University of Wisconsin Milwaukee UWM Digital Commons Theses and Dissertations May 2015 Microbially Induced Sedimentary Structures as an Ecological Niche in Subtidal Early Triassic Environments of Eastern Panthalassa Erin Wimer University of Wisconsin-Milwaukee Follow this and additional works at: https://dc.uwm.edu/etd Part of the Ecology and Evolutionary Biology Commons, Geology Commons, and the Paleontology Commons Recommended Citation Wimer, Erin, "Microbially Induced Sedimentary Structures as an Ecological Niche in Subtidal Early Triassic Environments of Eastern Panthalassa" (2015). Theses and Dissertations. 847. https://dc.uwm.edu/etd/847 This Thesis is brought to you for free and open access by UWM Digital Commons. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of UWM Digital Commons. For more information, please contact [email protected]. MICROBIALLY INDUCED SEDIMENTARY STRUCTURES AS AN ECOLOGICAL NICHE IN SUBTIDAL EARLY TRIASSIC ENVIRONMENTS OF EASTERN PANTHALASSA by Erin E. Wagner A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Geosciences at The University of Wisconsin-Milwaukee May 2015 ABSTRACT MICROBIALLY INDUCED SEDIMENTARY STRUCTURES AS AN ECOLOGICAL NICHE IN SUBTIDAL EARLY TRIASSIC ENVIRONMENTS OF EASTERN PANTHALASSA by Erin Wagner The University of Wisconsin-Milwaukee, 2015 Under the Supervision Dr. Margaret Fraiser, PhD Early Triassic microbially induced sedimentary structures (MISS) are a critical link in understanding the dynamics between changing environmental conditions and their effect on marine communities. The Permo-Triassic mass extinction (PTME) resulted in vacated ecospace and reduced bioturbation that allowed MISS to expand into Early Triassic subtidal environments. Data from southern Idaho and Montana indicate that MISS inhabited and proliferated in subtidal marine environments during the Griesbachian. This propagation led to changes in shallow substrate geochemical conditions that directly affected macrofaunal communities. The proliferation of microbial mats would have created anoxic and euxinic porewaters and made vertical bioturbation physiologically difficult. Geochemical data shows the bottom water signals associated with MISS were oxic to suboxic, but the porewaters below the microbial mat surface could have been anoxic even if the overlying water column was oxygenated. However, some metazoans adapted to these low-oxygen, shallow euxinic environments, allowing them to expand their ecological range during this period of crisis. Two ii metazoans with such adaptations were the lingulid brachiopods, which have the ability to oxidize hydrogen sulfide in their blood, and the bivalve Claraia, which was well suited to low oxygen environments. These specific disaster taxa, defined as opportunists that occupy vacated ecospaces during recovery periods but are subsequently forced into marginal settings when the recovery gains momentum, were found in direct contact with these MISS. These findings indicate that the subtidal proliferation of MISS during the Early Triassic provided an ecological niche in which specific metazoans had complex and extensive relationships. iii ©Copyright by Erin Wagner, 2015 All Rights Reserved iv TABLE OF CONTENTS List of Figures…………………………………………………………………………………………………………… vii List of Tables……………………………………………………………………………………………………………. x 1) Chapter 1: Introduction…………………………………………………………………………….. 1 a) Permo-Triassic Mass Extinction………………………………………………………………... 1 b) Early Triassic Aftermath……….………………………………………………………………….. 4 i) Evidence for Continued Environmental Stresses…………………………... 4 ii) Biotic Recovery and Restructuring ……………………………………………….. 7 c) Microbially Induced Sedimentary Structures…………………………………………… 9 i) Description…………………………………………………………………………………… 9 ii) Previous Work on Early Triassic MISS………………………………………….. 11 d) Scientific Significance……………………………………………………………………………… 12 i) MISS as an Ecological Niche Hypothesis ………………………………………. 12 ii) Contributions of this Research ……………..……………………..……………… 13 2) Chapter 2: Geologic Setting………………………………………………………………………. 13 3) Chapter 3: Methods………………………………………………………………………………….. 16 i) Field Methods………………………………………………………………………………… 16 ii) Lab Methods…………………………………………………………………………………. 18 1) Photogrammetry………………………………………………………………. 18 2) Thin Sections…………………………………………………………………….. 20 3) XRF…………………………………………………………………………………….. 22 v 4) Chapter 4: Results: Stratigraphic Analysis…………………………………………………. 25 i) Bear Lake, ID………………………………………………………………………………….. 25 1) Interpretation……………………………………………………………………. 29 ii) Montpelier Canyon, ID………………………………………………………………….. 29 1) Interpretation…………………………………………………………………… 32 iii) Hidden Pasture, MT…………………………………………………………………….. 33 1) Interpretation……………………………………………………………….... 