Mark may have been alluding to the introductory words of Genesis ("In the beginning...") as he began writing his account ("The beginning of the gospel..."). This language points to Christ as the New Adam who presides over a new heaven and a new earth. There are two different narratives of events in a single glorious story of redemption.
To be called the "Son of God" entailed deity from a Jewish point of view and thus the usage of that title would be blasphemous if given to a mere man. Moreover, the Roman Emperor would be called the son of a god. The Kingship of Jesus Christ would have presented a dilemma to both worldviews. Following is an excerpt from Dr. Thomas Constable's expository notes:
"Mark further identified Jesus Christ as the "Son of God." This title does not appear is some important early manuscripts of Mark, but it is probably legitimate. [Note: See Carson and Moo, p187.] It expresses Jesus" unique relationship to God and identifies an important theme in the second Gospel (cf. Mark 1:11; Mark 3:11; Mark 5:7; Mark 9:7; Mark 12:6; Mark 13:32; Mark 14:36; Mark 14:61; Mark 15:39). The title is messianic, but it connotes a subordinate relationship to God. Mark presented Jesus as the Servant of God particularly in this book. Rather than recording a nativity narrative that showed that Jesus was the Son of God, Mark simply stated that fact with this title. [Note: See Herbert W. Bateman IV, "Defining the Titles "Christ" and "Son of God" in Mark"s Narrative Presentation of Jesus," Journal of the Evangelical Theological Society50:3 (September2007):537-59.]"