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Geologic "Closeness"

How much time is shown in a rock outcrop?

Explore Evolution says:

Textbooks also frequently fail to mention that the different skeletons shown in transitional sequences (including the mammal-like reptiles) were not found close together geologically.
Explore Evolution, p. 27

The problem with this idea is the definition of "close." To a Young Earth creationist, close might mean hundreds or perhaps thousands of years. To a geologist or paleontologist, gaps of tens of millions of years are commonplace.

To give you an idea of the scale gaps involved, let's examine the layers (stratigraphy) of the Grand Canyon. The oldest rocks of the Grand Canyon, called the Vishnu Schist, began forming about 2 Ga (billion years ago) as marine sediment that was then metamorphosed and intruded by the younger Zoroaster Granite. All this completed by about 1.7 Ga.

The next sequence of rocks in the Grand Canyon, the Grand Canyon Supergroup, is a set of highly-tilted sediments deposited between 1.2 and 0.8 Ga.

The third sequence involves the relatively younger, flat-lying rocks that make up the majority of what one sees in the Grand Canyon's cliffs. These were deposited between ~500 Ma to ~250 Ma.

To summarize:

Sequence Age Range Time Gap
Upper Sequence 500-250 Ma 250 Ma missing above, 300 Ma missing below
Grand Canyon Supergroup 1.2 - 0.8 Ga 300 Ma missing above, 500 Ma missing below
Vishnu Schist 2.0-1.7 Ga 500 Ma missing above

These kinds of sequences--where more time is missing than is shown--are common in the rocks of the world. Geologists call these gaps "unconformities"; unconformities are so common that it is rare to find a continuous, uninterrupted sequence of rock. Therefore, to argue that fossil finds not being "close together geologically" is evidence against them is to misunderstand the nature of how rock layers are actually deposited.

Explore Evolution goes on to quote Henry Gee:

As zoologist Henry Gee writes, referring to fossil vertebrates in general, "The intervals of time that separate the fossils are so huge that we cannot say anything definite about their possible connection through ancestry and descent."
Explore Evolution, p. 29

Gee's full quote is:

It is impossible to know, for certain, that the fossil I hold in my hand [found at LO5] is my lineal ancestor. Even if it really was my ancestor, I could never know this unless every generation between the fossil and me had preserved some record of its existence and its pedigree…It might have been, but we can never know this for certain… We cannot know if the fossil found at LO5 was the lineal ancestor of the specimens found at Olduvai Gorge or Koobi Fora. It might have been, but we can never know this for certain. The intervals of time that separate the fossils are so huge that we cannot say anything definite about their possible connection through ancestry and descent.
Henry Gee, 1999, In Search of Deep Time 068485421x, p. 22-23

Gee was therefore not, as Explore Evolution claims, talking about fossils in general, but about a specific hominid tooth, which he recognized to have some relationship to his own species. The real doubt in his mind was exactly how direct the connection was. Moreover, Gee explains that the only way he could know for sure would be to have some preserved record of the entire family sequence, and he recognizes that this would be an unreasonable standard of evidence.

Gee makes a broader point, which he summarizes as:

The disconnection and isolation of events worsens further as centuries turn into millennia, tens of millennia, and finally into millions of years: intervals so vast that they dwarf the events within them… This is geological time, far beyond everyday human experience.
Henry Gee, 1999, In Search of Deep Time, 068485421x, p. 26

Gee is correct to point out that the fossil record does not contain an exact, year-by-year sequence of evidence, which is how most people think of time. By acknowledging his personal connection to the hominid tooth he is discussing, Gee posits that despite the gaps in time, we may still understand relationships between fossils, even if "we cannot say anything definite."