Geology topics

F. Snyder

Publications and source records attributed to F. Snyder.

4 recordsLinked to original sources

USGS2014

A conception of runoff‐phenomena

The problem of transforming observed precipitation into stream‐flow for a natural drainage‐basin can be divided into two parts. The first part requires a procedure for determining the amount and kind of runoff that occurs under various conditions. The second part is concerned with the shaping of the runoff into a discharge‐hydrograph for a particular gaging station. (Rainfall‐eccentricities often provide more difficulties than either of the above.) Considerable investigation has been made and is being continued along both lines of research. The unit‐hydrograph and related methods now provide a means of shaping discharge‐hydrographs as accurately as is required by the practical considerations of most problems. However, it is believed that methods for determining the amount and kind of runoff which occur under various conditions have not been demonstrated to an equivalent refinement. It is with the latter problem that this paper is concerned.

Eos, Transactions, American Geophysical Union↗

USGS2014

Report of Committee on Runoff, 1942–43

The Committee on Runoff was not formally constituted until February 6, 1943, when the members of the Section, as listed above, were asked to serve. At the suggestion of President CHURCH the Committee has been so selected that there is Nation‐wide geographic distribution from West to East with the majority of the Committee composed of younger men. If the 33 papers prepared for discussion at the regular sessions of the Section of Hydrology at the annual meeting of 1943 can be used as a measure, war instead of curtailing the activities of the Section has acted as an impetus. Also in the field of hydrology as a whole, war activities have apparently not resulted in a decrease of activities. There has been, however, a gradual decrease of activities in the field of research and an increase of activities in the field of applied hydrology. The enormous expansion of our industrial machine and the great concentration of armies and industrial workers into restricted areas; the demands for water, for power, for food and for municipal use; and operations underlying many of our war efforts, secret and otherwise—all these have created problems requiring the full‐time effort of hydrologists, both in private and governmental service. It is with some degree of satisfaction that each one of us can feel that either as a result of our past research or in our present positions we have been or are doing our bit to win the war.

Eos, Transactions, American Geophysical Union↗

USGS2008

Geologic framework of the 2005 Keathley Canyon gas hydrate research well, northern Gulf of Mexico

The Keathley Canyon sites drilled in 2005 by the Chevron Joint Industry Project are located along the southeastern edge of an intraslope minibasin (Casey basin) in the northern Gulf of Mexico at 1335 m water depth. Around the drill sites, a grid of 2D high-resolution multichannel seismic data designed to image depths down to at least 1000 m sub-bottom reveals 7 unconformities and disconformities that, with the seafloor, bound 7 identifiable seismic stratigraphic units. A major disconformity in the middle of the units stands out for its angular baselapping geometry. From these data, three episodes of sedimentary deposition and deformation are inferred. The oldest episode consists of fine-grained muds deposited during a period of relative stability in the basin (units e, f, and g). Both the BSR and inferred gas hydrate occur within these older units. The gas hydrate occurs in near-vertical fractures. A second episode (units c and d) involved large vertical displacements associated with infilling and ponding of sediment. This second interval corresponds to deposition of intercalated fine and coarse-grained material that was recovered in the drill hole that penetrated the thin edges of the regionally much thicker units. The final episode of deposition (units a and b) occurred during more subdued vertical motions. Hemipelagic drape (unit a) characterizes the modern seafloor. The present-day Casey basin is mostly filled. Its sill is part of a subsiding graben structure that is only 10-20 m shallower than the deepest point in the basin, indicating that gravity-driven transport would mostly bypass the basin. Contemporary faulting along the basin margins has selectively reactivated an older group of faults. The intercalated sand and mud deposits of units c and d are tentatively correlated with Late Pleistocene deposition derived from the western shelf-edge delta/depocenter of the Mississippi River, which was probably most active from 320 ka to 70 ka [Winker, C.D., Booth, J., 2000. Sedimentary dynamics of the salt-dominated continental slope, Gulf of Mexico: integration of observations from the seafloor, near-surface, and deep subsurface. In: Proceedings of the GCSSEPM Foundation 20th Annual Research Conference, Deep-water Reservoirs of the World, pp. 1059-1086]. The presence of sand within the gas hydrate stability zone (in units c and d) is not sufficient to concentrate gas hydrate even though dispersed gas hydrate occurs deeper in the fractured mud/clay-rich sections of units e and f.

Gulf of Mexico↗

USGS2008

Gas and gas hydrate distribution around seafloor seeps in Mississippi Canyon, Northern Gulf of Mexico, using multi-resolution seismic imagery

To determine the impact of seeps and focused flow on the occurrence of shallow gas hydrates, several seafloor mounds in the Atwater Valley lease area of the Gulf of Mexico were surveyed with a wide range of seismic frequencies. Seismic data were acquired with a deep-towed, Helmholz resonator source (220-820 Hz); a high-resolution, Generator-Injector air-gun (30-300 Hz); and an industrial air-gun array (10-130 Hz). Each showed a significantly different response in this weakly reflective, highly faulted area. Seismic modeling and observations of reversed-polarity reflections and small scale diffractions are consistent with a model of methane transport dominated regionally by diffusion but punctuated by intense upward advection responsible for the bathymetric mounds, as well as likely advection along pervasive filamentous fractures away from the mounds.

Marine and Petroleum Geology↗