mapped in Fig. 14, distributes along the shelf in a southeastern direction, wider in the west but narrower and branching northward and southward in the Neptune sector, near Kangaroo Island. Globigerinoides ruber is a next-order, warmer-water representative, and highs in the Gs. ruber to Gr. inflata ratio have been used to indicate the flow of

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Bivariate Normal Ellipse (P=O.800:

0J 0.6E 2

0.50.4 -

I -0.2

0.0

0.2

0.8

1.0

Fig. 13. X-Y plot of the factors 1 and 2 (Fig. 5). The five assemblages are shown in different symbols, and each is bounded by a bivariate normal ellipse (P=O.8). Like the cluster analysis (Fig. 2), the factor analysis reveals a relationship between samples and water depth. Slightly out of the sequence, the relict-enriched assemblage B is probably controlled by a lagoonal depositional environment and subsequent wave abrasion other than solely by present water depth (see Fig. 12 and text).

the Leeuwin Current in the Great Australia Bight (Almond et al., 1993). On the Lincoln Shelf, the ruber/inJata high meanders from inner mid-shelf assemblage B in the Great Australian Bight sector (Line I) to outer shelf assemblage D in the Neptune sector (Line IV) and back to outer midshelf assemblage C at Line V, in parallel with the distribution of Globigerinoides trilobus. We attribute all this to the prevailing warm-water surface flow. The benthos also bear supportive evidence, though they primarily evince the bottom environment. Forms referable to the larger benthic Sorites-Marginopora group occur sporadically in the Great Australian Bight sector, at Lines I and II, but not in the eastern Neptune sector of the shelf (Fig. 14). Like many other larger taxa, this

group flourishes in tropical seas (Murray, 1991). In southern Australia, Marginopora has been found along the pathway of the Leeuwin Current from western Australia to the Great Australia Bight, but not on Lacepede Shelf or shelves farther east (James et al., 1994; Li et al., 1995). In our material, there are two types of SoritesMarginopora specimens. Those with large tests are brown or heavily abraded and must be relict. Those with smaller ones may be the products of the most recent, because they are fresh and, from side view, the chamberlets are still covered with the membrane-like shelly layer. We are unable to distinguish whether these small tests are species of Sorites or Amphisorus or they represent some small-sized Marginopora. Their occurrence on Lincoln Shelf but not further east forms a modem

305

Q. Li et al./Marine Geology I29 (1996) 285-312 135"

134"

I ‘> \

_ .

136"

1

137"

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c/-X.Y

‘KANGAROO

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Fig. 14. Distribution of the typical warm-water planktonic species Gs. trilobus (including Gs. sacculifer). The percentage value also includes another warm-water form Neogloboquadrina dutertrei. The larger benthic and phytosymbiotic group Sorites-Marginopora occurs only in the eastern Great Australian Bight sector of the shelf.

distribution limit of this group in southern Australia. Murginopora bears algal symbionts and inhabits at least a warmer, nearly oligotrophic to oligotrophic bottom environment. Therefore, the occurrence of these forms implies that the water in the Great Australian Bight sector is warmer than that in the Neptune sector. It also indicates that the Lincoln Shelf water as a whole is warmer than that from the neighbouring Lacepede Shelf. A warmer, mesotrophic to nearly oligotrophic environment on shelf is also inferred by an epifauna-dominated fauna (Fig. 15). Only such a condition could have favoured the epifauna but impeded the infauna from flourishing (Murray, 1991). Our concept of infauna follows that of

Corliss ( 1985) and Murray ( 1991) and includes mainly the cassidulinids, bolivinid-uvigerinids, lagenids and nonionids. They primarily live in muddy sediments under deep or cold waters, but may also occur at shallower depths when conditions suit (Murray, 1991), and many appear to have a complex vertical distributional pattern (Corliss and Van Weering, 1993). When enriched, most infaunal species are good indicators of high productivity (Altenbach and Sarnthein, 1989). Coupled with planktonic signals, four unusual abundance peaks (50-70%) of infauna in a Miocene shelf sequence from southeastern Australia could indicate upwelling-related, high productivity (Li and McGowran, 1994). The

