'I marveled that' is correct and can be used in written English.
You can use it when expressing amazement or admiration. For example, "I marveled that he could finish the marathon in such a short time."
When I returned home, I marveled that the household employed a maid who washed my clothes.
The markings in the book return me to a time when, sitting in my cramped dorm room, I suddenly grasped some principle that governs the way objects interact, whether here on earth or light years distant, and I marveled that such vastness and complexity could be reducible to the equation I had highlighted in my book.
My grandmother has lived in the same apartment for 56 years, and as I lugged my bags up to the third floor, I marveled that the building had not changed substantially: the same shabby paint I remembered from my childhood, the same cracks on the wall, the same narrow staircase.
Of course, when the finished suit arrived in New York, packed in tissue in a large white box printed in heavy face with "Chanel 31, rue Cambon-Paris," it was perfect, and I marveled that something that had taken so many hours to make, and was obviously exceptional, could feel like nothing when it's on.
At the conclusion of each search, I marveled that this world is huge and so different from the culture I am used to.
I marveled that this was part of the curriculum.
We marveled that -- had he arrived a second or two later -- I would have been in the house, and he would've had no idea where to find me.
I marveled at the beauty of that plane.
I marveled at the stork nests that had been built atop the ramparts.
Working my way thru the stylish crowd on the opening night I marveled at the interlocking personalities that converged to create this exhibition.
I marveled at the fact that I was feeling this familiar emotion in the financial district of Manhattan, an unusual place to be in shock.
