Resolving MISS Conceptions and Misconceptions: a Geological Approach to Sedimentary Surface Textures Generated by Microbial and Abiotic Processes
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Earth-Science Reviews 154 (2016) 210–246 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Resolving MISS conceptions and misconceptions: A geological approach to sedimentary surface textures generated by microbial and abiotic processes Neil S. Davies a,⁎, Alexander G. Liu b, Martin R. Gibling c, Randall F. Miller d a Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom b School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, United Kingdom c Department of Earth Sciences, Dalhousie University, PO Box 15000, Halifax, Nova Scotia B3H 4R2, Canada d Steinhammer Palaeontology Laboratory, New Brunswick Museum, Saint John, New Brunswick E2K 1E5, Canada article info abstract Article history: The rock record contains a rich variety of sedimentary surface textures on siliciclastic sandstone, siltstone and Received 30 October 2015 mudstone bedding planes. In recent years, an increasing number of these textures have been attributed to surfi- Received in revised form 7 January 2016 cial microbial mats at the time of deposition, resulting in their classification as microbially induced sedimentary Accepted 11 January 2016 structures, or MISS. Research into MISS has developed at a rapid rate, resulting in a number of misconceptions in Available online 15 January 2016 the literature. Here, we attempt to rectify these MISS misunderstandings. The first part of this paper surveys the stratigraphic and environmental range of reported MISS, revealing that contrary to popular belief there are more Keywords: Microbial induced sedimentary structures reported MISS-bearing rock units of Phanerozoic than Precambrian age. Furthermore, MISS exhibit a pan- Siliciclastic environmental and almost continuous record since the Archean. Claims for the stratigraphic restriction of MISS Microbial mats to intervals prior to the evolution of grazing organisms or after mass extinction events, as well as claims for Sedimentary structures the environmental restriction of MISS, appear to result from sampling bias. In the second part of the paper we Precambrian suggest that raised awareness of MISS has come at the cost of a decreasing appreciation of abiotic processes Palaeozoic that may create morphologically similar features. By introducing the umbrella term ‘sedimentary surface tex- Ediacaran tures’, of which MISS are one subset, we suggest a practical methodology for classifying such structures in the Cambrian geological record. We illustrate how elucidating the formative mechanisms of ancient sedimentary surface tex- Permian Triassic tures usually requires consideration of a suite of sedimentological evidence from surrounding strata. Resultant Mass extinction interpretations, microbial or non-microbial, should be couched within a reasonable degree of uncertainty. This Mars approach recognizes that morphological similarity alone does not constitute scientific proof of a common origin, Kinneyia and reinstates a passive descriptive terminology for sedimentary surface textures that cannot be achieved with Wrinkle structures the current MISS lexicon. It is hoped that this new terminology will reduce the number of overly sensational Runzelmarken and misleading claims of MISS occurrence, and permit the means to practically separate initial observation Adhesion ripples from interpretation. Furthermore, this methodology offers a scientific approach that appreciates the low likeli- Synaeresis cracks hood of conclusively identifying microbial structures from visual appearance alone, informing the search for Raindrop impressions true MISS in Earth's geological record and potentially on other planetary bodies such as Mars. Trace fossils Bioturbation © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Contents 1. Introduction.............................................................. 211 2. MISSconceptionsandmisconceptions.................................................. 213 2.1. MISSintherockrecord...................................................... 215 2.2. SurveyofMISSdistribution.................................................... 215 2.2.1. StratigraphicrangeofreportedMISS............................................ 217 2.2.2. EnvironmentalrangeofreportedMISS........................................... 219 2.2.3. Implicationsfornon-actualisticandanachronisticfacies................................... 219 2.2.4. Implicationsfortaphonomicstudies............................................ 