广东深圳湾和海南新村港底质中的有孔虫

FORAMINIFERA FROM SEDIMENTS OF THE SHENZHEN BAY, GUANGDONG, AND THE XINCUN HARBOUR, HAINAN ISLAND

广东深圳湾和海南新村港均为非正常海相的潟湖型港湾,有孔虫十分贫乏,分异度很低,经初步坚定,计18属34种,其中包括3新种及3未定种。深圳湾以胶结壳有孔虫占优势,几乎不见瓷状壳,称Haplophragmoides shenzhenensis sp.nov.-Ammonia of.beccarii(Linne)组合;新村港则以瓷状壳占优势,未见胶结型壳,建立Triloculina trigonula(Lamaark)-Peneroplis planatus(Fichtel et Moll)组合。对两地各种不同类型的有孔虫壳体作成分分析及酸溶试验,表明水体的pH值是有孔虫分布差异的控制因子。

A total of 34 benthic foraminiferal species belonging to 18 genera were obtained from54 surface sediment samples from Shenzhen Bay and Xincun Harbour, including 3 newspecies, viz., Haplophragmoides shenzhenensis. Elphidiella biseripora, and Pararotaliaxincunensis. The Shenzhen Bay is a low pH brackish lagoon, while the almost completely enclosedXincun Harbour is of high salinity and high pH. Foraminiferal species from the two locali-ties are quite different in composition. Generally speaking, in the Shenzhen Bay agglutinat-ed Foraminifera are dominant, represented by the Haplophragmoides shenzhenensis sp. nov.-Ammonia cf. beccarii (Linne) Assemblage, accounting for 67.5% of the total number ofthe foraminifera (with very few porcelaneous forms). Xincun Harbour is characterized bythe Triloculina trigonula (Lamarck)-Peneroplis planatus (Fichtel et Moll) Assemblage, withporcelaneous forms accounting for 78% of the total number of the foraminifera (with noagglutinated forms). Results of acid dissolving tests on porcelaneous, hyaline and agglutinated tests showthat porcelaneous tests are less resistant to the HAc-NaAc solution (pH= 5) than thehyaline tests, and that the agglutinated tests almost do not dissolve in this solution. Results from energy dispersion X-ray analysis or the foraminiferal test compositionshow that porcelaneous tests contain higher Mg than hyaline tests, whereas agglutinatedtests contain very high Si. The acid-resistance of the three types or benthic foraminiferaseems to be determined not only by the wall struture, but also by the test composition, andtherefore it can be concluded that the distribution of the three types of benthic foraminiferais closely related to pH. Thus, pH is a controlling factor causing the great differences in species composition ofthe foraminifera in the two localities. Description of new species Haplophragmoides shenzhenensis sp. nov. (Pl. Ⅰ, figs. 16--19) Description Test planispirally enrolled, partially evolute. Periphery slightly rounded.Umbilical region depressed. Chambers distinct, with 7 or 8 in the last whorl, increasinggradually in size as added. Sutures slightly depressed, nearly radial. Wall finelyagglutinated, with surface smoothly finished. Aperture showing a rounded opening at thebase of the apertural face. Diameter 0.41mm; thickness 0.16mm. Remarks This new species differs from Haplopragmoides canariensis (d'Orbigny) inthe more compressed coil, less rounded chambers, more finely agglutinated wall, and therounded instead of long, narrow sli-like aperture. Elphidiella biseripora sp. nov. (Pl. Ⅰ, fig. 4) Description Test large, planispiral and involute; broadly lenticular in face view.Periphery bluntly rounded. Umbilical region with large pores, occupying about 1 / 3 ormore of the test diameter. Chambers numerous, gradually enlarging in size as added, usual-ly with 26 in the last-formed coil. Sutures slightly depressed, showing a double row ofopenings. Wall calcareous, smooth and finely perforate. Aperture showing a single row ofpores at the base of apertural face. Diameter 1 .12mm; thickness 0.62mm. Remarks This species resembles Elphidium guangdongensis (He et Lin), but the for-mer is large and broadly lenticular in face view, with a double row of pores along thesutures. Pararotalia xincunensis sp. nov. (Pl. Ⅱ, figs. 3. 4) Description Test in a low trochospiral coil, biconvex, medium-sized. Periphery acute,slightly lobulate, with a broad margin and small spines. Chambers distinct, 9 to 10 in thelast whorl, increasing gradually in size as added. Umbilical region covered with several largetubercles. Dorsal sutures curved, slightly depressed; dorsal surface pustulose. Ventralsutures radiate, strongly depressed, ornamented with a double row of fairly large beads.Wall finely perforate. Aperture showing a low arched opening at the base of the ventral sideof the last chamber. Diameter 0.57mm; thickness 0.34mm. Remarks This new species somewhat resembles Pararotalia ozawata (Asano), but inthe former, the ventral sutures are ornamented with a double row or beads, the dors