There are many ways of deleting fields saved in drupal features such as creating .install and using hook update. The other way that I found esier is to delete the field with drush and then update the feature. Here are the steps:
Check where the filed is being used
grep -r <field-name>
if this is used elsewhere you would need to update the code appropiratly 1) Delete field
Drush field-delete <field_name>
drush field-info fields | grep field_marketing_blurb or using mysql
3) using sql command:
show tables like '%field_marketing_blurb%'
select * from variable where name like '%field_marketing_blurb%';
4) recreate the feature
drush fu --yes <feature_name>
5) But, if you are using field_group, you might have some references left for that so go to your managed fields page for the content type and click the save button and then repeat last two steps.
6) And, if you use Display Suite, you might have some references left for that so go to the manage display page for EACH view mode and click save and then repeat last two steps