306

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Geology 129 (1996) 285-312

135”

0

x)

40

60

60

136”

1370

1

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Fig. 15. Abundance distribution map of the infauna. They are richer in numbers and species in deeper waters, and a higher abundance is elevated in the eastern Neptune sector of the shelf. A combined message from Figs. 14 and 15 is that mixing between gulf, shelf and oceanic waters is prevailing here.

infauna on the Lincoln Shelf is negligible in samples < 100 m, about 5-20% between 100 and 200 m and 20-35% in deeper waters (Fig. 15). This depth range, however, is somewhat elevated in the western Neptune sector of the shelf, particularly along Lines IV and V. There, several samples from about 110 to 130 m contain about 25% infauna, and in shallower sites the infauna is also high (Fig. 15). About half of the infauna in these samples are composed of only two species: Globocassidulina subglobosa and Uvigerina bassensis.

A lower infauna from the Great Australian Bight sector supports the previous conclusion that the water on that part of the shelf is warmer and

more oligotrophic. On the other hand, a higher infauna from samples offshelf may denote a colder and more fertile bottom water. Corliss (1979) reported that G. subglobosa was, among others, the species characterising Antarctic Bottom Water off the Great Australia Bight. Consequently, the elevated infauna rich in G, subglobossa in the eastern Neptune sector might have been resulted from a stronger influence of the colder, deeper water. As the deeper water moves southeasterly, the shelf current from the eastern part of the shelf may be subsequently mixed and becomes cooler when it reaches the east. In the east, on the Neptune sector, there is a steeper slope with canyons and the northeasterly oceanic swehs are

Q. Li et al./Marine Geology 129 (1996) 285-312

the strongest (Fig. 1). Thus it is not impossible for the deeper water to invade that part of the shelf. Instead of deeper waters being the sole influence, a mixing between gulf, shelf and oceanic waters may be largely responsible for the higher infauna on the eastern shelf. According to Lennon et al. (1987) warmer more saline gulf water sinks to the bottom and flows southward from the eastern mouth of the Spencer Gulf, across the eastern shelf and into the deep ocean. The Leeuwin Current from the west meets the gulf and oceanic waters, so a mixed water may exist on the eastern Neptune sector of the shelf. This mixed water has probably exerted its influence as far north as to the southern Spencer Gulf, resulting in a complex sedimentation during the Holocene (Fuller et al., 1994). The shelf water could have been only weakly mixed should no barriers block its pathway to the east. In this respect, the role of Kangaroo Island as a barrier cannot be overlooked. 7.3. Kangaroo Island: a biogeographic barrier? We have discussed above the similarity between foraminiferal biofacies on the Lincoln and Lacepede Shelves, respectively from the west and the east of Kangaroo Island. Though having many species in common, these two regions also show different fauna1 features. Two such features are ( 1) more species on the Lincoln Shelf, but (2) more local assemblages on the Lacepede Shelf. Over ten benthic species are found restricted to Lincoln Shelf, resulting in a higher diversity. They include epifaunal and infaunal taxa, and the environmentally most useful one is the SoritesMarginopora bioseries which occurs only in several samples from the northwestern Great Australian Bight sector of the Lincoln Shelf (Fig. 13). The agglutinated form Cribrobulimina mixta is also restricted to the west. “Svratkina” sp. and a flattened morphotype of Parredicta porifera appear to be new, as they have not been recorded elsewhere. Unlike other transects, Line V in the Neptune sector, near the Kangaroo Island, has a D3 subassemblage (Fig. 5), which is believed to be transitional between those from the Lincoln and Lacepede shelves. The distribution of the warm-water, planktonic

