• Geology
The investigated landfill is located in the piedmont alluvial-pluvial plain of the
secondary basin at the northern margin of the Qaidam Basin. Geotectonically, it sits
on the compound of the inner side of the western reflex arc of the
Qilv-Lvliang-Helian epsilon-type tectonic system and the peripheral diffusion zone
in the head of the Qinghai-Tibet-Yunan eta-type tectonic system. In terms of
regional tectonic characteristics, the Dachaidan Basin falls into the secondary zone
of subsidence in the northern margin of the Qaidam Basin.
Under the north-south stress, the Qaidam Basin is dominated by NWW and
NW-trending tectonic zones. During the Neotectonic period, the tectonic evolution
in northern Qaidam Mountains mainly included NWW-trending shear-dominated
transpressional thrust faults and the axial surfaces of folds, as well as associated
folds of different grades, faults of different natures, and other evolutional tectonic
elements of different scales and orders. In the southern Lvliang Mountain, the
tectonic evolution was mainly characterized by NW-trending transpressional tectonic transformations, including thrust faults and axial surfaces of folds, and
associated series of tensile and shear faults and joints.
Since the Neogene period, the neotectonic movements have been extremely
strong in the region, manifested in large-scale oscillatory and differential
uplift-subsidence movements of fault blocks based on old structures. As a result, the
northern and southern parts of the detailed investigation area have risen sharply to
form mountainous areas, while Dachaidan has relatively subsided to form basins
and lakes. The oscillatory uplift of fault blocks was stronger in northern mountainous areas, i.e. Qaidam Mountain, than southern mountainous areas, i.e. the
Lvliang Mountain. Due to such imbalance, the discharge center of surface water
and groundwater in the basin has changed under the effects and restrictions of the
north-south stress. The Baligou and Reshuigou surface water gradually turned from
east-west runoff to north-south runoff, giving rise to current river landforms. For
example, there are no terraces or Quaternary deposits on the west of the mouth of
the Baligou River, while cliffs and terraces have been created on the east, with
cutting depth of about 50 m. This also proves that the relocation of the Baligou
River is affected by regional tectonic movements.
Amid oscillating uplifts of faults block in the northern mountainous areas,
multi-level high terraces have been formed asymmetrically in Baligou and
Reshuigou valleys. In front of the mountain, asymmetrical multi-level terraces
emerged in the valley as a result of oscillating uplifts. According to the survey data,
the NW-trending transpressional thrust fault near the mouth of Baligou River
control the basic trend of the Qaidam Mountains and the Qaidam Basin, as well as
the main faults in the mountainous areas and the basin. This transpressional thrust
fault extends in the NW-SE direction beyond the study area, reaching about
100 km. It controls the lithological trend and distribution of regional strata, and has
been inherited with large scale and great cutting depth (deep to the mantle) in many
tectonic movements. Therefore, the fault is presumed to be a regional deep fault.
There are a large number of hot springs distributed from the fracture to Reshuigou
158
5 Application Cases
The investigated landfill is located in the piedmont alluvial-pluvial plain of the
secondary basin at the northern margin of the Qaidam Basin. Geotectonically, it sits
on the compound of the inner side of the western reflex arc of the
Qilv-Lvliang-Helian epsilon-type tectonic system and the peripheral diffusion zone
in the head of the Qinghai-Tibet-Yunan eta-type tectonic system. In terms of
regional tectonic characteristics, the Dachaidan Basin falls into the secondary zone
of subsidence in the northern margin of the Qaidam Basin.
Under the north-south stress, the Qaidam Basin is dominated by NWW and
NW-trending tectonic zones. During the Neotectonic period, the tectonic evolution
in northern Qaidam Mountains mainly included NWW-trending shear-dominated
transpressional thrust faults and the axial surfaces of folds, as well as associated
folds of different grades, faults of different natures, and other evolutional tectonic
elements of different scales and orders. In the southern Lvliang Mountain, the
tectonic evolution was mainly characterized by NW-trending transpressional tectonic transformations, including thrust faults and axial surfaces of folds, and
associated series of tensile and shear faults and joints.
Since the Neogene period, the neotectonic movements have been extremely
strong in the region, manifested in large-scale oscillatory and differential
uplift-subsidence movements of fault blocks based on old structures. As a result, the
northern and southern parts of the detailed investigation area have risen sharply to
form mountainous areas, while Dachaidan has relatively subsided to form basins
and lakes. The oscillatory uplift of fault blocks was stronger in northern mountainous areas, i.e. Qaidam Mountain, than southern mountainous areas, i.e. the
Lvliang Mountain. Due to such imbalance, the discharge center of surface water
and groundwater in the basin has changed under the effects and restrictions of the
north-south stress. The Baligou and Reshuigou surface water gradually turned from
east-west runoff to north-south runoff, giving rise to current river landforms. For
example, there are no terraces or Quaternary deposits on the west of the mouth of
the Baligou River, while cliffs and terraces have been created on the east, with
cutting depth of about 50 m. This also proves that the relocation of the Baligou
River is affected by regional tectonic movements.
Amid oscillating uplifts of faults block in the northern mountainous areas,
multi-level high terraces have been formed asymmetrically in Baligou and
Reshuigou valleys. In front of the mountain, asymmetrical multi-level terraces
emerged in the valley as a result of oscillating uplifts. According to the survey data,
the NW-trending transpressional thrust fault near the mouth of Baligou River
control the basic trend of the Qaidam Mountains and the Qaidam Basin, as well as
the main faults in the mountainous areas and the basin. This transpressional thrust
fault extends in the NW-SE direction beyond the study area, reaching about
100 km. It controls the lithological trend and distribution of regional strata, and has
been inherited with large scale and great cutting depth (deep to the mantle) in many
tectonic movements. Therefore, the fault is presumed to be a regional deep fault.
There are a large number of hot springs distributed from the fracture to Reshuigou
158
5 Application Cases