(Bloomberg) -- Bitcoin speculators banking on a seasonal October meltup face an early reality check as deepening tension in the Middle East drives a bout of caution across global markets.Most Read from BloombergA 7,000-Year-Old City Emerges as a Haven from Dubai’s Sky-High RentsGang Violence Is Moving to the Amazon’s Fast-Growing CitiesA Housing Crisis Brews in Rwanda’s Capital CityNew Rowhouses in London That Offer a Bridge to the 19th CenturyClimate Migrants Stand to Overwhelm World’s Megaciti