By Nick Timiraos 

The Federal Reserve Bank of New York said Thursday that Lorie Logan, a longtime executive at the bank, will become the manager of the central bank's asset portfolio, while Daleep Singh, an economist who previously served as the Treasury Department, will run the bank's markets group.

Ms. Logan will oversee the central bank's $4 trillion securities portfolio and open market operations, implementing Fed officials' interest rate decisions. Mr. Singh will handle the markets group's operations and technology.

The two positions were created to assume the responsibilities previously handled by one person, Simon Potter, who left the bank in June after New York Fed President John Williams decided to install new leaders.

The leadership shuffle has unfolded during a period of intense operational engineering to stem money-market volatility that erupted in mid-September and interfered with officials' ability to control very short-term interest rates.

Ms. Logan served as the deputy to Mr. Potter and has worked at the New York Fed since 1999. She played a prominent role in developing and implementing the Fed's post-crisis-era policies, including the expansion of the $4 trillion asset portfolio and the tools used to help unwind that support when the Fed lifted interest rates from near zero earlier this decade.

Mr. Singh is currently chief North American economist at SPX Capital, a Brazilian investment fund. He served in the Treasury Department's international division and markets room from 2011 to 2016, when he was named acting assistant secretary for financial markets, a position he served in until the end of the Obama administration in 2017. Before that, he worked at Goldman Sachs Group Inc.

Since the 2008 financial crisis, the head of the New York Fed's markets desk has been the most high-profile staff job at the central bank. The people who have held the role were highly influential in helping officials create and employ new policy tools.

The markets desk implements Fed policy by buying and selling securities in trades with private financial firms, and the officer briefs top officials at each policy meeting on the state of the markets and the working of central-bank policies.

Ms. Logan has been the most senior staffer involved in shaping Fed policy makers' understanding of September's money-market volatility and designing the options for how they would respond to it.

Interest rates in very short-term lending markets rose sharply in mid-September due to shortages of funds that banks were willing to lend.

The Fed responded by injecting billions of dollars into markets to pull rates down to its target range. The central bank is facing another big test through year's end as regulatory deadlines could create new funding strains.

Ms. Logan assumes her new role Jan. 1. Mr. Singh takes his post in February.

Wall Street veterans and former Fed officials said that failing to select Ms. Logan for the job after Mr. Potter and another longtime executive were ousted earlier this year would have further damaged low morale at the bank.

Insiders said Ms. Logan had been groomed to succeed Mr. Potter and said she is highly regarded within the bank for her experience and dedication.

"It is an honor to be entrusted with this work," she said Thursday in a statement.

The New York Fed also said Christopher Armstrong would serve as head of the financial services group. He replaces Richard Dzina, a longtime executive who was ousted by Mr. Williams. Mr. Armstrong has worked at the New York Fed for more than 10 years, the bank said.

Write to Nick Timiraos at nick.timiraos@wsj.com

(END) Dow Jones Newswires

December 12, 2019 17:25 ET (22:25 GMT)

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