Susan, I am from Chile and I have ALderete ancestor´s as well. I´ve been looking for Alderete´s surnames for several years on church records, so I will check my papers to see if I find any Agustin Alderete. Don´t you remember the other last name? You might know that here in Chile we use two lastnames, father´s and mother´s, that way is much easier to find an ancestor. A few years ago some genealogists wrote 3 books about Founder Families of Chile, and you can find the Alderete family there. The only problem is they only chose the most "important" persons to put into their book. I tell you that because my great grandmother is not in the book, but his brother is. You might find that book in a University library there. The name is "Familias Fundadoras de Chile, 1601-1655. El segundo contingente". Good luck, and If I see an Agustin I´ll let u know.