The postglacial history of three Picea species in New England, USA

Given the difficulty of separating the three Picea species—P. glauca, P. mariana, and P. rubens (white, black, and red spruce)—in the pollen record, little is known about their unique histories in eastern North America following deglaciation. Here we report the first use of a classification tree analysis (CART) to distinguish pollen grains of these species. It was successfully applied to fossil pollen from eight sites in Maine and one in Massachusetts. We focused on the late glacial/early Holocene (14,000 to 8000 cal yr B.P.) and the late Holocene (1400 cal yr B.P. to present)—the two key periods since deglaciation when Picea has been abundant in the region. The result shows a shift from a Picea forest of P. glauca and P. mariana in the late glacial to a forest of P. rubens and P. mariana in the late Holocene. The small number of P. rubens grains identified from the late glacial/early Holocene samples (<5%) suggests that that species was either absent or rare at most of the sites. The occurrence and distribution of the three species do not reveal any geographic or temporal trend during late glacial time, but the data suggest that they were distributed in local patches on the landscape. The results of this study indicate that the recent population expansion of Picea (1000 to 500 cal yr B.P.) was likely the first time since deglaciation that P. rubens was abundant in the region.     

A record of late-Holocene environmental change from southern New England, USA

Analyses of a sediment core from Little Pond, located in the town of Bolton, Massachusetts, provide new insights into the history of environmental and ecological changes in southern New England during the late Holocene. Declines in organic content and peaks in the abundance of Isoetes spores indicate reduced water depth at 2900–2600, 2200–1800, and 1200–800 calibrated years before present (cal yr BP), generally consistent with the timing of dry conditions in records from elsewhere in the northeastern United States. The Little Pond pollen record features little change over the last 3000 yr, indicating that the surrounding vegetation was relatively insensitive to these periods of drought. The 1200–800 cal yr BP dry interval, however, coincides with increased abundance of Castanea pollen, suggesting that the expansion of Castanea in southern New England may have been influenced by late-Holocene climatic variability.     

Use of CART analysis to differentiate pollen of red pine (Pinus resinosa) and jack pine (P. banksiana) in New England

The identification of fossil pollen at the generic rather than species level is hampering progress in understanding the biogeography and dynamics of paleo-vegetation. We used CART analysis to facilitate the differentiation of fossil pollen of Pinus banksiana and Pinusresinosa, which are morphologically similar and nearly always combined in paleoecological studies. The CART model, using four of the ten morphological traits measured, exhibited a high level of correct identification for pollen of each of the species and shows promise as a tool for increasing the detail of paleoecological records and inferences.     

A re-evaluation of Ophiomorpha burrows in the Wealden Group (Lower Cretaceous) of southern England

Attribution of burrows in the Wealden Group of southern England to Ophiomorpha is rejected. The burrows are essentially cylindrical, unlined and with a meniscate fill. Any outer knobbly appearance is due to diagenetic poikilotopic cementation or to differential weathering of a mudchip-sand fill. The variable nature of meniscate fill reflects passage of the producer through the thin-bedded, alternating sand-mud sediments or along sand-mud interfaces. The burrows are assigned to Beaconites, though, since the identity of this ichnotaxon has been questioned, reference is also made to Taenidium. Two ichnoassociations are recognized: (1) a Beaconites antarcticus-Scoyenia (or Taenidium-Scoyenia) association (Weald Clay) of marginal lacustrine situation with fluvial input, and (2) a Beaconites barretti-Planolites (or Taenidium-Planolites ) association of the fluvial (lacustrine delta) of the Lee Ness Sandstone (Ashdown Formation). The Wealden burrows offer no inherent indications of palaeosalinity, and inferences made on supposed occurrences of Ophiomorpha in the Wealden Group must be reassessed. Other occurrences of Ophiomorpha in non-marine facies are questioned.     

Palynodinium minus sp. nov., a new dinoflagellate cyst from the Cretaceous–Paleogene transition in New Zealand; its significance and palaeoecology

This is the first record of a representative of the organic-walled dinoflagellate cyst genus Palynodinium from the New Zealand region. Previously, Palynodinium grallator has been reported from two sites in offshore Tasmania during Ocean Drilling Program, Leg 189. The new species Palynodinium minus is found consistently in latest Maastrichtian? and earliest Danian strata (latest Haumurian–earliest Teurian) in two sections located along the mid-Waipara and Grey rivers, North Canterbury, South Island. It occurs in a narrow stratigraphic interval at the Cretaceous–Paleogene transition and is potentially a stratigraphically important index species in the region. Its range coincides with that of the global earliest Danian index fossil Carpatella cornuta and a basal Danian acme interval of Trithyrodinium evittii, and is correlated to ca. 65.5–65.2 Ma. Its highest occurrence is at the base of an acme interval of Palaeoperidinium pyrophorum. It has only been recorded from sections composed of siliciclastic shelf sediments, suggesting that it might have had a palaeoecological preference for relatively near-shore environments.     

1982~2022年《岩石矿物学杂志》期刊数据与研究主题分析

岩石学和矿物学是地球科学的重要分支学科,相关研究能够深入了解行星形成演化、宜居地球的资源富集与环境变化等重要科学问题。《岩石矿物学杂志》是国内岩石学和矿物学领域的重要期刊,对其发表文章的深入挖掘有助于梳理学科研究进展,为学科从业人员深入研究提供背景信息,为该刊未来刊文方向提供借鉴参考。采用大数据分析和可视化技术对《岩石矿物学杂志》1982~2022年发表的文献进行计量化研究。研究发现,岩石学和矿物学一直是该刊的主要发文领域,地球化学、花岗岩、锆石U-Pb定年、吸附和矿物学是高频率主题关键词。其中,地球化学的共现强度最高,与花岗岩、岩石成因、火山岩和岩石学等关键词关系密切;其次是晶胞参数,相关关键词有光学性质、粉晶数据和新矿物等。具体研究内容包括5个不同主题:岩石成分和特征分析、变质作用和岩石变质过程研究、矿床特征和成矿过程研究、沉积环境和地层特征分析以及环境矿物学研究。与国内外岩石学、矿物学领域知名期刊数据进行对比,认为未来刊文鼓励新技术、新方法的开发与应用、多学科交叉研究、大数据和机器学习驱动的新范式研究等。