Question: where are the oldest rocks in north america
[{'answer': 'northwestern Canada', 'provenance': [{'wikipedia_id': '4087668', 'title': 'Oldest dated rocks', 'start_paragraph_id': 2, 'start_character': 419, 'end_paragraph_id': 2, 'end_character': 438, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4087668', 'title': 'Oldest dated rocks', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 936, 'bleu_score': 0.739168961959041, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5071992396441068330}, 'section': 'Section::::Abstract.'}]}]