220 ⁎ Corresponding author. E-mail address: [email protected] (N.S. Davies). http://dx.doi.org/10.1016/j.earscirev.2016.01.005 0012-8252/© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). N.S. Davies et al. / Earth-Science Reviews 154 (2016) 210–246 211 2.2.5. Implicationsforthecompositionofmicrobialcommunities................................. 220 2.3. SummaryofthedistributionofreportedinstancesofMISS..................................... 221 3. RevaluatingMISSterminology...................................................... 221 3.1. Thewrinkleproblem...................................................... 221 3.2. Sedimentarysurfacetextures:anumbrellatermforMISS,problematicandabioticfeatures....................... 222 3.3. Theformationofsedimentarysurfacetextures........................................... 223 3.3.1. Textures formed by sticking (adhesion, accretion and baffling)(Figs.6-8)........................... 224 3.3.2. Texturesformedbyloading(Fig.9)............................................ 224 3.3.3. Textures formed by fluidorgasescape(Fig.10)...................................... 224 3.3.4. Texturesformedbyimpression(Fig.11).......................................... 227 3.3.5. Texturesformedbyshear(Fig.12)............................................ 229 3.3.6. Texturesformedbyshrinkage(Fig.13).......................................... 230 3.3.7. Textureswithpalimpsest,mimicandproblematicorigins.................................. 231 3.4. Pseudo-MISS.......................................................... 233 3.5. Preservationofsedimentarysurfacetextures............................................ 234 4. Distinguishingbioticandabioticsedimentarysurfacetexturesintherockrecord............................... 235 4.1. Associationofbioticandabiotictextures.............................................. 236 4.2. Criteriaforbiogenicityandthinsectionevidence.......................................... 236 4.3. Interpreting sedimentary surface textures in the field — a practical classification............................ 236 5. Conclusions.............................................................. 240 Acknowledgements............................................................. 242 References................................................................. 242 1. Introduction repeated: (1) that MISS are more common in the Precambrian than the Phanerozoic; (2) that MISS are most often associated with non- Bedding surfaces in siliciclastic strata commonly preserve a wide va- actualistic environmental and taphonomic conditions in certain inter- riety of textures and small-scale sedimentary structures formed during, vals of geological history; (3) that MISS are predominantly shallow- or shortly after, deposition by physical, chemical or biological processes marine or tidal features; (4) that MISS were mostly, or exclusively, pro- (Fig. 1a-x). Such textures have an array of forms including, but not re- duced by photoautotrophic cyanobacteria; and (5) that MISS rarely stricted to, small pits, wrinkles, millimetre-scale ripples, bubble-like occur in conjunction with higher metazoan life. A further unfortunate textures, warts and a variety of intermediate forms. Modern analogy and unintended effect of the rapid rise of MISS studies has been that can clearly be used to explain certain textures, such as the pitted im- the abiotic role in forming certain sedimentary surface textures, includ- pressions left by raindrop impact, whereas some textures, such as wrin- ing some wrinkle structures, has become increasingly overlooked. A kle structures or runzelmarken (Häntzschel and Reineck, 1968; Reineck, wealth of largely 20th century research showing how sedimentary sur- 1969; Teichert, 1970; Hagadorn and Bottjer, 1997; Porada and Bouougri, face textures of almost identical form to proven MISS may be formed by 2007a, 2007b) have, until recent years, often been regarded as more purely physical processes including adhesion, loading, fluid escape, im- enigmatic. When observed in the rock record, sedimentary surface tex- pact, flow and shrinkage is at risk of being lost in the literature as studies tures may be divorced from their formative mechanisms by millions or increasingly focus on searching for a microbial role. The potential impact billions of years. Furthermore, the interpretation of these mechanisms of overlooking such abiotic forms may be detrimental, not only because can be problematic where modern and experimental analogues show some reported “MISS” in the literature may actually be abiotic features that different processes result in almost identical forms. Debates about (Wellman and Strother, 2015), but also because physical structures which formation mechanisms may best explain given sedimentary themselves can reveal important palaeoenvironmental