Land Surface Stability Research Articles

Paleoenvironmental and geoarchaeologic implications of late quaternary sediments and paleosols: north-central to southwestern San Juan Basin, New Mexico

Soil/sediment relationships from the West Fork of Gallegos Canyon near Farmington, NM to the Manuelito Plateau northwest of Gallup, NM provide insight into the Late Pleistocene and Holocene history of the north-central to southwestern San Juan Basin. Soil formation suggests six widespread episodes of land-surface stability. The oldest and strongest paleosol is in eolian, alluvial, and playa sediments that were buried between 9560 and 7800 14C yrs B.P. The second oldest paleosol developed within eolian and alluvial sediments and was buried at ca. 4500 14C yrs B.P. Subsequent eolian, alluvial, and playa deposits contain a third paleosol that was buried ca. 3100 14C yrs B.P. In turn, these sediments are mantled by eolian, alluvial, and playa sediments that exhibit remnants of a fourth paleosol that was buried by ca. 2100 14C yrs B.P. A fifth paleosol within eolian and alluvial sediments is associated with Basketmaker III-Pueblo III cultural materials dating from 1300 to 660 14C yrs B.P. The sixth soil/sediment unit consists of eolian and alluvial deposits that date from 660 14C yrs B.P. to the present and exhibits the modern soil. In addition, a very weak paleosol that was buried at ca. 300 14C yrs B.P. was encountered at a few locales. Because of discontinuous burial and preservation, not all of these units are present at every locale within the study area. Several locales across the basin, however, exhibit five to six of these units in stratigraphic succession. The widespread occurrence of these paleosols suggests that six episodes of regional stability and soil formation occurred in the western San Juan Basin during the Holocene.

ケニヤ山，Ｔｙｎｄａｌｌ氷河の後退過程と植生の遷移およびその立地条件

The retreat process of Tyndall Glaciers and the vegetation were surveyed in Mount Kenya (5, 199m). Tyndall Glacier have retreated since early in this century and is retreating at an average rate of 2.88m/yr in the last 35 years. The first colonist of new till is Senecio keniophytum, which occurs at a distance of 18m from the 1992 ice-front. The speed of advance of this plant (1958-1984.2.65m/yr, 1984-1992: 2.13m/yr) is similar to the retreat rate of the glacier. The next species encountered is Arabis alpina, at 37m. This species advance at rate of 4.38m/yr (1958-1984), 4.63m/yr (1984-1992). Moss and lichen are next, at 70m and its speed of advance is 3.47m/yr. The species growing near ice-front of Tyndall Glacier advance in connection with retreat of the glacier. The species growing at distance over 100m from ice-front colonize irregularly independently of retreat process of the glacier.Till age and stability of land surface are important environment factors controlling vegetation pattern around Tyndall Glacier. Till age is affected by the glacial fluctuation. Stability of land surface is governed by particle-size of surface materials. Former climatic condition affects both glacial fluctuation and particle-size of surface material, and landform controls particle-size of surface material. On new till, plants is restrained from colonizing because of poor soil condition even if the slope is stable. Species growing on such slope are restricted to a few species, as Senecio keniophytum and so on, and vegetation coverage is low. On old till, environmental factors affecting both vegetation coverage and growing species are stability of land surface governed by particle-size of surface materials. On stable slope covered by big debris, vegetation coverage is high and such large plants as Senecio keniodendron, Lobelia telekii and so on are distributed. Slope covered by fine-rubble is unstable and shows low vegetation coverage by the effect of needle ice creep and solifluction because diurnal range of temperature is large.Although time of snow release is important environment factor governing alpine vegetation pattern in Japan because of heavy snow in winter, that is not very important factor for Mt.Kenya without enough snow. Wind is not very important factor because wind in Mt. Kenyais not strong. Environment of Mt. Kenya is similar to that of alpine wind-blown slope of high mountains in Japan, because both Mt. Kenya and alpine wind-blown slope in Japan don't have enough snow which work for repression of thermal fluctuation. Therefore, stability of land surface affected by particle-size of surface materials, which is important environment factor controlling vegetation pattern on Japanese alpine wind-blown slope, is important factor for alpine vegetation pattern in Mt. Kenya.

