Abstract Samples from six ocean drilling sites were analyzed quantitatively across a paleolatitude transect of the North Atlantic Ocean to determine the paleolatitudinal distribution of calcareous nannofossils in the late Oligocene and the effects of that distribution on biostratigraphic resolution. Quantitative methodology utilized a Detrended Correspondence Analysis (DCA), Nannofossil Temperature Index (NTI), and Shannon Index (H) to examine the paleoenvironmental gradients which exerted the most control over the distribution of species and their abundances. The DCA produced two axes which explain 82% of the data matrix. The DCA1 explaining 57% of the variance significantly correlates with the NTI suggesting that thermal controls were the most important factor in the paleoceanographic distribution of nannofossils. The DCA2 explained 25% of the variance and significantly correlates with the percent abundance of the taxon Reticulofenestra minuta as well as the Shannon Index, suggesting that surface water productivity was an important secondary control. The characteristics of the nannofossil assemblage distributions indicate the existence of a well-developed latitudinal diversity gradient in the late Oligocene of the North Atlantic. Based on the loss of biostratigraphic index taxa in higher paleolatitudes the primary limiter on biostratigraphic resolution for the late Oligocene North Atlantic is sea surface temperature, particularly cold-water regimes.

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北大西洋晚渐新世古纬度横断面钙质纳米化石的定量分析

摘要 对来自北大西洋古纬度横断面的六个大洋钻探地点的样品进行了定量分析，以确定晚渐新世钙质纳米化石的古纬度分布以及该分布对生物地层分辨率的影响。定量方法利用去趋势对应分析 (DCA)、纳米化石温度指数 (NTI) 和香农指数 (H) 来检查对物种分布及其丰度施加最大控制的古环境梯度。DCA 产生了两个轴，它们解释了 82% 的数据矩阵。解释 57% 方差的 DCA1 与 NTI 显着相关，表明热控制是纳米化石古海洋学分布中最重要的因素。DCA2 解释了 25% 的方差，并与分类群 Reticulofenestra minuta 的丰度百分比以及香农指数显着相关，表明地表水生产力是一个重要的二级控制。纳米化石组合分布特征表明北大西洋渐新世晚期存在发育良好的纬度多样性梯度。基于较高古纬度生物地层指数类群的损失，晚渐新世北大西洋生物地层分辨率的主要限制因素是海面温度，特别是冷水状态。纳米化石组合分布特征表明北大西洋渐新世晚期存在发育良好的纬度多样性梯度。基于较高古纬度生物地层指数类群的损失，晚渐新世北大西洋生物地层分辨率的主要限制因素是海面温度，特别是冷水状态。纳米化石组合分布特征表明北大西洋渐新世晚期存在发育良好的纬度多样性梯度。基于较高古纬度生物地层指数类群的损失，晚渐新世北大西洋生物地层分辨率的主要限制因素是海面温度，特别是冷水状态。