Deschamps Marianne, Zilhão João
UNIARQ - Centro de Arqueologia da Universidade de Lisboa, Faculdade de Letras de Lisboa, Universidade de Lisboa, Alameda da Universidade, Lisboa, Portugal.
CNRS UMR 5608 TRACES, Université de Toulouse Jean Jaurès, Toulouse, France.
PLoS One. 2018 Feb 16;13(2):e0192423. doi: 10.1371/journal.pone.0192423. eCollection 2018.
We use stone tool refitting to assess palimpsest formation and stratigraphic integrity in the basal units of the Gruta da Oliveira archeo-stratigraphic sequence, layers 15-27, which TL and U-series dating places in late Marine Isotope Stage (MIS) 5 or early MIS 4. As in most karst contexts, the formation of this succession involved multiple and complex phenomena, including subsidence, bioturbation, carnivore activity and runoff as agents of potential post-depositional disturbance. During phases of stabilization, such as represented by layers 15, 21 and 22, the excavated area was inhabited and refits corroborate that post-depositional displacement is negligible. Layers 23-25 and 16-19 correspond to subdivisions that slice thick geological units primarily formed of material derived from the cave's entrance via slope dynamics. Refit links are consistent with rapid fill-up of the interstitial spaces found in the Karren-like bedrock (for layers 23-25), or left between large boulders after major roof-collapse events (for layers 16-19). Layers 26 (the "Mousterian Cone") and 27 are a "bottom-of-hourglass" deposit underlying the main sedimentary body; the refits show that this deposit consists of material derived from layers 15-25 that gravitated through fissures open in the sedimentary column above. Layer 20, at the interface between two major stratigraphic ensembles, requires additional analysis. Throughout, we found significant vertical dispersion along the contact between sedimentary fill and cave wall. Given these findings, a preliminary analysis of technological change across the studied sequence organized the lithic assemblages into five ensembles: layer 15; layers 16-19; layer 20; layers 21-22; layers 23-25. The lower ensembles show higher percentages of flint and of the Levallois method. Uniquely at the site, the two upper ensembles feature bifaces and cleavers.
我们利用石器再修整来评估格鲁塔·达奥利维拉考古地层序列底部单元（第15 - 27层）中的叠覆形成和地层完整性，热释光（TL）和铀系测年将其置于晚海洋同位素阶段（MIS）5或早MIS 4。与大多数岩溶环境一样，这一序列的形成涉及多种复杂现象，包括沉降、生物扰动、食肉动物活动以及作为潜在沉积后干扰因素的径流。在稳定阶段，如第15、21和22层所代表的，挖掘区域有人居住，再修整证实沉积后位移可忽略不计。第23 - 25层和16 - 19层对应于细分部分，这些细分部分切割了主要由通过斜坡动力学从洞穴入口衍生而来的物质形成的厚地质单元。再修整联系与在似喀斯特基岩中发现的间隙空间（对于第23 - 25层）或在重大顶板坍塌事件后大石块之间留下的间隙空间（对于第16 - 19层）的快速填充一致。第26层（“莫斯特期锥”）和第27层是主要沉积体下方的“沙漏底部”沉积物；再修整表明该沉积物由从第15 - 25层通过上方沉积柱中开放的裂缝重力作用而来的物质组成。位于两个主要地层组合之间界面的第20层需要进一步分析。总体而言，我们在沉积填充物与洞穴壁的接触处发现了显著的垂直分散。基于这些发现，对整个研究序列的技术变化进行的初步分析将石器组合分为五个组合：第15层；第16 - 19层；第20层；第21 - 22层；第23 -
