[1] Because the BHT is covered by Phanerozoic rocks, its extent is uncertain and only known from aeromagnetic data and drill cores.
[1] In its southern end the BHT is intruded by the Peace River Arch, a cratonic uplift active since the Proterozoic.
The Rae craton is of similar age and isotopic signature which suggest it and the BHT formed a single crustal entity at 2.4 Ga. 2.34 Ga mafic to ultramafic rocks between BHT och Rae indicate separation by this time.
The lack of indicator minerals such as harzburgitic garnet suggests a mantle composition different from those of other diamond occurrences.
Drilling restricted to upper 200 m (660 ft) but the carrot-shaped kimberlite diatremes reach below the Proterzoic boundary and contain crater facies.