Environmental determinism in Holocene research: causality or coincidence?

The past decade has seen a revival of environmental determinism in palaeoenvironmental research, with palaeoclimatic shifts implicated in the collapse of many past civilizations. Implicit in these studies is a belief that the observed cultural transitions can be causally related to the magnitude of climatic change. However, examination of the processes of these declines suggests that many exhibit patterns characteristic of complexity cascading within self-organized systems. If so, the nonlinear nature of these systems' responses to external forcing means that the assumption of causality in many of these cases should be considered questionable.     

Wildfires and seasonal aridity recorded in Late Cretaceous strata from south-eastern Arizona, USA

Lithostratigraphic and organic chemostratigraphic studies of fluvial/lacustrine sediments in the Late Cretaceous Fort Crittenden Formation in south-eastern Arizona USA, reveal changes in palaeoclimate and tectonics as well as associated fluctuations in lake level. The lower Fort Crittenden is dominated by marginal wetland to deep-water lake deposits, whereas the upper Fort Crittenden is characterized by wetland to deltaic deposits. Abundance of polycyclic aromatic hydrocarbons (PAH) and reflectance of fusinite substantiate the impact of wildfires within the watershed. Organic geochemical evidence of wildfires is linked with sedimentological indicators of seasonal aridity suggesting that wildfires were common occurrences. Sedimentological evidence for seasonal aridity includes mottles and pseudoslickensides on ped structures within wetland mudstones. Distinct variations in PAH assemblages, characterized by the number of aromatic rings, indicate that there were variations in the intensities of wildfires, assuming no variations in the types of fuel. Fusinite reflectance values are consistent with combustion temperatures from 470 to 550 °C observed in modern wildfires.     

四川盆地非海相三叠系-侏罗系界线研究

对四川盆地几条典型的三叠系一侏罗系界线剖面的生物标志、岩性特点、沉积层序及古气候变化进行综合研究，发现Coniopteris属的始现为三叠系一侏罗系界线的古植物标志、双壳类Margaritifern（Qiyangia）的首现和孢粉中孢子与花粉百分含量在界线上、下的显著变化也可作为三叠系一侏罗系界线的生物标志，三叠系一侏罗系界线之上的岩石组合大致可分为4种基本类型：砾岩型、石英砂岩夹砾岩型、石英砂岩型和粉砂质泥岩型。建议重庆合川炭坝剖面及宣汉七里峡剖面分别为四川盆地非海相三叠系一侏罗系界线层型剖面和副层型剖面。     

Reconstructing the Palaeoclimate of Jæren, Southwestern Norway, for the Period 1821–1850, from Historical Documentary Records

Documentary data provide long time series and sometimes high-resolution, detailed data from historical times to the present and can give valuable information about palaeoclimate, and for the prediction of future climates. In this paper, documentary data containing qualitative information on climate, in the form of a diary written by the farmer I.G. Grude, and two newspapers, were used for the reconstruction of the palaeoclimate at Jæren, in the county of Rogaland, in southwestern Norway, during the period 1821–50. An index method to quantify the qualitative climate data was developed and used for a low-resolution reconstruction of winter, summer and annual temperatures. A high-resolution climate reconstruction of temperature and precipitation for the winter of 1837/38 is also presented, making use of a method that keeps the climate data in a qualitative form. The climate reconstructions are compared to an instrumental temperature series from Bergen, for the same period. The two data sets are in good agreement except for summer temperature (annual temperature: r = 0.75, winter temperature: r = 0.77, summer temperature: r = 0.44). Compared to average temperatures during 1961–90, the instrumental data from Bergen during the 1821–50 period show slightly different temperatures: annual average was 0.3°C lower, winter 0.4°C lower, and summer 0.1°C lower than at present, implying conditions consistent with the "Little Ice Age" climate.     

山西大同煤田晚石炭世晚期和早二叠世早期植物群

对山西大同煤田晚石炭世晚期和早二叠世早期植物化石进行了研究，共鉴定植物化石２１属４８种，划分２个植物组合，讨论了植物群的特征和时代；此外，还论证了本区晚石炭世晚期和早二叠世早期植物群指示的古气候条件     

北京延庆盆地早更新世孢粉组合及其气候地层学意义

本文孢粉化石是通过延庆盆地杨户庄、阜高营及东龙湾地区地层剖面研究的。自上而上划分个孢粉组合带、植被演替和气候变化阶段。１．Ｑｕｅｒｃｕｓ－Ｒａｎｕｎｃｕｌａｃｅａｅ－Ｇｒａｍｉｎａｅ，针阔混交林－草原，气候温暖偏干。２．Ｐｉｎｕｓ－Ｐｏｌｅｍｏｎｉａｃｅａｅ，森林－草原，气候温凉干爽。３．Ｑｕｅｒｃｕｓ－Ｐｉｎｕｓ－Ｇｒａｍｉｎａｅ，针阔混交林－草原，气候温暖干燥。４．Ａｂｉｅｓ－Ｐｉｃｅａ－Ｐｏ     

定量重建贵州梵净山一万年以来的植被与气候

在孢粉分析和＾１４Ｃ测定年龄资料的基础上，以现代梵净山植被带及其气候状况为类比系统，应用主成分分析方法，定量重建贵州梵净山１万年以来的古植被和古气候演化历史，将其分为三个阶段：１０－７．８ｋａＢ．Ｐ．，７．８－２．７ｋａＢ．Ｐ．和２．７ｋａ Ｂ．Ｐ到现在，依次为升温期，高温期和降温期、其中高温期年平均温度比现代年平均温度高出１．６－３．３℃。１万年以来的年降水量比较稳定，使本地区一直处于较湿润状态     

云南西部羊邑和龙陵地区晚上新世植被和古气候

云南西部羊邑和龙陵地区晚上新世孢粉组合均以被子植物占优势，蕨类和裸子植物次之，藻类类群少。龙陵孢粉组合比羊邑孢粉组合含有更丰富的亚热带被子植物成分；裸子植物类群相对较少；蕨类类群较多，但孢子含量低。与研究地区现生植被对比研究的结果显示羊邑孢粉组合的大部分类群来自常绿针阔叶混交林，现在分布于羊邑地区海拔2800-3100m的地带，其余部分来自海拔3200m以上的云冷杉林；而龙陵孢粉组合的大部分类群来自山地湿润常绿阔叶林，分布于今日龙陵地区海拔1600-2500m的地带，其余部分来自海拔2300-2900m的常绿针阔叶混交林。这些云南西部晚上新世植被反映了湿润的亚热带山地立体气候。