Geologic Framework and Consolidation Settlement Potential of the Lafourche Delta, Topstratum Valley Fill; Implications for Wetland Loss in Terrebonne and Lafourche Parishes, Louisiana.

Wetland loss in Terrebonne and Lafourche Parishes, Louisiana, largely results from two subsurface processes: (1) consolidation of recently deposited deltaic materials; and (2) active faulting. The impact of each is addressed. Cryogenic sampling techniques were utilized to obtain in-situ sediment samples from seven (7) modern deltaic environments in the greater Mississippi River delta plain. Consolidometer testing identifies peaty facies as most-subject to consolidation settlement, followed by prodelta and bay mud facies. Sandy facies from the other tested environments are not subject to significant consolidation settlement. Compression index values generated here are used to calculate settlement in a vertical stack at the P-1-90 and P-6S-93 borings. Results indicate most settlement occurs in the uppermost two (2) meters of section, although the uppermost ten (10) meters is identified in density studies. Data indicate a direct relationship between the thickness of peaty facies capping the recently abandoned Lafourche Delta and present patterns of coastal tract land loss. Locally, consolidation settlement is high where the thickness of consolidation-prone peaty sediments is great and vice versa. Interdistributary areas contain thick deposits of peaty sediments, and these areas are preferentially being lost to the expansion of greater Terrebonne Bay. A model for the development of Terrebonne Bay, which includes initiating erosion and subsequent compactional deformation is proposed. Active faults produce thicker Topstratum and Lafourche Delta sections and preferentially accumulate consolidation-prone sediments on their downthrown sides. The mapped distribution of faults is coincident with new areas of marsh development in the western and central parts of the study area

The dominant processes responsible for subsidence of coastal wetlands in south Louisiana

Wetland loss in coastal areas of Terrebonne and Lafourche Parishes, Louisiana, largely results from two subsurface processes: (1) consolidation of recently deposited Holocene deltaic sediments and (2) active growth faulting. Locally, settlement is high where the thickness of valley fill is great and in broad interdistributary basins where the thickness of consolidation-prone, peaty soils is great. The delta cycle is identified as the fundamental sedimentologic unit that constitutes the lower delta plain. Peaty soils from the waning phase of the delta cycle are identified as the deltaic facies most subject to consolidation settlement. Data indicate direct relationships between the thickness of deltaic sediments in individual delta cycles, and the thickness of peaty soils capping these cycles, with present patterns of coastal tract land loss. In addition, active growth faulting is correlated with new areas of interior tract wetland loss. Consolidation and faulting largely explain the curious nature of wetland loss patterns in south Louisiana. Subsidence in The Netherlands has been attributed to similar causes, i.e. thick deposits of consolidation-prone sediments that accumulate on the downthrown sides of basin margin faults

Sediment compaction rates and subsidence in deltaic plains : numerical constraints and stratigraphic influences

This paper is not subject to U.S. copyright. The definitive version was published in Basin Research 19 (2007): 19-31, doi:10.1111/j.1365-2117.2006.00310.x.Natural sediment compaction in deltaic plains influences subsidence rates and the evolution of deltaic morphology. Determining compaction rates requires detailed knowledge of subsurface geotechnical properties and depositional history, neither of which is often readily available. To overcome this lack of knowledge, we numerically forward model the incremental sedimentation and compaction of stochastically generated stratigraphies with geotechnical properties typical of modern depositional environments in the Mississippi River delta plain. Using a Monte Carlo approach, the range of probable compaction rates for stratigraphies with compacted thicknesses <150 m and accumulation times <20 kyr. varies, but maximum values rarely exceed a few mm yr-1. The fastest compacting stratigraphies are composed primarily of peat and bar sand, whereas the slowest compacting stratigraphies are composed of prodelta mud and natural levee deposits. These results suggest that compaction rates can significantly influence vertical and lateral stratigraphic trends during deltaic evolution

