Main point summary
Jesus is the Son of God (as shown by a progression of four testimonies)
The beginning of the gospel of Jesus Christ,
a the Son of God. 1
b As it is written in Isaiah the prophet, 1 c “Behold, I send my messenger before your face, who will prepare your way,
d the voice of one crying in the wilderness: e ‘Prepare 1 the way of the Lord, make his paths straight,’”
f John appeared, baptizing in g the wilderness and proclaiming h a baptism of i repentance j for the forgiveness of sins.
And all the country of Judea and all Jerusalem were going out to him and were being baptized by him in the river Jordan, k confessing their sins.
Now John was l clothed with camel’s hair and l wore a leather belt around his waist and ate m locusts and n wild honey.
And he preached, saying, o “After me comes he who is mightier than I, the strap of whose sandals I am not worthy to stoop down and untie.
p I have baptized you with water,
but q he will baptize you with the Holy Spirit.”
r In those days Jesus s came from Nazareth of Galilee and was baptized by John in the Jordan.
And when he came up out of the water, immediately he t saw u the heavens being torn open v and the Spirit descending on him like a dove.
And w a voice came from heaven, x “You are my beloved Son; 1 with you I am well pleased.”
This passage consists of four testimonies that Jesus is the Son of God: Mark (1:1), the prophets (1:2-3), John the Baptist (1:4-8), and God from heaven (1:9-11).
The passage builds to a climax with this sense of progression. Mark testifies to the identity of Jesus as prophesied beforehand by Isaiah and Malachi. The prophets foretold of a forerunner for the Messiah and he comes on the scene in verses 4-8. John prepares the people for the Lord, who suddenly comes on the scene in verses 9-11. The climax of the whole passage is when God the Father directly testifies that Jesus is the Son of God (v. 11)
Please note that when I work with a large passage, I try to avoid subdividing too much. Each instance of direct speech could be subdivided as Idea (And he preached, saying) followed by explanation (After me comes he...). The various adverbial participles could also be broken up into separate propositions.