Exploring Challenges and Opportunities in Recognizing the Signature of Sea Level, Tectonic Subsidence, and Sediment Supply in the Stratigraphic Record: A Comparison of Field-based and Model-generated Data from Carbonate Sedimentary Records

Abstract:

Integrating field and model observations of marine carbonate strata, we investigate how distinct sedimentary basins respond to the same eustatic sea level history, specifically in terms of the preserved record of lithofacies and meter-scale depositional cycles. First, we compare two coeval Devonian sedimentary records characterized by different subsidence regimes (North American ‘stable’ cratonic interior vs. ‘passive’ continental margin) and rock accumulation rates (measured over m.y. time scales). Despite the greater potential for subaerial exposure due to minimal accommodation space, stratigraphic and petrographic analyses revealed the apparently significant role of suppressed subtidal sedimentation rates, along with submarine erosion and non-deposition, in limiting both the thickness and number of facies and cycles preserved in the cratonic record compared to the continental margin.

To explore insights gained from the field, we use a previously-developed, one-dimensional forward model to generate stratigraphic columns. Knowing the true history underlying each model run, we can test the sensitivity of the resultant stratigraphy to variation in subsidence and sedimentation rates, while maintaining the same eustatic sea level curve. For the model conditions explored, 1) thicker component depositional units reflect higher sedimentation rates; 2) total stratigraphic thickness, numbers of units, and stratigraphic completeness reflect combinations of low enough sedimentation rates and high enough subsidence rates to maintain sufficient accommodation space; and 3) the preserved stratal patterns rarely faithfully record sea level history. The model results lead to new questions that can direct future field studies. Overall, this approach can inform similar investigations in other carbonate, siliciclastic and non-marine records, especially over stratigraphic scales finer than the temporal resolution typically afforded by numerical ages and correlation techniques.