Stratigraphic aliasing and the transient nature of deep-water depositional sequences: Revisiting the Mississippi Fan

Abstract

Sequence stratigraphy remains the foremost methodology used to describe the stratigraphic record and to interpret the controls on deposition; yet, it relies on long-standing assumptions that few studies have sought to validate. Here, we present results from testing hypotheses related to the deep-water depositional sequence model by revisiting the seismic-based type locality: the Mississippi Fan, in the central Gulf of Mexico. By independently testing the relationship between cycles of relative sea-level change and those of sedimentation, we demonstrate that >98% of Neogene-Quaternary deep-water sequences do not accumulate in a manner prescribed by long-held sequence stratigraphic conventions. Instead, over the past 5.5 Myr, sequences show a temporal mismatch in frequency, phase, and amplitude with cycles of relative sea-level change, a concept we refer to as stratigraphic aliasing. Divergences are attributed to variable rates of sedimentation, which were responsible for creating cycle frequencies that were both higher and lower than those of relative sea-level change, and that resulted in two modes of Mississippi Fan accumulation: lower average sedimentation rates in older sediments, and an opposite trend in younger successions. The latter mode occurred ~2.2 Myr after the onset of North American glaciation, a period marked by significant continental drainage reorganization and salt-tectonic deformation. Based on our conclusions, we recommend that the future of sequence stratigraphy be rooted firmly in assessing the reproducibility of preexisting spatiotemporal predictions and in the rigorous use of multiple working hypotheses.

Reproducibility in Subsurface Geoscience

“…Similar studies have been undertaken in geospatial research such as Konkol et al (2019) who demonstrated technical issues with spatial statistics results they reproduced from several papers. In addition to these, targeted studies focusing on specific type localities which inform many of our subsurface models, such as Madof et al (2019) reassessment of the Mississippi Fan sequences should be encouraged.…”

Peak Cenozoic warmth enabled deep-sea sand deposition

“…Nevertheless, coarse-grained deep-marine deposition during high sea level may occur at a local level (1) along narrow shelves of tectonically active margins 12 – 15 ; (2) if shelf-penetrating canyons intersect the shoreline 12 – 14 , 16 ; (3) during episodes of exceptionally voluminous sediment supply 15 , 17 , 18 ; and (4) via other factors such as turbidite initiation by shelf undercurrents, longshore drift, orbital forcing, subglacial meltwater, and monsoons 13 , 19 , 20 . Despite such exceptions, and some debate about the general applicability of sequence stratigraphy 21 , the prevailing paradigm predicts minimal development of sand-rich deep-water systems along passive margins during high sea level. To test this hypothesis, we look to one of the most notable periods of elevated eustatic sea level of the Cenozoic: the warm early Eocene interval 22 , 23 .…”

Reproducibility in subsurface geoscience

“…Testing of and modification to this model soon ensued (e.g., Hunt & Tucker 1992), and alternative models/interpretations (Helland-Hansen & Gjelbeg 1994) arose. Madof et al (2019) revisited one of the type locations (the Mississippi Fan) to re-evaluate the original models, concluding that sequence stratigraphy presents an oversimplification and called into question the concepts of accommodation-driven reciprocal sedimentation. This is not to say that the ideas within sequence stratigraphy are not useful, in fact they have been extremely important for hydrocarbon exploration.…”