Tolstoj Quadrangle - Geologic History

Geologic History

The interpretable geologic history within the Tolstoj quadrangle begins with the period of formation of the intercrater plains, which persisted until shortly after impact of the asteroid that created the Tolstoj Basin. After this event was a period of only slightly less intense bombardment. This period was followed by impact of the asteroid that created the Caloris Basin and deposits of the Caloris Group. Although the intermediate plains were resurfaced at the time of the Caloris impact, their formation actually extended from the end of the intercrater plains-forming period through the end of formation of c3 craters. At about the time the last c3 craters and the first c4 craters were being formed, the upper surface of the smooth plains and Caloris floor plains were being emplaced. Part of the smooth plains and Caloris floor plains materials may have been deposited during or immediately after the Caloris event.

After the emplacement of most of the smooth plains, some late c3 craters and all c4 and c5 craters, including the large crater Mozart, were superposed on all previous deposits. The recognizable geologic history of the quadrangle ends with these events probably several billion years ago. A summary of the generalized geology history of Mercury was given by Guest and O’Donnell and Davies and others.