what does this notification icon mean?

[dr4sight]

A few days ago a notification icon came on just to the right of the wifi signal. It's a red x on what looks like a white document page.
The G Pad manual lists some common notification icons but does not show this one.
Does anyone recognize it and know what it is supposed to be telling me?
Thanks.

 

[dr4sight]

Under storage there is no mention of micro SD.
Under SD (which is in light gray) there is an option to Mount SD Card and Erase SD Card.

The interesting thing is that that notification now has been gone for over 24 hours while I did not change any settings at all.
Quite odd.

 

[Mikestony]

Like what @jhtalisman suggested, it does appear to be sd card related.
I'm wondering if your card is starting to go on the fritz.

Better to backup your card just in case it decides to go south

 

[jhtalisman]

It there is the option to mount it, try to mount and see what it says. It may have unreadable sectors, if so, need to back up anything important.

 

[dr4sight]

I don't have a Sim Card or micro SD card on this tablet. And the notification icon is gone for over 24 hours now.