Explaining accusative case marking on locative arguments in South Bolivian Quechua

Abstract

In South Bolivian Quechua, a nominative-accusative language, locative arguments can surface with either spatial case markers such as -man ‘allative’, -manta ‘ablative’, and -pi ‘locative’, or the canonical accusative suffix -ta. We identify three recurrent patterns: in some contexts only spatial case is grammatical, in others only accusative is acceptable, and in still others both options are possible but yield discourse contrasts. We argue that this variation follows from the interaction of three constraints plus an information-structural distinction. The Proto-Patient Constraint permits accusative marking on locative arguments when they instantiate key proto-patient properties such as being an incremental theme or undergoing a change of state. The Agreement Constraint blocks accusative but requires spatial case to satisfy lexical semantic agreement when the verb root or the verbal suffix encodes directionality. The Competition Constraint blocks accusative-marked locative argument to avoid argument structure ambiguity when another noun is already marked with accusative. Where both case options are possible, spatial case foregrounds the locative as focal or newly introduced, whereas accusative presents the event as discourse-new. Typological parallels suggest that the South Bolivian Quechua pattern belongs to a broader tendency for accusative marking to extend to non-canonical arguments under constrained semantic and discourse conditions.