Succession and Environmental Conditions of Alpine Vegetation in Relation to Glacial Fluctuations of Tyndall Glacier of the Mt. Kenya

The retreat process of Tyndall Glaciers and the vegetation were surveyed in Mount Kenya (5, 199m). Tyndall Glacier have retreated since early in this century and is retreating at an average rate of 2.88m/yr in the last 35 years. The first colonist of new till is Senecio keniophytum, which occurs at a distance of 18m from the 1992 ice-front. The speed of advance of this plant (1958-1984.2.65m/yr, 1984-1992: 2.13m/yr) is similar to the retreat rate of the glacier. The next species encountered is Arabis alpina, at 37m. This species advance at rate of 4.38m/yr (1958-1984), 4.63m/yr (1984-1992). Moss and lichen are next, at 70m and its speed of advance is 3.47m/yr. The species growing near ice-front of Tyndall Glacier advance in connection with retreat of the glacier. The species growing at distance over 100m from ice-front colonize irregularly independently of retreat process of the glacier.Till age and stability of land surface are important environment factors controlling vegetation pattern around Tyndall Glacier. Till age is affected by the glacial fluctuation. Stability of land surface is governed by particle-size of surface materials. Former climatic condition affects both glacial fluctuation and particle-size of surface material, and landform controls particle-size of surface material. On new till, plants is restrained from colonizing because of poor soil condition even if the slope is stable. Species growing on such slope are restricted to a few species, as Senecio keniophytum and so on, and vegetation coverage is low. On old till, environmental factors affecting both vegetation coverage and growing species are stability of land surface governed by particle-size of surface materials. On stable slope covered by big debris, vegetation coverage is high and such large plants as Senecio keniodendron, Lobelia telekii and so on are distributed. Slope covered by fine-rubble is unstable and shows low vegetation coverage by the effect of needle ice creep and solifluction because diurnal range of temperature is large.Although time of snow release is important environment factor governing alpine vegetation pattern in Japan because of heavy snow in winter, that is not very important factor for Mt.Kenya without enough snow. Wind is not very important factor because wind in Mt. Kenyais not strong. Environment of Mt. Kenya is similar to that of alpine wind-blown slope of high mountains in Japan, because both Mt. Kenya and alpine wind-blown slope in Japan don't have enough snow which work for repression of thermal fluctuation. Therefore, stability of land surface affected by particle-size of surface materials, which is important environment factor controlling vegetation pattern on Japanese alpine wind-blown slope, is important factor for alpine vegetation pattern in Mt. Kenya.

K-Ar dating of the Cima volcanic field, eastern Mojave Desert, California: Late Cenozoic volcanic history and landscape evolution

Thirty-four K-Ar ages and supporting paleomagnetic measurements from flows of the Cima volcanic field provide a detailed volcanic history and a temporal basis for analysis of evolving landforms. The Cima field has undergone three periods of volcanic activity, spanning late Miocene through latest Pleistocene time: (1) 7.6 to 6.5, (2) 4.5 to 3.6, and (3) 1.0 to at least 0.015 m.y. ago. These precisely dated sequences afford a unique opportunity to quantify the long-term effects of pedogenesis and erosion on volcanic landforms in an arid environment. Morphologic and pedologtc data indicate that the most stable geomorphic surfaces in the field occur on flows between 0.25 and 0.75 m.y. old. Younger flows are dominated by eolian aggradation and outcrop rubbling, and older flows are dominated by surface runoff and fluvial dissection. A process-response model involving progressive pedogenesis and a subsequent shift from infiltration to surface runoff is proposed to explain this temporal variation in land-surface stability.