The Palaeocene-Eocene organic sedimentary archives comprising lignites, carbonaceous shales, and shales from the Palana Formation of the Bikaner-Nagaur Basin, Rajasthan, India, are investigated in this study using elemental and biogeochemical proxies. The objectives of this investigation are to elucidate the sources of organic matter and their responses to palaeoredox and palaeoclimatic conditions, as well as to reconstruct the palaeoenvironment of the organic matter deposition. Elemental distributions, Rock Eval pyrolysis, stable carbon isotope, n-alkane and its ratios, acyclic isoprenoids and terpenoid biomarkers are employed as the tools to carry out this research. The hydrogen index shows that the samples contain type III, admixed type II-III and type II kerogen. The presence of admixed type II-III kerogen in the samples may indicate mixing of terrestrial plant-derived organic matter with autochthonous organic matter in a coastal depositional setting. Deposition in a coastal setting may also raise the possibility of organic matter supply from coastal vegetation. The large HI values (>300 mg HC/g TOC) may result from selective preservation of hydrogen-rich biomolecules derived from terrestrial and coastal vegetation. The stable carbon isotopic composition of bulk organic matter (−30.66 to −25.51‰) and the organic carbon to organic nitrogen ratio (26.62–131.12) may suggest that the organic matter was sourced primarily from C₃ plants. The integration of these two parameters may also indicate that mangroves supplied significant amount of organic matter to the coastal peatland. The n-alkane distributions and carbon preference indices show the derivation of organic matter from waxy terrestrial plants, aquatic submerged vegetation, and microbial communities. The palaeohydrological proxies, i.e., proxy-aqueous ratio (0.24–0.86), proxy-wax ratio (0.33–0.84), and average chain length (26.32–28.30) may illustrate intermittent changes in organic matter sources (mangrove-dominated emergent vegetation and waxy plants to aquatic submergent plants and vice-versa) and their relations with shifts in palaeohydrological conditions of mire and associated palaeoclimatic oscillations between wet (high rainfall) and dry spells (low rainfall). Additionally, terpenoid distributions reveal organic matter input from angiosperms (including mangroves) (olean-12-ene, de-A-olean-13(18)-ene, de-A-lupane, and other de-A-triterpenoids), conifers (C₁₈ diterpane, abietane, and ent-beyerane) and microbial sources (hopanoids). Besides, regarding the palaeodepositional environment, acyclic isoprenoid distributions (pristane and phytane), relative hydrocarbon potential, and the newly introduced palaeoredox factor may put forward mostly suboxic to oxic redox conditions of organic matter deposition. The total organic carbon and sulfur contents may further imply deposition of organic matter in topogenous-transitional mire conditions under a marginal marine/coastal environment. In complementary, the ranges of production index (0.01–0.19), T_max (388–422 °C) and the presence of 17β(H),21β(H)-hopanes (ββ hopanes), 17α(H),21β(H)-homohopane, hop-17(21)-ene, ββ-hopanes, norhopanes and angiosperm-derived unsaturated triterpenoids may suggest thermal immaturity of organic matter in the studied samples.

本研究使用元素和生物地球化学代理研究了古新世-始新世有机沉积档案，包括褐煤、碳质页岩和印度拉贾斯坦邦比卡内尔-纳高尔盆地 Palana 组的页岩。本次调查的目的是阐明有机质的来源及其对古氧化还原和古气候条件的响应，重建有机质沉积的古环境。元素分布，Rock Eval 热解，稳定碳同位素，n-烷烃及其比率、无环类异戊二烯和萜类生物标志物被用作开展这项研究的工具。氢指数显示样品含有III型、混合II-III型和II型干酪根。样品中混合的 II-III 型干酪根的存在可能表明陆生植物来源的有机质与沿海沉积环境中的本土有机质混合。沿海环境中的沉积也可能增加沿海植被提供有机物质的可能性。大的 HI 值（>300 mg HC/g TOC）可能是由于选择性保存来自陆地和沿海植被的富氢生物分子所致。大块有机质的稳定碳同位素组成（-30.66 至 -25.51‰）和有机碳与有机氮的比率（26.62-131.₃种植物。这两个参数的整合也可能表明红树林为沿海泥炭地提供了大量的有机物质。该ñ- 烷烃分布和碳偏好指数显示来自蜡质陆生植物、水生植物和微生物群落的有机物质。古水文指标，即代理水比 (0.24–0.86)、代理蜡比 (0.33–0.84) 和平均链长 (26.32–28.30) 可能说明有机物质来源（以红树林为主的新兴植被和蜡质植物到水生沉水植物，反之亦然）以及它们与泥沼古水文条件变化和潮湿（高降雨量）和干旱（低降雨量）之间相关古气候振荡的关系。此外，萜类分布揭示了来自被子植物（包括红树林）（olean-12-ene、de-A-olean-13(18)-ene、de-A-lupane 和其他 de-A-triterpenoids）、针叶树的有机质输入（C_{18 二}萜、松香烷和 ent-beyerane）和微生物来源（hopanoids）。此外，关于古沉积环境，无环类异戊二烯分布（原始烷烃和植烷烃）、相对烃潜力和新引入的古氧化还原因子可能会提出有机质沉积的主要是低氧到好氧的氧化还原条件。总有机碳和硫含量可能进一步暗示有机物质在边缘海洋/沿海环境下地源过渡泥沼条件下的沉积。作为补充，生产指数的范围（0.01-0.19），T _max (388–422 °C) 和 17β(H),21β(H)-hopanes (ββhopanes), 17α(H),21β(H)-homohopane, hop-17(21)-ene, ββ- hopanes、norhopanes 和被子植物衍生的不饱和三萜类化合物可能表明所研究样品中有机物质的热不成熟。