37 5) Chapter 5: Results: Photogrammetry………………………………………………………… 38 6) Chapter 6: Results: Thin Sections………………………………………………………………. 40 7) Chapter 7: Results: Classification of MISS in the Griesbachian…………………… 43 8) Chapter 8: Results: Geochemical Analysis……………………………………………….... 47 9) Chapter 9: Results: MISS and their Associated Fossils……………………………….. 52 10) Chapter 10: Discussion……………………………………………………………………………… 54 i) Environmental Implications of MISS Following the PTME……………… 54 ii) Geochemical Evidence Against Anoxia………………………………………….. 57 ii) Opportunism and Disaster Taxa……………………………………………………. 59 iv) MISS as an Ecological Niche…………………………………………………………. 62 11) Chapter 11: Conclusion……………………………………………………………………………… 64 12) References………………………………………………………………………………………………… 65 vi LIST OF FIGURES Figure Page 1. δ13C record for the Late Permian through the Middle Triassic. δ13C data from stratigraphic sections on the Great Bank of Guizhou in southern China. Modified from Payne and Kump, 2007. …………………… 5 2. Image showing the 17 different types of MISS classified by their Modes of formation. Modified from Noffke, 2009. …………………………... 10 3. Inferred map of Early Triassic globe (~252 My). Star indicates relative area of study locations on Eastern Panthalassan low-to-mid paleolatitude section. Image modified from Ron Blakely & Colorado Plateau Geosystems. …………………………………………………………………………. 14 4. Map of western United States showing boundary and inferred boundary of the Dinwoody Formation during the Griesbachian. Blue triangles indicate localities studied: BC = Blacktail Creek, Montana, HP = Hidden Pasture, Montana, MC = Montpelier Canyon, Idaho, and BL = Bear Lake, Idaho. Image modified from Paull and Paull, 1983. ….. 15 5. Genetic process diagram for MISS from both muddy and sandstone substrates. Modified from Schieber et al., 2007. ………………………………… 17 6. Diagram showing how photogrammetry develops x, y, and z coordinates for each point and triangulates the aiming angles for each image. Modified from Geodetic Systems website (http://www.geodetic.com/v-stars/what-is-photogrammetry.aspx). … 19 7. Biolaminate containing matrix-supported sediment grains with their long axes parallel to the laminations. Modified from Schieber et al., 2007. …………………………………………………………………………. 21 8. (Left) Base of Dinwoody Formation at Bear Lake. Section is overturned, overlying strata is Permian-aged Phosphoria Formation. (Right) Top of Dinwoody section at Bear Lake. ………………………………………………………… 25 9. Basal unit of Dinwoody at Bear Lake. ………………………………………………… 26 10. (Top) Sample from top unit of Dinwoody at Bear Lake. Arrows indicate the bivalve Claraia and circle indicates MISS on same bedding plane. (Bottom) Magnified image of MISS from above image. ……………………… 27 vii 11. Stratigraphic column of Bear Lake, Idaho. Includes ichnofabric indices (ii) chart to the right of the column. Dots on ii graph indicate data Points where information was collected. …………………………………………… 28 12. (Left) Image of Dinwoody Formation at Montpelier Canyon. Circle indicates basal unit containing MISS. (Right) Close up of basal unit of Dinwoody showing laminations and bedding. …………………………………… 29 13. MISS from basal unit of Dinwoody Formation at Montpelier Canyon. .. 30 14. Stratigraphic column of Montpelier Canyon, Idaho. Includes ichnofabric indices (ii) chart to the right of the column. Dots on ii graph indicate data points where information was collected. ……………. 31 15. Stratigraphic column of Hidden Pasture, Montana. Includes ichnofabric indices (ii) chart to the right of the column. Dots on ii graph indicate data points where information was collected. …………………………………… 34 16. MISS from Dinwoody Formation at Hidden Pasture. (Left) Found at approximately 180 m and (Right) and 225 m respectively. ………………… 35 17. Ripples from Dinwoody Formation at Hidden Pasture at approximately 195 m. ……………………………………………………………………………………………….. 36 18. (Top) Photogrammetry trial run that produced an image that created a “+” configuration of pictures. The blue boxes represent individual pictures taken. (Bottom) Photogrammetry attempt that developed an “H” shaped configuration. ………………………………………………………………... 39 19. (Left) Image of Montpelier Canyon thin section under 10x magnification. Yellow line indicates outline of alternating light and dark laminations. Dashed yellow line indicates inferred boundary of light and dark laminations. (Right) Same Montpelier Canyon thin section under 10x magnification. Yellow arrows indicate elongate mica grains oriented parallel to the crinkles and laminations. Orange arrows indicate altered minerals. Both of these thin sections are from Bed 1 of the Dinwoody Formation at Montpelier Canyon. ……………………………….. 40 viii 20. (Left) Image of Hidden Pasture thin section