{"title":"通过对沉积学和有机岩石学的综合分析,厘清绿亨地层桥溪石灰岩组石灰岩-泥灰岩叠层的成因","authors":"","doi":"10.1016/j.coal.2024.104640","DOIUrl":null,"url":null,"abstract":"<div><div>Although limestone-marl bedding couplets in the Cenomanian-Turonian Bridge Creek Limestone (BCL) have been widely attributed to changes in environmental conditions ultimately driven by Earth's orbital cycles, the causes of short-term variations in organic matter (OM) enrichment and composition (i.e., types and proportions of different macerals) in the bedding couplets through the BCL have rarely been examined in detail. To fill this gap, this study examined the BCL through an integrated sedimentological and organic petrology analysis. With the well-developed depositional context, organic petrology analysis was conducted on 17 samples from seven limestone-marl bedding couplets consisting of different sedimentary facies types in the USGS #1 Portland Core to systematically examine differences in the maceral composition among different expressions of the limestone-marl bedding couplets. The BCL in the #1 Portland Core has overall low thermal maturity (∼0.60 % vitrinite reflectance). All BCL samples contain dominant marine OM including bituminite (dominantly micrinized), alginite, and liptodetrinite and minor but persistently present terrigenous OM including vitrinite and inertinite. The OM composition and characteristics, combined with sedimentary facies characteristics and TOC data, suggest that the OM enrichment and preservation through the BCL is subject to various processes such as bottom current reworking and burial, bioturbation, early diagenesis, and pulses of volcanic ash input. The interplay of these processes led to changes in sedimentation rate, which can be associated with short-term relative changes in sea level and episodic volcanic input. Direct examinations of the composition and texture of OM in fine-grained sedimentary rocks can provide valuable insights into the causes of short-term variations in depositional conditions on a process basis, which should be integrated with other datasets (e.g., sedimentology, geochemistry) to fully resolve the specific mechanism(s) that modulated sedimentation in similar fine-grained marine systems characterized by apparently cyclic lithological alternations.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6000,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Disentangling causes of the limestone-marl bedding couplets in the Bridge Creek Limestone Member of the Greenhorn Formation through an integrated sedimentological and organic petrology analysis\",\"authors\":\"\",\"doi\":\"10.1016/j.coal.2024.104640\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Although limestone-marl bedding couplets in the Cenomanian-Turonian Bridge Creek Limestone (BCL) have been widely attributed to changes in environmental conditions ultimately driven by Earth's orbital cycles, the causes of short-term variations in organic matter (OM) enrichment and composition (i.e., types and proportions of different macerals) in the bedding couplets through the BCL have rarely been examined in detail. To fill this gap, this study examined the BCL through an integrated sedimentological and organic petrology analysis. With the well-developed depositional context, organic petrology analysis was conducted on 17 samples from seven limestone-marl bedding couplets consisting of different sedimentary facies types in the USGS #1 Portland Core to systematically examine differences in the maceral composition among different expressions of the limestone-marl bedding couplets. The BCL in the #1 Portland Core has overall low thermal maturity (∼0.60 % vitrinite reflectance). All BCL samples contain dominant marine OM including bituminite (dominantly micrinized), alginite, and liptodetrinite and minor but persistently present terrigenous OM including vitrinite and inertinite. The OM composition and characteristics, combined with sedimentary facies characteristics and TOC data, suggest that the OM enrichment and preservation through the BCL is subject to various processes such as bottom current reworking and burial, bioturbation, early diagenesis, and pulses of volcanic ash input. The interplay of these processes led to changes in sedimentation rate, which can be associated with short-term relative changes in sea level and episodic volcanic input. Direct examinations of the composition and texture of OM in fine-grained sedimentary rocks can provide valuable insights into the causes of short-term variations in depositional conditions on a process basis, which should be integrated with other datasets (e.g., sedimentology, geochemistry) to fully resolve the specific mechanism(s) that modulated sedimentation in similar fine-grained marine systems characterized by apparently cyclic lithological alternations.</div></div>\",\"PeriodicalId\":13864,\"journal\":{\"name\":\"International Journal of Coal Geology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.6000,\"publicationDate\":\"2024-11-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"International Journal of Coal Geology\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0166516224001976\",\"RegionNum\":2,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ENERGY & FUELS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Coal Geology","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0166516224001976","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
Disentangling causes of the limestone-marl bedding couplets in the Bridge Creek Limestone Member of the Greenhorn Formation through an integrated sedimentological and organic petrology analysis
Although limestone-marl bedding couplets in the Cenomanian-Turonian Bridge Creek Limestone (BCL) have been widely attributed to changes in environmental conditions ultimately driven by Earth's orbital cycles, the causes of short-term variations in organic matter (OM) enrichment and composition (i.e., types and proportions of different macerals) in the bedding couplets through the BCL have rarely been examined in detail. To fill this gap, this study examined the BCL through an integrated sedimentological and organic petrology analysis. With the well-developed depositional context, organic petrology analysis was conducted on 17 samples from seven limestone-marl bedding couplets consisting of different sedimentary facies types in the USGS #1 Portland Core to systematically examine differences in the maceral composition among different expressions of the limestone-marl bedding couplets. The BCL in the #1 Portland Core has overall low thermal maturity (∼0.60 % vitrinite reflectance). All BCL samples contain dominant marine OM including bituminite (dominantly micrinized), alginite, and liptodetrinite and minor but persistently present terrigenous OM including vitrinite and inertinite. The OM composition and characteristics, combined with sedimentary facies characteristics and TOC data, suggest that the OM enrichment and preservation through the BCL is subject to various processes such as bottom current reworking and burial, bioturbation, early diagenesis, and pulses of volcanic ash input. The interplay of these processes led to changes in sedimentation rate, which can be associated with short-term relative changes in sea level and episodic volcanic input. Direct examinations of the composition and texture of OM in fine-grained sedimentary rocks can provide valuable insights into the causes of short-term variations in depositional conditions on a process basis, which should be integrated with other datasets (e.g., sedimentology, geochemistry) to fully resolve the specific mechanism(s) that modulated sedimentation in similar fine-grained marine systems characterized by apparently cyclic lithological alternations.
期刊介绍:
The International Journal of Coal Geology deals with fundamental and applied aspects of the geology and petrology of coal, oil/gas source rocks and shale gas resources. The journal aims to advance the exploration, exploitation and utilization of these resources, and to stimulate environmental awareness as well as advancement of engineering for effective resource management.