Does Arima (1,0,1) exist? Are there any articles station Arima (1,0,1)? How to intrpret Arima (1,0,1) summary results?

Question

I have dataset that corresponds to year (from 1930-2020) and volume of sediment. I have to predict the volume for next 50 years. While trying ARIMA in R I tried different models like (1,0,0), (1,1,0) (2,2,0) etc. But the forecast summary show same volume through out except for (1,0,1). So I am not sure if ARIMA (1,0,1) exists as I found no articles or topis talking about (1,0,1). so I am confused if I can use it or not? Can someone tell me what does arima (1,0,1) mean? and how to intrepret? Will that even make sense if I use (1,0,1), as my forecast summary is giving different values? Rest all the models giving same value except for (1,0,1).