Geodiversity Atlas—Central Alaska I&M Network Index

Geology and Stratigraphy of the Central Alaska I&M Network

The Central Alaska Inventory & Monitoring Network (CAKN) consists of three NPS units in south-central, east-central, and southeastern Alaska: Denali National Park and Preserve (DENA), Wrangell-St. Elias National Park and Preserve (WRST), and Yukon-Charley Rivers National Preserve (YUCH). It is important to note that Wrangell-St. Elias belongs to both the CAKN and the Southeast Alaska Inventory & Monitoring Network (SEAN). The SEAN monitors about 193 km (120 mi) of WRST coastline and the outer coast of Glacier Bay. It is difficult for the CAKN to address park vital signs south of the Bagley ice field and there is an ecological contrast to the rest of the network making it a better fit with SEAN.

The geologic history of the parks of the CAKN is complex and subject to evolving scientific interpretations (Santucci et al. 2011). Southern Alaska lies along a tectonically active continental margin that records convergence between the North American continental plate and the Pacific oceanic plate. The tall mountain ranges, volcanoes and other features are evidence of the geologic history along the continental margin and plate boundary. The geology of this geographic area, particularly DENA and WRST, is dominated by a series of terranes accreted during the latter half of the Mesozoic Era (Christeson et al. 2010; see Geologic Time Scale). Accreted terranes are large assemblages of rocks that originally formed elsewhere, were subsequently transported by plate tectonic processes, and ultimately collided with and accreted onto a different plate, in this case North America. Rocks deposited after the terrane accretion, referred to as “post-accretionary rocks”, are also exposed in the parks.

YUCH is geographically located further from the continental margin than DENA and WRST, and so consequently the park is less heavily influenced by terrane accretion. Rocks within the northeastern portion of YUCH are further from the western continental margin and were not impacted by the tectonic events along the plate boundary. The Tintina Fault divides YUCH into two distinct geologic areas: one northeast and one southwest of the fault. The area southwest of the Tintina Fault consists of a complex sequence of igneous rocks and metamorphosed sedimentary rocks. These rocks were probably metamorphosed and juxtaposed against the western margin of North America when several small microplates (or terranes) collided during the Mesozoic. Northeast of the Tintina Fault, the northeast corner of YUCH consists of a sequence of un-metamorphosed Precambrian and Paleozoic passive margin (non-volcanic continental margin characterized by carbonate, shale [mudstone], and sandstone rocks) rocks that represents the westernmost extension of the Paleozoic North American continent. The northeastern portion of YUCH is one of the rare locations in North America where such an extensive geologic history is preserved, spanning from the Precambrian to the Cenozoic. The northwest corner of YUCH, lying north of the Tintina Fault and separated to the east from the northeast corner by a northeast-trending belt of Cretaceous flysch (forming the Kandik Basin), represents a poorly understood collage of accreted terranes. The Yukon River and its tributaries cut through these ancient sedimentary rocks, exposing a remarkable record of the floral and faunal history of east-central Alaska (Santucci et al. 2011).

A Brief Geologic History

A few examples of events and Network resources in each geologic time period are highlighted below, from youngest to oldest.

• See also, Geologic Time Scale - Geology (U.S. National Park Service)

Geology & Soils—Central Alaska Network Parks

Type Sections—Central Alaska Network

The geologic history above is excerpted from a report titled, "National Park Service geologic type section inventory: Central Alaska Inventory & Monitoring Network". Type sections are essential reference locations for the geoscientists who study geologic history and paleontology. A summary of the type sections in each park can be found at the links below.

• Denali National Park & Preserve, Alaska (contains three identified stratotypes)

• Wrangell-St. Elias National Park, Alaska (contains 25 identified stratotypes)

• Yukon-Charley Rivers National Preserve, Alaska (contains 17 identified stratotypes)

The full Network report is available in digital format from:

• DataStore - National Park Service geologic type section inventory: Central Alaska Inventory & Monitoring Network (nps.gov)

Please cite this publication as:

• Henderson TC, Santucci VL, Connors T, Tweet JS. 2022. National Park Service geologic type section inventory: Central Alaska Inventory & Monitoring Network. Natural Resource Report. NPS/CAKN/NRR—2022/2369. National Park Service. Fort Collins, Colorado.

NPS Stratotype Inventory

Fossil Resources—Central Alaska Network

Between 2002 and 2011, network-based paleontological resource inventories were completed for all the 32 I&M networks, and six of the earliest were completely updated between 2012 and 2016. The report linked below summarizes the paleontological resources of all park units in the Central Alaska Inventory & Monitoring Network (CAKN). The report provides geologic background and paleontological resource data for each park to support management operations, planning, and science-based decision making as required by NPS management policies and the Paleontological Resources Preservation Act (2009).

The full report is available in digital format from

• DataStore - Paleontological resource inventory and monitoring: Central Alaska Network (nps.gov)

Please cite this publication as:

• Santucci, V. L., R. B. Blodgett, W. P. Elder, J. S. Tweet, and J. P. Kenworthy. 2011. Paleontological resource inventory and monitoring: Central Alaska Network. Natural Resource Technical Report NPS/NRSS/NRTR—2011/510. National Park Service, Fort Collins, Colorado.

Related Links

• Central Alaska Inventory & Monitoring Network
• NPS Geodiversity Atlas
• NPS—Geologic Resources Inventory

Geodiversity Atlas pages—by Inventory & Monitoring Network

Geodiversity Atlas pages—by State, U.S. Commonwealth, and Territories