I don't think you can dominate the market with only 1k coins. the total volume of okcoin is 56,682.36฿ alone.(in last 24h).
What exchange are you looking at, bitstamp?
Bitstamp doesn't lead, bitstamp follows okcoin.(because of the 'low' volume)
So if there was any manipulation it would happen on okcoin.

Besides these blocks are probably just an accumulation of coins from a lot of people.