A new orbit for comet C/1858 L1 (Donati)

A new orbit for comet C/1858 L1 (Donati), based on 1036 observations in α and 971 in σ made between 7 June 1858 and 5 March 1859, is calculated using iteratively reweighted least squares. Residuals were weighted by the Welsch weighting function. The orbit represents a high eccentricity ellipse, e = 0.996265, with large semi‐major axis, a = 154.8612 AU, and long period, P = 1927.22 yr. The residuals are relatively random, a 10.7% chance of being random, but with a slight indication of possible nongravitational forces influencing the motion. The comet will not return until the year 3759, when it will pass 0.8442 AU from the Earth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

川蔓藻在湖泊水位重建和环境变化研究中的应用

沉水被子植物川蔓藻广泛分布于海湾、泻湖、河口湿地以及内陆湖泊、沼泽、湿地中,是水生动物重要的食物和栖息地,具有改善水质和保护堤岸的作用。由于川蔓藻只能在小于0.5~4m深的浅水环境中生存,因此原地保存在湖泊沉积物中的化石种子可作指示古湖水深的定量指标。该项指标在闭流型湖泊水位重建和气候变化研究中有着不可忽视的重要作用。科学管理川蔓藻,对水体环境的改善、海洋污染的治理和湿地生物多样性下降的缓解具有重要价值。     

Chronology of Early to Mid-Pleistocene sediments in the northern North Sea: New evidence from amino acid and strontium isotope analyses

Sediments deposited during glacial-interglacial cycles through the Early to Mid-Pleistocene in the North Sea are chronologically poorly constrained. To contribute to the chronology of these units, amino acid racemization (AAR) and strontium (Sr) isotope analyses have been performed on samples from four shallow borings and one oil well along a transect in the northern North Sea. D/L Asp (aspartic acid) values obtained through reverse-phase liquid chromatography in the benthic foraminiferal species Elphidium excavatum is focused on because of consistent results and a good stratigraphic distribution of this benthic species. For the Early Pleistocene, an age model for the well 16/1–8, from the central part of the northern North Sea based on Sr ages allows for dating of the prograding wedges filling the pre-Quaternary central basin. A regional calibration curve for the racemization of Asp in Elphidium excavatum is developed using published ages of radiocarbon-dated samples and samples associated with the previously identified Bruhnes/Matuyama (B/M) paleomagnetic boundary and a Sr age from this study. Based on all the available geochronological evidence, samples were assigned to marine oxygen isotope stages (MIS) with uncertainties on the order of 10–70 ka.Sr ages suggest a hiatus of <2 million years (Ma) possibly due to non-deposition or low sedimentation between the Utsira Formation (Pliocene) and the Early Pleistocene. An increase in sedimentation rates around 1.5 ± 0.07 Ma (∼MIS 51) may partly be due to sediment supply from rivers from the south-east and partly due to the extension of ice sheet around 1.36 ± 0.07 Ma from the Norwegian coast to the central North Sea. A possible basin-wide glaciation occurred around 1.1 Ma (∼ MIS 32) (upper regional unconformity/top of unit Q4 in this study), resulting in erosion and regional unconformity. Two interglacials in the Norwegian Channel have been dated: the Radøy Interglacial to 1.07 ± 0.01 Ma (possibly MIS 31, the ‘super interglacial’), and the Norwegian Trench Interglacial to 0.50 ± 0.02 Ma (possibly MIS 13). A massive till unit identified at the same stratigraphic level in all shallow borings may partly represent an extensive MIS 12 glaciation. This study shows that the combined use of amino acid racemization data and Sr isotope chronology can refine the chronological ambiguities of Quaternary North Sea sediments related partly to the impact of glacial processes.