Wall Street's 4 top banks just had $55 billion wiped off their market value in a single day

• Four of America's biggest banks lost a combined $55 billion of market value in a single day as financial stocks plunged.
• US bank shares took a beating Thursday amid fears of contagion effects from the turmoil at Silicon Valley Bank and Silvergate.
• JPMorgan saw the biggest tumble in market value among US lenders, losing $22 billion. 

Wall Street's biggest banks took quite a thrashing in the stock market Thursday as investors spooked the turmoil at Silicon Valley Bank and Silvergate Capital dumped financial shares.