During IODP expedition 359 multiple holes recovered Modern to Middle Miocene sediments from the Kardiva Drift which is strongly influenced by monsoonally-driven currents. Two holes continued below the drift into Lower Miocene sediments that were deposited under rather different conditions following Oligocene subsidence of the Maldives Ridge. These sediments are characterised by marked alternation between dark organic-rich sapropelic sediments and pale nannofossil oozes. This interval is also characterised by generally good to excellent nannofossil preservation. Nannofossil assemblages from the sapropel and non-sapropel intervals are broadly similar; both sediment types contain diverse normal marine assemblages and no taxa are confined to either sediment type. In the sapropels nannofossil abundance and diversity tends to be lower and Cyclicargolithus floridanus specimens are smaller. In addition Umbilicosphaera abundances are higher in the non-sapropel layers whilst Discoaster abundance is higher in most sapropels. These differences are more marked in the better developed sapropels. The nannofossil evidence supports the interpretation from geochemistry that sapropel formation was primarily driven by changes in bottom water ventilation linked to sea-level change rather than surface water productivity.

在IODP远征期间，有359个孔从Kardiva漂流中恢复了中新世至中新世的沉积物，这受到季风驱动流的强烈影响。在漂移下方继续有两个孔进入下中新世沉积物，这些沉积物是在马尔代夫山脊渐新世沉降之后在完全不同的条件下沉积的。这些沉积物的特征是深色富含有机物的腐泥沉积物和浅色纳米化石软泥之间明显交替。该间隔的特征还在于通常良好至优异的纳米化石保存。腐殖质和非腐殖质间隔的纳米化石组合大致相似。两种沉积物类型都包含各种正常的海洋组合，并且没有分类单元局限于任何一种沉积物类型。在腐烂植物中，纳米化石的丰度和多样性趋于降低，Cyclicargolithus floridanus标本较小。此外Umbilicosphaera的富足是在非腐泥层较高，而Discoaster丰度是最腐泥高。在更好的腐烂食品中，这些差异更为明显。纳米化石的证据支持了地球化学的解释，即腐殖质的形成主要是由与海平面变化相关的底部通风而不是地表水生产力引起的。