SEPM Field Conference - Assessing the competing roles of 

gravitational versus bottom-current processes from slope-to-basin across the southern margin of North America (E.-M. Mississippian)

Revising ramp depositional concepts!

Dates: 18-22 October 2026 (18-20 October Cookeville, Tennessee; 21 October 2026 Huntsville, Alabama)

Lead By:  C. Robertson Handford; Juan J. Fedele; and Buddy Price

Contact Robert Handford for additional information robert.handford@icloud.com

PREMISE

During the past two decades, oceanographic studies using multi-beam bathymetry surveys and shallow sub-bottom profiles have produced stunning, high-resolution images of present-day seafloor topography and shallow stratigraphy. They demonstrate that continental slopes and basin-floors are replete with erosional and depositional features indicating a more hydrodynamically active seafloor than previously recognized. For example, multi-beam surveys of upper to lower slopes in the Bahamas surprisingly revealed (1) abundant and widespread sediment-wave fields of upslope-migrating large-scale bedforms interpreted as cyclic steps (Betzler et al. 2014), and (2) numerous gullies with cyclic step bedforms, large-scale slide scars, and mass transport complexes (Mulder et al. 2012; Wunsch et al. 2017). It is generally thought that the sediment wave-fields and gullies were formed by dense shelf-water cascades (DSWC) that reached supercritical flow conditions of Fr>1 as they passed downslope. Furthermore, studies from the Bahamas and around the globe are showing that bottom currents (geostrophic and thermohaline) are extremely important in redistributing slope and basin-floor sediment to form extensive drift deposits with varying amounts of elongation and mounding (Hernandez-Molina et al. 2008; Rebesco et al. 2014). More recently, studies of continental slopes have shown that varying interaction between downslope gravity-driven flows and persistent but weaker along-slope bottom currents build significant accumulations of turbidite-dominated mixed systems, synchronous systems, and contourite-dominated mixed systems (Rodrigues et al. 2022). 

Discoveries showing a very rugose and dynamic seafloor molded by a variety of density flows and bottom-currents have surprised sedimentary geologists who study modern and ancient systems.  Most of the features were either unknown or underappreciated, and now their economic importance is beginning to impact hydrocarbon exploration, and CCUS investigations in under-explored and mature sedimentary basins. This was demonstrated at IMAGE 2025 during the SEPM Research Symposium – Mixed Turbidite-Contourite Reservoirs, which highlighted examples of these types of reservoirs and their importance towards changing paradigms about slope and basin-floor depositional systems.  In addition, locating submarine hazards requires fundamental understanding of these systems. 

Most of the documentation is from subsurface settings where they are imaged and mapped using high-resolution seismic reflection data. The ground-truth information that would come from direct examination of the sedimentological and stratigraphic characteristics by geoscientists in outcrops and/or cores is deficient and the only way to close that gap is by way of comparative studies. There are numerous outcrops around the world containing either gravitational-flow or along-slope deposits, but there are few places where they have been documented to occur together in accessible, slope-to-basin transects through the same stratigraphic interval, or formation. 

We propose an SEPM Research Conference to assess (1) the relative roles of downslope vs along-slope processes of density flows and bottom currents and (2) their temporal evolution in the classic Lower-Middle Mississippian carbonate shelf and ramp system along the southern margin of North America (Laurussia). The 5-day conference will include (a) field examination of world-class roadcuts, outcrops, and a quarry in a slope-to-basin transect through the Fort Payne Formation from south-central Kentucky, through Tennessee and into north Alabama and (b) evening oral/poster presentations, and discussions about the competing roles of downslope and along-slope processes and the global occurrence of these types of systems in the rock record. 

We have chosen the Lower-Middle Mississippian carbonates as the centerpoint of discussion and a field excursion because current and recently completed investigations (Handford, 2024; Handford and Betzler, 2024; Janson et al. 2025) have uncovered abundant sedimentological and stratigraphic evidence of gravitational downslope and along-slope bottom-current processes in basinward-transecting outcrops.  These new findings have led to a major revision of the standard hypothesis of a shelf-ramp system with low-angle clinothems built entirely by downslope sediment processes (Gutschick and Sandberg, 1983). In the Fort Payne Formation alone, outcrops display giant sediment waves, slope gullies, mass transport deposits, hybrid-event beds, and bedforms associated with Froude supercritical flow conditions, and along-slope bottom currents. Our conference will focus on (1) examining and characterizing stratal geometry, facies successions, and sedimentary structures, (2) discussing the possible range of sediment transport processes for the extraordinary assortment of crinoid-dominated bioclastic grains, and (3) sort out the relative roles of downslope gravity vs alongslope bottom-currents from proximal to distal settings.  

Registration Fee:  $1,125 

Includes:  All transportation via bus from Nashville Airport (BNA) to Cookeville, TN, Huntsville, AL and return to Nashville Airport (BNA); Field refreshments; Discounted hotel room block (breakfasts included at Cookeville and Huntsville - paid individually by attendees) - and Field safety equipment.

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Cancellation Policy: July 20th – 90% Refund; August 19th 50% Refund - Cancellations received after September 3rd no refund is available. 

PLANNED PROGRAM

Day 1 Sunday October 18: 

Participants arrive at Nashville International Airport (BNA), depart (time TBD) and travel 1.5 hours to Cookeville, Tennessee by bus to hotel.  

          Evening – informal gathering for introductions and overview of conference agenda and objectives and brief overview of regional Mississippian ramp system across southern margin of North America.

Day 2 Monday October 19 :

Gravitational deposits in the field. Visit outcrops displaying mass transport deposits (some interpreted previously as Waulsortian-type mounds), turbidites, stacked slope channels, and laterally accreting channel margins with hybrid-event beds, near Burkesville, Kentucky 

          Evening – Discussions of the field-stops and informal presentations by participants

Day 3 Tuesday October 20:

Morning – Gravitational and possible bottom-current deposits in the field. Visit roadcuts displaying mass transport deposits, thick mud-dominated slope deposits,   crinoid-rudstone sediment-waves, backset-beds in lee side of sediment waves, hydraulic-jump zone, and giant climbing antidunes near Celina, Tennessee

Afternoon – Gravitational and probable bottom-current deposits associated with muddy sediment waves and crinoid-grainstone and rudstone-filled gullies in 2d-3d orientation near Celina, Tennessee. 

Evening – Discussions of the field-stops and informal presentations by participants

Day 4 Wednesday October 21:

 Check-out from hotel in Cookeville and travel south to Huntsville, AL.

Morning – Overview of bottom-set migrating bedforms at Burgess Falls State Park. 

Afternoon – Transect giant sediment-wave train at Rock Island State Park. Upslope-migrating anti-dune sediment waves, detailed examination of bedforms in sediment wave troughs and lee slopes. Continue travel to Huntsville, Alabama and check-in to hotel.

Evening – Discussions of the field stops and informal presentations by participants

Day 5: Thursday October 22:

Check out from hotel in Huntsville and travel to Tanner quarry near Athens, Alabama.

Morning – Examine 3d high walls of quarry exposing large-scale sediment waves, truncation surfaces and bi-gradational beds indicating bottom current processes. Wrap-up discussion. Continue travel to Nashville International Airport (BNA). End of field trip and conference.