Complex sentence: She conducted archaeological and ethnographic research in the Southwestern United States; and undertook some of the first dendrochronological research in eastern North America in the mid 20th century, examining samples from a number of archaeological sites.
Split into simpler sentences: She conducted archaeological and ethnographic research in the Southwestern United States. She also undertook some of the first dendrochronological research in eastern North America in the mid 20th century, examining samples from a number of archaeological sites.