A boundary is diachronous when its age changes from place to place along it. The boundaries of formations and of facies are commonly diachronous; the boundaries of chronostratigraphic units are, by definition, not.
বইগুলো এখনো বাংলা ভাষায় পাওয়া যায় না — ইংরেজি সংস্করণ দেখানো হচ্ছে।
Earth and Space Sciences · পরিভাষা