Deleting individual events is easy and straightforward from the calendar or the list / edit events view.

To delete a whole block of events though you need to first go to the recurring events menu - then you can delete "en masse" anything that was booked as a recurring block.

Go to Calendar | Admin Menu | Option # 4 - Events and choose Recurring events. 



This will give you a list of all your recurring events.  Note that the list is sortable by column heading (click the column heading to alternate between ascending and descending).

To delete an entire block, click "delete" in the right hand column.  To delete individual instances of a recurring block, open the block by clicking on the "First Event Date".  That will open up a list of each individual event where you can choose which dates to delete.