Grouse Creek block

[1] Together, these terranes comprise part of the basement rock of the North American continent[1] and have been critical to studies of crustal accretion in the Precambrian.

Ongoing study of the Grouse Creek block will contribute to understanding the paleogeography of the Wyoming craton prior to its incorporation into the supercontinent Laurentia approximately 1.86 billion years ago.

Initial geochronology of the Grouse Creek block in 1967 provided age dates identical to those of the Wyoming craton, causing the margin between the two to be blurred.

[14][18] Geologists proposed three hypotheses for the provenance of the Grouse Creek block:[1][14] Geo- and thermochronologic data indicates mountain building and magmatism in the Farmington Canyon Complex at 2.45 and 1.8 billion years ago[1][15] can be attributed to accretion of the Grouse Creek block to the Wyoming craton in the Paleoproterozoic.

[17][18] The Wyoming craton can be differentiated from other Archean terranes by an enriched 207Pb/204Pb ratio that is hypothesized to represent early crustal extraction, as well as samarium and neodymium ratios providing rock ages of up to 4.0 Ga.[14] Investigation of lead and neodymium isotope ratios in the Grouse Creek block provide evidence that it is chemically unique with respect to the Wyoming craton, corroborating past studies indicating the accretion of the terrane to the western margin of the Wyoming craton in the Paleoproterozoic (Fig.

Fig. 1. Location of the Grouse Creek block and relevant adjacent geologic and geographic landmarks. [ 1 ]
Fig. 2. Possible sequence of an accretionary event involving an exotic terrane and a continental landmass. Accretion of the Grouse Creek block onto the Wyoming craton is proposed to occur through this process. [ 19 ]