What Is This Weird Signal On 16.2 KHz VLF??

I made this recording on 16.2 KHz using a preamplified loop antenna down the bottom of the garden feeding my SDR. The recording was made on February the 2nd 2018 at 11am local time. I have no idea if the signal is local or thousands of miles away as signals at this frequency can propagate over very long distances if they are powerful enough. The signal starts off being very narrow but gets wider after a few minutes. By 7 minutes into the video the signal gets very wide and extra sidebands start to appear either side of the transmission. I watched the transmission repeat itself a couple of times, taking about 18 minutes to cycle. VLF is typically used by the military to contact submarines whilst they are underwater as signals at these frequencies can penetrate water. The signal you can see in the waterfall at 16.5KHz is indeed one such transmission. The signal disappeared at around 11:45am local time. Does anyone know what the signal on 16.2 KHz might be?

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