17 May 2023
 | 17 May 2023
Status: this preprint is currently under review for the journal BG.

Deciphering the origin of dubiofossils from the Pennsylvanian of the Paraná Basin, Brazil

João Pedro Saldanha Saldanha, Joice Cagliari, Rodrigo Sacalise Horodyski, Lucas Del Mouro, and Mírian Liza Alves Forancelli Pacheco

Abstract. Minerals are the fundamental record of abiotic processes over time, while biominerals, are one of the most common records of life due to their easy preservation and abundance. However, distinguishing between biominerals and abiotic minerals is challenging because the record is defined by the superimposition and repetition of geologic processes and the interference of ubiquitous and diverse life on Earth's surface and crust. Mineral dubiofossils, located on the threshold between abiotic and biotic, can help resolve this issue. The aim of this contribution is to decipher the origin and history of branched mineralized structures that were previously considered mineral dubiofossils. While this material has different forms and refers to biological aspects, it is difficult to associate it with any known Fossil Group due to the overlapping geological processes that occur in the Rio do Sul Formation (Pennsylvanian of the Paraná Basin), very close to the contact from a sill of the Serra Geral Group – Lower Cretaceous with a proven thermal effect. The samples were described using a protocol that evaluated: 1) morphology, texture, and structure; 2) relationship with the matrix; 3) composition and 4) context, assessing indigeneity and syngenicity, and comparing them with abiotic and biotic products. Despite conducting an extensive comparison with abiotic minerals, as well as controlled, induced, and influenced biominerals, no more probable hypothesis was found, excluding the possibility of it being a controlled biomineral due to its patternless diversity of forms and the purely thermometamorphic origin due to the branched elongated form. The occurrence of these structures suggests a complex history: a syndepositional or eodiagenetic origin of some carbonate or sulfate (gypsum, ikaite, dolomite, calcite, siderite), which may be linked to the presence of microbial mats, could have served as a template for mineralization and possibly mediated mineral growth. Mesodiagenesis could have also modified the occurrence, but the main agent responsible for its formation was the Cretaceous intrusion, which dissolved and replaced the initial mineral and precipitated calcite, resulting in the dubiofossil. Throughout these steps, physical-chemical and biological reactions, aided by the intrinsic characteristics of the matrix, amount of organic matter, and distance from contact with the intrusive body, may have increased the morphological complexity. This material illustrates how dubiofossils can be the result of a complex history and overlapping geological processes. It also highlights the difficulty in differentiating biominerals from abiotic minerals due to the scarcity of biogenicity arguments.

João Pedro Saldanha Saldanha et al.

Status: open (until 28 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2023-56', Gregory Retallack, 23 May 2023 reply

João Pedro Saldanha Saldanha et al.

João Pedro Saldanha Saldanha et al.


Total article views: 192 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
154 32 6 192 0 2
  • HTML: 154
  • PDF: 32
  • XML: 6
  • Total: 192
  • BibTeX: 0
  • EndNote: 2
Views and downloads (calculated since 17 May 2023)
Cumulative views and downloads (calculated since 17 May 2023)

Viewed (geographical distribution)

Total article views: 184 (including HTML, PDF, and XML) Thereof 184 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 01 Jun 2023
Short summary
the geological record is complex regardless of whether it is the result of biotic or abiotic processes. Overlapping and repeating chemical reactions occur over time, producing objects with exotic shapes or compositions distinct from the norm. Assessing the geological history is crucial particularly given the ubiquitous presence of life throughout the planet's surface and crust. We provide a detailed description to unravel the material's intricate history and evaluate the role of microorganisms.