Tributary Canyons Research Articles

Geomorphic effects of a 10‐year storm on a small drainage Basin in the Texas Panhandle

AbstractBedded Permian salt in the Palo Duro Basin of the Texas Panhandle is being considered for isolation of nuclear waste. Studies underway to evaluate the geomorphic processes affecting any waste repository that may be sited in the region include studies of the geomorphic events associated with individual storms. On 26 May, 1978, thunderstorms occurred near Canyon, Texas, which received 130mm of rain, and on a small instrumented watershed at Buffalo Lake, 16 km to the southwest, which received 71 mm of rain. Rainfall at Buffalo Lake was concentrated in a period of 3 hours, representing a return period of approximately 10 years and a maximum 30‐minute intensity of 64 mm/hour.Erosion‐pin fields, topographic surveys, and stakes for headcut monitoring had been established 2 to 3 months before the storm in a 640‐m long tributary canyon to Tierra Blanca Creek downstream of Buffalo Lake. Canyon slopes of moderately to slightly calichified sands and gravels of the Ogallala Formation are capped by well‐indurated caliche on the canyon rim. Erosion‐pin fields showed average net erosion of 2·4 cm (0° to 9° slope) to 2·7 cm (10° to 19° slope) and a single‐pin maximum value of 6·2 cm in the 20° to 29° slope class. Headcuts 1 to 2 m deep in alluvial‐colluvial material on the floor of the canyon migrated as much as 12 m upstream. Canyon floor deposition occurred as a series of elongate bars, 16m long and longer, located at the mouth of tributary gullies, downstream from scours, and at slope breaks. Grain sizes ranged from boulders up to 70cm in intermediate axis deposited in the upper canyon to fine to very fine sand deposited as a sheet up to 25cm thick beyond the mouth of the canyon at Tierra Blanca Creek.In an adjacent canyon a sequence of irregular beds of caliche gravel, mixed sand and gravel, and fine sand up to 3 m thick is exposed. Comparison of this sequence with deposits resulting from the 26 May, 1978, storm suggests that the coarse fraction of the alluvial sequence is deposited by repetitive major storm events. Cobble and boulder units 30 to 70cm thick can evidently be deposited in a few hours. Under the continental climate of the Texas Panhandle, erosion, deposition, and stream incision are taking place primarily in discrete steps related to episodes of intense rainfall.

The Meander anticline, Canyonlands, Utah: An unloading structure resulting from horizontal gliding on salt

The axial trace of the Meander anticline, which has a cumulative length of 25.5 mi, coincides with the Colorado River in Canyonlands National Park. On the southeast side of the river, eight tributary canyons also contain anticlines. In all cases, the anticlines occupy canyons that are eroded between 400 and 1,800 ft into the Pennsylvanian-Permian section. A system of closely spaced grabens has developed in the Pennsylvanian-Permian rocks which comprise the plateaus adjacent to the deeper canyons. The grabens are most extensively developed southeast of the Colorado River, where they follow the strike of the Meander anticline for 17 mi and extend 9 mi into the plateau. The Pennsylvanian Paradox evaporites, consisting of 85% salt, underlie the entire anticline-graben complex. Principal stress axes can be deduced from the intersections between conjugate thrust faults in the cores of the anticlines and from the downward intersections of normal faults bounding the grabens. The maximum principal stresses associated with the anticlines are horizontal and perpendicular to the axial planes regardless of the strikes of the anticlines. In contrast, the maximum principal stresses associated with the grabens are near vertical and normal to the strikes of the faults. The conclusions of this study are that (1) the anticlines are unloading structures, and (2) the mechanism which best accounts for the observed stresses is one involving the breakup of the brittle plate above the Paradox salts and its simultaneous gliding toward nearby canyons. The breakup and motion within the brittle plate involve a three-dimensional deformation which is analogous to the deformation that takes place within large unbounded landslides. Through compaction of the section, largely accounted for by the downdropping of grabens, the deforming mass expands laterally, yet maintains horizontal continuity. The result is the establishment of horizontal stress gradients at depth which produce compression within the rocks that bridge the floors of the deep canyons regardless of the orientations of the canyons. Through a combination of horizontal shortening and arching, the compressed rocks fold into the observed anticlines. Salt flowage into the cores of the anticlines is not the causative mechanism in their development.