307

species Gs. trilobus shows south- and northoffshoots near the Kangaroo Island (Fig. 14). How can we explain this without considering the Island as an oceanographic and biogeographic barrier? The Lacepede Shelf not only yields a lower benthic diversity, but the mixed biofacies is so strong that fewer assemblages in common with those from the Lincoln Shelf have been identified (Table 2). Two local assemblages, however, are characteristic. The mixed A assemblage on the Bonney Shelf is upwelling-related, and the shallowrelict one near the River Murray mouth is rich in relict Ammonia beccarii (Fig. 10). The shallowrelict assemblage occupied much of the inner Lacepede Shelf, and has been, uniquely, related to the influence of the River Murray in the past (Li et al., 1995). In contrast, no significant river systems ever influenced the Lincoln Shelf, and few samples there have Ammonia beccarii >2%. This comparison encourages us to conclude that Kangaroo Island has acted, and may still act, as a barrier to the distribution of foraminifera. Perhaps its role was more significant in the past, during the times of sea-level fall. It separates the shelf water regime into Lincoln and Lacepede sectors. The Lincoln Shelf water is warmer and nearly oligotrophic because it receives the southeast flowing Leeuwin Current. This also explains why, to the east of Kangaroo Island, the Lacepede Shelf is bathed mainly in cooler, mesotrophic shelf waters, with local upwelling occuring from time to time. 7.4. Relict forms as evidence of sea level and wave abrasion Sea level fluctuated over tens of metres or even > 100 m from the late Pleistocene to Recent. Several studies investigated the response of local fauna and flora to the sea-level change, though the actual metres of sea-level changes through time are still in dispute (Cann et al., 1988, 1993; MurrayWallace and Belperio, 1991; Bryant, 1992). A magnitude of over tens of metres is enough to account for the occurrence on the present midshelf of the former shallow-water biofacies. In many other areas, previous biofacies have been buried beneath the recent sediments and can only be

308

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Geology 129 (1996) 285-312

studied in drilling cores. On the southern Australian shelves, however, such older sediments are readily available, as they are abundant in dredged seabed samples from the inner shelf to upper slope (e.g., James et al., 1992, 1994). Mostly brown to reddish brown, they can be easily differentiated. Any brown specimens are surely relict, with an age from 17,000 to >30,000 years BP, as dated on similarly brown bryozoans and bivalves (James et al., 1992). It is a rule, rather than an exception, that on most southern Australian shelves the wave energy is high and sedimentation is low, for Recent sediments have been removed or “shaved” (James et al., 1992, 1994; Boreen et al., 1993, and references). The maximum wave abrasion at about 70 m has led these authors to correlate wave abrasion with relict sediments, because at that depth the relict elements are highest. On the Lacepede Shelf, relict foraminifera are more abundant in sites shallower than 70 m, thus supporting this explanation (Li et al., 1995). With no exception, the foraminiferal biofacies on the Lincoln Shelf is mixed between recent and relict forms. Samples likely to have more relict individuals are from shallow-water sites, particularly those in assemblage B, at 50-90 m, and less so in assemblage A, < 50 m (Table 1). Typical relict taxa are mainly from the miliolid, discorbid and elphidiid groups, including numerous species of Quinqueloculina and Triloculina, Discorbis dimidiatus, Ammonia beccarii, Elphidium spp., and Parrellina imperatrix (Fig. 6). In any single sample from assemblages A and B, about 10 species are relict, having no fresh specimens. A richer relict fauna in the inner mid-shelf assemblage B would have been also due to a stronger wave abrasion. However, the relict fauna from this assemblage is well defined among the hyaline groups (Fig. 12), and its distribution pattern in factor analysis appears to be slightly out of sequence (Fig. 13), indicating that factors other than the water depth are more influential. A stronger wave abrasion may only obscure the original depth zone of sediments, but it cannot be the major factor causing the accumulation of those relict tests in sites between 50 and 90 m on the Lincoln Shelf. Why and how did these relict forms become

