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根据鄂尔多斯盆地神木煤田延安组1~(-1)、1~(-2)及2~(-2)煤层的平均光泽和结构特征,划分出了12种宏观煤岩类型。显微研究表明,该区煤中均质镜质体的含量较高,且多为草本植物和灌木类所组成,因此认为根皮镜质体的大量存在是该区煤的主要煤岩特征之一。此外,一些过渡型显微组分,如半镜质体和半丝质体的含量也相对高。依据因子分析和聚类分析结果并结合凝胶化指数和结构保存指数,划分出4种沼泽相:开阔水域水生植物淤泥相、深覆水草甸沼泽相、浅覆水草本灌木混生沼泽相和陆地森林沼泽相。 相似文献
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Mathematical Geosciences - 相似文献
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Mathematical Geosciences - 相似文献
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Cathy Whitlock Maria Martha Bianchi Vera Markgraf Megan Walsh 《Quaternary Research》2006,66(2):187-201
The history of the low-elevation forest and forest-steppe ecotone on the east side of the Andes is revealed in pollen and charcoal records obtained from mid-latitude lakes. Prior to 15,000 cal yr BP, the vegetation was characterized by steppe vegetation with isolated stands of Nothofagus. The climate was generally dry, and the sparse vegetation apparently lacked sufficient fuels to burn extensively. After 15,000 cal yr BP, a mixture of Nothofagus forest and shrubland/steppe developed. Fire activity increased between 13,250 and 11,400 cal yr BP, contemporaneous with a regionally defined cold dry period (Huelmo/Mascardi Cold Reversal). The early-Holocene period was characterized by an open Nothofagus forest/shrubland mosaic, and fire frequency was high in dry sites and low in wet sites; the data suggest a sharp decrease in moisture eastward from the Andes. A shift to a surface-fire regime occurred at 7500 cal yr BP at the wet site and at 4400 cal yr BP at the dry site, preceding the expansion of Austrocedrus by 1000-1500 yr. The spread of Austrocedrus is explained by a shift towards a cooler and wetter climate in the middle and late Holocene. The change to a surface-fire regime is consistent with increased interannual climate variability and the onset or strengthening of ENSO. The present-day mixed forest dominated by Nothofagus and Austrocedrus was established in the last few millennia. 相似文献
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C. G. Adams 《Geological Journal》1985,20(2):187-190
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