Late Proterozoic Submarine Canyons of Adelaide Geosyncline, South Australia

A well-exposed series of major basin-slope submarine canyons of late Proterozoic age occur within the mixed carbonate and siliclastic Wonoka Formation of the Adelaide Supergroup (Adelaide geosyncline), Flinders Ranges, South Australia. They were cut to depths of about 1.5 km into an underlying deltaic and basin-slope progradational sequence which includes the Brachina Formation and the ABC Range Quartzite. The canyons occur in close association with local synclinal structures. An unfolded section across one canyon (Patsy Springs Canyon) shows steep, almost vertical canyon walls, two axial channels, and a tributary canyon. The canyon-filling sequence includes canyon-wall and axial debris flow material, axial channel conglomerates, ripple cross-laminated sands and silts, hin- and thick-bedded turbidite sands, and a series of spectacular sand-filled megachannels which markedly truncate underlying units. Lenticular olistostromes of micritic carbonate clast breccias of carbonate-platform derivation occur throughout canyon-fill and immediately overlying strata. The sedimentary sequence preserved in the canyons demonstrates an episodic process of canyon backfilling by onlap of an aggrading submarine-fan sequence. Backfilled canyons were finally buried by progradation of a complex unit comprising interdeltaic carbonate platform, delta, and basin and slope environments. Evidence from the Wonoka Formation canyons suggests that initial canyon incision was triggered by a significant fall in relative sea level, which allowed fluvial systems to deliver their bed loa s directly to the contemporary basin slope. A subsequent relative rise in sea level was required during latter stages of canyon filling to account for delta and basin-slope progradation of the Wonoka Formation.

Landslides in Valles Marineris, Mars

Large landslides in the Martian equatorial troughs have been investigated with respect to morphology, geologic structure of the troughs, time of emplacement, similarity to terrestrial landslides, and origin and mechanism of transport. Viking Orbiter images provided a base for morphologic analyses, mapping, crater counts, and volumetric considerations. Results showed that the morphologic variations of the landslides can be attributed mainly to their degree of confinement on trough floors. Many prominent landslides appear to be of similar age and were emplaced after a major episode of faulting that created scarps of great relief. Most sliding apparently occurred after these scarps were dissected into spurs, gullies, and tributary canyons. Much of the slide activity coincided with a major late eruptive phase of the Tharsis volcanoes, as deduced from the crater density, over the total deposit area, of 570±130 craters larger than 1 km in diameter per 106 km2. The huge size of many landslides is due to their occurrence on fault scarps that may have attained several kilometers in height in the absence of vigorous fluvial erosion on Mars. The mechanical efficiency of the Martian landslides is high but in accord with predictions from large landslides on earth. The slides may have originated as gigantic mudflows with slump blocks at their heads; water that may have existed in aquifers in the wallrock below and behind a lid of ice may have been liberated through minor disturbances from Marsquakes. Liquefaction and collapse of extensive wall sections may then have ensued, and the debris rushed out onto the trough floors at speeds exceeding 100 km/h.

Development of the Canyons of the South Nahanni River, N.W.T.

In its middle section, the South Nahanni River flows through four deep, meandering canyons incised through ranges of the southern Mackenzie Mountains. The downstream canyon, First Canyon, contains fossil solution caves of shallow phreatic type developed in limestone. The stratigraphy of the most extensive caves indicates that there was an interglacial climate between 300 000–200 000 years B.P., (from U Decay Series dating of stalagmites), which was preceded by a 'First Canyon Glaciation'. There has been no subsequent glaciation of the canyon and its environs. The position of the caves above the River, plus morphological evidence from cutoff meanders and a tributary canyon, indicates that since the First Canyon Glaciation the river has been entrenching into a rising anticlinal arch and that the maximum postglacial uplift of the arch has been not less than 1600 ft (486 m). The other three canyons of the South Nahanni River are also of antecedent type and are probably of similar age with a similar history.

Late Precambrian Chuar Group, Grand Canyon, Arizona

The Chuar Group is exposed in tributary canyons to the Colorado River over an area some 15 mi (24 km) long and 4 mi (6 km) wide. The rocks are faulted against Paleozoic rocks by the Butte fault on the east, and unconformably overlain by Paleozoic rocks to the west. The group is 6,610 ft (2,013 m) thick and has been divided into three formations and seven members. The lower two formations, Galeros (below) and Kwagunt (above) are predominantly argillaceous with subordinate thin limestone beds, while the highest, Sixty Mile Formation, is mostly coarse breccia. Stromatolites are present at three horizons, one of them biohermal. The form-genera Inzeria , Baicalia , and Boxonia indicate an upper Riphean age. The mega-planktonic fossil Chuaria occurs near the top of the Kwagunt Formation. The Chuar rocks are probably younger than any other Precambrian rocks in Arizona. They may be contemporary with rocks below the Cambrian in eastern California, and with the Windermere Formation of the northern Cordillera.