concentrated in the inner mid-shelf assemblage B? Changing sea level may be part of the answer, because all these forms are primarily nearshore species preferring a variable environment, from brackish to hyposaline. Their enrichment at sites as deep as 90 m is an artifact and must have been subject to early sea-level fluctuations. It is more likely that they represent multiple depositions in the past 30,000 years as sea level rose and fell. When only the relict supergroups are plotted, most of the samples fall into the normal marine lagoon category of Murray (1973) indicating that a saline lagoonal environment in the past was largely responsible for the accumulation of these relict specimens (Fig. 11). The modern Spencer Gulf and the adjacent St. Vincent Gulf contain a foraminiferal fauna rich in miliolids, elphidiids and discorbids, and can be regarded as representing an open saline lagoon environment (Cann et al., 1988, 1993; J.H. Cann, pers. commun., 1994). The seagrass assemblage is typified particularly by Discorbis dimidiatus and some elphidiids. As described above, these forms also characterize the inner mid-shelf assemblage B on Lincoln Shelf, particularly the relict part. Whether the recent gulf faunas can be viewed as an analogue of the relict assemblage B awaits further studies, but the fauna1 similarity indicates such a possibility. During the previous low sea level, coastal environments similar to those of the present-day would shift offshore. Had the sea level fallen to -50 m, open or semi-closed lagoons would develop on areas now belonging to middle shelf, and a lagoonal fauna would flourish. The iron-stained tests may have been subject to exposure at maximum low sea level when climate was more arid, but periods of their major accumulation must lie between the maximum low sea level and - 50 m, because a lowest sea level (- 121+ 5 m, Fairbanks, 1989) could cause not only stronger erosion but more frequent redeposition, and because fewer relict forms are found in samples from the nearshore assemblage A (< - 50 m) than in those from the inner mid-shelf assemblage B (Table 1). The prevailing lagoonal environment may have been exaggerated by stronger aridity in southern Australia during the previous sea-level low stands.

Q. Li et al. IMarine Geology 129 (1996) 285-312

While a large area on what is now the Lincoln Shelf was covered with semi-isolated lagoons in the late Pleistocene, a slightly different situation might exist to the east of the Kangaroo Island, on the Lacepede Shelf. Though the relict Discorbis dimidiatus was also distinct on mid-shelf, Ammonia beccarii dominated the relict fauna on the inner part of the Lacepede Shelf (Table 2). We attributed the origin of the Ammonia-dominated relict fauna to the Murray River which nurtured this famous brackish-water species (Li et al., 1995). At the time of a low sea level, when the surface topographical gradient was higher, discharge from the Murray River may have intensified, resulting in a benthic fauna dominated by A. beccarii. The Kangaroo Island barrier would have been more significant as a biogeographic barrier, because there would have been no passage between the Lincoln Shelf and Lacepede Shelf when sea level dropped to about -50 m.

8. Conclusions (1) Like those from other southern Australian shelves, foraminiferal assemblages on the Lincoln Shelf are a strong mixture of modern and relict Pleistocene forms. A lack of recent sediments on the shallower parts of the shelf probably resulted from strong wave abrasion causing sediment starvation. (2) Five assemblages A-E are identified from nearshore to upper slope. Shallow to inner midshelf assemblages A and B are rich in relict forms, but low in all other fauna1 variables. Assemblage C from outer mid-shelf is transitional between assemblages from shallower and deeper waters. Outer shelf and slope assemblages D and E, including sub-assemblages D 1-D3, are characterized by having fewer relict tests but many deeper-water taxa, such as Karreria maoria and Hoeglundina elegans. (3) An environment

warmer than that on the neighbouring Lacepede Shelf, east of Kangaroo Island, is inferred from the occurrence of the larger benthic Sorites-Marginopora bioseries, from a higher benthic diversity, and from the presence of warmer-water planktonic species. The extended

