Jon Lima-Zaloumis, Jack D. Farmer, Elizabeth Trembath-Reichert
{"title":"Rapid diagenesis and microbial biosignature degradation in spring carbonates from Crystal Geyser, Utah, U.S.A.","authors":"Jon Lima-Zaloumis, Jack D. Farmer, Elizabeth Trembath-Reichert","doi":"10.2110/jsr.2023.028","DOIUrl":null,"url":null,"abstract":"Carbonate rocks retain a well preserved record of biologically associated structures at the outcrop to millimeter scale; however, microscale features such as cellular fossils are rarely represented. The lack of microscale textural information in ancient carbonates is commonly attributed to processes relating to carbonate diagenesis. However, there are relatively few examples of precisely how and when these destructive processes occur, particularly in active precipitating systems. To better understand the taphonomy of carbonate precipitating environments through early diagenesis, we investigated Crystal Geyser, an active cold-water carbonate spring (∼ 18°C) located in Grand County, Utah. Here we show that rapid precipitation is effective at initially capturing cell-like structures and forming associated microscale laminated stromatolites; however, these morphologies degrade immediately after their formation. We attribute destructive diagenetic effects to the recrystallization of metastable aragonite into the more stable polymorph calcite (i.e., inversion) and the associated textural coarsening that homogenizes and erases the original fabric (i.e., aggrading neomorphism). Despite the loss of microscale morphological information, chemical biosignatures in the form of macromolecular organics remain dispersed throughout the disrupted carbonate textures. These observations provide an example of penecontemporaneous diagenesis that obliterates primary microscale textures in carbonate rocks. Similar mechanisms and their rapid timing, as shown here, likely contributes to the observed lack of microscale morphological biosignatures in many ancient carbonates. This work further highlights that in such systems, permineralization by a more stable crystalline phase, such as chert, must occur rapidly after deposition to effectively retain these signatures over geological timescales.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0000,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Sedimentary Research","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.2110/jsr.2023.028","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Carbonate rocks retain a well preserved record of biologically associated structures at the outcrop to millimeter scale; however, microscale features such as cellular fossils are rarely represented. The lack of microscale textural information in ancient carbonates is commonly attributed to processes relating to carbonate diagenesis. However, there are relatively few examples of precisely how and when these destructive processes occur, particularly in active precipitating systems. To better understand the taphonomy of carbonate precipitating environments through early diagenesis, we investigated Crystal Geyser, an active cold-water carbonate spring (∼ 18°C) located in Grand County, Utah. Here we show that rapid precipitation is effective at initially capturing cell-like structures and forming associated microscale laminated stromatolites; however, these morphologies degrade immediately after their formation. We attribute destructive diagenetic effects to the recrystallization of metastable aragonite into the more stable polymorph calcite (i.e., inversion) and the associated textural coarsening that homogenizes and erases the original fabric (i.e., aggrading neomorphism). Despite the loss of microscale morphological information, chemical biosignatures in the form of macromolecular organics remain dispersed throughout the disrupted carbonate textures. These observations provide an example of penecontemporaneous diagenesis that obliterates primary microscale textures in carbonate rocks. Similar mechanisms and their rapid timing, as shown here, likely contributes to the observed lack of microscale morphological biosignatures in many ancient carbonates. This work further highlights that in such systems, permineralization by a more stable crystalline phase, such as chert, must occur rapidly after deposition to effectively retain these signatures over geological timescales.
期刊介绍:
The journal is broad and international in scope and welcomes contributions that further the fundamental understanding of sedimentary processes, the origin of sedimentary deposits, the workings of sedimentary systems, and the records of earth history contained within sedimentary rocks.