Submarine valley systems around the Coral Sea Basin (Australia)

Several major and a host of minor submarine valleys and canyons lead into the deep (4,650 m) Coral Sea Basin from the surrounding land, reef, and submarine plateau areas. Moresby Valley, 500 km long, and comprising Pandora Trough, Moresby Trough, and Moresby Canyon, plus all their tributary canyons, is an integrated submarine drainage system that collects sediment from nearly the entire Papuan coast and channels it onto the floor of the basin. The Bligh System, including Queensland Trough, Bligh Trough, and Bligh Canyon, drains a 900 km sweep of the Great Barrier Reef coast of Queensland, and parts of the Queensland Submarine Plateau. Reflection profiles of the valleys show that they are mainly located in structural depressions, but that the submarine relief has been further accentuated by erosional entrenchment of the valleys into older, probably pelagic, sediments to a depth of as much as 750 m. Since the time of the entrenchment, the valleys and many canyons have been backfilled by as much as 500 m of sediment (assuming a sound velocity of 2 km/sec in the fill). The valleys may be thought of as graded, and their filling is assigned to adjustments in the long profiles of the valleys as the Coral Sea Basin fills with sediment.

Shelf to Deep-Sea Sediment Transportation in The Gully Submarine Canyon Off Nova Scotia: ABSTRACT

Submarine canyons on the Atlantic continental margin off northeastern North America received large amounts of fluvial and fluvio-glacial sediment from emerged shelves during glacial stages. It has been stated that the supply of sediment to canyon heads, especially to those located far from coast lines, was virtually cut off after the Holocene sea-level rise, and that at the present time there is little sediment movement down these canyons. An examination of numerous piston cores collected in The Gully, the largest canyon on the highly dissected continental slope off Nova Scotia, Canada, indicates that the above generalizations do not apply to all canyons of this region. The Gully heads on the outer Scotian shelf between Sable Island and Banquereau Banks, more than 100 nautical miles from the mainland. The Gully trends downslope southeastward in sinuous fashion for a distance of 35 miles to a depth of about 1,400 fathoms. The canyon is V-shaped and the walls are steep with gradients of 1 on 2. The longitudinal gradient ranges from 1 on 9 to 1 on 18. Small, precipitous tributary canyons enter the main canyon, especially along the west wall. Long cores collected at the base of the slope show an upward change in coloration from red (reworked till origin) to gray and olive (post-glacial). The number of coarse strata increases with depth, indicating that sediment rates decreased after the last rise in sea-level. However, the sediment sequence along the canyon length is proof of modern active sedimentation. Lenses of relatively clean sand in the upper reaches and near the steep walls of lateral tributary canyons are clearly derived from adjacent banks on the basis of minerology and faunal composition. Normal bottom currents, slumps, and sand flows probably moved these materials. In the same areas, contorted lenses of silty and sandy clay abound; localized slumping toward the canyon axis is the most important downslope transpo tation process. Pockets of sand and gravel, lying above mud in the canyon axis, and scour structures indicate that coarse clastics presently are being funneled downslope along the axis. Graded layers, 1-10 centimeters thick, are uncovered within the canyon and correlation is not possible between adjacent cores. Turbidity currents presumably are active in moving some material to the deep sea but, in this area, are of lesser importance than either slumps or bottom currents. End_of_Article - Last_Page 482------------

Clarkston Stage of the Northwest Pleistocene

An episode of proglacial aggradation, here named the stage, is recorded in the Lewiston Basin region on the lower Snake River. Stream gravels accumulated to a depth of more than 400 feet in the Snake River canyon and in the lower portions of most tributary canyons. One or two tributary streams were ponded by the fill of the main canyon. The deposits are characterized by considerable cementation, weathering of basalt and granitic stones, and iron oxide stain. Two-story canyons were formed by cessation of erosion beneath the fill, prolonged lowering of slopes above, and later excavation of the fill. The Clarkston stage followed earlier Pleistocene deposition, deformation, and dissection but antedated the Wisconsin stage.