Bulletin of the Marine Geology (Jul 2017)
ENVIRONMENTAL CONTROL OF NANNOPLANKTON AND FORAMINIFERA ASSEMBLAGES IN MADURA WATERS
Abstract
Nannoplankton is widely used for determining age of sediments following the other microorganism foraminifera since the late 1960s; and it was started being used for marine geography study in the year of 1984. This topic interests to be done in Indonesia as one of the tropic region. The research covered a study about environment using nannoplankton and it is compared with the same study using foraminifera. Methods of the study include: (1) collecting secondary data and samples; (2) collecting field data record; (3) laboratory analyses upon sediment samples to determine the content of nannoplankton and foraminifera (micropaleontology analyses), the texture and composition of minerals (by means of grain size, petrology megascopic and microscopic analyses) (4) intergrating all of the analyses result. Madura waters can be divided into four zones, among all : (I) inner shelf (water depth less than 30 m) in Madura Strait, (II) inner shelf in open marine north of Madura, (III) outer shelf (water depth 30 to 80 m) in Madura Strait, and (IV) outer shelf in open marine north of Madura. Inner shelf in the Madura Strait (Zone I) is characterized by less than 1% sediment of nannoplankton (are made up of Gephyrocapsa oceanica); rare assemblages of benthic foraminifera only (Ammonia spp., arenaceous carbonate test taxa such as : Ammobaculites spp., Textularia agglutinans, Haplophragmoides spp., and milliolidae). Inner shelf open marine north of Madura (Zone II) yielded few nannoplankton assemblages, dominated by Gephyrocapsa oceanica with low number of Emiliania huxleyi, Helicosphaera carteri, H. pavimentum, H. walichii and Pontosphaera spp; common foraminifera assemblages consist of rare planktic Globigerinoides ruber, G. trilobus sacculiferus, G. conglobatus with one or two dominant benthic (Elphidium spp, Ammonia spp., Pseudorotalia spp., Asterorotalia spp.). Outer shelf of Madura Strait (Zone III) assigned by common nannoplankton assemblages, dominated by Gephyrocapsa oceanica and Emiliania huxleyi with few to common Helicosphaera carteri, H. pavimentum, H. wallichii, Pontosphaera spp., Calcidiscus leptoporus, Umbellosphaera irregularis and Umbilicosphaera spp.; common benthic foraminifera assemblages Elphidium spp, Ammonia spp., Cibicides spp., Pseudorotalia spp., and Asterorotalia spp. with rare planktic Globigerinoides ruber, G. trilobus sacculiferus, and G. conglobatus. In the outer shelf open marine north of Madura (Zone IV), it is recorded abundant of nannoplankton Gephyrocapsa oceanica, Emiliania huxleyi, Helicosphaera carteri, H. pavimentum, H. wallichii, Pontosphaera spp., Discoaster spp., Calcidiscus leptoporus, Umbellosphaera irregularis, Umbilicosphaera spp.; the presence of moderate divers and abundance of planktic foraminifera Globigerina calida, Pulleniatina obliquiloculata, Orbulina universa, Hastigerina aequilateralis with common abundance benthic Bolivina spp., Bulimina spp., Cibicides spp., Pseudorotalia spp., Asterorotalia spp., Lenticulina spp., Cassidulina spp., Siphonina spp., the presence of Uvigerina spp. are noted. The most significant physical environment parameter of each zone controlling appearance of marker species and abundancy of microorganism assemblages are bathymetry, salinity, temperature, pH and sediment due to fluvial supply.