309

Leeuwin Current is largely responsible for this warmer shelf water, while the difference between the Lincoln and Lacepede shelves is due to the blocking effect of Kangaroo Island which acts as an oceanographic and biogeographic barrier. (4) The less abundant infauna on the shelf suggests a nearly oligotrophic bottom condition, in contrast to cooler, deeper waters where the infauna is high. A higher infauna is shallower on the eastern Neptune sector of the shelf, reflecting a mixing of gulf, shelf and deeper ocean waters. The southeast-flowing shelf water is warm and saline, the gulf water from Spencer Gulf is warmer and more saline and flows southward as a bottom water across the eastern shelf, while the deep-sea water is cold and less saline, but its vigour is greatly enhanced by the prevailing swells flowing northeast towards the coast. They meet and mix on the Neptune sector of the shelf. As a result a higher infauna and a D3 sub-assemblage are recorded here. (5) We suggest that the distribution of Marginopora signals the flow of the Leeuwin Current, a southerly and then southeasterly flowing, warm water system originating to the west of Australia. Marginopora is abundant in western Australian waters and is restricted to the Lincoln Shelf and farther west. Its absence from the neighbouring Lacepede Shelf suggests that the influence of the Leeuwin Current is weaker there. (6) Relict specimens are richer in the inner midshelf assemblages, in sites from 50 to 90 m, and are similar to those from the modern saline lagoons. Shallow-water lagoons at low sea levels might have accounted for their accumulation during the late Pleistocene.

Acknowledgements We thank V. Gostin, S. Hageman and crew of the R.V. Franklin for assisting in sample collection. B. Huber and an anonymous reviewer critically reviewed the manuscript. Support from the Australian Research Council and from the Natural Sciences and Engineering Research Council of Canada (to NPJ) is acknowledged. For further information, the senior author can

Q. Li et aLlMarine Geology 129 (1996) 285-312

310

be also contacted delaide.edu.au.

via e-mail at [email protected]

Appendix List of common foraminiferal Shelf, South Australia.

species from the Lincoln

I. Planktonic taxa Globigerina bulloides d’orbigny

G. falconensis Blow Globigerinella obesa (Bolli, Globorotalia) Ge. siphonifera (d’orbigny, Globigerina) Globigerinita glutinata (Egger, Globigerina) Globigerinoides ruber (d’orbigny, Globigerina) Gs. trilobus (Reuss, Globigerina) Globorotalia infata (d’orbigny, Globigerina) Gr. scitula (Brady, Pulvinulina) Gr. truncatulinoides (d’orbigny, Rotalia) Neogloboquadrina dutertrei (d’orbigny, Globigerina) Orbulina universa d’orbigny

II. Benthic taxa 1. Agglutinated forms (mainly epifauna) Ammobaculites agglutinans (d’orbigny) Ammodiscus spp. Bigenerina nodosaria d’orbigny Clavulina multicamerata Chapman Cribrobulimina mixta (Parker and Jones, Valvulina) Cylindroclavulina bradyi (Cushman, Clavulina) Discammina compressa (Goes, Lituolina irregularis var.) Dorothia scabra (Brady, Gaudryina) Gaudryina convexa (Karrer, Textularia) G. quadrangularis Bagg Martinottiella nodulosa Cushman Reophax dentalintformis Brady Rhizammina algaeformis Brady Siphotextularia spp. Textularia agglutinans d’orbigny T. jistulosa Brady (Textularia sagittula var.) T. porrecta Brady T. pseudogramen Chapman T. sagittula Defiance i? cf. siphontfera Brady Trochammina squamata Jones and Parker

2. Miliolids (mainly epifauna) Cornuspiroides foliaceus (Philippi) Flintina triquetra (Brady, Miliolina) Marginopora sp. Miliolinella australis (Parr, Quinqueloculina) M. circularis (Bornemann) s.1. Peneroplis planatus (Fitchtel and Moll, Nautilus) P. depressa (d’orbigny, Biloculina) P. elongata (d’orbigny) P. subpisum Parr Ptychomiliola separans (Brady, Miliolinaj Quinqueloculina bradyana Cushman Q. elongata Natland Q. lamarckiana d’orbigny Q. poeyana d’orbigny Q. seminula (Linne, Serpula) Q. subpolygona Parr Q. venusta Karrer Sigmoilina sigmoidea (Brady, Planispirina) Sigmoilopsis schhanbergeri (Silvestri, Sigmoilina) Sorites sp. Spirillina decorata Brady S. denticulata Brady S. involvens ( Reuss, Operculina) Spiroloculina communis Cushman and Todd Triloculina oblonga (Montagu, Vermiculum) T. striatotrigonula Parker and Jones T. trigonula (Lamarck, Miliola) T. tricarinata d’orbigny

