* Marianne Lake to replace Doug Braunstein as CFO
* Lake to join operating committee, report to Dimon
* Braunstein to become a vice chairman, focus on clients
By David Henry
Nov 19 (Reuters) - JPMorgan Chase & Co named little-known executive Marianne Lake as its chief financial officer on Monday, making her one of the most powerful women on Wall Street and the top ambassador to investors for the largest U.S. bank.
Lake, 43, will replace Doug Braunstein as CFO early next year and join only a handful of other women in top Wall Street roles, such as Ruth Porat, the chief financial officer of Morgan Stanley.
Lake will answer directly to CEO Jamie Dimon in her new role, reestablishing a reporting line taken away from the CFO post this summer after a massive $6.2 billion trading loss hurt the company's credibility with securities analysts.
She will also join the bank's powerful operating committee, which has about a dozen members.
"I hope to be described as a great partner and someone who helped drive and develop the business," Lake said in a interview.
Braunstein, 51, a long-time investment banker, will become a vice chairman at JPMorgan and "focus on serving top clients," according to an announcement from the company.
His move could mark the last exit from the public spotlight of JPMorgan executives linked to the trading loss.
Braunstein, like Dimon, had insisted to analysts in April that press reports were wrong about risks the bank's Chief Investment Office faced from positions taken by Bruno Iksil, who was known to hedge funds as the "London Whale" for the size of his trades in derivatives.
When talk of Braunstein's possible move surfaced last month, a person familiar with the matter said giving up the CFO post would be Braunstein's decision and unrelated to the bad credit trades.
The change also comes as Dimon grooms a younger group of executives at the bank.
In a reshuffle over the summer, Dimon named Michael Cavanagh and Daniel Pinto - both in their late 40s at the time - co-chiefs of commercial and investment banking. Both Cavanagh and Pinto are seen as prime candidates to succeed Dimon, 56, when he is ready to retire.
Lake was far removed from the derivatives debacle. Though she has been the CFO for JPMorgan's retail branch systems since 2009, she has had a relatively low profile outside the bank.
She has not been a member of the company's Executive Committee, whose roughly 50 members are listed in JPMorgan's annual report and who meet quarterly.
Lake has had some experience in the last five years meeting with Wall Street securities analysts, whom she will address in future quarterly conference calls after earnings reports.
In her previous roles, she saw the financial crisis up close as JPMorgan acquired investment bank Bear Stearns and then as the U.S. housing crisis battered JPMorgan's mortgage investments.
From 2007-09, she worked in JPMorgan's investment bank as global controller in finance and business management.
Lake first met Dimon when he came to the bank in 2004. Dimon, in the company's statement, said Lake "has developed an impressive breadth of knowledge and experience in finance across both our wholesale and our consumer businesses."
Lake, a chartered accountant, managed global finance infrastructure and control functions in JPMorgan's corporate finance group from 2004 to 2007. Before that, she was a senior financial officer for the company in the United Kingdom.
She also worked for PriceWaterhouseCoopers in London and Sydney before joining JPMorgan.
Lake is a citizen of both the United States and the United Kingdom, having been born to an American mother and a British father.
Dimon took Braunstein out of his line of direct reports in July, assigning him to answer first to Matt Zames, a top mortgage markets executive whom he had just named co-chief operating officer of the company.
Dimon, in testimony before a congressional committee in Washington in June, cited Braunstein as being among top lieutenants whom he had relied upon to check the London Whale reports.
Others he cited were company risk officers. In October, former Chief Risk Officer Barry Zubrow said that he would retire at the end of the year. Another person whom Dimon cited was Ina Drew, who was head of the Chief Investment Office and who left shortly after the losses surfaced.
Besides the shakeups this year, Dimon shuffled some of his top executives at least once in each of the three previous years. He has said that he likes to rotate his top staff through different positions as part of preparing potential successors.
In June 2011, Dimon replaced retail banking chief Charlie Scharf, who has since become CEO of Visa Inc.
In June 2010, Dimon named Braunstein to be CFO after Cavanagh had held the post for six years. Cavanagh was then put in charge of JPMorgan's Treasury & Securities Services unit which handles payments and other transactions for corporations and governments.
Cavanagh's assignment changed somewhat in this year's July shuffle when Dimon said the bank would combine the treasury services business with its investment bank and that Cavanagh would become co-head of the new unit, with Pinto.
In 2009, Dimon named Jes Staley to take over the investment bank, replacing its co-chief executives Bill Winters and Steve Black. At the time, it look like Staley could become a successor to Dimon, though they are about the same age.
But in July of this year, Staley was moved out of that executive role to become chairman of the combined corporate and investment bank.