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The structural framework of the northern Gulf of Mexico coastal zone includes numerous growth fault systems. Neotectonic processes in coastal environments here have been shown to be important contributors to subsidence and relative sea-level rise, as well as having significant influences on sedimentary accretion processes. One active growth fault at East Matagorda Peninsula, Texas was subjected to detailed study to address the hypotheses that (1) this fault was present and active before the peak of regional hydrocarbon recovery in the mid-20th century, and that (2) slip along this fault has been episodic over the resolved period of record. To characterize the late Holocene behavior of this fault, three core transects were established normal to the surface fault trace, and stratigraphic analysis was conducted with the use of radiocarbon (14C) for chronological control. Correlation of time-equivalent stratigraphic boundaries reveals a maximum total late Holocene offset of 0.7 m. The Matagorda fault was in place long before the peak of regional oil and gas extraction, but experienced a late Holocene rejuvenation, initiated between 2500 and 1500 years BP. The kinematic behavior of the fault expressed as temporally and spatially variable measures of expanded stratigraphic thicknesses on the downthrown extent suggest that sediment loading from the transgressive Matagorda barrier complex may have contributed to this rejuvenation, and that slip along the fault persists to the present. Radiocarbon chronology also revealed clear differences in the magnitude of fault throw during the late Holocene, with maximum displacement (0.7 m) occurring at the southwestern-most transect and minimum throw at the northeastern-most transect (0.2 m).

Increases in human development of the coastal zone, sea level rise and intensity of coastal storms will test the resilience of coastal systems. An integrated approach is needed to describe geomorphic–biologic dependencies, feedbacks between processes and responses, and determine how coastal systems can be maintained or restored. The 2013 Binghamton geomorphology symposium focused on three themes in these research areas (1) the geomorphic response of coastal landforms to changes in sea level and episodic storms; (2) the way these stressors alter geomorphic–biotic interactions and reduce the resilience of coastal environments; and (3) the way natural and human processes are being integrated to restore or maintain dynamic geomorphic and biologic linkages. This issue contains eighteen papers presented at the symposium; six papers are devoted to each of these themes. The papers point to the importance of ecological systems in modulating the responses to natural physical processes and, in turn, responding to geomorphic change and the role of humans in assisting natural processes.

Active growth faults contribute to the subsidence of deltaic basins around the world and can significantly augment local rates of relative sea level rise, which can inundate and drown wetlands. Little information exists on the temporal frequency and spatial magnitude of motion along these faults. Our objective was to quantify fault activity and displacement at multiple time scales in a salt marsh wetland on the East Matagorda Peninsula, Texas. We present evidence of this activity that includes remotely sensed aerial imagery, LiDAR data, ground penetrating radar data, shallow seismic data, lithostratigraphic and biostratigraphic evidence from core data, and sub-centimeter GPS and survey monitoring. The results support the interpretation that the Matagorda fault is currently active, and has been active in the past. Subsurface data to depths of ~ 150 m displays evidence of disrupted strata at the fault plane, as well as thicker strata on the downthrown side of the fault. In the shallow subsurface down to ~ 3 m of depth, vertical displacement in stratigraphic markers and surface deformation exhibits a sinusoidal pattern that runs perpendicular to the fault plane, which we interpret to represent fault-propagation folding. Maximum throw on this fault is estimated at ~ 0.75 m over the last ~ 40–50 years. We also recorded a vertical drop of − 0.208 m in the span of a single year, at a location close to the fault on its downthrown side. Records of yearly elevation change also show evidence of ongoing fault-propagation folding. We conclude that whereas the surface at the Matagorda fault moves intermittently up and down at the yearly time scale, fault displacement manifests as a sinusoidal pattern of displacement and deformation which has been integrated into the stratigraphic record at decadal-to-millennial time scales. This study presents a rare look into active motion and details its effects on the modern evolution of unconsolidated sedimentary surfaces.

Neotectonic processes influence marsh accretion in the lower Pearl River valley. Active growth faults are suggested by groupings of ponded river channel sections, transverse and linear river channel sections, and down- and across-valley contrasts in channel sinuosity. Seismic profiles identified several likely, fault-induced structural anomalies, two of which parallel the axes of surface distributary networks. Lithostratigraphy and biostratigraphy of six cores from across a suspected fault in the West Middle River, combined with 14 C-based age control, yielded evidence of vertical offsets, indicating that this river section is on the plane of a growth fault. These data were used to estimate fault slip rates over two time intervals, 1.2 mm/y over the last 1300 yr, and 0.2 mm yr − 1 over the last 3700 yr, and delineated a sinusoidal pattern of deformation moving distally from the fault, which we interpret as resulting from fault-propagation folding. Higher rates of sediment accumulation (of the order of cm yr − 1 from 210 Pb xs and 137 Cs activity data) on the down-thrown side are consistent with sedimentary response to increased accommodation space, and mass-based sediment accumulation rates (g cm − 2 yr − 1 ) exhibit a pattern inverse of that shown by fault-driven sinusoidal deformation. We contend that near-surface growth faults are critically important to driving accretion rates and marsh response to sea-level rise.