{"title":"A report on palaeontological excavations and sampling in mudrocks: some guidelines","authors":"Walter Etter","doi":"10.1186/s13358-024-00305-w","DOIUrl":null,"url":null,"abstract":"More than 60% of the world’s sedimentary rocks are mudrocks (Potter et al., 1980; Schieber, 1998; Potter, 2003; the term mudrock is favored here over mudstone because the latter term was used to characterize a limestone texture; Dunham, 1962). From a palaeontological perspective these are, compared to sandstones and limestones, heavily undersampled. The main reason for this is that mudrocks decay in surface exposures to small chips, which develop with sun/heat and rain into an awkward pulp. The decay of the mudstone concomitantly destroys all macrofossils which are not durable. This comprises fossils with an aragonitic or delicate calcitic shell unless they are preserved as pyritic or internal calcitic molds or preserved within calcareous concretions. Therefore, most of the fossils are not recorded in surface exposures. In addition, sedimentologic investigations of mudrocks are hampered because (i) compaction makes sedimentary structures hardly recognizableand (ii) good thin sections of mudrocks are exceedingly difficult to manufacture. For micropalaeontological investigations, mudrocks rich in organic material are especially difficult to process. Standard treatments with boiling water, sodium carbonate solution, or peroxide H2O2 generally fail to dissolve much of the sediment so that the fine fraction (and in mudrocks we usually need the 63μm-fraction) largely consists of clay particle aggregates. Yet there are methods to dissolve these aggregates. Otherwise, picking the microfossils would become extremely laborious. In this paper, some guidelines for successful palaeontological work in mudrocks are outlined. These are based on the author’s personal experience. Examples from Jurassic mudrocks of Switzerland/Europe show that such excavations can be very rewarding.","PeriodicalId":56059,"journal":{"name":"Swiss Journal of Palaeontology","volume":null,"pages":null},"PeriodicalIF":3.0000,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Swiss Journal of Palaeontology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1186/s13358-024-00305-w","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"PALEONTOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
More than 60% of the world’s sedimentary rocks are mudrocks (Potter et al., 1980; Schieber, 1998; Potter, 2003; the term mudrock is favored here over mudstone because the latter term was used to characterize a limestone texture; Dunham, 1962). From a palaeontological perspective these are, compared to sandstones and limestones, heavily undersampled. The main reason for this is that mudrocks decay in surface exposures to small chips, which develop with sun/heat and rain into an awkward pulp. The decay of the mudstone concomitantly destroys all macrofossils which are not durable. This comprises fossils with an aragonitic or delicate calcitic shell unless they are preserved as pyritic or internal calcitic molds or preserved within calcareous concretions. Therefore, most of the fossils are not recorded in surface exposures. In addition, sedimentologic investigations of mudrocks are hampered because (i) compaction makes sedimentary structures hardly recognizableand (ii) good thin sections of mudrocks are exceedingly difficult to manufacture. For micropalaeontological investigations, mudrocks rich in organic material are especially difficult to process. Standard treatments with boiling water, sodium carbonate solution, or peroxide H2O2 generally fail to dissolve much of the sediment so that the fine fraction (and in mudrocks we usually need the 63μm-fraction) largely consists of clay particle aggregates. Yet there are methods to dissolve these aggregates. Otherwise, picking the microfossils would become extremely laborious. In this paper, some guidelines for successful palaeontological work in mudrocks are outlined. These are based on the author’s personal experience. Examples from Jurassic mudrocks of Switzerland/Europe show that such excavations can be very rewarding.
期刊介绍:
The Swiss Journal of Palaeontology publishes original research and review articles of interest to the international community in the fields of palaeontology, taxonomy and systematics, while recognising at the same time the importance of documenting high-quality palaeontological data in a regional context. Palaeobiology in combination with alpha taxonomy is a core topic of the journal.
Submitted papers should have an appeal as wide as possible, directed towards an international readership. Contributions should not have been simultaneously submitted elsewhere, and the overlap of content between related articles should be minimal. Duplications of text and the use of previously published illustrations without adequate citation are unacceptable. If a manuscript has two or more authors, both or all have to sign to confirm they all were involved in the work and have agreed to its submission. The preferred manuscript language is UK English, but consistently used US English is also acceptable. We encourage the publication of proceedings of international meetings as well as special thematic issues. Short contributions and book reviews are also accepted.
An international editorial team as well as guest editors guarantee that the thematic issues as well as all articles in regular issues are peer-reviewed and meet the highest standards.