Catalan Institution for Research and Advanced Studies, Research Group for Palaeoecological and Geological Studies, Department of Prehistory, Ancient History and Archaeology, University of Barcelona, Montalegre 6-8, Barcelona, Spain.
J Hum Evol. 2012 Aug;63(2):342-50. doi: 10.1016/j.jhevol.2011.05.010. Epub 2011 Sep 19.
As part of ongoing research at Olduvai Gorge, Tanzania, to determine the detailed paleoenvironmental setting during Bed I and Bed II times and occupation of the basin by early hominins, we present the results of phytolith analyses of Tuff IF which is the uppermost unit of Bed I. Phytoliths were identified in most of the levels and localities on the eastern paleolake margin, but there are not always sufficient numbers of identifiable morphologies to infer the specific type of vegetation due to dissolution. Some surge surfaces and reworked tuff surfaces were vegetated between successive ash falls, as indicated by root-markings and the presence of a variety of phytolith morphotypes. Dicotyledonous wood/bark types were dominant except at the FLK N site just above Tuff IF when monocots are dominant and for the palm-dominated sample from the reworked channel cutting down into Tuff IF at FLK N. The area between the two fault scarps bounding the HWK Compartment, approximately 1 km wide, was vegetated at various time intervals between some of the surges and during the reworking of the Tuff. By lowermost Bed II times the eastern margin was fully vegetated again. Climate and tectonic activity probably controlled the fluctuating lake levels but locally the paleorelief and drainage were probably the controlling factors for the vegetation changes. These data support a scenario of small groups of hominins making brief visits to the paleolake during uppermost Bed I times, followed by a more desirable vegetative environment during lowermost Bed II times.
作为坦桑尼亚奥杜威峡谷持续研究的一部分，旨在确定 I 层和 II 层时期的详细古环境背景以及早期人类在盆地中的活动情况，我们介绍了 I 层最上层的 IF 凝灰岩的植硅体分析结果。在东部古湖边缘的大多数地层和地点都发现了植硅体，但由于溶解作用，并非总能识别出足够数量的可识别形态来推断特定的植被类型。有些涌浪面和再作用凝灰岩表面在连续的火山灰降落后被植被覆盖，这表明有根迹和各种植硅体形态类型的存在。除了在 IF 凝灰岩上方的 FLK N 点以 monocots 为主导，以及在 FLK N 处切入 IF 凝灰岩的再作用渠道中以棕榈为主导的样本外，被子植物木/树皮类型占主导地位。在 HWK 隔槽两侧的两个断层崖之间的区域，宽约 1 公里，在一些涌浪和再作用凝灰岩期间的不同时间间隔都有植被生长。到最下层 II 层时期，东部边缘再次完全被植被覆盖。气候和构造活动可能控制了湖泊水位的波动，但局部的古地形和排水可能是植被变化的控制因素。这些数据支持了一个情景，即在最上层 I 层时期，小群人类短暂访问古湖，随后在最下层 II 层时期出现了更适宜的植被环境。
