Science. 1963 Feb 22;139(3556):727-37. doi: 10.1126/science.139.3556.727.
For a hundred years students of the Pleistocene have looked for evidence of the climatic change which initiated the Pleistocene epoch. Glacial deposits on the continents have been of little help because of their discontinuity and because of the destructive effect of later glaciations. Hence, Pleistocene geologists have turned to the uplifted Pliocene-Pleistocene marine sediments of the Mediterranean region. In the absence of evidence of a single, clearly defined climatic change in this sedimentary section, they have agreed to define the beginning of the Pleistocene by the first appearance of Anomalina baltica, a species of benthic Foraminifera tolerant of cool water. This definition leaves much to be desired: It rests on a single benthic species whose areal distribution must have been partly determined by local conditions on the sea floor; it is useless outside of the Mediterranean region; and there is no convincing evidence that the first appearance of Anomalina baltica in the Mediterranean coincided with the onset of the first glaciation.
一百年来，研究更新世的学生一直在寻找引发更新世的气候变化的证据。由于大陆冰川沉积物的不连续性以及后来的冰川作用的破坏性影响，它们的帮助不大。因此，更新世地质学家转而研究地中海地区抬升的上新世-更新世海洋沉积物。由于在这段沉积层中没有单一的、明确界定的气候变化的证据，他们同意将始新世的开始定义为波罗的海异常种的首次出现，这是一种对冷水有耐受性的底栖有孔虫。这个定义还有很多不足之处：它依赖于一个单一的底栖物种，其地域分布在一定程度上必须由海底的局部条件决定；在地中海地区以外，它毫无用处；而且没有令人信服的证据表明，波罗的海异常种在地中海的首次出现与第一次冰川作用的开始相吻合。
