I'm not sure how you can delete all catalogue records at once, but you can achieve that in piecemeal.
Click "Technical Processing", and from the drop-down menu, click "Search Catalogue". On the next screen you will see, type the name of the author you want to delete their record(s) in the field named "Search For", or the title you want to delete, or any keyword that helps you locate the record(s) you want to delete. On the "As" button, choose the appropriate search parameter and click "Quick Search".
On the search result, click the check box on the left hand side of the record(s) you want to delete and click the delete icon (the wastebasket icon) at the bottom of the page, and there you go.
I hope this helps