Renton Formation

coal mining

The coal seams in the Renton Formation at Squak Mountain were identified as a possible source of commercially viable coal as early as 1859, but large-scale operations didn’t begin until rail transportation reached the area in 1887.

coal seams

The bedrock of Squak Mountain is made up of rocks that formed from sediments carried by rivers into an ancient coastal estuary, where their increasing weight caused the land to sink, only to be buried by even more sediments. In time, the sedimentary layers accumulated more than one mile of thickness. As the sediments slowly collected, sub-tropical forests flourished on the landscape. Trees died and were buried before they began to decay, slowly converting into peat. Further burial and heat, possibly from regional molten magma intrusions in the Cascade Mountains, reduced the water, methane and carbon dioxide in the peat, and changed it into coal. The coal seams are found today in a layer of sedimentary rocks that geologists have named the Renton Formation.

geologic map

Geologic Map of the East Half of the Bellevue South 7.5’ x 15’ Quadrangle, Issaquah Area, King County, Washington The Issaquah area includes several of the most outstanding geologic features of the eastern Puget Lowland region. Folds have warped thousands of meters of Tertiary sedimentary and volcanic rocks. Several hundred meters of both glacial and postglacial sediment have accumulated in a deep glacial trough, which is now partly occupied by Lake Sammamish but which was previously the conduit for massive volumes of meltwater during ice-sheet occupation and retreat. The eastern projection of an east-west-oriented crustal structure, which reflects Tertiary through Holocene fault displacement, extends across the eastern part of the map area.

geological formation of

near

Tukwila Formation

path on GitHub

https://github.com/davepinch/pinchy.cc/blob/master/content/topics/places/formations/renton-formation/renton-formation.md

properties

Renton Formation—Nonmarine fine- to medium-grained arkosic sandstone and siltstone containing abundant subbituminous coal beds and carbonaceous shale.

random

Fort Ward to Blakely Harbor Trail

tags

geological formation

Wikidata

https://www.wikidata.org/wiki/Q17508361

Wikipedia

Renton Formation (Wikipedia) The Renton Formation is a geologic formation in Washington (state) within the Puget Group. It preserves fossils dating back to the Paleogene period.