Stable isotopic (δ13C and δ18O) signatures of biogenic calcretes marking discontinuity surfaces: a case study from Upper Cretaceous carbonates of central Dalmatia and eastern Istria, Croatia

Brlek, Mihovil; Glumac, Bosiljka

doi:10.1007/s10347-014-0403-7

Cited by 12 publications

(9 citation statements)

References 61 publications

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“…Therefore, although these results must be taken with caution, because of the crucial issues making isotope data interpretation of calcretes problematic, namely polyphased calcretization, influence of host rock, diagenetic re-setting and time-averaging (cf. Budd et al, 2002;Wright, 2007;Brlek and Glumac, 2014;Narkiewicz and Rettalack, 2014), to which in the present case likely late fluid circulation related to burial compaction may have to be added, the overall data consistency suggests that these are meaningful trends.…”

Section: Isotopesmentioning

confidence: 48%

“…Wright et al, 1997;Cerling, 1999;Tandon and Andrews, 2001;Budd et al, 2002;Brlek and Glumac, 2014;Narkiewicz and Rettalack, 2014) and with the other sedimentological data of this study. Therefore, although these results must be taken with caution, because of the crucial issues making isotope data interpretation of calcretes problematic, namely polyphased calcretization, influence of host rock, diagenetic re-setting and time-averaging (cf.…”

Section: Isotopesmentioning

confidence: 93%

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Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal

Azerêdo

Wright

Filho

et al. 2015

Sedimentary Geology

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Section: Isotopesmentioning

confidence: 48%

Section: Isotopesmentioning

confidence: 93%

Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal

Azerêdo

Wright

Filho

et al. 2015

Sedimentary Geology

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“…Our analyses compared samples from the limey Turonian age Shivta Formation located in the arid region with samples from the dolomitic Turonian age Gerofit Formation located in the hyperarid environment. The Negev Desert, Israel, has maintained arid to hyperarid conditions since the Holocene and has an aridity index (P/PET) of 0.05-0.005 (Amit et al, 2010;Bruins, 2012), which is similar to other arid and hyperarid areas worldwide, e.g. the Namib and Atacama deserts (Azua-Bustos et al, 2012;Viles and Goudie, 2007).…”

Section: Study Sitementioning

confidence: 97%

The origin and role of biological rock crusts in rocky desert weathering

et al. 2019

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Abstract. In drylands, microbes that colonize rock surfaces have been linked to erosion because water scarcity excludes traditional weathering mechanisms. We studied the origin and role of rock biofilms in geomorphic processes of hard lime and dolomitic rocks that feature comparable weathering morphologies, although these two rock types originate from arid and hyperarid environments, respectively. We hypothesized that weathering patterns are fashioned by salt erosion and mediated by the rock biofilms that originate from the adjacent soil and dust. We used a combination of microbial and geological techniques to characterize rock morphologies and the origin and diversity of their biofilms. Amplicon sequencing of the SSU rRNA gene suggested that bacterial diversity is low and dominated by Proteobacteria and Actinobacteria. These phyla only formed laminar biofilms on rock surfaces that were exposed to the atmosphere and burrowed up to 6 mm beneath the surface, protected by sedimentary deposits. Unexpectedly, the microbial composition of the biofilms differed between the two rock types and was also distinct from the communities identified in the adjacent soil and settled dust, showing a habitat-specific filtering effect. Moreover, the rock bacterial communities were shown to secrete extracellular polymeric substances (EPSs) that form an evaporation barrier, reducing water loss rates by 65 %–75 %. The reduced water transport rates through the rock also limit salt transport and its crystallization in surface pores, which is thought to be the main force for weathering. Concomitantly, the biofilm layer stabilizes the rock surface via coating and protects the weathered front. Our hypothesis contradicts common models, which typically consider biofilms to be agents that promote weathering. In contrast, we propose that the microbial colonization of mineral surfaces acts to mitigate geomorphic processes in hot, arid environments.

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“…Such values are typical indicators to carbon isotope exchange of primary marine CaCO 3 (abundant in the bedrock) with CO 2 released by microbial respiration (i.e. of carbon originating from photosynthesis) with subsequent precipitation of pedogenic calcrete (Brlek & Glumac, 2014;Mora, Driese, & Seager, 1991). Analysing δ 13 C, together with δ 18 O, compositions of pedogenic carbonates is a useful way of reconstructing paleo-vegetation (e.g., C3/C4 plant ratio; Ehleringer, Cerling, & Helliker, 1997;Mora et al, 1991).…”

Section: Composition and Chemical Characteristics Of The Rock Crustsmentioning

confidence: 99%

Reply to Anonymous Reviewer #1

Angel¹

2019

Preprint

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This article is a non-peer reviewed preprint published at EarthArXiv Highlights/significance:  Tafoni (honeycomb) weathering patterns were observed at similar frequency and magnitude in hard lime and dolomitic rocks originating from arid and hyperarid environments, respectively, despite different lithologies and climate.  In drylands, rock surfaces are colonised by an epilithic microbial community, dominated by bacteria that form a biological rock crusts.  The microbial communities on the hard lime and dolomitic rocks were dominated by members of the phyla Proteobacteria and Actinobacteria that are typical to drylands.  The two BRC communities were nevertheless distinct from each other, but also from the surrounding soil and dust, showing the habitat filtering effect of the rock surfaces.  Microbial and geological tools applied in this study suggest that in drylands biological rock crusts mitigate rock weathering processes by forming an evaporation barrier.

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Stable isotopic (δ13C and δ18O) signatures of biogenic calcretes marking discontinuity surfaces: a case study from Upper Cretaceous carbonates of central Dalmatia and eastern Istria, Croatia

Cited by 12 publications

References 61 publications

Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal

Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal

The origin and role of biological rock crusts in rocky desert weathering

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