Struktur und elektrische Leitfaehigkeit von duennen metallischen Mehrlagenschichtsystemen

SIGLETIB Hannover: DR 6296 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Influence of additive coadsorption on copper superfill behavior

The interaction between the additive components chloride, accelerator, and suppressor is the focus of the present paper. Based on Frumkin and Damaskin's adsorption theory, an advanced concept for the superfilling mechanism is introduced. Cyclovoltammetry measurements show the additive impact on the current-potential behavior and their synergetic effect on the charge transfer across the electrode-electrolyte interface. The measurements are supported by partial fill experiments. Cross-section scanning electron microscopy micrographs reveal that the synergetic impact of an accelerator and a suppressor is very different from their individual contributions. Chloride ions support the adsorption of suppressor molecules, while the accelerator enhances the desorption of the suppressor molecules from the copper surface. The higher the local accelerator concentration in an electrolyte, the more suppressor molecules desorb from the surface. The synergetic behavior between the chloride, suppressor, and accelerator can be explained by coadsorption, which is an important key in the process of copper superfilling

Environmental geophysics, offshore Bush River Peninsula, Aberdeen Proving Ground, Maryland

Geophysical studies in shallow waters adjacent to the Bush River Peninsula, Edgewood Area of Aberdeen Proving Ground, Maryland, have delineated the extent of waste disposal sites and established a hydrogeologic framework, which may control contaminant transport offshore. These studies indicate that during the Pleistocene Epoch, alternating stands of high and low sea levels resulted in a complex pattern of shallow channel-fill deposits around the Bush River Peninsula. Ground-penetrating radar studies reveal paleochannels greater than 50 ft deep. Some of the paleochannels are also imaged with marine seismic reflection. Conductivity highs measured with the EM-31 are also indicative of paleochannels. This paleochannel depositional system is environmentally significant because it may control the shallow groundwater flow regime beneath the peninsula. Magnetic, conductivity, and side-scan sonar anomalies outline anthropogenic anomalies in the study area. On the basis of geophysical data, underwater anthropogenic materials do exist in some isolated areas, but large-scale offshore dumping has not occurred in the area studied

Evidence for active growth faulting in the terrebonne delta plain, South Louisiana: Implications for wetland loss and the vertical migration of petroleum

Two regional growth faults, the Golden Meadow Fault and the Lake Hatch Fault, were mapped in Terrebonne and Lafourche Parishes, Louisiana, utilizing over 3000 line kilometers of seismic data. The subcropping location of these faults identify major vegetation biozonations, new areas of wetland loss, and the position of transgressive lakes. The proposed mechanism governing these fault-related manifestations of subsidence involves the venting of fluid (and gas) from geopressured shales vertically up fault planes. Saline fluids and gases exiting a basin via growth faults provide accommodation space at depth, resulting in active, fault-induced subsidence in the down-thrown block. By contrast, areas along the fault trend where no fluids or gases were migrating would not result in an increase of accommodation space and would be considered inactive regarding fault-induced subsidence. The model that emerges is a growth fault trace that does not act in concert but more closely resembles a key-stepping system with sections alternating between active and inactive. These findings are relevant to the role of growth faults in subsidence-related coastal land loss and the vertical migration of hydrocarbons. © 2001, AAPG/DEG

Subsidence properties of holocene sediments: S. LA.

As part of a comprehensive USGS-sponsored study of processes that drive subsidence and wetland loss in south Louisiana, two continuously cored deep borings (60 m and 72 m) were acquired in south Terrebonne Parish marshlands. Both borings were supported with in-situ geotechnical data acquired by cone penetration testing. Additional laboratory testing included X-ray radiography, lithologic description, radiocarbon dating, selected shear strength and consolidation tests, pore water geochemistry, and solid phase diagenetic properties examination (X-ray diffraction for mineralogy, thin-section petrology, and scanning electron microscopy)