Geology topics

John R. Suter

Publications and source records attributed to John R. Suter.

5 recordsLinked to original sources

USGS1991

Late quaternary geologic framework, north-central Gulf of Mexico

The geologic framework of the north-central Gulf of Mexico shelf is composed of multiple, stacked, delta systems. Shelf and nearshore sedimentary facies were deposited by deltaic progradation, followed by shoreface erosion and submergence. A variety of sedimentary facies has been identified, including prodelta, delta fringe, distributary, lagoonal, barrier island, and shelf sand sheet. This study is based on the interpretation and the synthesis of > 6,700 km of high-resolution seismic profiles, 75 grab samples, and 77 vibracores. The nearshore morphology, shallow stratigraphy, and sediment distribution of the eastern Louisiana shelf are the products of transgressive sedimentary processes reworking the abandoned St. Bernard delta complex. Relatively recent Mississippi delta lobe consists primarily of fine sand, silt, and clay. In the southern portion of the St. Bernard delta complex, asymmetrical sand ridges (>5 m relief) have formed as the result of marine reworking of distributary mouth-bar sands. Silty sediments from the modern Mississippi Birdsfoot delta onlap the St. Bernard delta complex along the southern edge. The distal margin of the St. Bernard complex is distinct and has a sharp contact on the north near the Mississippi Sound barrier island coastline and a late Wisconsinan delta to the south. The Chandeleur Islands and the barrier islands of Mississippi Sound have been formed by a combination of Holocene and Pleistocene fluvial processes, shoreface erosion, and ravinement of the exposed shelf. Sediments underlying the relatively thin Holocene sediment cover are relict fluvial sands, deposited during the late Wisconsinan lowstand. Subsequent relative sea-level rise allowed marine processes to rework and redistribute sediments that formed the nearshore fine-grained facies and the shelf sand sheet.

Conference Paper↗

USGS1989

Morphodynamic signature of the 1985 hurricane impacts on the northern Gulf of Mexico

Three hurricanes hit Lousiana (LA), Mississippi (MS), Alabama (AL), and the Florida (FL) panhandle in 1985, producing dramatic geomorphic changes in a wide variety of coastal environments. The impact zone for hurricanes Danny, Elena, and Juan stretched 1000 km between the Sabine River in LA to the Apalachicola River in FL. Barrier shorelines experienced repeated intense overwash events, producing beach and dune erosion exceeding 30 m, as well as producing classic examples of storm surge deposits. Pre- and post-storm airborne videotape surveys, sequential vertical mapping photography, and field surveys provide the data base for this regional hurricane impact assessment on the northern Gulf of Mexico. Hurricane impacts on the low-profile and high-profile barrier shorelines, as well as on the marine terrace cliffs were systematic and predictable. Controlling the direction of overwash flow and the impact distribution pattern is the relationship among shoreline orientation, hurricane storm track, and regional wind field. The relationship between shore-zone geomorphology and storm surge overwash controls the impact response.

Conference Paper↗

USGS1989

Holocene sand shoals offshore of the Mississippi River delta plain

Offshore of the Mississippi River delta plain lies a series of Holocene sand shoals marking the position of ancient submerged shorelines associated with younger shelf-phase delta plains. These submerged shorelines represent positions when sea level stood lower than present. Short periods of rapid sea level rise during the Holocene transgression, in combination with subsidence, led to the submergence of these sandy shorelines, which can be recognized at the -33 ft (-10 m) and -66 ft (-20 m) isobaths on the Louisiana continental shelf The -33 ft (-10 m) shoreline trend is represented by Trinity Shoal and Ship Shoal, which are associated with the late Holocene Mississippi River delta plain. Trinity Shoal is derived from the Cypremont-Sale delta complex and is located 12 mi (20 km) offshore of Marsh Island. This shoal is 22 mi (35 km) long, 5 mi (8 km) wide, and 16 - 20 ft (5 - 6 m) thick. The facies relationships indicate that Trinity Shoal is a submerged barrier system in the initial stages of shoreface reworking. To the east is Ship Shoal which is associated with the Maringouin-Teche delta complex. This shoal is located 12 mi (20 km) offshore of the Isles Dernieres and is 31 mi (50 km) long, 5 - 6 mi (8 - 10 km) wide, and 13 - 20 ft (4 - 6 m) thick. The facies relationships indicate that Ship Shoal is a marine sand body derived from shoreface reworking of a submerged barrier island. The -66 ft (-20 m) shoreline trend is represented by the Outer Shoal and St. Bernard Shoals, which are associated with the early Mississippi River delta plain. The Outer Shoal is a low relief sand body, which lies seaward of Ship Shoal immediately west of the Mississippi Canyon. The eastern continuation of the -66 ft (-20 m) shoreline trend is the St. Bernard Shoals, which lie 16 mi (25 km) offshore of the Chandeleur Islands. In contrast to the other shoal systems, the St. Bernard Shoals form a shore-parallel zone of more than seven smaller sand shoals which, in many respects, are similar to a shore-oblique sand-ridge field. Collectively, these sand shoals represent a large potential source of aggregate for shoreline restoration and erosion control as well as possible hard mineral resources. Scientifically, these shoals provide insight into the processes which control coastal evolution and shelf sand development under the condition of relative sea level rise.

