Phytoliths, pollen, and microcharcoal from the Baringo Basin, Kenya reveal savanna dynamics during the Plio-Pleistocene transition
Phytoliths, pollen, and microcharcoal from the Baringo Basin, Kenya reveal savanna dynamics during the Plio-Pleistocene transition
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DOI：
10.1016/j.palaeo.2020.109779
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
Chad Yost;S. Ivory;A. Deino;N. Rabideaux;J. Kingston;A. Cohen
中科院分区：
文献类型：
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作者：
Chad Yost;S. Ivory;A. Deino;N. Rabideaux;J. Kingston;A. Cohen
作为古人类遗址和古湖泊钻探项目（HSPDP）的一部分，对228米（3.29至2.56 Ma）Baringo-Tugen Hills-Barsemoi钻孔岩芯（BTB 13）的植硅体、花粉和微炭进行了检查。总共收集了652个样本，间隔约为10至32厘米，对应于千年至千年尺度的时间分辨率。微炭保存完好，整个核心，并经常达到高峰，丰富约5 kyr之前和之后的日照高峰。植硅体保存在整个岩芯的交替间隔中从优秀到完全溶解。花粉很少保存。这些组合数据表明，在~3.1 Ma之前，木本覆盖在开阔的稀树草原（< 40%覆盖），林地（40-80%覆盖）和森林（> 80%覆盖）之间波动，具有典型的岁差（19-23 kyr）周期。在中期Piacenzian温暖期（MPWP; 3.26-3.01马），异常高的微碳丰度的间隔表明，区域营业额从树木繁茂的开放栖息地是由火驱动。在~3.1 Ma之后，低海拔木本植被覆盖可能从未超过40%，在岁差周期中，金属高草与旱生短草稀树草原之间存在振荡。Mesic C4高草（Panicoideae）在日照最大期间达到高峰，而旱生C4短草（Chloridoideae）在日照最小期间达到高峰。北方冰川作用（NHG）在~2.75 Ma开始，与深湖相的出现、草地密度和火灾频率的增加相一致。光谱分析和保存完好的植硅体的间隔表明，岁差和半球间的日照梯度影响植被通过其对赤道降水和火灾的影响。这项研究填补了东非大裂谷及其相关人类地点上新世植被重建的一个重要空白。它还提供了轨道分辨的区域植被数据，可用于MPWP（通常用作未来变暖的模拟）和NHG开始的古数据模型比较。
As part of the Hominin Sites and Paleolakes Drilling Project (HSPDP), phytoliths, pollen, and microcharcoal were examined from the 228 m (3.29 to 2.56 Ma) Baringo-Tugen Hills-Barsemoi drill core (BTB13). A total of 652 samples were collected at ~10 to 32 cm intervals, corresponding to sub-millennial to millennial scale temporal resolution. Microcharcoal was well-preserved throughout the core and often peaked in abundance ~5 kyr before and after insolation peaks. Phytolith preservation varied between excellent to total dissolution in alternating intervals throughout the core. Pollen was rarely preserved. These combined datasets indicate that prior to ~3.1 Ma, woody cover fluctuated between open savanna (< 40% cover), woodland (40–80% cover), and forest (> 80% cover) at typically precessional (19–23 kyr) periodicities. During the mid-Piacenzian Warm Period (MPWP; 3.26–3.01 Ma), intervals with exceptionally high microcharcoal abundance suggest that regional turnover from wooded to open habitats was driven in part by fire. After ~3.1 Ma, low-elevation woody cover likely never exceeded 40%, with oscillations between mesic tall-grass vs. xeric short-grass savanna at precessional periodicities. Mesic C4tall-grass (Panicoideae) peaked in abundance during insolation maxima, whereas xeric C4short-grass (Chloridoideae) peaked during insolation minima. The onset of Northern Hemisphere glaciation (NHG) at ~2.75 Ma coincided with the appearance of deep lake phases and increases in grass density and fire frequency. Spectral analysis and intervals with well-preserved phytoliths indicate that precession and interhemispheric insolation gradients influenced vegetation via their effects on equatorial precipitation and fire. This study fills a crucial gap in Pliocene vegetation reconstructions from the East African Rift Valley and its associated hominin localities. It also provides orbitally resolved regional vegetation data useful in paleodata–model comparisons for the onset of the MPWP (which is often used as an analog for future warming) and NHG.