Cut the fennel quarter in half lengthwise, and then cut away the core. Using a mandoline or a sharp knife, shave the fennel lengthwise into paper-thin slices. Add the fennel slices and tangerine segments to the bowl. Drizzle the olive oil and lemon juice into the bowl, and season the salad with pinches of salt and pepper to taste. Using your hands, toss the salad gently, mixing well.