Paper No. 282-16
Presentation Time: 9:00 AM-6:30 PM
FORWARD MODELING δ13CCARB CHEMOSTRATIGRAPHIES ACROSS CARBONATE PLATFORMS
Across a carbonate platform, aliasing and distortion of a primary δ13Ccarb signal can arise from numerous syn-depositional processes, including local change in accommodation and heterogeneous geographic distribution of lithofacies, and post-depositional processes, such as diagenesis and stratigraphic sampling (Myrow and Grotzinger, 2000; Dyer et al., 2018). Nevertheless, local δ13Ccarb records routinely correlate across and between depositional settings. To explore the relative importance of these processes in dictating a local δ13Ccarb signal and the correlation of these signals across space, we adapted a numerical forward model of 3-D carbonate deposition (CarboCAT; Burgess, 2013) to include δ13Ccarb chemostratigraphy. CarboCAT employs a cellular automata modeling approach to model accommodation (parameterizing eustatic sea level and subsidence) and sediment accumulation (by tuning carbonate production rates and down-dip sediment transport). We present a variety of scenarios for two platform morphologies—a homoclinal ramp and flat-top platform—that isolate the role of carbonate production, carbonate transport, basin subsidence, and eustasy in dictating a local δ13Ccarb signal. The simplest scenarios neglect carbonate transport and explore how different parameterizations of the three depth-dependent carbonate production factories embedded in CarboCAT (proxies for lithofacies) fill accommodation over time. Subsequent scenarios add complexity by introducing sediment transport; time-dependent changes in accommodation through constant/differential subsidence or sinusoidal, multi-period sea level fluctuations; and, finally, combinations thereof. We alter δ13Ccarb values in cells adjacent to subaerial exposure surfaces to mimic diagenesis. Reference model parameterizations allow us to vary individual syn- or post-depositional processes to isolate their impact on intrabasinal δ13Ccarb correlation (e.g, across ramp or platform in a strike or dip direction). Comparison of model δ13Ccarb signals between the two platform morphologies probe the feasibility of interbasinal correlation (e.g, the δ13Ccarb record of the same geographic cell for the ramp versus platform model). We employ an algorithm to assess the alignment of modeled δ13Ccarb signals (Hay et al., 2019).