Mumbai, Jan. 9 -- The Indian rupee fell sharply today back beyond Rs 90 per dollar mark tracking sharp selloff in domestic equities and sustained firmness in dollar overseas. The benchmark BSE Sensex plummeted 604.72 points, or 0.72 percent, to 83,576.24, with selling seen across the board. The broader NSE Nifty index fell 193.55 points, or 0.75 percent, to 25,683.30. Besides, elevated global crude oil prices and persistent foreign fund outflows amid rising geopolitical tensions also weighed down the local unit. The rupee declined 26 paise to settle at 90.16 (provisional) against the US dollar. At the interbank foreign exchange, the rupee opened higher at 89.88 but lost ground through the day to settle at 90.16 (provisional) against the U...