3. Acervnlinids and carpenteriids (mainly epifauna) Acervulina inhaerens Schultze Carpenteria sp. Cymbaloporetta bradyi (Cushman, Cymbalopora poeyi var.) Gypsina glob&s ( Reuss, Ceriopora) G. vesicularis (Parker and Jones) Miniacina miniacea (Palla, Millepora)

4. Elphidiids and rotaliids (infauna and epifauna) Ammonia beccarii (Linne, Nautilus) A. convexa (Collins, Streblus) Elphidium crispum (Linne, Nautilus) E. cf. aculeatum (Silvestri, Polystomella macella var.) E. jenseni (Cushman, Polystomella) E. macelltforme McCulloch Parrellina imperatrix (Brady, Polystomella) Notorotalia clathrata (Brady, Rotalia)

5. Cibicidids (mainly epifauna) ‘Anomalina” semipunctata (Bailey, Rotalia) Anomalinoides fasciatus (Stache, Rotalia)

Q. Li et al./&iarine Geology I29 (1996) 285-312 A. macraglabra (Finlay, Anomalina) Cibicides mediocris Finlay C. lobatulus (Walker and Jacob, Nautilus) C. refulgens Mot&fort Cibicidoides floridanus (Cushman, Truncatulina) C. pseudoungerianus (Cushman, Truncatulina) Dyocibicides variabilis d’orbigny Gyroidinoides sp. Heterolepa opaca (Carter, Cibicides) H. subhaidingeri (Parr, Cibicides)

Discorbids and rosalinids (mainly epifauna) Discorbina spp. Discorbis dimidiatus (Jones and Parker, Discorbina) D. sp. A (with sigmoid sutures) Discorbinella bertheloti (d’orbigny, Rosalina) Glabratella australensis (Heron-Allen and Earland, Discorbis) Patellina corrugata Williamson Patellinella inconspicua (Brady, Textularia) Planulina biconcava (Jones and Parker, Discorbina) Rosalina australis (Parr, Discorbis) Rosalina bradyi (Cushman, Discorbis globularis var.) Tretomphalus sp.

Other trochospiral forms (mainly epifauna) Baggina phillippinensis (Cushman, Pulvinulina) Cancris sp. Eponides lornensis Finlay Heronallenia sp. Hoeglundina elegans (d’orbigny, Rotalina) Karreria maoria (Finlay, Vagocibicides) Oridorsalis tener (Brady, Truncatulina) Parredicta porifera (Parr, Valvulineria) Siphonina australis Cushman Sphaeroidina bulloides d’orbigny Stomatorbina concentrica (Parker and Jones, Pulvinulina)

Nonionids (mainly infauna) Astrononion sp. Melonis a&is ( Reuss, Nonionina) Pseudononion victoriense (Cushman, Nonion) Pullenia bulloides ( Reuss,Nonionina)

Lagenids (mainly infauna) Amphicoryna scalaris (Batsch, Nautilus) s.1. Dentalina communis d’orbigny Fissurina spp. Guttulina problema d’orbigny G. cf. yabei Cushman and Ozawa Globulina gibba (d’orbigny, Polymorphina) Lagena spp.

311

Lenticulina spp. Nodosaria spp. Oolina hexagona (Williamson, Entosolenia squamosa var.) Polymorphina spp. Sigmoidella elgantissima (Parker and Jones, Polymorphina) 10. Cassidulinids (mainly infauna) Buliminella missilis Vella Cassidulina kazusaensis Asano and Nakanura C. laevigata d’orbigny C. margareta Karrer Evolvocassidulina orientalis (Cushman, Cassidulina) Globocassidulina subglobosa (Brady, Cassidulina) G. pacifica (Cushman, Cassidulina) Robertina tasmanica Parr

Il. Bolivinids and uvigerinids (mainly infauna) Bolivina bassensis Parr B. spp. Bolivinella folia (Parker and Jones) Bulimina aculeata d’orbigny s.1. Globobulimina pactjica Cushman Reussella sp. Siphogenerina costata Schlumberger Trifarina bradyi Cushman Uvigerina bassensis Parr

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