The paper offers a descriptive account of the syntactic properties of some temporal and causal adjuncts belonging to different Catalan dialects. These constructions are headed by a temporal or causal preposition that selects an infinitive clause as a complement. The nature of the adjunct is, thus, prepositional. It is a complex prepositional phrase.
The prepositions analyzed -a 'at/in', en 'in', and amb 'with'- are coincidence prepositions. They are prepositions that express a relation of coincidence, or contiguity, in a place or time. The paper deals with the conditions under which the coincidence preposition can act as a causal operator. Such conditions vary in their application depending on the dialect.