Mississippi River↗

USGS1989

Inner shelf deposits of the Louisiana-Mississippi-Alabama region, Gulf of Mexico

The late Quaternary morphology, shallow stratigraphy and sediment distribution of the Louisiana-Mississippi-Alabama inner shelf region are the product of transgressive and regressive sedimentary processes. Shelf sedimentary facies were deposited by deltaic progradation, followed by shoreface erosion and submergence. This information is based on interpretations and synthesis of more than 4,160 mi (6,700 km) of high resolution seismic profiles, 75 grab samples, and 77 vibracores. The shelf can be divided into two main depositional regions. The southwestern region, east and south of the Mississippi River plain, was formed by early Holocene delta complexes, overlying a late Wisconsinan delta. Deposits of the late Wisconsinan delta consist of well-defined coarsening-upward sequences and represent deltaic progradation during low sea level stands. The relatively recent Mississippi delta complexes have deposits which consist of fine-grained sands, silt and clay. With the late Holocene rise in sea level, asymmetrical sand ridges (16 ft, or 5 m, relief) have formed due to marine reworking of shoreline features. The northeastern region, offshore of the Mississippi-Alabama barrier islands, was formed by Pleistocene fluvial systems and Recent shoreface erosion and ravinement. Underlying the relatively thin Holocene sediment cover are relict fluvial sands which were deposited during the late Wisconsinan lowstand. Subsequent sea level rise allowed marine processes to rework and redistribute sediments forming the nearshore fine-grained facies and shelf sands sheet.

Gulf of Mexico↗

USGS1985

Barrier island arcs along abandoned Mississippi River deltas

Generation of transgressive barrier island arcs along the Mississippi River delta plain and preservation of barrier shoreline facies in their retreat paths on the inner shelf is controlled by: (1) shoreface translation; (2) age of the transgression; and (3) the thickness of the barrier island arc sediment package. Barrier island arcs experience an average relative sea level rise of 0.50–1.00 cm yr −1 and shoreface retreat rates range from 5–15 m yr −1 . Young barrier island arc sediment packages (Isles Dernieres) are thin and have experienced limited landward retreat of the shoreface. Older barrier island arcs (Chandeleur Islands) are thicker and have experienced significant landward movement of the shoreface because of the greater time available for retreat. If the transgressed barrier shoreline sediment package lies above the advancing ravinement surface, the entire sequence is truncated. A thin reworked sand sheet marks the shoreface retreat path. The base of the transgressive sediment package can lie below the ravinement surface in older barrier shorelines. In this setting, the superstructure of the barrier shoreline is truncated, leaving the basal portion of the transgressive sequence preserved on the inner shelf. A variety of transgressive stratigraphic sequences from sand sheets to truncated barrier islands to sand-filled tidal inlet scars have been identified by high resolution seismic profiling across the shoreface retreat paths of Mississippi delta barrier island arcs. One of these examples, the Isles Dernieres, represents a recently detached barrier island arc in the early stages of transgression. An older example, the Chandeleur Islands, represents a barrier island arc experiencing long-term shoreface retreat. This paper describes the stratigraphic character and preserved transgressive facies for the Isles Dernieres and Chandeleur Islands.

Marine Geology↗