DISTRIBUTION PATTERNS OF NANNOFOSSIL GEPHYROCAPSA OCEANICA IN SURFICIAL SEDIMENTS OF JIAOZHOU BAY, SOUTHERN SHANDONG PENINSULA,CHINA
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Abstract:
Surficial sediment samples were collected from the Jiaozhou Bay and adjoining seawaters to study the spatial distribution patterns of calcareous nannofossils within the embayment. The result shows that Gephyrocapsa oceanica monopolized the nannofossil assemblage, whilst some subordinate taxa Braarudosphaera bigelowii, Syracosphaera histrica, S. lamina and Acantholithus sp. etc. scarcely occur in some samples. Three zones for the distribution of Gephyrocapsa oceanica are recognized, according to variations in its abundance value: They are the onshore common zone, shallow water rich zone and deep water accumulation zone, from the coastline to deep waters. Geomorphologically, these zones successively correspond to silty clay tidal flat, sub tidal erosional channels and submarine erosional highlands. The same nannofossil assemblage with an analogous distribution pattern is also observed on the adjacent continental shelf. It is well known that Emiliania huxleyi is one of the most common species in the ocean and Florisphaera profunda is a marker of deep water environments. However, these two species were not found in the study area, which may be explained by ecological controls related to water fertility and quality, and to water depth.
