science

Type 1 and type 2 sequence

Type 1 and type 2 sequence is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Type 1 and type 2 sequence rather than just read about it. In short: In sequence stratigraphy, a sub discipline of geology, type 1 sequences and type 2 sequences are special sequences that are defined by having distinct types of sequence boundaries. In modern literature, the distinction in type 1 sequences and type 2 sequences was abandoned.

Key takeaways

Type 1 and type 2 sequence belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Type 1 and type 2 sequence to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Type 1 and type 2 sequence from memory before moving on to harder problems.

Reference excerpt

In sequence stratigraphy, a sub discipline of geology, type 1 sequences and type 2 sequences are special sequences that are defined by having distinct types of sequence boundaries. In modern literature, the distinction in type 1 sequences and type 2 sequences was abandoned.

Definition

Type 1 and 2 sequence boundary A type 1 sequence boundary is defined to be a sequence boundary "characterized by subaerial exposure and concurrent subaerial erosion associated with stream rejuvenation, a basinward shift of facies, a downward shift in coastal onlap, and onlap of overlying strata". Similarly, a type 2 sequence boundary is "marked by subaerial exposure and a downward shift in coastal onlap landward of the depositional-shoreline break; however, it lacks both subaerial erosion associated with stream rejuvenation and a basinward shift in facies" So the main distinction between type 1 and type 2 sequence boundaries is the amount of subaerial exposure. Type 2 sequence boundaries display, in contrast to type 1 sequence boundaries, only little subaerial exposure.

Type 1 and 2 sequence With the notions introduced above, a type 1 sequence is a sequence that is bounded by a type 1 sequence boundary below and a type 1 or a type 2 sequence boundary above. Similarly, a type 2 sequence is a sequence that is bounded by a type 2 sequence boundary below and a type 1 or a type 2 sequence boundary above.

Usage The definition of a type 1 and type 2 sequence was first introduced by Vail et al. (1984). Since they were hard to recognize, they were redefined in 1990 by Van Wagoner et al.. However even with this new definition, type 2 sequence boundaries were hard to recognize in the field due to their lack of subaerial exposure. Therefore, the abandonment of this nomenclature was recommended by Posamentier and Allen in 1999.

References

Worked examples

Example 1 — a first encounter with Type 1 and type 2 sequence

Start with the simplest possible case. Write down what Type 1 and type 2 sequence claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Type 1 and type 2 sequence before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Type 1 and type 2 sequence ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Type 1 and type 2 sequence

In research: Type 1 and type 2 sequence appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Type 1 and type 2 sequence in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Type 1 and type 2 sequence is common in secondary-school and first-year university syllabi. It links to neighbouring topics Sequence stratigraphy, Stratigraphy stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Type 1 and type 2 sequence outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Type 1 and type 2 sequence in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Type 1 and type 2 sequence means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Type 1 and type 2 sequence out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Type 1 and type 2 sequence in simple terms?

Why does Type 1 and type 2 sequence matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Type 1 and type 2 sequence?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Type 1 and type 2 sequence.