Lacustrine stromatolites: Useful structures for environmental interpretation – an example from the Miocene Ebro Basin. Issue 6 (18th March 2019)

• Record Type: Journal Article
• Authors: Martin‐Bello, Leticia; Arenas, Concha; Jones, Brian
• Editors: Brasier, Alexander
• Is Part Of: Sedimentology. Volume 66:Issue 6(2019)
• Page Start: 2098
• Page End: 2133
• Publication Date: 2019-03-18
• Subjects: Environmental indicators -- lacustrine stromatolites -- lamination patterns -- morphogenesis factors -- saline carbonates -- storm and fair‐weather conditions; Sedimentology -- Periodicals; 552.5
• DOI: 10.1111/sed.12577
• Languages: English
• ISSNs: 0037-0746

Abstract

Abstract: The significance of stromatolites as depositional environmental indicators and the underlying causes of lamination in the lacustrine realm are poorly understood. Stromatolites in a ca 600 m thick Miocene succession in the Ebro Basin are good candidates to shed light on these issues because they are intimately related to other lacustrine carbonate and sulphate facies, grew under variable environmental conditions and show distinct lamination patterns. These stromatolites are associated with wave‐related, clastic‐carbonate laminated limestones. Both facies consist of calcite and variable amounts of dolomite. Thin planar stromatolites (up to 10 cm thick and less than 6 m long) occurred in very shallow water. These stromatolites represented first biological colonization after: (i) subaerial exposure in the palustrine environment (i.e. at the beginning of deepening cycles); or (ii) erosion due to surge action, then coating very irregular surfaces on laminated limestones (i.e. through shallowing or deepening cycles). Sometimes they are associated with evaporative pumping. Stratiform stromatolites (10 to 30 cm high and tens of metres long) and domed stromatolites (10 to 30 cm high and long) developed in deeper settings, between the surge periods that produced hummocky cross‐stratification and horizontal lamination offshore. Changes in stromatolite lamina shape, and thus in the growth forms through time, can be attributed to changes in water depth, whereas variations in lamina continuity are linked to water energy and sediment supply. Growth of the stromatolites resulted from in situ calcite precipitation and capture of minor amounts of fine‐grained carbonate particles. Based on texture, four types of simple laminae are distinguished. The simple micrite and microsparite laminae can be grouped into light and dark composite laminae, which represent, respectively, high and low Precipitation/Evaporation ratio periods. Different lamination patterns provide new ideas for the interpretation of microbial laminations as a function of variations in climate‐dependent parameters (primarily the Precipitation/Evaporation ratio) over variable timescales.