Geomorphic Surfaces, Fluvial Erosion, and Landscape Evolution

1. Geomorphic Surfaces, Fluvial Erosion, and Landscape Evolution

2. What is the oldest point on this hillslope? Lincoln NE Schoeneberger 2007

3. Geomorphic Surface Defined • A portion of a landscape that can be defined by space and time. • It may include multiple landforms. • It is a mappable feature with definable borders. • A geomorphic surface is two-dimensional. • It has no thickness (Ruhe 1975).

5. Utility and Scientific Value of Geomorphic Surfaces • Partitions the landscape into spatial units that originate from a common set of processes. • Provides the scientific principles that establish age (relative or actual) relationships among landscapes, landforms, and soils.

6. Elements of a Geomorphic Surface • Depositional (formed by deposition of sediment). • Erosional (formed by removal of earth material). • Both may be present; but the deposition component is often removed by younger erosion.

7. Late Wisconsin to Recent Erosional Surface Depositional Surface E.E. Gamble Turkey Creek, IA

8. Geomorphic Surfaces ( oldest surface is on top Younger surfaces cross cut older surfaces) The principle of ascendency Establishes relative age relationships within a landscape

10. NC E.E. Gamble

11. Erosional Surface B

12. inset relationship; northeast KS Wysocki

13. Erosional Surface Depositional Surface E.E. Gamble Valley Forge, PA

14. Criteria for Identifying Geomorphic Surfaces • Landscape morphometry • Sediment bodies or packages • Weathering profiles, paleosols including surface soils.

15. Recognition of Geomorphic Surfaces Requires: • Field observations and use of spatial information (topo maps, aerial photos). • Field identification of landscape features, landforms, and sediments resulting from erosion and/or deposition during a given time.

16. Age Tenets of Geomorphic Surfaces • An erosional geomorphic surface is younger than any surface to which it ascends (cross cuts). • An erosional component of a geomorphic surface is the same age as depositional component to which it descends.

18. Ducktown, TN E.E. Gamble

19. Age Nuances • An erosional surface is the same age as the depositional surface to which it descends, and therefore, no older than the youngest alluvium beneath depositional surface. • The alluvium beneath a depositional surface may be a time transgressive deposit. Maximum age of a depositional surface equals basal alluvium age.

20. Age of Geomorphic Surfaces

21. Late Wisconsin to Recent Erosional Surface Depositional Surface E.E. Gamble Turkey Creek, IA

22. Geomorphic Surface 2 (depositional) older burial = age of deposit younger Fan 2 Geomorphic Surface (depositional) Buried Exposed Fan 1

23. What is the surface age on the Hatcher alluvium? Daniels & Jordan, Huddleston

26. Surry Scarp (middle vs. lower) Coastal Plain, NC E.E. Gamble

27. Faceted (Stepped) Surfaces • Geomorphic evidence of erosion surfaces is a number of inclined facets (stepped surfaces) on a hillslope. The facets must be repeating and traceable across hillslopes. • Until geologic erosion obscures the morphometric relationships these facets are discernible geomorphic surfaces.

28. Faceted (stepped) surface remnants (typically only erosional component remains) Ozarks, MO

29. Gamble (1982) MO Ozarks Soil-Geomorphic Study S1 S1

30. s3 s1 e4 s2 ?? e5

31. Ozarks, MO

32. S-2 Surface Laclede County MO Gamble

33. E-4 Surface Laclede County MO Gamble

34. Exceptions: Bedrock control ( tectonic displacement, mass movement )

35. soil B buried soil A EROSIONAL AND DEPOSITIONAL SURFACES 1. deposition of BED 2 2. stabilization and pedogenesis 3. Fluvial erosion down cutting or headward. BED 2 (massive unconsolidated sand) incision BED 1 (thinly interbedded silt and sand) Wysocki et al, (2000)

36. EROSIONAL AND DEPOSITIONAL SURFACES 3. erosion 4. stabilization and pedogenesis More developed soil on older surface There is not necessarily a 1:1 relationship of soil to geomorphic surface. soil B Two less developed soils on the younger erosional surface BED 2 (massive unconsolidated sand) soil C buried soil A soil D BED 1 (thinly interbedded silt and sand) Wysocki et al, (2000)

37. Fluvial Landscape Erosion & Evolution

39. Fluvial Erosion effects / controls much of the earth’s surface. • Fluvial erosion establishes relationships and provides tools for assessing relative age of portions of the landscape and the soils on them. • [ Constructional landscapes (e.g. young lava flows, intense eolian deposition, etc.) play by a different set of rules. ]

40. FLUVIAL EROSION SURFACES • Start from a controlling stream. • Move up interfluve flanks toward divide. • Cut older geomorphic surfaces. Ruhe (1967)

42. FLUVIAL EROSION SURFACES Erosion surface profile is curvate and concave upward toward divide. Ruhe (1967)

44. Surface 1 Surface 2 Surface 3

45. Schoeneberger / Wysocki stepped geomorphic surfaces; Las Animas Arroyo (Caballo Reservoir area), NM

46. FLUVIALEROSION SURFACES • Erosion strips weathering products of older surfaces forming a young, fresh surface. • New soil forming cycle begins.. Ruhe (1967)

47. Late Sangamon Pediment Wisconsin age erosion surface Adair Soil – Loess/Paleosol Fine Oxyaquic Vertic Argiudoll Shelby Soil Loess/Till Fine-loamy Typic Argiudoll

48. FLUVIAL EROSION SURFACES • Divides remain as a stable portion of the landscape until beveled by an encroaching erosion surface. Ruhe etal. (1967)

49. Drew Quadrangle MO After Gamble 1993 Ozarks, MO

50. BED 1 (thinly interbedded silt and sand) EROSIONAL AND DEPOSITIONAL SURFACES 1. deposition of BED 1