214-7 Beyond Morphology – Reading Stromatolites As Accretionary Structures

Session: The Neoproterozoic Earth and Life Co-evolution, Part II

Presenting Author:

Authors:

Abstract:

Stromatolites have long been understood to be accretionary organosedimentary structures, whose final, observed morphology necessarily results from the accumulation of layers across time and environment. Despite this, stromatolites are generally described as single, coherent entities with a final, fixed morphology, rather than as composite structures resulting from multiple superposed morphologies. Linnaean nomenclature and non-genetic descriptive schemes both approach stromatolite form in this way. We argue that explicit treatment of stromatolites as accretionary structures provides a critical framework for interpreting stromatolite genesis and understanding stromatolite diversity over time.

Some stromatolite workers have recognized characteristic patterns and have sought to refine stromatolite nomenclature to specifically include accretionary phenomena. Explicit consideration of vertical morphological transitions, such as columnar to stratiform, columnar to branching, or conical to branching, record changes in synsedimentary conditions, such as water depth, water energy, or sedimentation rate. Seen this way, stromatolite ‘diversity’ is, in part, produced by changes in form linked to these environmental fluctuations. Therefore, the ability of a depositional system to foster stromatolite growth across multiple environments will, in part, determine the diversity of stromatolite form expressed in a basin. At the broadest scale, the late Mesoproterozoic peak of stromatolite morphological diversity can be explained by the intersection of a wide range of stromatolite-producing environments and low-relief, epeiric carbonate platforms that produced a spatial and temporal mosaic of such environments. Despite overall lower global diversity, the widespread epeiric carbonate platforms of the early Paleozoic also commonly contain stromatolites, suggesting an uptick in stromatolite-producing environments across low-relief continental substrates at this time. By examining stromatolites as accretionary structures, we may better unravel the factors that contribute to stromatolite distribution and diversity over time.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9300

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