Change of arrows’ shape – post navigation

First of all I would like to thank you for awesome theme.
I do really appreciate your work and fact that you gave us such a great tool for free.

Now, let’s get to the bottom line.
I would like to change the type/shape of the arrows that appear when you navigate between the posts. I can see from the code that the arrow is implemented as a font.

Could you please let me know how can I change the shape of the arrow?

Looking forward to your feedback.