Accelerated block generation According to http://btc.blockr.io/ :

Height  Block created   Transactions    Block fee   Size (kb)   Days destroyed
318525  2 minutes ago   28              0.00370000  8.36 kB     2.00
318524  3 minutes ago   64              0.00746243  25.76 kB    527.97
318523  4 minutes ago   140             0.02336649  67.67 kB    1,666.43
318522  2 minutes ago   16              0.00130000  4.64 kB     10.19
318521  8 minutes ago   359             0.05072184  205.02 kB   4,148.84
318520  16 minutes ago  92              0.01266343  49.22 kB    112.75
318519  7 minutes ago   128             0.01682150  54.51 kB    2,146.34
318518  20 minutes ago  137             0.02128600  86.23 kB    1,213.50
318517  24 minutes ago  657             0.10664839  353.93 kB   6,502.12


So during the past 24 minutes, 9 blocks have been found. One would expect this time to be approximately an hour and a half (90 minutes). 


How is this explained? Why is the block generation process currently running so fast? 
Is it safe to assume that the 6 confirmations, which took less that 10 minutes, implies an irreversible transaction?
Block finding is random. The number of blocks in a period of time follows the Poisson distribution. If the average is 10 minutes per block, then the chance of at least 9 blocks in a given 24 minute period is roughly 0.086%. Not a lot but it can happen occasionally. Also, if momentarily the hashrate has increased without the difficulty catching up, the rate, and the probability, will be higher.
Yes, 6 confirmations that due to luck took, say, 30 minutes, are even safer than 6 confirmations that took 60 minutes, since the attacker would have had less time to find blocks in his alternative branch.