Eight Thousand Years of Sedimentation and Arroyo Formation, Hanson Creek, Yakima Training Center, Washington
Document Type
Oral Presentation
Campus where you would like to present
SURC Ballroom B/C/D
Start Date
21-5-2015
End Date
21-5-2015
Keywords
Arroyo, Hanson Creek, Sedimentation
Abstract
The causes and timing of cycles of sedimentation in the Hanson Creek drainage in central Washington provide insight into changes in channel morphology and paleoenvironment within the region over the last 8,000 years. Using LiDAR imagery and field surveys, recent processes such as degree of modern channel incision, accumulation of valley floor sediment, and channel morphology and gradient were evaluated. The spatial distribution of these channel characteristics was assessed in relation to proximal land forms such as spring mounds, colluvial deposits, and basalt outcrops. Sixteen stratigraphic profiles in the arroyo walls were used to delineate and correlate past depositional episodes based on sediment characteristics. Basal ages of the earliest documented depositional period were constrained using geochemical analysis of tephra beds. Intermediate dates were obtained from 14C analysis of charcoal. Stratigraphic evidence suggests multiple transitions from an aggrading braided system to an expansive, fine-grained, alluvial step-pool sequence that aggraded a minimum of 3.5 m throughout the last 8,000 years. Low gradient, fine-grained, organic-rich, sediment suggests prolonged periods of saturation at three locations throughout the incised reach, adjacent to evidence of groundwater springs. The intervening reaches exhibit comparatively high gradients for unconsolidated alluvium. A single and unprecedented 9 m deep incision of a 1.8 km reach occurred around AD 1900. The timing and physical environmental conditions associated with Holocene sedimentation in the Hanson Creek watershed will supplement the minimal data available on arroyo formation in the northwestern United States, and allow a comparison with the timing of archaeological occupation sites adjacent to Hanson Creek.
Recommended Citation
Windingstad, Levi, "Eight Thousand Years of Sedimentation and Arroyo Formation, Hanson Creek, Yakima Training Center, Washington" (2015). Symposium Of University Research and Creative Expression (SOURCE). 15.
https://digitalcommons.cwu.edu/source/2015/posters/15
Poster Number
10
Department/Program
Geological Sciences
Additional Mentoring Department
Geological Sciences
Eight Thousand Years of Sedimentation and Arroyo Formation, Hanson Creek, Yakima Training Center, Washington
SURC Ballroom B/C/D
The causes and timing of cycles of sedimentation in the Hanson Creek drainage in central Washington provide insight into changes in channel morphology and paleoenvironment within the region over the last 8,000 years. Using LiDAR imagery and field surveys, recent processes such as degree of modern channel incision, accumulation of valley floor sediment, and channel morphology and gradient were evaluated. The spatial distribution of these channel characteristics was assessed in relation to proximal land forms such as spring mounds, colluvial deposits, and basalt outcrops. Sixteen stratigraphic profiles in the arroyo walls were used to delineate and correlate past depositional episodes based on sediment characteristics. Basal ages of the earliest documented depositional period were constrained using geochemical analysis of tephra beds. Intermediate dates were obtained from 14C analysis of charcoal. Stratigraphic evidence suggests multiple transitions from an aggrading braided system to an expansive, fine-grained, alluvial step-pool sequence that aggraded a minimum of 3.5 m throughout the last 8,000 years. Low gradient, fine-grained, organic-rich, sediment suggests prolonged periods of saturation at three locations throughout the incised reach, adjacent to evidence of groundwater springs. The intervening reaches exhibit comparatively high gradients for unconsolidated alluvium. A single and unprecedented 9 m deep incision of a 1.8 km reach occurred around AD 1900. The timing and physical environmental conditions associated with Holocene sedimentation in the Hanson Creek watershed will supplement the minimal data available on arroyo formation in the northwestern United States, and allow a comparison with the timing of archaeological occupation sites adjacent to Hanson Creek.
Faculty Mentor(s)
Lisa Ely